android的ShapeDrawable源码解析

相信很多人都用XML里面的shape标签,就能实现椭圆,矩形等图形.然后直接当做Drawable来使用.比如ImageView.setImageDrawable(Drawable). 没错,这个shape标签所实现的图形Drawable其实就是ShapeDrawable对象,而ShapeDrawable是 Drawable的子类.(按照这个规律,也许你还会发现Drawable的子类还有GradientDrawable什么的,这些都是Drawable的子类) 这里解析下ShapeDrawable的源码,看看里面的方法.就知道怎么去用它了. 解析已经写在注释了,所以不再另外写.

/* * Copyright (C) 2007 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.graphics.*;import android.graphics.drawable.shapes.Shape;import android.content.res.Resources;import android.content.res.TypedArray;import android.util.AttributeSet;import org.xmlpull.v1.XmlPullParser;import org.xmlpull.v1.XmlPullParserException;import java.io.IOException;/** *一个绘制原始形状(shapes)的Drawable对象.一个ShapeDrawable在屏幕获取一个相应的对象并管理它的存在.如果 *没有提供的shape,那么ShapeDrawable会默认一个RectShape(矩形shape). * * A Drawable object that draws primitive shapes.  * A ShapeDrawable takes a {@link android.graphics.drawable.shapes.Shape} * object and manages its presence on the screen. If no Shape is given, then * the ShapeDrawable will default to a  * {@link android.graphics.drawable.shapes.RectShape}. * *这个对象能在XML文件里通过<shape>标签去定义 - 就是说<shape>标签里定义的就是这个ShapeDrawable * <p>This object can be defined in an XML file with the <code><shape></code> element.</p> * * <div class="special reference"> * <h3>Developer Guides</h3> * *要知道更多关于如何使用ShapeDrawable的信息,可以去这个链接 *{@docRoot}guide/topics/graphics/2d-graphics.html#shape-drawable 阅读. * * <p>For more information about how to use ShapeDrawable, read the * <a href="{@docRoot}guide/topics/graphics/2d-graphics.html#shape-drawable"> * Canvas and Drawables</a> document. For more information about defining a ShapeDrawable in * XML, read the * <a href="{@docRoot}guide/topics/resources/drawable-resource.html#Shape">Drawable Resources</a> * document.</p></div> * * @attr ref android.R.styleable#ShapeDrawablePadding_left * @attr ref android.R.styleable#ShapeDrawablePadding_top * @attr ref android.R.styleable#ShapeDrawablePadding_right * @attr ref android.R.styleable#ShapeDrawablePadding_bottom * @attr ref android.R.styleable#ShapeDrawable_color * @attr ref android.R.styleable#ShapeDrawable_width * @attr ref android.R.styleable#ShapeDrawable_height */public class ShapeDrawable extends Drawable {    private ShapeState mShapeState;    private boolean mMutated;    /**     * ShapeDrawable constructor.     */    public ShapeDrawable() {        this((ShapeState) null);    }        /** * 传入具体的Shape可以创建一个ShapeDrawable对象. * 比如我们在XML文件中通过shape标签定义的draw资源,其实就是这个ShapeDrawable, * 而在代码中,我们可以通过诸如 * new ShapeDrawable(new RectShape()); //矩形shape * new ShapeDrawable(new OvalShape()); //椭圆shape * 这些方法去创建一个ShapeDrawable对象 *     * Creates a ShapeDrawable with a specified Shape.     *      * @param s the Shape that this ShapeDrawable should be     */    public ShapeDrawable(Shape s) {        this((ShapeState) null);                mShapeState.mShape = s;    }    //上面的构造方法都指向这个私有方法去创建ShapeDrawable.//从下面的方法看到,ShapeState是包含了很多Drawable状态信息(比如绘制当前Drawable对象的paint,宽高值等等)的对象//ShapeState是个静态类,最后面会提到.    private ShapeDrawable(ShapeState state) {        mShapeState = new ShapeState(state);    }    /** * getShape()方法获取ShapeDrawable的形状(Shape是rect,oval等等)     * Returns the Shape of this ShapeDrawable.     */    public Shape getShape() {        return mShapeState.mShape;    }        /** * 设置shape     * Sets the Shape of this ShapeDrawable.     */    public void setShape(Shape s) {        mShapeState.mShape = s;//更新shape        updateShape();    }        /**     * Sets a ShaderFactory to which requests for a      * {@link android.graphics.Shader} object will be made.     *      * @param fact an instance of your ShaderFactory implementation     */    public void setShaderFactory(ShaderFactory fact) {        mShapeState.mShaderFactory = fact;    }        /** * ShaderFactory,这是个抽象的工厂类,每次drawable被调整大小的时候, * 都会回调ShaderFactory的抽象方法abstract Shader resize(int width, int height). * 比如上面的setShape()方法就会令drawable重新去绘制图形并调整大小,于是就会回调这个resize()方法. * 也可以看出每一个Drawable对象(当然ShapeDrawable也是Drawable的子类)都应该有自己的ShaderFactory. *     * Returns the ShaderFactory used by this ShapeDrawable for requesting a      * {@link android.graphics.Shader}.     */    public ShaderFactory getShaderFactory() {        return mShapeState.mShaderFactory;    }    /** * 获取用于绘制shape的Paint对象.     * Returns the Paint used to draw the shape.     */    public Paint getPaint() {        return mShapeState.mPaint;    }        /** * 传入left, top, right, bottom 四个参数去依次设置shape的Padding属性     * Sets padding for the shape.     *      * @param left    padding for the left side (in pixels)     * @param top     padding for the top (in pixels)     * @param right   padding for the right side (in pixels)     * @param bottom  padding for the bottom (in pixels)     */    public void setPadding(int left, int top, int right, int bottom) {        if ((left | top | right | bottom) == 0) {            mShapeState.mPadding = null;        } else {            if (mShapeState.mPadding == null) {                mShapeState.mPadding = new Rect();            }            mShapeState.mPadding.set(left, top, right, bottom);        }//重要的绘制刷新方法,下面会提到.        invalidateSelf();    }        /**     * Sets padding for this shape, defined by a Rect object.     * Define the padding in the Rect object as: left, top, right, bottom.     */    public void setPadding(Rect padding) {        if (padding == null) {            mShapeState.mPadding = null;        } else {            if (mShapeState.mPadding == null) {                mShapeState.mPadding = new Rect();            }            mShapeState.mPadding.set(padding);        }        invalidateSelf();    }        /** * 设置默认的宽度     * Sets the intrinsic (default) width for this shape.     *      * @param width the intrinsic width (in pixels)     */    public void setIntrinsicWidth(int width) {        mShapeState.mIntrinsicWidth = width;        invalidateSelf();    }        /** * 设置默认的高度     * Sets the intrinsic (default) height for this shape.     *      * @param height the intrinsic height (in pixels)     */    public void setIntrinsicHeight(int height) {        mShapeState.mIntrinsicHeight = height;        invalidateSelf();    }        @Override    public int getIntrinsicWidth() {        return mShapeState.mIntrinsicWidth;    }        @Override    public int getIntrinsicHeight() {        return mShapeState.mIntrinsicHeight;    }        @Override    public boolean getPadding(Rect padding) {        if (mShapeState.mPadding != null) {            padding.set(mShapeState.mPadding);            return true;        } else {            return super.getPadding(padding);        }    }//调整Alpha值的私有方法,不重要    private static int modulateAlpha(int paintAlpha, int alpha) {        int scale = alpha + (alpha >>> 7);  // convert to 0..256        return paintAlpha * scale >>> 8;    }    /** * 画布被准备好,会在Drawable的draw()中回调这个方法.任何Drawable的子类都可以覆盖重写这个方法. *      * Called from the drawable's draw() method after the canvas has been set     * to draw the shape at (0,0). Subclasses can override for special effects     * such as multiple layers, stroking, etc.     */    protected void onDraw(Shape shape, Canvas canvas, Paint paint) {        shape.draw(canvas, paint);    }//绘画方法    @Override    public void draw(Canvas canvas) {//获取大小,画笔,透明度的信息        Rect r = getBounds();        Paint paint = mShapeState.mPaint;        int prevAlpha = paint.getAlpha();        paint.setAlpha(modulateAlpha(prevAlpha, mShapeState.mAlpha));        if (mShapeState.mShape != null) {            // need the save both for the translate, and for the (unknown) Shape//这里涉及底层绘画的原理方法.canvas.restoreToCount()被调用前,必须先使用canvas.save()去保存画布的状态,不然会报错.            int count = canvas.save();            canvas.translate(r.left, r.top);            onDraw(mShapeState.mShape, canvas, paint);//原句是now the canvas is back in the same state it was before the initial. //画布被重置到初始化前的状态.等于可以重新在画布上去绘画新的东西            canvas.restoreToCount(count);        } else {//上面提到如果创建ShapeDrawable传入的参数为null,就默认创建矩形的ShapeDrawable//这个方法就是默认处理绘画矩形的实现            canvas.drawRect(r, paint);        }                // restore        paint.setAlpha(prevAlpha);    }//当Drawable发生变化时 ,调用该方法返回Drawable的configuration参数    @Override    public int getChangingConfigurations() {        return super.getChangingConfigurations()                | mShapeState.mChangingConfigurations;    }        /** * 设置alpha的大小,这里会结合color的alpha值和drawable的alpha值去的到一个新的alpha值, * 这个新的alpha值才是真正的绘画时用到的alpha值. *      * Set the alpha level for this drawable [0..255]. Note that this drawable     * also has a color in its paint, which has an alpha as well. These two     * values are automatically combined during drawing. Thus if the color's     * alpha is 75% (i.e. 192) and the drawable's alpha is 50% (i.e. 128), then     * the combined alpha that will be used during drawing will be 37.5%     * (i.e. 96).     */    @Override public void setAlpha(int alpha) {        mShapeState.mAlpha = alpha;        invalidateSelf();    }    //设置ColorFilter.    @Override    public void setColorFilter(ColorFilter cf) {        mShapeState.mPaint.setColorFilter(cf);        invalidateSelf();    }    //获取透明度    @Override    public int getOpacity() {        if (mShapeState.mShape == null) {            final Paint p = mShapeState.mPaint;            if (p.getXfermode() == null) {                final int alpha = p.getAlpha();                if (alpha == 0) {                    return PixelFormat.TRANSPARENT;                }                if (alpha == 255) {                    return PixelFormat.OPAQUE;                }            }        }        // not sure, so be safe        return PixelFormat.TRANSLUCENT;    }//给Paint设置flag属性,比如常用的paint.setFlags(Paint.ANTI_ALIAS_FLAG); 用于去掉锯齿.//dither为true - dither会被设入, 为false则清除paint的flags.    @Override    public void setDither(boolean dither) {        mShapeState.mPaint.setDither(dither);        invalidateSelf();    }//覆盖drawable的同名方法,当确定drawable的子类重绘时调用该方法    @Override    protected void onBoundsChange(Rect bounds) {        super.onBoundsChange(bounds);        updateShape();    }    /** * 子类覆盖这个方法去实现对XML文件中标签的分析,如果确定去实现它,就返回true.否则就返回super.inflateTag(...) * 一般不建议自己去写.好吧,除非你是有特别需求. *     * Subclasses override this to parse custom subelements.     * If you handle it, return true, else return <em>super.inflateTag(...)</em>.     */    protected boolean inflateTag(String name, Resources r, XmlPullParser parser,            AttributeSet attrs) {        if ("padding".equals(name)) {            TypedArray a = r.obtainAttributes(attrs,                    com.android.internal.R.styleable.ShapeDrawablePadding);            setPadding(                    a.getDimensionPixelOffset(                            com.android.internal.R.styleable.ShapeDrawablePadding_left, 0),                    a.getDimensionPixelOffset(                            com.android.internal.R.styleable.ShapeDrawablePadding_top, 0),                    a.getDimensionPixelOffset(                            com.android.internal.R.styleable.ShapeDrawablePadding_right, 0),                    a.getDimensionPixelOffset(                            com.android.internal.R.styleable.ShapeDrawablePadding_bottom, 0));            a.recycle();            return true;        }        return false;    }//覆盖重写了父类的方法,解析XML文件,读取XML的各种参数...    @Override    public void inflate(Resources r, XmlPullParser parser, AttributeSet attrs)                        throws XmlPullParserException, IOException {        super.inflate(r, parser, attrs);        TypedArray a = r.obtainAttributes(attrs, com.android.internal.R.styleable.ShapeDrawable);        int color = mShapeState.mPaint.getColor();        color = a.getColor(com.android.internal.R.styleable.ShapeDrawable_color, color);        mShapeState.mPaint.setColor(color);        boolean dither = a.getBoolean(com.android.internal.R.styleable.ShapeDrawable_dither, false);        mShapeState.mPaint.setDither(dither);        setIntrinsicWidth((int)                a.getDimension(com.android.internal.R.styleable.ShapeDrawable_width, 0f));        setIntrinsicHeight((int)                a.getDimension(com.android.internal.R.styleable.ShapeDrawable_height, 0f));        a.recycle();        int type;        final int outerDepth = parser.getDepth();        while ((type=parser.next()) != XmlPullParser.END_DOCUMENT               && (type != XmlPullParser.END_TAG || parser.getDepth() > outerDepth)) {            if (type != XmlPullParser.START_TAG) {                continue;            }                        final String name = parser.getName();            // call our subclass            if (!inflateTag(name, r, parser, attrs)) {                android.util.Log.w("drawable", "Unknown element: " + name +                        " for ShapeDrawable " + this);            }        }    }//每次设置shape后都要去绘制并更新    private void updateShape() {        if (mShapeState.mShape != null) {//获取宽高,重新调整shape的大小            final Rect r = getBounds();            final int w = r.width();            final int h = r.height();            mShapeState.mShape.resize(w, h);            if (mShapeState.mShaderFactory != null) {                mShapeState.mPaint.setShader(mShapeState.mShaderFactory.resize(w, h));            }        }//这个方法比较重要,需要实现Callback接口里面的invalidateDrawable(Drawable who),//scheduleDrawable(Drawable who, Runnable what, long when)和unscheduleDrawable(Drawable who, Runnable what)方法.//如果接口为null,那么就不会回调Callback.invalidateDrawable()方法,也就无法完成重新绘制更新的动作.Drawable的刷新就会失败.//上面的很多方法,比如setPadding(),setShape()等等都调用invalidateSelf()去实现,呈现最终的Drawable效果.可见这个方法有多关键哦.        invalidateSelf();    }    //获取ConstantState对象.它保存了一些和其他Drawable分享共用的常量状态和数据.//为什么会有共用常量状态和数据的情况? 比如当开发者从相同的资源中去创建Drawable的时候,这些Drawable之间就能分享共用它们的状态了.    @Override    public ConstantState getConstantState() {        mShapeState.mChangingConfigurations = getChangingConfigurations();        return mShapeState;    }//这个方法是如果Drawable确定要变化的时候,会设入一个mutate的值,这个时候当前的Drawable子类就不会再和其他Drawable分享状态参数.//这个方法比较少用到的,不必太关心.    @Override    public Drawable mutate() {        if (!mMutated && super.mutate() == this) {            mShapeState.mPaint = new Paint(mShapeState.mPaint);            mShapeState.mPadding = new Rect(mShapeState.mPadding);            try {                mShapeState.mShape = mShapeState.mShape.clone();            } catch (CloneNotSupportedException e) {                return null;            }            mMutated = true;        }        return this;    }    /** * 继承了ConstantState的静态类 * 给特定ShapeDrawable的shape定义默认的属性,这里验证了最初的想法,ShapeState包含了当前Drawable的重要属性. * ShapeState是Drawable自己的保存状态量和数据的重要对象.     * Defines the intrinsic properties of this ShapeDrawable's Shape.     */    final static class ShapeState extends ConstantState {        int mChangingConfigurations;        Paint mPaint;        Shape mShape;        Rect mPadding;        int mIntrinsicWidth;        int mIntrinsicHeight;        int mAlpha = 255;        ShaderFactory mShaderFactory;                ShapeState(ShapeState orig) {            if (orig != null) {                mPaint = orig.mPaint;                mShape = orig.mShape;                mPadding = orig.mPadding;                mIntrinsicWidth = orig.mIntrinsicWidth;                mIntrinsicHeight = orig.mIntrinsicHeight;                mAlpha = orig.mAlpha;                mShaderFactory = orig.mShaderFactory;            } else {                mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);            }        }                @Override        public Drawable newDrawable() {            return new ShapeDrawable(this);        }                @Override        public Drawable newDrawable(Resources res) {            return new ShapeDrawable(this);        }                @Override        public int getChangingConfigurations() {            return mChangingConfigurations;        }    }        /** * (上面开始的时候分析过这个类,这里就不在重复了.)     * Base class defines a factory object that is called each time the drawable     * is resized (has a new width or height). Its resize() method returns a     * corresponding shader, or null.     * Implement this class if you'd like your ShapeDrawable to use a special     * {@link android.graphics.Shader}, such as a      * {@link android.graphics.LinearGradient}.      *      */    public static abstract class ShaderFactory {        /**         * Returns the Shader to be drawn when a Drawable is drawn.         * The dimensions of the Drawable are passed because they may be needed         * to adjust how the Shader is configured for drawing.         * This is called by ShapeDrawable.setShape().         *          * @param width  the width of the Drawable being drawn         * @param height the heigh of the Drawable being drawn         * @return       the Shader to be drawn         */        public abstract Shader resize(int width, int height);    }        // other subclass could wack the Shader's localmatrix based on the    // resize params (e.g. scaletofit, etc.). This could be used to scale    // a bitmap to fill the bounds without needing any other special casing.}

在XML里面使用shape标签创建ShapeDrawable大家都很熟悉,所以下面只在代码中简单创建了一个ShapeDrawable对象:

ShapeDrawable shapeDrawable = new ShapeDrawable();        OvalShape oval = new OvalShape();        //设置默认高度,宽度        shapeDrawable.setIntrinsicHeight(100);        shapeDrawable.setIntrinsicWidth(100);        //设置椭圆        shapeDrawable.setShape(oval);        //设置填充的颜色        shapeDrawable.getPaint().setColor(Color.BLUE);        ImageView imageView = new ImageView(getActivity());        imageView.setLayoutParams(new ViewGroup.LayoutParams(200,200));        imageView.setImageDrawable(shapeDrawable);        linearLayout.addView(imageView);

效果图就这样,很简单吧~