聊聊PhoneWindow,getDecorView(),setContentView

来源:互联网 发布:淘宝换货售后卡怎么写 编辑:程序博客网 时间:2024/03/29 21:04

转载请注明出处
csdn:http://blog.csdn.net/dreamsever/article/details/78440417
简书:http://www.jianshu.com/p/a4618a9290e1

前言

最近想实现一下滑动返回,看了一下几个开源的滑动返回的库,或多或少都有点问题,就想自己做一下。看了一下他们的源码,发现直接被activity.getWindow().getDecorView(),activity.getWindow().getDecorView().getChildAt(0),activity.findViewById(Window.ID_ANDROID_CONTENT)整蒙了,它们具体代表一个界面的哪些区域。作为一个三年的Android开发我竟然说不清楚,好惭愧。今天就来总结一下PhoneWindow,activity.getWindow().getDecorView(),statusBar,activity.findViewById(Window.ID_ANDROID_CONTENT)等等它们的边边角角,前生今生。

分析

先谈谈window,PhoneWindow,getDecorView()
这里大部分参考自Android窗口机制(二)Window,PhoneWindow,DecorView,setContentView源码理解

Window

它是一个抽象基类,代表顶级窗口的外观及行为策略,这个类的一个实例应该被用作添加到窗口管理器的顶层视图。它提供了标准的UI策略,如背景,标题区域,默认密钥处理等。
这个抽象类的唯一现有的实现是android.view.PhoneWindow,当你需要一个Window的时候你应该实例化它。

以上是官方描述,我的理解Window就是一个窗口,最直观的表现就是一个界面的载体。

延伸一下:
那么Activity跟Window又是什么关系呢?Activity是我们开发app中打交道最多的一个类,它是一个用户交互界面。那么它怎么是一个用户交互界面呢?你不能说它是它就是,Activity的用户交互体现在setContentView(@LayoutRes int layoutResID)方法,布局xml文件就是界面展现,有布局肯定就是有界面了。使用Activity的setContentView(@LayoutRes int layoutResID)将布局文件与Activity绑定,那么它是怎么绑定的,绑定到哪去了?这里就要用到Window了,Window是一个窗口,它有一个DecorView,而DecorView就是具体承载布局文件的view,后面具体分析

PhoneWindow

它是Window的唯一实现类,也就是说Window就是一个抽象,想要具体实现,具体操作还是要靠这个PhoneWindow

getDecorView()

这个方法在Window的源码中

/** * Retrieve the top-level window decor view (containing the standard * window frame/decorations and the client's content inside of that), which * can be added as a window to the window manager. * * <p><em>Note that calling this function for the first time "locks in" * various window characteristics as described in * {@link #setContentView(View, android.view.ViewGroup.LayoutParams)}.</em></p> * * @return Returns the top-level window decor view. */public abstract View getDecorView();

这个方法是获取到顶层窗口的装饰视图(包含标准窗口框架/装饰以及其内部的客户端内容),可以将其作为窗口添加到窗口管理器。
那么什么是装饰视图DecorView呢,

/** @hide */public class DecorView extends FrameLayout implements RootViewSurfaceTaker, WindowCallbacks {      ...    DecorView(Context context, int featureId, PhoneWindow window,            WindowManager.LayoutParams params) {        super(context);        mFeatureId = featureId;        mShowInterpolator = AnimationUtils.loadInterpolator(context,                android.R.interpolator.linear_out_slow_in);        mHideInterpolator = AnimationUtils.loadInterpolator(context,                android.R.interpolator.fast_out_linear_in);        mBarEnterExitDuration = context.getResources().getInteger(                R.integer.dock_enter_exit_duration);        mForceWindowDrawsStatusBarBackground = context.getResources().getBoolean(                R.bool.config_forceWindowDrawsStatusBarBackground)                && context.getApplicationInfo().targetSdkVersion >= N;        mSemiTransparentStatusBarColor = context.getResources().getColor(                R.color.system_bar_background_semi_transparent, null /* theme */);        updateAvailableWidth();        setWindow(window);        updateLogTag(params);        mResizeShadowSize = context.getResources().getDimensionPixelSize(                R.dimen.resize_shadow_size);        initResizingPaints();    }      ...}

在PhoneWindow里面,出现了成员变量DecorView,它是一个window的顶层视图,DecorView继承于FrameLayout,我们那些标题栏,内容栏,顶级上看是加载在DecorView上的。而DecorView则是由PhoneWindow负责添加。

setContentView

上面我们有个疑问,Activity的setContentView(@LayoutRes int layoutResID)将布局文件与Activity绑定,那么它是怎么绑定的,绑定到哪去了?这里我们就好好分析一下Activity的setContentView,说Activity是一个界面,那只是抽象的描述,具体还是要体现在布局和view上。一个Activity包含一个Window,这个Window的实例化就是PhoneWindow,PhoneWindow中又有一个DecorView,DecorView继承自FrameLayout,好了现在布局有了,往里面添加View那不就是布局和View都有了,那不就是可以组成一个完整的界面了。请看源码娓娓道来
下面是Activity的setContentView

/**     * Set the activity content from a layout resource.  The resource will be     * inflated, adding all top-level views to the activity.     *     * @param layoutResID Resource ID to be inflated.     *     * @see #setContentView(android.view.View)     * @see #setContentView(android.view.View, android.view.ViewGroup.LayoutParams)     */    public void setContentView(@LayoutRes int layoutResID) {        getWindow().setContentView(layoutResID);        initWindowDecorActionBar();    }

指向的是Window的setContentView

/**     * Convenience for     * {@link #setContentView(View, android.view.ViewGroup.LayoutParams)}     * to set the screen content from a layout resource.  The resource will be     * inflated, adding all top-level views to the screen.     *     * @param layoutResID Resource ID to be inflated.     * @see #setContentView(View, android.view.ViewGroup.LayoutParams)     */    public abstract void setContentView(@LayoutRes int layoutResID);

也就是PhoneWindow的具体实现

@Override    public void setContentView(int layoutResID) {        // Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window        // decor, when theme attributes and the like are crystalized. Do not check the feature        // before this happens.        if (mContentParent == null) {            installDecor();        } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {            mContentParent.removeAllViews();        }        if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {            final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,                    getContext());            transitionTo(newScene);        } else {            mLayoutInflater.inflate(layoutResID, mContentParent);        }        mContentParent.requestApplyInsets();        final Callback cb = getCallback();        if (cb != null && !isDestroyed()) {            cb.onContentChanged();        }        mContentParentExplicitlySet = true;    }

我们看到当mContentParent为null的时候会执行installDecor()第一次进来mContentParent肯定为null

private void installDecor() {        mForceDecorInstall = false;        if (mDecor == null) {            mDecor = generateDecor(-1);            mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);            mDecor.setIsRootNamespace(true);            if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {                mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);            }        } else {            mDecor.setWindow(this);        }        if (mContentParent == null) {            mContentParent = generateLayout(mDecor);            // Set up decor part of UI to ignore fitsSystemWindows if appropriate.            mDecor.makeOptionalFitsSystemWindows();            final DecorContentParent decorContentParent = (DecorContentParent) mDecor.findViewById(                    R.id.decor_content_parent);            if (decorContentParent != null) {                mDecorContentParent = decorContentParent;                mDecorContentParent.setWindowCallback(getCallback());                if (mDecorContentParent.getTitle() == null) {                    mDecorContentParent.setWindowTitle(mTitle);                }                final int localFeatures = getLocalFeatures();                for (int i = 0; i < FEATURE_MAX; i++) {                    if ((localFeatures & (1 << i)) != 0) {                        mDecorContentParent.initFeature(i);                    }                }                mDecorContentParent.setUiOptions(mUiOptions);                if ((mResourcesSetFlags & FLAG_RESOURCE_SET_ICON) != 0 ||                        (mIconRes != 0 && !mDecorContentParent.hasIcon())) {                    mDecorContentParent.setIcon(mIconRes);                } else if ((mResourcesSetFlags & FLAG_RESOURCE_SET_ICON) == 0 &&                        mIconRes == 0 && !mDecorContentParent.hasIcon()) {                    mDecorContentParent.setIcon(                            getContext().getPackageManager().getDefaultActivityIcon());                    mResourcesSetFlags |= FLAG_RESOURCE_SET_ICON_FALLBACK;                }                if ((mResourcesSetFlags & FLAG_RESOURCE_SET_LOGO) != 0 ||                        (mLogoRes != 0 && !mDecorContentParent.hasLogo())) {                    mDecorContentParent.setLogo(mLogoRes);                }                // Invalidate if the panel menu hasn't been created before this.                // Panel menu invalidation is deferred avoiding application onCreateOptionsMenu                // being called in the middle of onCreate or similar.                // A pending invalidation will typically be resolved before the posted message                // would run normally in order to satisfy instance state restoration.                PanelFeatureState st = getPanelState(FEATURE_OPTIONS_PANEL, false);                if (!isDestroyed() && (st == null || st.menu == null) && !mIsStartingWindow) {                    invalidatePanelMenu(FEATURE_ACTION_BAR);                }            } else {                mTitleView = (TextView) findViewById(R.id.title);                if (mTitleView != null) {                    if ((getLocalFeatures() & (1 << FEATURE_NO_TITLE)) != 0) {                        final View titleContainer = findViewById(R.id.title_container);                        if (titleContainer != null) {                            titleContainer.setVisibility(View.GONE);                        } else {                            mTitleView.setVisibility(View.GONE);                        }                        mContentParent.setForeground(null);                    } else {                        mTitleView.setText(mTitle);                    }                }            }            ...        }    }

通过看installDecor的源码我们发现,这个方法中做了两件事:
生成DecorView
mDecor = generateDecor(-1);
和生成布局
mContentParent = generateLayout(mDecor);

protected DecorView generateDecor(int featureId) {        // System process doesn't have application context and in that case we need to directly use        // the context we have. Otherwise we want the application context, so we don't cling to the        // activity.        Context context;        if (mUseDecorContext) {            Context applicationContext = getContext().getApplicationContext();            if (applicationContext == null) {                context = getContext();            } else {                context = new DecorContext(applicationContext, getContext().getResources());                if (mTheme != -1) {                    context.setTheme(mTheme);                }            }        } else {            context = getContext();        }        return new DecorView(context, featureId, this, getAttributes());    }

generateDecor这个方法我们不用多看,也没什么东西,我们只需要知道生成一个DecorView的实例名字叫mDecor就行了

protected ViewGroup generateLayout(DecorView decor) {       。。。        // Inflate the window decor.        int layoutResource;        int features = getLocalFeatures();        // System.out.println("Features: 0x" + Integer.toHexString(features));        if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {            layoutResource = R.layout.screen_swipe_dismiss;        } else if ((features & ((1 << FEATURE_LEFT_ICON) | (1 << FEATURE_RIGHT_ICON))) != 0) {            if (mIsFloating) {                TypedValue res = new TypedValue();                getContext().getTheme().resolveAttribute(                        R.attr.dialogTitleIconsDecorLayout, res, true);                layoutResource = res.resourceId;            } else {                layoutResource = R.layout.screen_title_icons;            }            // XXX Remove this once action bar supports these features.            removeFeature(FEATURE_ACTION_BAR);            // System.out.println("Title Icons!");        } else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0                && (features & (1 << FEATURE_ACTION_BAR)) == 0) {            // Special case for a window with only a progress bar (and title).            // XXX Need to have a no-title version of embedded windows.            layoutResource = R.layout.screen_progress;            // System.out.println("Progress!");        } else if ((features & (1 << FEATURE_CUSTOM_TITLE)) != 0) {            // Special case for a window with a custom title.            // If the window is floating, we need a dialog layout            if (mIsFloating) {                TypedValue res = new TypedValue();                getContext().getTheme().resolveAttribute(                        R.attr.dialogCustomTitleDecorLayout, res, true);                layoutResource = res.resourceId;            } else {                layoutResource = R.layout.screen_custom_title;            }            // XXX Remove this once action bar supports these features.            removeFeature(FEATURE_ACTION_BAR);        } else if ((features & (1 << FEATURE_NO_TITLE)) == 0) {            // If no other features and not embedded, only need a title.            // If the window is floating, we need a dialog layout            if (mIsFloating) {                TypedValue res = new TypedValue();                getContext().getTheme().resolveAttribute(                        R.attr.dialogTitleDecorLayout, res, true);                layoutResource = res.resourceId;            } else if ((features & (1 << FEATURE_ACTION_BAR)) != 0) {                layoutResource = a.getResourceId(                        R.styleable.Window_windowActionBarFullscreenDecorLayout,                        R.layout.screen_action_bar);            } else {                layoutResource = R.layout.screen_title;            }            // System.out.println("Title!");        } else if ((features & (1 << FEATURE_ACTION_MODE_OVERLAY)) != 0) {            layoutResource = R.layout.screen_simple_overlay_action_mode;        } else {            // Embedded, so no decoration is needed.            layoutResource = R.layout.screen_simple;            // System.out.println("Simple!");        }        mDecor.startChanging();        mDecor.onResourcesLoaded(mLayoutInflater, layoutResource);        ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);        if (contentParent == null) {            throw new RuntimeException("Window couldn't find content container view");        }        if ((features & (1 << FEATURE_INDETERMINATE_PROGRESS)) != 0) {            ProgressBar progress = getCircularProgressBar(false);            if (progress != null) {                progress.setIndeterminate(true);            }        }        if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {            registerSwipeCallbacks();        }        // Remaining setup -- of background and title -- that only applies        // to top-level windows.        if (getContainer() == null) {            final Drawable background;            if (mBackgroundResource != 0) {                background = getContext().getDrawable(mBackgroundResource);            } else {                background = mBackgroundDrawable;            }            mDecor.setWindowBackground(background);            final Drawable frame;            if (mFrameResource != 0) {                frame = getContext().getDrawable(mFrameResource);            } else {                frame = null;            }            mDecor.setWindowFrame(frame);            mDecor.setElevation(mElevation);            mDecor.setClipToOutline(mClipToOutline);            if (mTitle != null) {                setTitle(mTitle);            }            if (mTitleColor == 0) {                mTitleColor = mTextColor;            }            setTitleColor(mTitleColor);        }        mDecor.finishChanging();        return contentParent;    }

generateLayout这个方法里面的东西太多,我前面删除一部分
这里layoutResource,是根据我们设置的状态栏主题,判断DecorView自动为我们加载什么样的布局。当我们将主题设置为NoTitleBar时,generateLayout方法中的layoutResource变量值为R.layout.screen_simple,所以我们看下系统这个screen_simple.xml布局文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:fitsSystemWindows="true"    android:orientation="vertical">    <ViewStub android:id="@+id/action_mode_bar_stub"              android:inflatedId="@+id/action_mode_bar"              android:layout="@layout/action_mode_bar"              android:layout_width="match_parent"              android:layout_height="wrap_content"              android:theme="?attr/actionBarTheme" />    <FrameLayout         android:id="@android:id/content"         android:layout_width="match_parent"         android:layout_height="match_parent"         android:foregroundInsidePadding="false"         android:foregroundGravity="fill_horizontal|top"         android:foreground="?android:attr/windowContentOverlay" /></LinearLayout>

当拿到这个layoutResource之后,执行的是mDecor.onResourcesLoaded(mLayoutInflater, layoutResource);

//DecorView的onResourcesLoaded方法void onResourcesLoaded(LayoutInflater inflater, int layoutResource) {        mStackId = getStackId();        if (mBackdropFrameRenderer != null) {            loadBackgroundDrawablesIfNeeded();            mBackdropFrameRenderer.onResourcesLoaded(                    this, mResizingBackgroundDrawable, mCaptionBackgroundDrawable,                    mUserCaptionBackgroundDrawable, getCurrentColor(mStatusColorViewState),                    getCurrentColor(mNavigationColorViewState));        }        mDecorCaptionView = createDecorCaptionView(inflater);        final View root = inflater.inflate(layoutResource, null);        if (mDecorCaptionView != null) {            if (mDecorCaptionView.getParent() == null) {                addView(mDecorCaptionView,                        new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));            }            mDecorCaptionView.addView(root,                    new ViewGroup.MarginLayoutParams(MATCH_PARENT, MATCH_PARENT));        } else {            // Put it below the color views.            addView(root, 0, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));        }        mContentRoot = (ViewGroup) root;        initializeElevation();    }

这里我们看到执行了一下mDecorCaptionView = createDecorCaptionView(inflater);

// Free floating overlapping windows require a caption.    private DecorCaptionView createDecorCaptionView(LayoutInflater inflater) {        DecorCaptionView decorCaptionView = null;        for (int i = getChildCount() - 1; i >= 0 && decorCaptionView == null; i--) {            View view = getChildAt(i);            if (view instanceof DecorCaptionView) {                // The decor was most likely saved from a relaunch - so reuse it.                decorCaptionView = (DecorCaptionView) view;                removeViewAt(i);            }        }        final WindowManager.LayoutParams attrs = mWindow.getAttributes();        final boolean isApplication = attrs.type == TYPE_BASE_APPLICATION ||                attrs.type == TYPE_APPLICATION || attrs.type == TYPE_DRAWN_APPLICATION;        // Only a non floating application window on one of the allowed workspaces can get a caption        if (!mWindow.isFloating() && isApplication && StackId.hasWindowDecor(mStackId)) {            // Dependent on the brightness of the used title we either use the            // dark or the light button frame.            if (decorCaptionView == null) {                decorCaptionView = inflateDecorCaptionView(inflater);            }            decorCaptionView.setPhoneWindow(mWindow, true /*showDecor*/);        } else {            decorCaptionView = null;        }        // Tell the decor if it has a visible caption.        enableCaption(decorCaptionView != null);        return decorCaptionView;    }

上面的代码我也没看懂,但是看结果是mDecorCaptionView的创建结果还是空,当mDecorCaptionView == null的时候会把我们加载出来的final View root = inflater.inflate(layoutResource, null);添加到DecorView的第0个位置,也就是一个FrameLayout视图最下面,就是是把刚才那个R.layout.screen_simple文件添加到DecorView最下面,也许看下面的Hierarchy View视图更直观一些,而且我们还看到了DecorView里面有一个LinearLayout并且index为0,细心的会发现DecorView还包含了NavigationBar View 还有StatusBar View,这些东西是什么时候加进去的呢?这个先不管,也可以自己去看DecorView的源码刨根问底。
image.png
现在我们在拐回到刚才的generateLayout方法
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
其实就是执行的getDecorView().findViewById,这个东西是谁呢?就是前面加载的R.layout.screen_simple文件里面的FrameLayout android:id=”@android:id/content”。最后contentParent作为generateLayout方法的返回赋值给mContentParent = generateLayout(mDecor);

/**     * Finds a view that was identified by the id attribute from the XML that     * was processed in {@link android.app.Activity#onCreate}.  This will     * implicitly call {@link #getDecorView} for you, with all of the     * associated side-effects.     *     * @return The view if found or null otherwise.     */    @Nullable    public View findViewById(@IdRes int id) {        return getDecorView().findViewById(id);    }

写了一大圈我们再回到PhoneWindow的setContentView(int layoutResID)方法,执行mLayoutInflater.inflate(layoutResID, mContentParent);将我们Activity的R.layout.activity_main布局加载到mContentParent里面去,再看下面的图也许会更清晰一些。

EF0FA9DD-9CAA-4BA2-BD0D-ED9BE3F3405C.png

回答几个问题

现在来回答几个疑问
1,activity.findViewById(Window.ID_ANDROID_CONTENT)拿到的是谁?
答:本文中拿到的是R.layout.sample布局文件的FrameLayout,其实根据不同的主题拿到不同的布局文件中的FrameLayout,它用来存放我们setContentView(id)时加载的布局
2,activity.getWindow().getDecorView().getChildAt(0)拿到的是谁?
答:本文中拿到的是R.layout.sample布局文件,其实根据不同的主题设置拿到不同的布局文件
3,statusBar在哪里?
答:在DecorView里面,可以去看上面的Hierarchy View视图,也可以自己使用Hierarchy View看自己布局的视图更直观些。

参考文章

http://blog.csdn.net/fuuckwtu/article/details/6519689
http://blog.csdn.net/yanbober/article/details/45970721
http://blog.csdn.net/mr_liabill/article/details/49534851
http://www.jianshu.com/p/983eb8d5bb1a
http://www.jianshu.com/p/afa921d8ed24
http://blog.csdn.net/hohohong/article/details/54412464