Window 机制源码分析
- 2019 年 12 月 26 日
- 筆記
Window 机制深入源码分析
Window 是一个抽象的基类，表示一个窗口，包含一个View tree和layout参数。
View tree的root View可以通过getDecorView得到。还可以设置Window的Content View。其实现类是PhoneWindow。Activity，Dialog，Toast，都包含一个Window，该Window在Activity的attach()函数中mWindow = new PhoneWindow(this);创建。 每一个Window对应一个View与ViewRootImpl，它与view是通过ViewRootImpl来建立关系的，它是以view的形式存在。在实际中无法直接访问，需要通过WindowManager这个应用程序窗口管理器进行访问。而WindowManager是一个接口，继承自ViewManager，真正实现的方法是在WindowManagerImpl中。
Window 添加过程
WindowManagerImpl内部调用了WindowManagerGlobal的addView方法，采用了懒汉式线程安全的方法进行初始化WindowManagerGlobal。addView，updateView，removeView全部都是通过WindowManagerGlobal进行操作实现的。 WindowManagerGlobal的addView 方法
public void addView(View view, ViewGroup.LayoutParams params, Display display, Window parentWindow) { if (view == null) { throw new IllegalArgumentException("view must not be null"); } if (display == null) { throw new IllegalArgumentException("display must not be null"); } if (!(params instanceof WindowManager.LayoutParams)) { throw new IllegalArgumentException("Params must be WindowManager.LayoutParams"); } final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params; if (parentWindow != null) { parentWindow.adjustLayoutParamsForSubWindow(wparams); } else { // If there's no parent, then hardware acceleration for this view is // set from the application's hardware acceleration setting. final Context context = view.getContext(); if (context != null && (context.getApplicationInfo().flags & ApplicationInfo.FLAG_HARDWARE_ACCELERATED) != 0) { wparams.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED; } } ViewRootImpl root; View panelParentView = null; synchronized (mLock) { // Start watching for system property changes. if (mSystemPropertyUpdater == null) { mSystemPropertyUpdater = new Runnable() { @Override public void run() { synchronized (mLock) { for (int i = mRoots.size() - 1; i >= 0; --i) { mRoots.get(i).loadSystemProperties(); } } } }; SystemProperties.addChangeCallback(mSystemPropertyUpdater); } int index = findViewLocked(view, false); if (index >= 0) { if (mDyingViews.contains(view)) { // Don't wait for MSG_DIE to make it's way through root's queue. mRoots.get(index).doDie(); } else { throw new IllegalStateException("View " + view + " has already been added to the window manager."); } // The previous removeView() had not completed executing. Now it has. } // If this is a panel window, then find the window it is being // attached to for future reference. if (wparams.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW && wparams.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) { final int count = mViews.size(); for (int i = 0; i < count; i++) { if (mRoots.get(i).mWindow.asBinder() == wparams.token) { panelParentView = mViews.get(i); } } } root = new ViewRootImpl(view.getContext(), display); view.setLayoutParams(wparams); mViews.add(view); mRoots.add(root); mParams.add(wparams); // do this last because it fires off messages to start doing things try { root.setView(view, wparams, panelParentView); } catch (RuntimeException e) { // BadTokenException or InvalidDisplayException, clean up. if (index >= 0) { removeViewLocked(index, true); } throw e; } } }
- 首先进行参数的检查，参数不对进行抛出异常 if (view == null) { throw new IllegalArgumentException("view must not be null"); } if (display == null) { throw new IllegalArgumentException("display must not be null"); } if (!(params instanceof WindowManager.LayoutParams)) { throw new IllegalArgumentException("Params must be WindowManager.LayoutParams"); }
- 如果当前父view不为空进行一些布局参数设置，否则父view为空时，必须在应用或Activity中设置硬件加速。 final Context context = view.getContext(); if (context != null && (context.getApplicationInfo().flags & ApplicationInfo.FLAG_HARDWARE_ACCELERATED) != 0) { wparams.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED; }
- 创建
ViewRootImpl，并将view添加到集合中 root = new ViewRootImpl(view.getContext(), display); view.setLayoutParams(wparams); mViews.add(view); mRoots.add(root); mParams.add(wparams); private final ArrayList<View> mViews = new ArrayList<View>(); private final ArrayList<ViewRootImpl> mRoots = new ArrayList<ViewRootImpl>(); private final ArrayList<WindowManager.LayoutParams> mParams = new ArrayList<WindowManager.LayoutParams>(); private final ArraySet<View> mDyingViews = new ArraySet<View>();mView集合中存储着Window所对应的view，而mRoots存储着Window所对应的ViewRootImpl，mParams存储着Window所对应的布局参数，mDyingViews存储着Window所对应的正在被删除的view。 - 调用ViewRootImpl来设置view，并完成view的添加过程 public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) { synchronized (this) { if (mView == null) { mView = view; mAttachInfo.mDisplayState = mDisplay.getState(); mDisplayManager.registerDisplayListener(mDisplayListener, mHandler); mViewLayoutDirectionInitial = mView.getRawLayoutDirection(); mFallbackEventHandler.setView(view); mWindowAttributes.copyFrom(attrs); if (mWindowAttributes.packageName == null) { mWindowAttributes.packageName = mBasePackageName; } requestLayout(); switch (res) { case WindowManagerGlobal.ADD_BAD_APP_TOKEN: case WindowManagerGlobal.ADD_BAD_SUBWINDOW_TOKEN: throw new WindowManager.BadTokenException( "Unable to add window — token " + attrs.token + " is not valid; is your activity running?"); case WindowManagerGlobal.ADD_NOT_APP_TOKEN: throw new WindowManager.BadTokenException( "Unable to add window — token " + attrs.token + " is not for an application"); case WindowManagerGlobal.ADD_APP_EXITING: throw new WindowManager.BadTokenException( "Unable to add window — app for token " + attrs.token + " is exiting"); case WindowManagerGlobal.ADD_DUPLICATE_ADD: throw new WindowManager.BadTokenException( "Unable to add window — window " + mWindow + " has already been added"); …… } 内部调用
requestLayout完成整个View的绘制，同时进行当前Window检查，可不可以添加当前view @Override public void requestLayout() { if (!mHandlingLayoutInLayoutRequest) { checkThread(); mLayoutRequested = true; scheduleTraversals(); } }scheduleTraversals内部最终会调用performTraversals来完成整个view的绘制 - 最后通过
WindowSession来完成Window的添加过程IWindowSession mWindowSession是一个binder接口对象，添加一个也就完成一个的Binder进程通信 try { mOrigWindowType = mWindowAttributes.type; mAttachInfo.mRecomputeGlobalAttributes = true; collectViewAttributes(); res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes, getHostVisibility(), mDisplay.getDisplayId(), mAttachInfo.mContentInsets, mAttachInfo.mStableInsets, mAttachInfo.mOutsets, mInputChannel); } catch (RemoteException e) { mAdded = false; mView = null; mAttachInfo.mRootView = null; mInputChannel = null; mFallbackEventHandler.setView(null); unscheduleTraversals(); setAccessibilityFocus(null, null); throw new RuntimeException("Adding window failed", e); } finally { if (restore) { attrs.restore(); } }addToDisplay方法，内部调用WindowManagerService的addWindow方法完成Window的添加过程，它会为每一个应用保留一个单独的Sessions对象。Window的添加过程最后统统交给了WindowManagerService的addWindow方法来完成。 @Override public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs, int viewVisibility, int displayId, Rect outContentInsets, Rect outStableInsets, Rect outOutsets, InputChannel outInputChannel) { return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId, outContentInsets, outStableInsets, outOutsets, outInputChannel); }
Window更新过程
Window更新过程照样调用的是WindowManagerGlobal的updateViewLayout方法。
public void updateViewLayout(View view, ViewGroup.LayoutParams params) { if (view == null) { throw new IllegalArgumentException("view must not be null"); } if (!(params instanceof WindowManager.LayoutParams)) { throw new IllegalArgumentException("Params must be WindowManager.LayoutParams"); } final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams)params; view.setLayoutParams(wparams); synchronized (mLock) { int index = findViewLocked(view, true); ViewRootImpl root = mRoots.get(index); mParams.remove(index); mParams.add(index, wparams); root.setLayoutParams(wparams, false); } }
首先获取需要更新的当前view，移除当前view位置的参数，并将新的布局参数添加进去，通过新的LayoutParams来替换旧的layoutParams。
Window 删除过程
Window删除过程调用的是WindowManagerGlobal的removeView方法。
public void removeView(View view, boolean immediate) { if (view == null) { throw new IllegalArgumentException("view must not be null"); } synchronized (mLock) { int index = findViewLocked(view, true); View curView = mRoots.get(index).getView(); removeViewLocked(index, immediate); if (curView == view) { return; } throw new IllegalStateException("Calling with view " + view + " but the ViewAncestor is attached to " + curView); } }
首先查找需要删除view的位置，再调用removeViewLocked进行删除，删除分为两种，一种是异步删除，一种是同步删除。mGlobal.removeView(view, false);，false为异步删除，true为同步删除mGlobal.removeView(view, true);异步删除主要是通过发送一个handler消息，然后调用die方法进行删除，这个删除不是立刻就删除了，而是添加到队列中，mDyingViews表示待删除的view列表。
/** * @param immediate True, do now if not in traversal. False, put on queue and do later. * @return True, request has been queued. False, request has been completed. */ boolean die(boolean immediate) { // Make sure we do execute immediately if we are in the middle of a traversal or the damage // done by dispatchDetachedFromWindow will cause havoc on return. if (immediate && !mIsInTraversal) { doDie(); return false; } if (!mIsDrawing) { destroyHardwareRenderer(); } else { Log.e(mTag, "Attempting to destroy the window while drawing!n" + " window=" + this + ", title=" + mWindowAttributes.getTitle()); } mHandler.sendEmptyMessage(MSG_DIE); return true; }
die方法内部做了一个判断，是否立即删除，立即删除（同步删除）就不用发消息，直接调用doDie方法，而异步删除需要发送一个消息。
void doDie() { checkThread(); if (LOCAL_LOGV) Log.v(mTag, "DIE in " + this + " of " + mSurface); synchronized (this) { if (mRemoved) { return; } mRemoved = true; if (mAdded) { dispatchDetachedFromWindow(); } if (mAdded && !mFirst) { destroyHardwareRenderer(); if (mView != null) { int viewVisibility = mView.getVisibility(); boolean viewVisibilityChanged = mViewVisibility != viewVisibility; if (mWindowAttributesChanged || viewVisibilityChanged) { // If layout params have been changed, first give them // to the window manager to make sure it has the correct // animation info. try { if ((relayoutWindow(mWindowAttributes, viewVisibility, false) & WindowManagerGlobal.RELAYOUT_RES_FIRST_TIME) != 0) { mWindowSession.finishDrawing(mWindow); } } catch (RemoteException e) { } } mSurface.release(); } } mAdded = false; } WindowManagerGlobal.getInstance().doRemoveView(this); }
真正的删除操作发生在dispatchDetachedFromWindow方法中
void dispatchDetachedFromWindow() { if (mView != null && mView.mAttachInfo != null) { mAttachInfo.mTreeObserver.dispatchOnWindowAttachedChange(false); mView.dispatchDetachedFromWindow(); } mAccessibilityInteractionConnectionManager.ensureNoConnection(); mAccessibilityManager.removeAccessibilityStateChangeListener( mAccessibilityInteractionConnectionManager); mAccessibilityManager.removeHighTextContrastStateChangeListener( mHighContrastTextManager); removeSendWindowContentChangedCallback(); destroyHardwareRenderer(); setAccessibilityFocus(null, null); mView.assignParent(null); mView = null; mAttachInfo.mRootView = null; mSurface.release(); if (mInputQueueCallback != null && mInputQueue != null) { mInputQueueCallback.onInputQueueDestroyed(mInputQueue); mInputQueue.dispose(); mInputQueueCallback = null; mInputQueue = null; } if (mInputEventReceiver != null) { mInputEventReceiver.dispose(); mInputEventReceiver = null; } try { mWindowSession.remove(mWindow); } catch (RemoteException e) { } // Dispose the input channel after removing the window so the Window Manager // doesn't interpret the input channel being closed as an abnormal termination. if (mInputChannel != null) { mInputChannel.dispose(); mInputChannel = null; } mDisplayManager.unregisterDisplayListener(mDisplayListener); unscheduleTraversals(); }
- 首先进行垃圾回收操作，清除数据与移除消息和监听；
- 通过
mWindowSession.remove(mWindow);，它是一次IPC进程操作，与addView一样，最后会调用WindowManager的removeWindow方法； View的dispatchDetachedFromWindow方法，内部会调用onDetachedFromWindow方法，方法中可以进行资源回收，比如停止动画，与线程操作；- 最后调用
WindowManagerGlobal的doRemoveView将之前的mRoots,mParams,mDyingView中的Window关联的ViewRootImpl对象移除 void doRemoveView(ViewRootImpl root) { synchronized (mLock) { final int index = mRoots.indexOf(root); if (index >= 0) { mRoots.remove(index); mParams.remove(index); final View view = mViews.remove(index); mDyingViews.remove(view); } } if (ThreadedRenderer.sTrimForeground && ThreadedRenderer.isAvailable()) { doTrimForeground(); } }
