android.graphics.drawable.Drawable注释翻译

/* * Copyright (C) 2006 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package android.graphics.drawable;import android.annotation.NonNull;import android.content.res.ColorStateList;import android.content.res.Resources;import android.content.res.Resources.Theme;import android.content.res.TypedArray;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.ColorFilter;import android.graphics.Insets;import android.graphics.NinePatch;import android.graphics.Outline;import android.graphics.PixelFormat;import android.graphics.PorterDuff;import android.graphics.PorterDuff.Mode;import android.graphics.PorterDuffColorFilter;import android.graphics.Rect;import android.graphics.Region;import android.graphics.Xfermode;import android.os.Trace;import android.util.AttributeSet;import android.util.DisplayMetrics;import android.util.StateSet;import android.util.TypedValue;import android.util.Xml;import android.view.View;import org.xmlpull.v1.XmlPullParser;import org.xmlpull.v1.XmlPullParserException;import java.io.IOException;import java.io.InputStream;import java.lang.ref.WeakReference;import java.util.Arrays;import java.util.Collection;/** * A Drawable is a general abstraction for "something that can be drawn."  Most * often you will deal with Drawable as the type of resource retrieved for * drawing things to the screen; the Drawable class provides a generic API for * dealing with an underlying visual resource that may take a variety of forms. * Unlike a {@link android.view.View}, a Drawable does not have any facility to * receive events or otherwise interact with the user. * Drawable是一个常见的抽象类，意味着可以被绘制的东西。你处理Drawable的大多数情况是把它当 * 做绘制在屏幕上的一种资源。Drawable通过了一些API用于处理不同类型的视觉资源，而不像View。 * Drawable没有任何的接收事件或者和用户交互的特性。 * <p>In addition to simple drawing, Drawable provides a number of generic * mechanisms for its client to interact with what is being drawn: * 除了简单的绘制，Drawable通过了一系列机制为客户端和被绘制的对象进行交互。 * <ul> *     <li> The {@link #setBounds} method <var>must</var> be called to tell the *     Drawable where it is drawn and how large it should be.  All Drawables *     should respect the requested size, often simply by scaling their *     imagery.  A client can find the preferred size for some Drawables with *     the {@link #getIntrinsicHeight} and {@link #getIntrinsicWidth} methods. * *     <li> The {@link #getPadding} method can return from some Drawables *     information about how to frame content that is placed inside of them. *     For example, a Drawable that is intended to be the frame for a button *     widget would need to return padding that correctly places the label *     inside of itself. * *     <li> The {@link #setState} method allows the client to tell the Drawable *     in which state it is to be drawn, such as "focused", "selected", etc. *     Some drawables may modify their imagery based on the selected state. * *     <li> The {@link #setLevel} method allows the client to supply a single *     continuous controller that can modify the Drawable is displayed, such as *     a battery level or progress level.  Some drawables may modify their *     imagery based on the current level. * *     <li> A Drawable can perform animations by calling back to its client *     through the {@link Callback} interface.  All clients should support this *     interface (via {@link #setCallback}) so that animations will work.  A *     simple way to do this is through the system facilities such as *     {@link android.view.View#setBackground(Drawable)} and *     {@link android.widget.ImageView}. * </ul> * * Though usually not visible to the application, Drawables may take a variety * of forms: * * <ul> *     <li> <b>Bitmap</b>: the simplest Drawable, a PNG or JPEG image. *     <li> <b>Nine Patch</b>: an extension to the PNG format allows it to *     specify information about how to stretch it and place things inside of *     it. *     <li> <b>Shape</b>: contains simple drawing commands instead of a raw *     bitmap, allowing it to resize better in some cases. *     <li> <b>Layers</b>: a compound drawable, which draws multiple underlying *     drawables on top of each other. *     <li> <b>States</b>: a compound drawable that selects one of a set of *     drawables based on its state. *     <li> <b>Levels</b>: a compound drawable that selects one of a set of *     drawables based on its level. *     <li> <b>Scale</b>: a compound drawable with a single child drawable, *     whose overall size is modified based on the current level. * </ul> * * <div class="special reference"> * <h3>Developer Guides</h3> * <p>For more information about how to use drawables, read the * <a href="{@docRoot}guide/topics/graphics/2d-graphics.html">Canvas and Drawables</a> developer * guide. For information and examples of creating drawable resources (XML or bitmap files that * can be loaded in code), read the * <a href="{@docRoot}guide/topics/resources/drawable-resource.html">Drawable Resources</a> * document.</p></div> */public abstract class Drawable {    private static final Rect ZERO_BOUNDS_RECT = new Rect();    static final PorterDuff.Mode DEFAULT_TINT_MODE = PorterDuff.Mode.SRC_IN;    private int[] mStateSet = StateSet.WILD_CARD;    private int mLevel = 0;    private int mChangingConfigurations = 0;    private Rect mBounds = ZERO_BOUNDS_RECT;  // lazily becomes a new Rect()    private WeakReference<Callback> mCallback = null;    private boolean mVisible = true;    private int mLayoutDirection;    /**     * Draw in its bounds (set via setBounds) respecting optional effects such     * as alpha (set via setAlpha) and color filter (set via setColorFilter).     * 在它的边界内绘制一些相关可选的效果，例如透明度，颜色过滤     * @param canvas The canvas to draw into     */    public abstract void draw(Canvas canvas);    /**     * Specify a bounding rectangle for the Drawable. This is where the drawable     * will draw when its draw() method is called.     * 为Drawable设置一个边界矩形。当draw()方法被调用，这个矩形是drawable会被绘制到的地方。     */    public void setBounds(int left, int top, int right, int bottom) {        Rect oldBounds = mBounds;        if (oldBounds == ZERO_BOUNDS_RECT) {            oldBounds = mBounds = new Rect();        }        if (oldBounds.left != left || oldBounds.top != top ||                oldBounds.right != right || oldBounds.bottom != bottom) {            if (!oldBounds.isEmpty()) {                // first invalidate the previous bounds                invalidateSelf();            }            mBounds.set(left, top, right, bottom);            onBoundsChange(mBounds);        }    }    /**     * Specify a bounding rectangle for the Drawable. This is where the drawable     * will draw when its draw() method is called.     * 为Drawable设置一个边界矩形。当draw()方法被调用，这个矩形是drawable会被绘制到的地方。     */    public void setBounds(Rect bounds) {        setBounds(bounds.left, bounds.top, bounds.right, bounds.bottom);    }    /**     * Return a copy of the drawable's bounds in the specified Rect (allocated     * by the caller). The bounds specify where this will draw when its draw()     * method is called.     * 返回Drawable的bounds的复制     * @param bounds Rect to receive the drawable's bounds (allocated by the     *               caller).     */    public final void copyBounds(Rect bounds) {        bounds.set(mBounds);    }    /**     * Return a copy of the drawable's bounds in a new Rect. This returns the     * same values as getBounds(), but the returned object is guaranteed to not     * be changed later by the drawable (i.e. it retains no reference to this     * rect). If the caller already has a Rect allocated, call copyBounds(rect).     * 返回Drawable的bounds的复制。这个和getBounds()返回一样的值，不过返回的是拷贝，保证     * 这个对象不会被drawabel修改.     * @return A copy of the drawable's bounds     */    public final Rect copyBounds() {        return new Rect(mBounds);    }    /**     * Return the drawable's bounds Rect. Note: for efficiency, the returned     * object may be the same object stored in the drawable (though this is not     * guaranteed), so if a persistent copy of the bounds is needed, call     * copyBounds(rect) instead.     * You should also not change the object returned by this method as it may     * be the same object stored in the drawable.     * 返回drawable的边界矩形。你不应该修改返回的对象，因为它可能和drawable里面的是同一个     * 引用。     * @return The bounds of the drawable (which may change later, so caller     *         beware). DO NOT ALTER the returned object as it may change the     *         stored bounds of this drawable.     *     * @see #copyBounds()     * @see #copyBounds(android.graphics.Rect)     */    public final Rect getBounds() {        if (mBounds == ZERO_BOUNDS_RECT) {            mBounds = new Rect();        }        return mBounds;    }    /**     * Return the drawable's dirty bounds Rect. Note: for efficiency, the     * returned object may be the same object stored in the drawable (though     * this is not guaranteed).     * 获取脏的边界矩形。     * <p>     * By default, this returns the full drawable bounds. Custom drawables may     * override this method to perform more precise invalidation.     * 默认返回整个矩形。常见的drawable可能会重载这个方法来实现更精确的失效。     * @return The dirty bounds of this drawable     */    public Rect getDirtyBounds() {        return getBounds();    }    /**     * Set a mask of the configuration parameters for which this drawable     * may change, requiring that it be re-created.     *     * @param configs A mask of the changing configuration parameters, as     * defined by {@link android.content.pm.ActivityInfo}.     *     * @see android.content.pm.ActivityInfo     */    public void setChangingConfigurations(int configs) {        mChangingConfigurations = configs;    }    /**     * Return a mask of the configuration parameters for which this drawable     * may change, requiring that it be re-created.  The default implementation     * returns whatever was provided through     * {@link #setChangingConfigurations(int)} or 0 by default.  Subclasses     * may extend this to or in the changing configurations of any other     * drawables they hold.     *     * @return Returns a mask of the changing configuration parameters, as     * defined by {@link android.content.pm.ActivityInfo}.     *     * @see android.content.pm.ActivityInfo     */    public int getChangingConfigurations() {        return mChangingConfigurations;    }    /**     * Set to true to have the drawable dither its colors when drawn to a device     * with fewer than 8-bits per color component. This can improve the look on     * those devices, but can also slow down the drawing a little.     * 设置为true,当华仔设备生的每个颜色组件小于8位时，保证drawable颜色效果。这个可以提高     * 外观，但是会稍微减慢绘制。     */    public void setDither(boolean dither) {}    /**     * Set to true to have the drawable filter its bitmap when scaled or rotated     * (for drawables that use bitmaps). If the drawable does not use bitmaps,     * this call is ignored. This can improve the look when scaled or rotated,     * but also slows down the drawing.     * 设置为true,drawable在被缩放或旋转的时候，会过滤它的bitmap(为那些使用bitmap的drawable准备)。     * 如果drawable没有使用bitmap，这个设置会被忽略。在缩放和旋转时这个可以提高外观，但是会稍微减慢绘制。     */    public void setFilterBitmap(boolean filter) {}    /**     * Implement this interface if you want to create an animated drawable that     * extends {@link android.graphics.drawable.Drawable Drawable}.     * Upon retrieving a drawable, use     * {@link Drawable#setCallback(android.graphics.drawable.Drawable.Callback)}     * to supply your implementation of the interface to the drawable; it uses     * this interface to schedule and execute animation changes.     * 继承这个接口如果你想创建一个继承自drawable动画drawable。对于drawable,使用它的setCallback()     * 方法去提供这个接口的实现。它使用这个接口去定时和执行动画转变。     */    public static interface Callback {        /**         * Called when the drawable needs to be redrawn.  A view at this point         * should invalidate itself (or at least the part of itself where the         * drawable appears).         * 当drawable需要重绘时，调用这个方法。View在这里应该使自己不可用(或者至少使drawable         * 出现的部分不可用)。         * @param who The drawable that is requesting the update.         */        public void invalidateDrawable(Drawable who);        /**         * A Drawable can call this to schedule the next frame of its         * animation.  An implementation can generally simply call         * {@link android.os.Handler#postAtTime(Runnable, Object, long)} with         * the parameters <var>(what, who, when)</var> to perform the         * scheduling.         * Drawable通过这个方法去安排动画的下一帧。实现者可以简单地调用android.os.Handler#postAtTime(Runnable, Object, long)         * @param who The drawable being scheduled.         * @param what The action to execute.         * @param when The time (in milliseconds) to run.  The timebase is         *             {@link android.os.SystemClock#uptimeMillis}         */        public void scheduleDrawable(Drawable who, Runnable what, long when);        /**         * A Drawable can call this to unschedule an action previously         * scheduled with {@link #scheduleDrawable}.  An implementation can         * generally simply call         * {@link android.os.Handler#removeCallbacks(Runnable, Object)} with         * the parameters <var>(what, who)</var> to unschedule the drawable.         * Drawable通过这个方法去取消scheduleDrawable()方法安排的行为。         * @param who The drawable being unscheduled.         * @param what The action being unscheduled.         */        public void unscheduleDrawable(Drawable who, Runnable what);    }    /**     * Bind a {@link Callback} object to this Drawable.  Required for clients     * that want to support animated drawables.     * 给Drawable绑定一个Callback对象。那些使用动态drawables的客户端会需要。     * @param cb The client's Callback implementation.     *     * @see #getCallback()     */    public final void setCallback(Callback cb) {        mCallback = new WeakReference<Callback>(cb);    }    /**     * Return the current {@link Callback} implementation attached to this     * Drawable.     * 返回绑定在当前drawable的Callback实现     * @return A {@link Callback} instance or null if no callback was set.     *     * @see #setCallback(android.graphics.drawable.Drawable.Callback)     */    public Callback getCallback() {        if (mCallback != null) {            return mCallback.get();        }        return null;    }    /**     * Use the current {@link Callback} implementation to have this Drawable     * redrawn.  Does nothing if there is no Callback attached to the     * Drawable.     * 使用当前Callback的实现去使这个Drawable重绘。如果没有为Drawable设置Callable，     * 则什么都不做     * @see Callback#invalidateDrawable     * @see #getCallback()     * @see #setCallback(android.graphics.drawable.Drawable.Callback)     */    public void invalidateSelf() {        final Callback callback = getCallback();        if (callback != null) {            callback.invalidateDrawable(this);        }    }    /**     * Use the current {@link Callback} implementation to have this Drawable     * scheduled.  Does nothing if there is no Callback attached to the     * Drawable.     * 使用当前Callback的实现去使这个Drawable定时。如果没有为Drawable设置Callable，     * @param what The action being scheduled.     * @param when The time (in milliseconds) to run.     *     * @see Callback#scheduleDrawable     */    public void scheduleSelf(Runnable what, long when) {        final Callback callback = getCallback();        if (callback != null) {            callback.scheduleDrawable(this, what, when);        }    }    /**     * Use the current {@link Callback} implementation to have this Drawable     * unscheduled.  Does nothing if there is no Callback attached to the     * Drawable.     * 使用当前Callback的实现去使这个Drawable取消定时。如果没有为Drawable设置Callable，     * @param what The runnable that you no longer want called.     *     * @see Callback#unscheduleDrawable     */    public void unscheduleSelf(Runnable what) {        final Callback callback = getCallback();        if (callback != null) {            callback.unscheduleDrawable(this, what);        }    }    /**     * Returns the resolved layout direction for this Drawable.     * 返回Drawable的布局方向     * @return One of {@link android.view.View#LAYOUT_DIRECTION_LTR},     *   {@link android.view.View#LAYOUT_DIRECTION_RTL}     *     * @hide     */    public int getLayoutDirection() {        return mLayoutDirection;    }    /**     * Set the layout direction for this drawable. Should be a resolved direction as the     * Drawable as no capacity to do the resolution on his own.     * 为Drawable设置布局方向。当Drawable没有能力解决方向问题的时候使用。     * @param layoutDirection One of {@link android.view.View#LAYOUT_DIRECTION_LTR},     *   {@link android.view.View#LAYOUT_DIRECTION_RTL}     *     * @hide     */    public void setLayoutDirection(@View.ResolvedLayoutDir int layoutDirection) {        if (getLayoutDirection() != layoutDirection) {            mLayoutDirection = layoutDirection;        }    }    /**     * Specify an alpha value for the drawable. 0 means fully transparent, and     * 255 means fully opaque.     * 设置透明度。0表示完全透明，255表示完全不透明。     */    public abstract void setAlpha(int alpha);    /**     * Gets the current alpha value for the drawable. 0 means fully transparent,     * 255 means fully opaque. This method is implemented by     * Drawable subclasses and the value returned is specific to how that class treats alpha.     * The default return value is 255 if the class does not override this method to return a value     * specific to its use of alpha.     * 获得当前透明度。这个方法被Drawable的子类使用并且返回值和子类怎么处理透明度有关。     * 默认返回255如果子类没有重载这个方法。     */    public int getAlpha() {        return 0xFF;    }    /**     * @hide Consider for future API inclusion     * 未来的API     */    public void setXfermode(Xfermode mode) {        // Base implementation drops it on the floor for compatibility. Whee!        // TODO: For this to be included in the API proper, all framework drawables need impls.        // For right now only BitmapDrawable has it.    }    /**     * Specify an optional color filter for the drawable. Pass {@code null} to     * remove any existing color filter.     * 指定一个颜色过滤器。传入null可以移除当前所有的过滤器。     * @param cf the color filter to apply, or {@code null} to remove the     *            existing color filter     */    public abstract void setColorFilter(ColorFilter cf);    /**     * Specify a color and Porter-Duff mode to be the color filter for this     * drawable.     * 为过滤器设置颜色和波特达夫模式     */    public void setColorFilter(int color, PorterDuff.Mode mode) {        setColorFilter(new PorterDuffColorFilter(color, mode));    }    /**     * Specifies a tint for this drawable.     * <p>     * Setting a color filter via {@link #setColorFilter(ColorFilter)} overrides     * tint.     * 设置明调。     * @param tint Color to use for tinting this drawable     * @see #setTintMode(PorterDuff.Mode)     */    public void setTint(int tint) {        setTintList(ColorStateList.valueOf(tint));    }    /**     * Specifies a tint for this drawable as a color state list.     * <p>     * Setting a color filter via {@link #setColorFilter(ColorFilter)} overrides     * tint.     * 通过一个color state list设置明调     * @param tint Color state list to use for tinting this drawable, or null to     *            clear the tint     * @see #setTintMode(PorterDuff.Mode)     */    public void setTintList(ColorStateList tint) {}    /**     * Specifies a tint blending mode for this drawable.     * <p>     * Setting a color filter via {@link #setColorFilter(ColorFilter)} overrides     * tint.     * 设置色彩混合模式     * @param tintMode Color state list to use for tinting this drawable, or null to     *            clear the tint     * @param tintMode A Porter-Duff blending mode     */    public void setTintMode(PorterDuff.Mode tintMode) {}    /**     * Returns the current color filter, or {@code null} if none set.     * 获得当前颜色过滤器     * @return the current color filter, or {@code null} if none set     */    public ColorFilter getColorFilter() {        return null;    }    /**     * Removes the color filter for this drawable.     * 清楚颜色过滤器     */    public void clearColorFilter() {        setColorFilter(null);    }    /**     * Specifies the hotspot's location within the drawable.     * 在drawable中指定热区     * @param x The X coordinate of the center of the hotspot     * @param y The Y coordinate of the center of the hotspot     */    public void setHotspot(float x, float y) {}    /**     * Sets the bounds to which the hotspot is constrained, if they should be     * different from the drawable bounds.     * 如果热区的边界要和drawable的边界不同，那么设置边界     * @param left     * @param top     * @param right     * @param bottom     */    public void setHotspotBounds(int left, int top, int right, int bottom) {}    /** @hide For internal use only. Individual results may vary. */    public void getHotspotBounds(Rect outRect) {        outRect.set(getBounds());    }    /**     * Whether this drawable requests projection.     * 是否需要投影     * @hide magic!     */    public boolean isProjected() {        return false;    }    /**     * Indicates whether this drawable will change its appearance based on     * state. Clients can use this to determine whether it is necessary to     * calculate their state and call setState.     * Drawable是否会根据状态改变外观。使用者可以以此决定是否需要去计算它们的状态和     * 设置状态     * @return True if this drawable changes its appearance based on state,     *         false otherwise.     * @see #setState(int[])     */    public boolean isStateful() {        return false;    }    /**     * Specify a set of states for the drawable. These are use-case specific,     * so see the relevant documentation. As an example, the background for     * widgets like Button understand the following states:     * [{@link android.R.attr#state_focused},     *  {@link android.R.attr#state_pressed}].     * 为drawable设置一系列状态。有一些特殊的使用例子可以看相关文档。例如，Button之类的     * 控件背景，有以下状态focused，pressed     *     * <p>If the new state you are supplying causes the appearance of the     * Drawable to change, then it is responsible for calling     * {@link #invalidateSelf} in order to have itself redrawn, <em>and</em>     * true will be returned from this function.     * 如果你使用的新状态会导致外观变化，那么主动调用nvalidateSelf引起重绘并且该方法将返回true     * <p>Note: The Drawable holds a reference on to <var>stateSet</var>     * until a new state array is given to it, so you must not modify this     * array during that time.</p>     * Drawable持有stateSet的引用直到赋给它一个新的状态数组，所以你必须在这段时间修改数组     * @param stateSet The new set of states to be displayed.     *     * @return Returns true if this change in state has caused the appearance     * of the Drawable to change (hence requiring an invalidate), otherwise     * returns false.     */    public boolean setState(final int[] stateSet) {        if (!Arrays.equals(mStateSet, stateSet)) {            mStateSet = stateSet;            return onStateChange(stateSet);        }        return false;    }    /**     * Describes the current state, as a union of primitve states, such as     * 返回当前状态数组     * {@link android.R.attr#state_focused},     * {@link android.R.attr#state_selected}, etc.     * Some drawables may modify their imagery based on the selected state.     * @return An array of resource Ids describing the current state.     */    public int[] getState() {        return mStateSet;    }    /**     * If this Drawable does transition animations between states, ask that     * it immediately jump to the current state and skip any active animations.     * 如果drwaable在状态之间有属性动画，调用这个方法立刻跳到当前状态，跳过所有动画     */    public void jumpToCurrentState() {    }    /**     * @return The current drawable that will be used by this drawable. For simple drawables, this     *         is just the drawable itself. For drawables that change state like     *         {@link StateListDrawable} and {@link LevelListDrawable} this will be the child drawable     *         currently in use.     * 返回当前被使用的drawale.对于简单的drawable，会返回本身。对于改变状态的drawable，会返回当前使用的子drawable     */    public Drawable getCurrent() {        return this;    }    /**     * Specify the level for the drawable.  This allows a drawable to vary its     * imagery based on a continuous controller, for example to show progress     * or volume level.     * 指定当前层。这允许drawable根据连续的控制者改变自己的图像，例如进度和音量水平。     * <p>If the new level you are supplying causes the appearance of the     * Drawable to change, then it is responsible for calling     * {@link #invalidateSelf} in order to have itself redrawn, <em>and</em>     * true will be returned from this function.     * 如果你使用的新层会导致外观变化，那么主动调用nvalidateSelf引起重绘并且该方法将返回true     * @param level The new level, from 0 (minimum) to 10000 (maximum).     *     * @return Returns true if this change in level has caused the appearance     * of the Drawable to change (hence requiring an invalidate), otherwise     * returns false.     */    public final boolean setLevel(int level) {        if (mLevel != level) {            mLevel = level;            return onLevelChange(level);        }        return false;    }    /**     * Retrieve the current level.     * 获取当前层     * @return int Current level, from 0 (minimum) to 10000 (maximum).     */    public final int getLevel() {        return mLevel;    }    /**     * Set whether this Drawable is visible.  This generally does not impact     * the Drawable's behavior, but is a hint that can be used by some     * Drawables, for example, to decide whether run animations.     * 设置是否可见。一般不会影响drawable的行为。但是可以被一些drawable作为依据，例如决定     * 是否运行动画     * @param visible Set to true if visible, false if not.     * @param restart You can supply true here to force the drawable to behave     *                as if it has just become visible, even if it had last     *                been set visible.  Used for example to force animations     *                to restart.     *                你可以设置为true强制drawable表现得就像刚可见一样，即使它持续了一段     *                时间才被设置为可见，例如强制动画重新启动。     *     * @return boolean Returns true if the new visibility is different than     *         its previous state.     */    public boolean setVisible(boolean visible, boolean restart) {        boolean changed = mVisible != visible;        if (changed) {            mVisible = visible;            invalidateSelf();        }        return changed;    }    public final boolean isVisible() {        return mVisible;    }    /**     * Set whether this Drawable is automatically mirrored when its layout direction is RTL     * (right-to left). See {@link android.util.LayoutDirection}.     * 设置Drawable是否自动映像当它的布局方向被设置为从右到左     * @param mirrored Set to true if the Drawable should be mirrored, false if not.     */    public void setAutoMirrored(boolean mirrored) {    }    /**     * Tells if this Drawable will be automatically mirrored  when its layout direction is RTL     * right-to-left. See {@link android.util.LayoutDirection}.     * 返回Drawable是否自动映像当它的布局方向被设置为从右到左     * @return boolean Returns true if this Drawable will be automatically mirrored.     */    public boolean isAutoMirrored() {        return false;    }    /**     * Applies the specified theme to this Drawable and its children.     * 为Drawable和它的孩子设置主题     */    public void applyTheme(@SuppressWarnings("unused") Theme t) {    }    public boolean canApplyTheme() {        return false;    }    /**     * Return the opacity/transparency of this Drawable.  The returned value is     * one of the abstract format constants in     * {@link android.graphics.PixelFormat}:     * {@link android.graphics.PixelFormat#UNKNOWN},     * {@link android.graphics.PixelFormat#TRANSLUCENT},     * {@link android.graphics.PixelFormat#TRANSPARENT}, or     * {@link android.graphics.PixelFormat#OPAQUE}.     * 返回透明度或者不透明度。返回值是以下格式的常量     * <p>Generally a Drawable should be as conservative as possible with the     * value it returns.  For example, if it contains multiple child drawables     * and only shows one of them at a time, if only one of the children is     * TRANSLUCENT and the others are OPAQUE then TRANSLUCENT should be     * returned.  You can use the method {@link #resolveOpacity} to perform a     * standard reduction of two opacities to the appropriate single output.     * 保守地返回值。例如如果有多个子drawable，并且一次只显示一个，如果其中一个是TRANSLUCENT，     * 而其他是OPAQUE，你应该返回TRANSLUCENT。你可以用resolveOpacity()老判断两个不透明度     * 哪个是合理的.     * <p>Note that the returned value does <em>not</em> take into account a     * custom alpha or color filter that has been applied by the client through     * the {@link #setAlpha} or {@link #setColorFilter} methods.     * 注意，返回值没有考虑alpha或者color filter     * @return int The opacity class of the Drawable.     *     * @see android.graphics.PixelFormat     */    public abstract int getOpacity();    /**     * Return the appropriate opacity value for two source opacities.  If     * either is UNKNOWN, that is returned; else, if either is TRANSLUCENT,     * that is returned; else, if either is TRANSPARENT, that is returned;     * else, OPAQUE is returned.     * 从两个不透明度中返回一个合理的。     * <p>This is to help in implementing {@link #getOpacity}.     *     * @param op1 One opacity value.     * @param op2 Another opacity value.     *     * @return int The combined opacity value.     *     * @see #getOpacity     */    public static int resolveOpacity(int op1, int op2) {        if (op1 == op2) {            return op1;        }        if (op1 == PixelFormat.UNKNOWN || op2 == PixelFormat.UNKNOWN) {            return PixelFormat.UNKNOWN;        }        if (op1 == PixelFormat.TRANSLUCENT || op2 == PixelFormat.TRANSLUCENT) {            return PixelFormat.TRANSLUCENT;        }        if (op1 == PixelFormat.TRANSPARENT || op2 == PixelFormat.TRANSPARENT) {            return PixelFormat.TRANSPARENT;        }        return PixelFormat.OPAQUE;    }    /**     * Returns a Region representing the part of the Drawable that is completely     * transparent.  This can be used to perform drawing operations, identifying     * which parts of the target will not change when rendering the Drawable.     * The default implementation returns null, indicating no transparent     * region; subclasses can optionally override this to return an actual     * Region if they want to supply this optimization information, but it is     * not required that they do so.     * 返回Drawable中完全透明的部分。这个可在绘制操作时使用，分辨哪些部分是不会改变的。默认实现     * 返回null,表明没有透明区域。子类可以有选择地复写从而返回确切区域，如果它希望提供这些优化信息的话。     * 但是不是要求它们都这样做。     * @return Returns null if the Drawables has no transparent region to     * report, else a Region holding the parts of the Drawable's bounds that     * are transparent.     */    public Region getTransparentRegion() {        return null;    }    /**     * Override this in your subclass to change appearance if you recognize the     * specified state.     * 在子类中复写用于改变外观，如果你认识指定的状态的话。     * @return Returns true if the state change has caused the appearance of     * the Drawable to change (that is, it needs to be drawn), else false     * if it looks the same and there is no need to redraw it since its     * last state.     */    protected boolean onStateChange(int[] state) { return false; }    /** Override this in your subclass to change appearance if you vary based     *  on level.     *  如果你希望根据层变化，在子类中复写去改变外观。     * @return Returns true if the level change has caused the appearance of     * the Drawable to change (that is, it needs to be drawn), else false     * if it looks the same and there is no need to redraw it since its     * last level.     */    protected boolean onLevelChange(int level) { return false; }    /**     * Override this in your subclass to change appearance if you vary based on     * the bounds.     *  在子类中复写用于改变外观，如果你希望根据边界改变。     */    protected void onBoundsChange(Rect bounds) {}    /**     * Return the intrinsic width of the underlying drawable object.  Returns     * -1 if it has no intrinsic width, such as with a solid color.     * 返回底层drawable对象的固有宽度。如果没有固有宽度返回-1，例如只有纯色。     */    public int getIntrinsicWidth() {        return -1;    }    /**     * Return the intrinsic height of the underlying drawable object. Returns     * -1 if it has no intrinsic height, such as with a solid color.     * 返回底层drawable对象的固有高度。如果没有固有宽度返回-1，例如只有纯色。     */    public int getIntrinsicHeight() {        return -1;    }    /**     * Returns the minimum width suggested by this Drawable. If a View uses this     * Drawable as a background, it is suggested that the View use at least this     * value for its width. (There will be some scenarios where this will not be     * possible.) This value should INCLUDE any padding.     * 返回该Drawable建议的最小宽度。如果一个view使用这个drawable作为背景，它建议View至少     * 使用这个宽度(有些情景下这是不可能的)。这个值不包含任何的内边距。     * @return The minimum width suggested by this Drawable. If this Drawable     *         doesn't have a suggested minimum width, 0 is returned.     */    public int getMinimumWidth() {        final int intrinsicWidth = getIntrinsicWidth();        return intrinsicWidth > 0 ? intrinsicWidth : 0;    }    /**     * Returns the minimum height suggested by this Drawable. If a View uses this     * Drawable as a background, it is suggested that the View use at least this     * value for its height. (There will be some scenarios where this will not be     * possible.) This value should INCLUDE any padding.     * 返回该Drawable建议的最小高度。如果一个view使用这个drawable作为背景，它建议View至少     * 使用这个高度(有些情景下这是不可能的)。这个值不包含任何的内边距。     * @return The minimum height suggested by this Drawable. If this Drawable     *         doesn't have a suggested minimum height, 0 is returned.     */    public int getMinimumHeight() {        final int intrinsicHeight = getIntrinsicHeight();        return intrinsicHeight > 0 ? intrinsicHeight : 0;    }    /**     * Return in padding the insets suggested by this Drawable for placing     * content inside the drawable's bounds. Positive values move toward the     * center of the Drawable (set Rect.inset).     * 返回为那些被放置在drawable边界里面的插入物设置的内边距。走向Drawable中心的正值。     * @return true if this drawable actually has a padding, else false. When false is returned,     * the padding is always set to 0.     */    public boolean getPadding(@NonNull Rect padding) {        padding.set(0, 0, 0, 0);        return false;    }    /**     * Return in insets the layout insets suggested by this Drawable for use with alignment     * operations during layout.     * 返回Drawable在布局时的对准操作使用的插入物     * @hide     */    public Insets getOpticalInsets() {        return Insets.NONE;    }    /**     * Called to get the drawable to populate the Outline that defines its drawing area.     * <p>     * This method is called by the default {@link android.view.ViewOutlineProvider} to define     * the outline of the View.     * <p>     * The default behavior defines the outline to be the bounding rectangle of 0 alpha.     * Subclasses that wish to convey a different shape or alpha value must override this method.     * 调用这个方法去填充决定绘制区域的框架。     * 这个方法默认被ViewOutlineProvider调用，用于决定View的框架。     * 默认设置框架为0透明度的边界矩形。希望传递不同形状或者透明度的子类，必须复写这个方法。     * @see android.view.View#setOutlineProvider(android.view.ViewOutlineProvider)     */    public void getOutline(@NonNull Outline outline) {        outline.setRect(getBounds());        outline.setAlpha(0);    }    /**     * Make this drawable mutable. This operation cannot be reversed. A mutable     * drawable is guaranteed to not share its state with any other drawable.     * This is especially useful when you need to modify properties of drawables     * loaded from resources. By default, all drawables instances loaded from     * the same resource share a common state; if you modify the state of one     * instance, all the other instances will receive the same modification.     * Calling this method on a mutable Drawable will have no effect.     * 使drawable易变。这个操作没有逆操作。一个易变的drawable保证不和其他drawable共享它的     * 状态。当你需要修改那些从资源加载的drawable的属性时，显得特别有用。所以从相同的资源加载     * 的drawable默认共享一个相同的状态。如果你修改其中一个，所有的其他对象会受到相同的而修改。     * 调用这个方法使其他不会受到影响。     *     * @return This drawable.     * @see ConstantState     * @see #getConstantState()     */    public Drawable mutate() {        return this;    }    /**     * Clears the mutated state, allowing this drawable to be cached and     * mutated again.     * <p>     * This is hidden because only framework drawables can be cached, so     * custom drawables don't need to support constant state, mutate(), or     * clearMutated().     * 清除异变状态，允许drawable被缓存并且再次易变。这是个隐藏方法，因为只有frameword     * drawable可以被缓存，所有一般的drawable不需要支持这个状态。     * @hide     */    public void clearMutated() {        // Default implementation is no-op.    }    /**     * Create a drawable from an inputstream     * 从输入流中创建drawable     */    public static Drawable createFromStream(InputStream is, String srcName) {        Trace.traceBegin(Trace.TRACE_TAG_RESOURCES, srcName != null ? srcName : "Unknown drawable");        try {            return createFromResourceStream(null, null, is, srcName);        } finally {            Trace.traceEnd(Trace.TRACE_TAG_RESOURCES);        }    }    /**     * Create a drawable from an inputstream, using the given resources and     * value to determine density information.     * 从输入流中创建drawable，使用给定的资源是值去决定密度信息。     */    public static Drawable createFromResourceStream(Resources res, TypedValue value,            InputStream is, String srcName) {        Trace.traceBegin(Trace.TRACE_TAG_RESOURCES, srcName != null ? srcName : "Unknown drawable");        try {            return createFromResourceStream(res, value, is, srcName, null);        } finally {            Trace.traceEnd(Trace.TRACE_TAG_RESOURCES);        }    }    /**     * Create a drawable from an inputstream, using the given resources and     * value to determine density information.     * 从输入流中创建drawable，使用给定的资源是值去决定密度信息。     */    public static Drawable createFromResourceStream(Resources res, TypedValue value,            InputStream is, String srcName, BitmapFactory.Options opts) {        if (is == null) {            return null;        }        /*  ugh. The decodeStream contract is that we have already allocated            the pad rect, but if the bitmap does not had a ninepatch chunk,            then the pad will be ignored. If we could change this to lazily            alloc/assign the rect, we could avoid the GC churn of making new            Rects only to drop them on the floor.            解析流协议是我们已经在pad rect中配置的，但是如果bitmap没有ninepatch块，            pad会被忽略。如果我们可以改变这个去设置rect,我们可以避免。。。(不会翻)        */        Rect pad = new Rect();        // Special stuff for compatibility mode: if the target density is not        // the same as the display density, but the resource -is- the same as        // the display density, then don't scale it down to the target density.        // This allows us to load the system's density-correct resources into        // an application in compatibility mode, without scaling those down        // to the compatibility density only to have them scaled back up when        // drawn to the screen.        /**         * 兼容方式：如果目标密度和设备密度不同，但是资源密度和设备密度相同，就不会缩放它         * 使之适用目标密度。这允许我们在兼容模式下，去加载系统的正确密度资源进app，不需         * 要去缩放它们到兼容密度，只是当它们被绘制到屏幕上时，缩放。         */        if (opts == null) opts = new BitmapFactory.Options();        opts.inScreenDensity = res != null                ? res.getDisplayMetrics().noncompatDensityDpi : DisplayMetrics.DENSITY_DEVICE;        Bitmap  bm = BitmapFactory.decodeResourceStream(res, value, is, pad, opts);        if (bm != null) {            byte[] np = bm.getNinePatchChunk();            if (np == null || !NinePatch.isNinePatchChunk(np)) {                np = null;                pad = null;            }            final Rect opticalInsets = new Rect();            bm.getOpticalInsets(opticalInsets);            return drawableFromBitmap(res, bm, np, pad, opticalInsets, srcName);        }        return null;    }    /**     * Create a drawable from an XML document. For more information on how to     * create resources in XML, see     * <a href="{@docRoot}guide/topics/resources/drawable-resource.html">Drawable Resources</a>.     * 从xml文件中返回drawable.     */    public static Drawable createFromXml(Resources r, XmlPullParser parser)            throws XmlPullParserException, IOException {        return createFromXml(r, parser, null);    }    /**     * Create a drawable from an XML document using an optional {@link Theme}.     * For more information on how to create resources in XML, see     * <a href="{@docRoot}guide/topics/resources/drawable-resource.html">Drawable Resources</a>.     * 适用特定的主题从xml文件返回drawable     */    public static Drawable createFromXml(Resources r, XmlPullParser parser, Theme theme)            throws XmlPullParserException, IOException {        AttributeSet attrs = Xml.asAttributeSet(parser);        int type;        while ((type=parser.next()) != XmlPullParser.START_TAG &&                type != XmlPullParser.END_DOCUMENT) {            // Empty loop        }        if (type != XmlPullParser.START_TAG) {            throw new XmlPullParserException("No start tag found");        }        Drawable drawable = createFromXmlInner(r, parser, attrs, theme);        if (drawable == null) {            throw new RuntimeException("Unknown initial tag: " + parser.getName());        }        return drawable;    }    /**     * Create from inside an XML document.  Called on a parser positioned at     * a tag in an XML document, tries to create a Drawable from that tag.     * Returns null if the tag is not a valid drawable.     * 从xml文件中返回drawable.调用在xml中的parser，尝试从这些标志中创建drawable.     * 返回null如果tag不是一个有效的drawable.     */    public static Drawable createFromXmlInner(Resources r, XmlPullParser parser, AttributeSet attrs)            throws XmlPullParserException, IOException {        return createFromXmlInner(r, parser, attrs, null);    }    /**     * Create a drawable from inside an XML document using an optional     * {@link Theme}. Called on a parser positioned at a tag in an XML     * document, tries to create a Drawable from that tag. Returns {@code null}     * if the tag is not a valid drawable.     * 适用特定的主题从xml文件返回drawable.调用在xml中的parser，尝试从这些标志中创建drawable.     * 返回null如果tag不是一个有效的drawable.     */    public static Drawable createFromXmlInner(Resources r, XmlPullParser parser, AttributeSet attrs,            Theme theme) throws XmlPullParserException, IOException {        final Drawable drawable;        final String name = parser.getName();        switch (name) {            case "selector":                drawable = new StateListDrawable();                break;            case "animated-selector":                drawable = new AnimatedStateListDrawable();                break;            case "level-list":                drawable = new LevelListDrawable();                break;            case "layer-list":                drawable = new LayerDrawable();                break;            case "transition":                drawable = new TransitionDrawable();                break;            case "ripple":                drawable = new RippleDrawable();                break;            case "color":                drawable = new ColorDrawable();                break;            case "shape":                drawable = new GradientDrawable();                break;            case "vector":                drawable = new VectorDrawable();                break;            case "animated-vector":                drawable = new AnimatedVectorDrawable();                break;            case "scale":                drawable = new ScaleDrawable();                break;            case "clip":                drawable = new ClipDrawable();                break;            case "rotate":                drawable = new RotateDrawable();                break;            case "animated-rotate":                drawable = new AnimatedRotateDrawable();                break;            case "animation-list":                drawable = new AnimationDrawable();                break;            case "inset":                drawable = new InsetDrawable();                break;            case "bitmap":                drawable = new BitmapDrawable(r);                if (r != null) {                    ((BitmapDrawable) drawable).setTargetDensity(r.getDisplayMetrics());                }                break;            case "nine-patch":                drawable = new NinePatchDrawable();                if (r != null) {                    ((NinePatchDrawable) drawable).setTargetDensity(r.getDisplayMetrics());                }                break;            default:                throw new XmlPullParserException(parser.getPositionDescription() +                        ": invalid drawable tag " + name);        }        drawable.inflate(r, parser, attrs, theme);        return drawable;    }    /**     * Create a drawable from file path name.     * 从文件路径中创建drawable     */    public static Drawable createFromPath(String pathName) {        if (pathName == null) {            return null;        }        Trace.traceBegin(Trace.TRACE_TAG_RESOURCES, pathName);        try {            Bitmap bm = BitmapFactory.decodeFile(pathName);            if (bm != null) {                return drawableFromBitmap(null, bm, null, null, null, pathName);            }        } finally {            Trace.traceEnd(Trace.TRACE_TAG_RESOURCES);        }        return null;    }    /**     * Inflate this Drawable from an XML resource. Does not apply a theme.     * 从xml资源找到drwale,没有使用主题     * @see #inflate(Resources, XmlPullParser, AttributeSet, Theme)     */    public void inflate(Resources r, XmlPullParser parser, AttributeSet attrs)            throws XmlPullParserException, IOException {        inflate(r, parser, attrs, null);    }    /**     * Inflate this Drawable from an XML resource optionally styled by a theme.     *  从xml资源找到drwale,使用主题指定的样式     * @param r Resources used to resolve attribute values     * @param parser XML parser from which to inflate this Drawable     * @param attrs Base set of attribute values     * @param theme Theme to apply, may be null     * @throws XmlPullParserException     * @throws IOException     */    public void inflate(Resources r, XmlPullParser parser, AttributeSet attrs, Theme theme)            throws XmlPullParserException, IOException {        final TypedArray a;        if (theme != null) {            a = theme.obtainStyledAttributes(                    attrs, com.android.internal.R.styleable.Drawable, 0, 0);        } else {            a = r.obtainAttributes(attrs, com.android.internal.R.styleable.Drawable);        }        inflateWithAttributes(r, parser, a, com.android.internal.R.styleable.Drawable_visible);        a.recycle();    }    /**     * Inflate a Drawable from an XML resource.     * 从xml资源找到drwale     * @throws XmlPullParserException     * @throws IOException     */    void inflateWithAttributes(Resources r, XmlPullParser parser, TypedArray attrs, int visibleAttr)            throws XmlPullParserException, IOException {        mVisible = attrs.getBoolean(visibleAttr, mVisible);    }    /**     * This abstract class is used by {@link Drawable}s to store shared constant state and data     * between Drawables. {@link BitmapDrawable}s created from the same resource will for instance     * share a unique bitmap stored in their ConstantState.     * 这个抽象类被drawable用于在drawable之间存储共享的常量状态和数据。从同一资源创建的BitmapDrawable将会     * 共享一个唯一的存储在ConstantState中的bitmap     * <p>     * {@link #newDrawable(Resources)} can be used as a factory to create new Drawable instances     * from this ConstantState.     * newDrawable()方法可以当成工厂去从ConstantState创建一个新的Drawable     * </p>     *     * Use {@link Drawable#getConstantState()} to retrieve the ConstantState of a Drawable. Calling     * {@link Drawable#mutate()} on a Drawable should typically create a new ConstantState for that     * Drawable.     * 使用getConstantState()获取drawable的ConstantState。在Drawable调用#mutate()会为这个drawable创建一个     * 新的ConstantState     */    public static abstract class ConstantState {        /**         * Create a new drawable without supplying resources the caller         * is running in.  Note that using this means the density-dependent         * drawables (like bitmaps) will not be able to update their target         * density correctly. One should use {@link #newDrawable(Resources)}         * instead to provide a resource.         * 创建drawable,不需要调用者提供资源。注意，使用它意味着依赖密度的drawables例如(bitmaps)         * 将不能正确更新它们的目标密度。应该使用newDrawable(Resources res)而不是提供一个资源。         */        public abstract Drawable newDrawable();        /**         * Create a new Drawable instance from its constant state.  This         * must be implemented for drawables that change based on the target         * density of their caller (that is depending on whether it is         * in compatibility mode).         * 从常状态中创建一个新的drawable对象。这个必须被那些变化依赖于目标状态密度的调用者         * 实现。         */        public Drawable newDrawable(Resources res) {            return newDrawable();        }        /**         * Create a new Drawable instance from its constant state. This must be         * implemented for drawables that can have a theme applied.         * 从常状态中创建一个新的drawable对象。这个必须被那些有主题的调用者实现。         */        public Drawable newDrawable(Resources res, Theme theme) {            return newDrawable(null);        }        /**         * Return a bit mask of configuration changes that will impact         * this drawable (and thus require completely reloading it).         * 返回会影响drawable的一个bit掩码变化设置。         */        public abstract int getChangingConfigurations();        /**         * @return Total pixel count 所有的像素         * @hide         */        public int addAtlasableBitmaps(Collection<Bitmap> atlasList) {            return 0;        }        /** @hide */        protected final boolean isAtlasable(Bitmap bitmap) {            return bitmap != null && bitmap.getConfig() == Bitmap.Config.ARGB_8888;        }        /**         * Return whether this constant state can have a theme applied.         * 返回这个常状态是否可以有主题         */        public boolean canApplyTheme() {            return false;        }    }    /**     * Return a {@link ConstantState} instance that holds the shared state of this Drawable.     * 返回Drawable共享的ConstantState实例     * @return The ConstantState associated to that Drawable.     * @see ConstantState     * @see Drawable#mutate()     */    public ConstantState getConstantState() {        return null;    }    private static Drawable drawableFromBitmap(Resources res, Bitmap bm, byte[] np,            Rect pad, Rect layoutBounds, String srcName) {        if (np != null) {            return new NinePatchDrawable(res, bm, np, pad, layoutBounds, srcName);        }        return new BitmapDrawable(res, bm);    }    /**     * Ensures the tint filter is consistent with the current tint color and     * mode.     * 保证色彩过滤器和当前色彩和色彩模式一致。     */    PorterDuffColorFilter updateTintFilter(PorterDuffColorFilter tintFilter, ColorStateList tint,            PorterDuff.Mode tintMode) {        if (tint == null || tintMode == null) {            return null;        }        final int color = tint.getColorForState(getState(), Color.TRANSPARENT);        if (tintFilter == null) {            return new PorterDuffColorFilter(color, tintMode);        }        tintFilter.setColor(color);        tintFilter.setMode(tintMode);        return tintFilter;    }    /**     * Obtains styled attributes from the theme, if available, or unstyled     * resources if the theme is null.     * 如果有效，从主题中取得样式属性。如果主题为空，则返回没有样式的资源。     */    static TypedArray obtainAttributes(            Resources res, Theme theme, AttributeSet set, int[] attrs) {        if (theme == null) {            return res.obtainAttributes(set, attrs);        }        return theme.obtainStyledAttributes(set, attrs, 0, 0);    }    /**     * Parses a {@link android.graphics.PorterDuff.Mode} from a tintMode     * attribute's enum value.     * 从tintMode解析出PorterDuff.Mode     * @hide     */    public static PorterDuff.Mode parseTintMode(int value, Mode defaultMode) {        switch (value) {            case 3: return Mode.SRC_OVER;            case 5: return Mode.SRC_IN;            case 9: return Mode.SRC_ATOP;            case 14: return Mode.MULTIPLY;            case 15: return Mode.SCREEN;            case 16: return Mode.ADD;            default: return defaultMode;        }    }}