https://blog.csdn.net/learnframework/article/details/131082401
堆栈日志
updateDivideBounds java.lang.Exception at com.android.wm.shell.common.split.SplitLayout.updateDivideBounds(SplitLayout.java:357) at com.android.wm.shell.common.split.SplitLayout.lambda$flingDividePosition$3(SplitLayout.java:451) at com.android.wm.shell.common.split.SplitLayout.$r8$lambda$hexmhTsCBFvDZRT1F14N6vZjPGA(Unknown Source:0) at com.android.wm.shell.common.split.SplitLayout$$ExternalSyntheticLambda3.onAnimationUpdate(Unknown Source:2) at android.animation.ValueAnimator.animateValue(ValueAnimator.java:1653) at android.animation.ValueAnimator.animateBasedOnTime(ValueAnimator.java:1440) at android.animation.ValueAnimator.doAnimationFrame(ValueAnimator.java:1572) at android.animation.AnimationHandler.doAnimationFrame(AnimationHandler.java:307) at android.animation.AnimationHandler.-$$Nest$mdoAnimationFrame(Unknown Source:0) at android.animation.AnimationHandler$1.doFrame(AnimationHandler.java:86) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1229) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1239) at android.view.Choreographer.doCallbacks(Choreographer.java:899) at android.view.Choreographer.doFrame(Choreographer.java:827) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1214) at android.os.Handler.handleCallback(Handler.java:942) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loopOnce(Looper.java:201) at android.os.Looper.loop(Looper.java:288) at android.app.ActivityThread.main(ActivityThread.java:7898) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)2. 拖动逻辑相关代码分析：
总结
用户触摸分割线
↓
onTouch 检测拖拽触发（超过 mTouchSlop）
↓
计算新位置 → updateDivideBounds(position)
↓
重新计算三个区域 Bounds
↓
onLayoutSizeChanging 在 VSync 点构建 Transaction
↓
updateSurfaceBounds 确定上下/左右 Stage 顺序
↓
applySurfaceChanges 原子写入：
- 分割线位置 + 最高层级
- 两个 Stage 的位置 + 裁剪
- IME 适配
- 阴影特效
↓
t.apply() → SurfaceFlinger 统一合成新一帧
区分 "View" 与 "Surface"：你的注释多次混淆这两个概念。分屏性能优化的关键就在于绕过 Android View 层级，直接操作底层 SurfaceControl。
Transaction 机制：Android 12+ 的分屏大量使用 SurfaceControl.Transaction，目的是多图层原子更新，注释应强调这一点。
Leash 模式：mRootLeash 是 Android 11+ 引入的 "Leash"（牵引层）机制，用于将整个 Task 的 Surface 挂接到一个父层，方便整体移动/缩放。理解这一点有助于看懂 onResizing 里做了什么。
public boolean onTouch(View v, MotionEvent event) { // android.util.Log.i("wsc_DividerView", "onTouch", new Exception()); if (mSplitLayout == null || !mInteractive) { return false; } if (mDoubleTapDetector.onTouchEvent(event)) { return true; } // Convert to use screen-based coordinates to prevent lost track of motion events while // moving divider bar and calculating dragging velocity. event.setLocation(event.getRawX(), event.getRawY()); final int action = event.getAction() & MotionEvent.ACTION_MASK; final boolean isLandscape = isLandscape(); final int touchPos = (int) (isLandscape ? event.getX() : event.getY()); switch (action) { case MotionEvent.ACTION_DOWN: mVelocityTracker = VelocityTracker.obtain(); mVelocityTracker.addMovement(event); setTouching(); mStartPos = touchPos; mMoving = false; break; case MotionEvent.ACTION_MOVE: mVelocityTracker.addMovement(event); if (!mMoving && Math.abs(touchPos - mStartPos) > mTouchSlop) { mStartPos = touchPos; mMoving = true; } if (mMoving) { final int position = mSplitLayout.getDividePosition() + touchPos - mStartPos; mSplitLayout.updateDivideBounds(position); } break; /** * Updates bounds with the passing position. Usually used to update recording bounds while * performing animation or dragging divider bar to resize the splits. */ void updateDivideBounds(int position) { android.util.Log.i("wsc_SplitLayout", "updateDivideBounds", new Exception()); updateBounds(position); mSplitLayoutHandler.onLayoutSizeChanging(this); } @Override public void onLayoutSizeChanging(SplitLayout layout) { final SurfaceControl.Transaction t = mTransactionPool.acquire(); t.setFrameTimelineVsync(Choreographer.getInstance().getVsyncId()); setResizingSplits(true /* resizing */);//设置分割线大小 //更新分割线位置界限 updateSurfaceBounds(layout, t, true /* applyResizingOffset */);//把对应的DividerView进行更新 mMainStage.onResizing(getMainStageBounds(), t);//通知主屏幕，你的大小有更新 mSideStage.onResizing(getSideStageBounds(), t);//通知副屏，你大小有更新 t.apply(); mTransactionPool.release(t);//线程释放 } void updateSurfaceBounds(@Nullable SplitLayout layout, @NonNull SurfaceControl.Transaction t, boolean applyResizingOffset) { //顶部确认 final StageTaskListener topLeftStage = mSideStagePosition == SPLIT_POSITION_TOP_OR_LEFT ? mSideStage : mMainStage; // 底部确认 final StageTaskListener bottomRightStage = mSideStagePosition == SPLIT_POSITION_TOP_OR_LEFT ? mMainStage : mSideStage; //关键调用，主要参数已经赋予此方法 (layout != null ? layout : mSplitLayout).applySurfaceChanges(t, topLeftStage.mRootLeash, bottomRightStage.mRootLeash, topLeftStage.mDimLayer, bottomRightStage.mDimLayer, applyResizingOffset); } /** * Return if this layout is landscape. */ public boolean isLandscape() { return isLandscape(mRootBounds); } /** Apply recorded surface layout to the {@link SurfaceControl.Transaction}. */ public void applySurfaceChanges(SurfaceControl.Transaction t, SurfaceControl leash1, SurfaceControl leash2, SurfaceControl dimLayer1, SurfaceControl dimLayer2, boolean applyResizingOffset) { //原调用一更新和初始化好上下分屏和分割线创建大小都已确认 //由此看出，此分割线可作为图层 final SurfaceControl dividerLeash = getDividerLeash(); if (dividerLeash != null) { mTempRect.set(getRefDividerBounds()); t.setPosition(dividerLeash, mTempRect.left, mTempRect.top); // Resets layer of divider bar to make sure it is always on top. t.setLayer(dividerLeash, Integer.MAX_VALUE); } mTempRect.set(getRefBounds1()); //设置上下分配的位置 t.setPosition(leash1, mTempRect.left, mTempRect.top) .setWindowCrop(leash1, mTempRect.width(), mTempRect.height()); mTempRect.set(getRefBounds2()); t.setPosition(leash2, mTempRect.left, mTempRect.top) .setWindowCrop(leash2, mTempRect.width(), mTempRect.height()); if (mImePositionProcessor.adjustSurfaceLayoutForIme( t, dividerLeash, leash1, leash2, dimLayer1, dimLayer2)) { return; } //设置对应的特效显示，拉到底部顶部的灰色显示 mSurfaceEffectPolicy.adjustDimSurface(t, dimLayer1, dimLayer2); if (applyResizingOffset) { mSurfaceEffectPolicy.adjustRootSurface(t, leash1, leash2); } } 我要探究分屏分割线功能，从以下代码： 中帮我分析，随便指出我中文注释（自己分析的）的不足和错误，在讲讲各调用方法的作用功能 总结 用户触摸分割线 ↓ onTouch 检测拖拽触发（超过 mTouchSlop） ↓ 计算新位置 → updateDivideBounds(position) ↓ 重新计算三个区域 Bounds ↓ onLayoutSizeChanging 在 VSync 点构建 Transaction ↓ updateSurfaceBounds 确定上下/左右 Stage 顺序 ↓ applySurfaceChanges 原子写入： - 分割线位置 + 最高层级 - 两个 Stage 的位置 + 裁剪 - IME 适配 - 阴影特效 ↓ t.apply() → SurfaceFlinger 统一合成新一帧 区分 "View" 与 "Surface"：你的注释多次混淆这两个概念。分屏性能优化的关键就在于绕过 Android View 层级，直接操作底层 SurfaceControl。 Transaction 机制：Android 12+ 的分屏大量使用 SurfaceControl.Transaction，目的是多图层原子更新，注释应强调这一点。 Leash 模式：mRootLeash 是 Android 11+ 引入的 "Leash"（牵引层）机制，用于将整个 Task 的 Surface 挂接到一个父层，方便整体移动/缩放。理解这一点有助于看懂 onResizing 里做了什么。3. 关于分割线的代码分析
所有拖动都是在这里 @Override public boolean onTouch(View v, MotionEvent event) { // android.util.Log.i("wsc_DividerView", "onTouch", new Exception()); if (mSplitLayout == null || !mInteractive) { return false; } if (mDoubleTapDetector.onTouchEvent(event)) { return true; } // Convert to use screen-based coordinates to prevent lost track of motion events while // moving divider bar and calculating dragging velocity. event.setLocation(event.getRawX(), event.getRawY()); final int action = event.getAction() & MotionEvent.ACTION_MASK; final boolean isLandscape = isLandscape(); //这里你是横屏还是竖屏？ final int touchPos = (int) (isLandscape ? event.getX() : event.getY()); switch (action) { case MotionEvent.ACTION_DOWN: mVelocityTracker = VelocityTracker.obtain(); mVelocityTracker.addMovement(event); //处于触摸中了 setTouching(); //记录开始触摸点 mStartPos = touchPos; mMoving = false; break; //移动 case MotionEvent.ACTION_MOVE: mVelocityTracker.addMovement(event); //有绝对值，要不要触发移动 if (!mMoving && Math.abs(touchPos - mStartPos) > mTouchSlop) { mStartPos = touchPos;//初始位移点更新 mMoving = true; } if (mMoving) { //最主要是这里，获取一下当前分割线位置，这个是比较重要的，直接决定updateDivideBounds更新的区域 //当前分割线的位置等于原来分割线位置+触摸位置-开始位置，后面加个绝对值比较好 final int position = mSplitLayout.getDividePosition() + touchPos - mStartPos; mSplitLayout.updateDivideBounds(position); } break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: //松手部分 releaseTouching(); if (!mMoving) break; //加速度计算，先不分析 mVelocityTracker.addMovement(event); mVelocityTracker.computeCurrentVelocity(1000 /* units */); final float velocity = isLandscape ? mVelocityTracker.getXVelocity() : mVelocityTracker.getYVelocity(); //计算当前分割线位置 final int position = mSplitLayout.getDividePosition() + touchPos - mStartPos; //找Target，也就是五大target，分别为顶，上中，中间，下中，底部，拖动落点在哪，就让落点往哪个落点靠 final DividerSnapAlgorithm.SnapTarget snapTarget = mSplitLayout.findSnapTarget(position, velocity, false /* hardDismiss */); // position上面已经更新位置，snapTarget为滑动目标，意义不知道，可能为吸附目标？ // snapTarget可能为分割线一个参照判断点，判断当前触摸点属那个位置好进行判定吸附 //找到了target，那就滑到哪个target中去，看参数就知道，拿到位置和target，开始操作 mSplitLayout.snapToTarget(position, snapTarget); mMoving = false; break; } return true; } 由以上move跳到下面这里来，更新bounds,根据分割线更新bounds /** * Updates bounds with the passing position. Usually used to update recording bounds while * performing animation or dragging divider bar to resize the splits. */ void updateDivideBounds(int position) { android.util.Log.i("wsc_SplitLayout", "updateDivideBounds", new Exception()); //靠着当前分割线位置更新bounds updateBounds(position); mSplitLayoutHandler.onLayoutSizeChanging(this); } /** Updates recording bounds of divider window and both of the splits. */ private void updateBounds(int position) { mDividerBounds.set(mRootBounds); mBounds1.set(mRootBounds); mBounds2.set(mRootBounds); final boolean isLandscape = isLandscape(mRootBounds); //判断横述屏 if (isLandscape) { position += mRootBounds.left; mDividerBounds.left = position - mDividerInsets; mDividerBounds.right = mDividerBounds.left + mDividerWindowWidth; mBounds1.right = position; mBounds2.left = mBounds1.right + mDividerSize; } else { //微小偏移 position += mRootBounds.top; mDividerBounds.top = position - mDividerInsets; //在这里，分割线顶部一般是0 mDividerBounds.bottom = mDividerBounds.top + mDividerWindowWidth; // mBounds1只需要更新下 //上分屏是bottom变，top不变，下分配相反， //所以此句bottom更新 mBounds1.bottom = position;// mBounds2.top = mBounds1.bottom + mDividerSize; } DockedDividerUtils.sanitizeStackBounds(mBounds1, true /** topLeft */); DockedDividerUtils.sanitizeStackBounds(mBounds2, false /** topLeft */); mSurfaceEffectPolicy.applyDividerPosition(position, isLandscape); } @Override public void onLayoutSizeChanging(SplitLayout layout) { final SurfaceControl.Transaction t = mTransactionPool.acquire(); t.setFrameTimelineVsync(Choreographer.getInstance().getVsyncId()); setResizingSplits(true /* resizing */);//设置分割线大小 //更新分割线位置界限, 绘制 updateSurfaceBounds(layout, t, true /* applyResizingOffset */);//把对应的DividerView进行更新 mMainStage.onResizing(getMainStageBounds(), t);//通知主屏幕，你的大小有更新 mSideStage.onResizing(getSideStageBounds(), t);//通知副屏，你大小有更新 t.apply(); mTransactionPool.release(t);//线程释放 } void updateSurfaceBounds(@Nullable SplitLayout layout, @NonNull SurfaceControl.Transaction t, boolean applyResizingOffset) { //顶部确认 final StageTaskListener topLeftStage = mSideStagePosition == SPLIT_POSITION_TOP_OR_LEFT ? mSideStage : mMainStage; // 底部确认 final StageTaskListener bottomRightStage = mSideStagePosition == SPLIT_POSITION_TOP_OR_LEFT ? mMainStage : mSideStage; //关键调用，主要参数已经赋予此方法 (layout != null ? layout : mSplitLayout).applySurfaceChanges(t, topLeftStage.mRootLeash, bottomRightStage.mRootLeash, topLeftStage.mDimLayer, bottomRightStage.mDimLayer, applyResizingOffset); } //主要对上区域，下区域的bounds进行更新 /** Apply recorded surface layout to the {@link SurfaceControl.Transaction}. */ public void applySurfaceChanges(SurfaceControl.Transaction t, SurfaceControl leash1, SurfaceControl leash2, SurfaceControl dimLayer1, SurfaceControl dimLayer2, boolean applyResizingOffset) { //原调用一更新和初始化好上下分屏和分割线创建大小都已确认 //由此看出，此分割线可作为图层 final SurfaceControl dividerLeash = getDividerLeash(); if (dividerLeash != null) { //这个 mTempRect.set(getRefDividerBounds());矩形区域就是获得的Divider分割线区域 mTempRect.set(getRefDividerBounds()); // 设置这个分割线区域，其实left没变，top是变的 t.setPosition(dividerLeash, mTempRect.left, mTempRect.top); // Resets layer of divider bar to make sure it is always on top. t.setLayer(dividerLeash, Integer.MAX_VALUE); } mTempRect.set(getRefBounds1()); //分割线重新设置好了，再重新设置上下屏 t.setPosition(leash1, mTempRect.left, mTempRect.top) .setWindowCrop(leash1, mTempRect.width(), mTempRect.height()); mTempRect.set(getRefBounds2()); t.setPosition(leash2, mTempRect.left, mTempRect.top) .setWindowCrop(leash2, mTempRect.width(), mTempRect.height()); if (mImePositionProcessor.adjustSurfaceLayoutForIme( t, dividerLeash, leash1, leash2, dimLayer1, dimLayer2)) { return; } //设置对应的特效显示，拉到底部顶部的灰色显示 mSurfaceEffectPolicy.adjustDimSurface(t, dimLayer1, dimLayer2); if (applyResizingOffset) { mSurfaceEffectPolicy.adjustRootSurface(t, leash1, leash2); } } /** Showing resizing hint. */ public void onResizing(ActivityManager.RunningTaskInfo resizingTask, Rect newBounds, SurfaceControl.Transaction t) { if (mResizingIconView == null) { return; } if (!mIsResizing) { mIsResizing = true; mBounds.set(newBounds); } //更新条件：新Bounds是新的比就的宽和高，然后就会重新更新Bounds //show就算要展示出背景家apk那个log的东西，是单独图层 final boolean show = newBounds.width() > mBounds.width() || newBounds.height() > mBounds.height(); final boolean animate = show != mShown; 下面是松手逻辑， case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: //松手部分 releaseTouching(); if (!mMoving) break; //加速度计算，先不分析 mVelocityTracker.addMovement(event); mVelocityTracker.computeCurrentVelocity(1000 /* units */); final float velocity = isLandscape ? mVelocityTracker.getXVelocity() : mVelocityTracker.getYVelocity(); //计算当前分割线位置 final int position = mSplitLayout.getDividePosition() + touchPos - mStartPos; //找Target，也就是五大target，分别为顶，上中，中间，下中，底部，拖动落点在哪，就让落点往哪个落点靠 final DividerSnapAlgorithm.SnapTarget snapTarget = mSplitLayout.findSnapTarget(position, velocity, false /* hardDismiss */); // position上面已经更新位置，snapTarget为滑动目标，意义不知道，可能为吸附目标？ // snapTarget可能为分割线一个参照判断点，判断当前触摸点属那个位置好进行判定吸附 //找到了target，那就滑到哪个target中去，看参数就知道，拿到位置和target，开始操作 mSplitLayout.snapToTarget(position, snapTarget); mMoving = false; break; } return true; /** * Sets new divide position and updates bounds correspondingly. Notifies listener if the new * target indicates dismissing split. */ public void snapToTarget(int currentPosition, DividerSnapAlgorithm.SnapTarget snapTarget) { switch (snapTarget.flag) { case FLAG_DISMISS_START: //触摸正在滑动的位置 flingDividePosition(currentPosition, snapTarget.position, () -> mSplitLayoutHandler.onSnappedToDismiss(false /* bottomOrRight */)); break; case FLAG_DISMISS_END: flingDividePosition(currentPosition, snapTarget.position, () -> mSplitLayoutHandler.onSnappedToDismiss(true /* bottomOrRight */)); break; default: flingDividePosition(currentPosition, snapTarget.position, () -> setDividePosition(snapTarget.position, true /* applyLayoutChange */)); break; } } //在松手时有一个动画自己滑过去，就是这个方法实现，顺便把那个分割线滑道对应的target中 @VisibleForTesting void flingDividePosition(int from, int to, @Nullable Runnable flingFinishedCallback) { if (from == to) { // No animation run, still callback to stop resizing. mSplitLayoutHandler.onLayoutSizeChanged(this); return; } InteractionJankMonitorUtils.beginTracing(InteractionJankMonitor.CUJ_SPLIT_SCREEN_RESIZE, mSplitWindowManager.getDividerView(), "Divider fling"); ValueAnimator animator = ValueAnimator .ofInt(from, to) .setDuration(250); animator.setInterpolator(Interpolators.FAST_OUT_SLOW_IN); animator.addUpdateListener( animation -> updateDivideBounds((int) animation.getAnimatedValue())); animator.addListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { if (flingFinishedCallback != null) { flingFinishedCallback.run(); } InteractionJankMonitorUtils.endTracing( InteractionJankMonitor.CUJ_SPLIT_SCREEN_RESIZE); } @Override public void onAnimationCancel(Animator animation) { setDividePosition(to, true /* applyLayoutChange */); } }); animator.start(); }（找Target，也就是五大target，分别为顶，上中，中间，下中，底部，）松手逻辑mSplitLayout.snapToTarget(position, snapTarget)为开始，看后面的代码注释
