窗口布局简介
在安卓的窗口管理系统中，经常要执行的一个操作是布局。
布局会做许多事情，例如更新焦点窗口、调整所有的窗口位置、设置wallpaperTarget以显示或隐藏壁纸、开始过渡动画等。
很多时候都需要进行窗口的布局，例如View的Surface创建流程中调用WindowManagerService的relayoutWindow方法时、窗口创建时、窗口销毁时、窗口可见性变化时等。
布局流程
窗口布局流程一般从frameworks/base/services/core/java/com/android/server/wm/WindowSurfacePlacer.java的performSurfacePlacement方法开始：
final void performSurfacePlacement() {
performSurfacePlacement(false /* force */);
}
final void performSurfacePlacement(boolean force) {
if (mDeferDepth > 0 && !force) {
mDeferredRequests++;
return;
}
int loopCount = 6;
do {
mTraversalScheduled = false;
performSurfacePlacementLoop();
mService.mAnimationHandler.removeCallbacks(mPerformSurfacePlacement);
loopCount--;
} while (mTraversalScheduled && loopCount > 0);
mService.mRoot.mWallpaperActionPending = false;
}
这里有一个循环，循环限制了最多循环6次。可以发现在窗口布局时，不能确保一次完成布局，可能会重复布局多次。这里循环体内主要是调用了WindowSurfacePlacer的performSurfacePlacementLoop方法：
private void performSurfacePlacementLoop() {
if (mInLayout) {
if (DEBUG) {
throw new RuntimeException("Recursive call!");
}
Slog.w(TAG, "performLayoutAndPlaceSurfacesLocked called while in layout. Callers="
+ Debug.getCallers(3));
return;
}
// TODO(multi-display):
final DisplayContent defaultDisplay = mService.getDefaultDisplayContentLocked();
if (defaultDisplay.mWaitingForConfig) {
// Our configuration has changed (most likely rotation), but we
// don't yet have the complete configuration to report to
// applications. Don't do any window layout until we have it.
return;
}
if (!mService.mDisplayReady) {
// Not yet initialized, nothing to do.
return;
}
mInLayout = true;
if (!mService.mForceRemoves.isEmpty()) {
// Wait a little bit for things to settle down, and off we go.
while (!mService.mForceRemoves.isEmpty()) {
final WindowState ws = mService.mForceRemoves.remove(0);
Slog.i(TAG, "Force removing: " + ws);
ws.removeImmediately();
}
Slog.w(TAG, "Due to memory failure, waiting a bit for next layout");
Object tmp = new Object();
synchronized (tmp) {
try {
tmp.wait(250);
} catch (InterruptedException e) {
}
}
}
try {
mService.mRoot.performSurfacePlacement();
mInLayout = false;
if (mService.mRoot.isLayoutNeeded()) {
if (++mLayoutRepeatCount < 6) {
requestTraversal();
} else {
Slog.e(TAG, "Performed 6 layouts in a row. Skipping");
mLayoutRepeatCount = 0;
}
} else {
mLayoutRepeatCount = 0;
}
if (mService.mWindowsChanged && !mService.mWindowChangeListeners.isEmpty()) {
mService.mH.removeMessages(REPORT_WINDOWS_CHANGE);
mService.mH.sendEmptyMessage(REPORT_WINDOWS_CHANGE);
}
} catch (RuntimeException e) {
mInLayout = false;
Slog.wtf(TAG, "Unhandled exception while laying out windows", e);
}
}
这里首先会删除mService.mForceRemoves中的窗口，然后调用了WindowContainer结构中窗口树结构的根结点frameworks/base/services/core/java/com/android/server/wm/RootWindowContainer.java的performSurfacePlacement方法：
void performSurfacePlacement() {
Trace.traceBegin(TRACE_TAG_WINDOW_MANAGER, "performSurfacePlacement");
try {
performSurfacePlacementNoTrace();
} finally {
Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
}
}
这里调用了窗口布局流程中一个很长的核心方法RootWindowContainer的performSurfacePlacementNoTrace方法：
// "Something has changed! Let's make it correct now."
// TODO: Super crazy long method that should be broken down...
void performSurfacePlacementNoTrace() {
if (DEBUG_WINDOW_TRACE) Slog.v(TAG, "performSurfacePlacementInner: entry. Called by "
+ Debug.getCallers(3));
int i;
if (mWmService.mFocusMayChange) {
mWmService.mFocusMayChange = false;
mWmService.updateFocusedWindowLocked(
UPDATE_FOCUS_WILL_PLACE_SURFACES, false /*updateInputWindows*/);
}
// Initialize state of exiting tokens.
final int numDisplays = mChildren.size();
for (int displayNdx = 0; displayNdx < numDisplays; ++displayNdx) {
final DisplayContent displayContent = mChildren.get(displayNdx);
displayContent.setExitingTokensHasVisible(false);
}
mHoldScreen = null;
mScreenBrightnessOverride = PowerManager.BRIGHTNESS_INVALID_FLOAT;
mUserActivityTimeout = -1;
mObscureApplicationContentOnSecondaryDisplays = false;
mSustainedPerformanceModeCurrent = false;
mWmService.mTransactionSequence++;
// TODO(multi-display): recents animation & wallpaper need support multi-display.
final DisplayContent defaultDisplay = mWmService.getDefaultDisplayContentLocked();
final WindowSurfacePlacer surfacePlacer = mWmService.mWindowPlacerLocked;
if (SHOW_LIGHT_TRANSACTIONS) Slog.i(TAG,
">>> OPEN TRANSACTION performLayoutAndPlaceSurfaces");
Trace.traceBegin(TRACE_TAG_WINDOW_MANAGER, "applySurfaceChanges");
mWmService.openSurfaceTransaction();
try {
applySurfaceChangesTransaction();
} catch (RuntimeException e) {
Slog.wtf(TAG, "Unhandled exception in Window Manager", e);
} finally {
mWmService.closeSurfaceTransaction("performLayoutAndPlaceSurfaces");
Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
if (SHOW_LIGHT_TRANSACTIONS) Slog.i(TAG,
"<<< CLOSE TRANSACTION performLayoutAndPlaceSurfaces");
}
mWmService.mAnimator.executeAfterPrepareSurfacesRunnables();
checkAppTransitionReady(surfacePlacer);
// Defer starting the recents animation until the wallpaper has drawn
final RecentsAnimationController recentsAnimationController =
mWmService.getRecentsAnimationController();
if (recentsAnimationController != null) {
recentsAnimationController.checkAnimationReady(defaultDisplay.mWallpaperController);
}
for (int displayNdx = 0; displayNdx < numDisplays; ++displayNdx) {
final DisplayContent displayContent = mChildren.get(displayNdx);
if (displayContent.mWallpaperMayChange) {
if (DEBUG_WALLPAPER_LIGHT) Slog.v(TAG, "Wallpaper may change! Adjusting");
displayContent.pendingLayoutChanges |= FINISH_LAYOUT_REDO_WALLPAPER;
if (DEBUG_LAYOUT_REPEATS) {
surfacePlacer.debugLayoutRepeats("WallpaperMayChange",
displayContent.pendingLayoutChanges);
}
}
}
if (mWmService.mFocusMayChange) {
mWmService.mFocusMayChange = false;
mWmService.updateFocusedWindowLocked(UPDATE_FOCUS_PLACING_SURFACES,
false /*updateInputWindows*/);
}
if (isLayoutNeeded()) {
defaultDisplay.pendingLayoutChanges |= FINISH_LAYOUT_REDO_LAYOUT;
if (DEBUG_LAYOUT_REPEATS) surfacePlacer.debugLayoutRepeats("mLayoutNeeded",
defaultDisplay.pendingLayoutChanges);
}
handleResizingWindows();
if (mWmService.mDisplayFrozen) {
ProtoLog.v(WM_DEBUG_ORIENTATION,
"With display frozen, orientationChangeComplete=%b",
mOrientationChangeComplete);
}
if (mOrientationChangeComplete) {
if (mWmService.mWindowsFreezingScreen != WINDOWS_FREEZING_SCREENS_NONE) {
mWmService.mWindowsFreezingScreen = WINDOWS_FREEZING_SCREENS_NONE;
mWmService.mLastFinishedFreezeSource = mLastWindowFreezeSource;
mWmService.mH.removeMessages(WINDOW_FREEZE_TIMEOUT);
}
mWmService.stopFreezingDisplayLocked();
}
// Destroy the surface of any windows that are no longer visible.
i = mWmService.mDestroySurface.size();
if (i > 0) {
do {
i--;
WindowState win = mWmService.mDestroySurface.get(i);
win.mDestroying = false;
final DisplayContent displayContent = win.getDisplayContent();
if (displayContent.mInputMethodWindow == win) {
displayContent.setInputMethodWindowLocked(null);
}
if (displayContent.mWallpaperController.isWallpaperTarget(win)) {
displayContent.pendingLayoutChanges |= FINISH_LAYOUT_REDO_WALLPAPER;
}
win.destroySurfaceUnchecked();
win.mWinAnimator.destroyPreservedSurfaceLocked();
} while (i > 0);
mWmService.mDestroySurface.clear();
}
// Time to remove any exiting tokens?
for (int displayNdx = 0; displayNdx < numDisplays; ++displayNdx) {
final DisplayContent displayContent = mChildren.get(displayNdx);
displayContent.removeExistingTokensIfPossible();
}
for (int displayNdx = 0; displayNdx < numDisplays; ++displayNdx) {
final DisplayContent displayContent = mChildren.get(displayNdx);
if (displayContent.pendingLayoutChanges != 0) {
displayContent.setLayoutNeeded();
}
}
mWmService.setHoldScreenLocked(mHoldScreen);
if (!mWmService.mDisplayFrozen) {
final float brightnessOverride = mScreenBrightnessOverride < PowerManager.BRIGHTNESS_MIN
|| mScreenBrightnessOverride > PowerManager.BRIGHTNESS_MAX
? PowerManager.BRIGHTNESS_INVALID_FLOAT : mScreenBrightnessOverride;
int brightnessFloatAsIntBits = Float.floatToIntBits(brightnessOverride);
// Post these on a handler such that we don't call into power manager service while
// holding the window manager lock to avoid lock contention with power manager lock.
mHandler.obtainMessage(SET_SCREEN_BRIGHTNESS_OVERRIDE, brightnessFloatAsIntBits,
0).sendToTarget();
mHandler.obtainMessage(SET_USER_ACTIVITY_TIMEOUT, mUserActivityTimeout).sendToTarget();
}
if (mSustainedPerformanceModeCurrent != mSustainedPerformanceModeEnabled) {
mSustainedPerformanceModeEnabled = mSustainedPerformanceModeCurrent;
mWmService.mPowerManagerInternal.powerHint(
PowerHint.SUSTAINED_PERFORMANCE,
(mSustainedPerformanceModeEnabled ? 1 : 0));
}
if (mUpdateRotation) {
ProtoLog.d(WM_DEBUG_ORIENTATION, "Performing post-rotate rotation");
mUpdateRotation = updateRotationUnchecked();
}
if (!mWmService.mWaitingForDrawnCallbacks.isEmpty()
|| (mOrientationChangeComplete && !isLayoutNeeded()
&& !mUpdateRotation)) {
mWmService.checkDrawnWindowsLocked();
}
final int N = mWmService.mPendingRemove.size();
if (N > 0) {
if (mWmService.mPendingRemoveTmp.length < N) {
mWmService.mPendingRemoveTmp = new WindowState[N + 10];
}
mWmService.mPendingRemove.toArray(mWmService.mPendingRemoveTmp);
mWmService.mPendingRemove.clear();
ArrayList<DisplayContent> displayList = new ArrayList();
for (i = 0; i < N; i++) {
final WindowState w = mWmService.mPendingRemoveTmp[i];
w.removeImmediately();
final DisplayContent displayContent = w.getDisplayContent();
if (displayContent != null && !displayList.contains(displayContent)) {
displayList.add(displayContent);
}
}
for (int j = displayList.size() - 1; j >= 0; --j) {
final DisplayContent dc = displayList.get(j);
dc.assignWindowLayers(true /*setLayoutNeeded*/);
}
}
forAllDisplays(dc -> {
dc.getInputMonitor().updateInputWindowsLw(true /*force*/);
dc.updateSystemGestureExclusion();
dc.updateTouchExcludeRegion();
});
// Check to see if we are now in a state where the screen should
// be enabled, because the window obscured flags have changed.
mWmService.enableScreenIfNeededLocked();
mWmService.scheduleAnimationLocked();
// Send any pending task-info changes that were queued-up during a layout deferment
mWmService.mAtmService.mTaskOrganizerController.dispatchPendingTaskInfoChanges();
if (DEBUG_WINDOW_TRACE) Slog.e(TAG, "performSurfacePlacementInner exit");
}
这里主要做的事情有：
1 如果mWmService.mFocusMayChange为true，调用WindowManagerService的updateFocusedWindowLocked更新焦点窗口；
2 调用RootWindowContainer的applySurfaceChangesTransaction方法调整窗口位置；
3 调用RootWindowContainer的checkAppTransitionReady方法执行过渡动画；
4 如果mWmService.mFocusMayChange为true，调用WindowManagerService的updateFocusedWindowLocked更新焦点窗口；
5 销毁mWmService.mDestroySurface中的窗口；
6 如果mUpdateRotation为true，则调用RootWindowContainer的updateRotationUnchecked方法处理转屏；
7 通过dc.getInputMonitor().updateInputWindowsLw方法更新输入法窗口。
布局有太多的细节有待完善补充。
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