Android framework学习笔记 -- 原生分屏原理

分屏代码在AOSP其实老早就存在了，就一直没有开启而已，在6.0版本可以通过设置系统属性ro.build.type改为userdebug,并在开发者选项中开启多窗口模式,然后在最近任务上就会个按钮可以实现分屏。

通过adb命令也可以实现分屏

$ am task resize 25 0 720 1080 1920

在最近任务的调用链

RecentsActivity#onTaskResize ->RecentsResizeTaskDialog#placeTasks ->SystemServicesProxy#resizeTask -> ActivityManagerNative#resizeTask -> ActivityManagerService#resizeTask -> ActivityStackSupervisor#resizeStackLocked

在am的调用链

Am#runTaskResize-> ActivityManagerNative#resizeTask -> ActivityManagerService#resizeTask -> ActivityStackSupervisor#resizeTaskLocked

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ActivityStackSupervisor的实现

foundStackWithBoundsActivityStackSupervisor#moveTaskToStackLocked ->ActivityStackSupervisor#resizeStackLockedActivityStackSupervisor#moveTaskToStackLocked - > WindowManagerService#moveTaskToStackActivityStackSupervisor#resizeStackLocked ->WindowManagerService#resizeStack

WindowManagerService的实现

WindowManagerService#resizeStack ->TaskStack#setBoundsTaskStack#resizeWindows ->updateLayout??

看来让人心情不好的乱七八糟源码分析

//---> frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.javavoid resizeTaskLocked(TaskRecord task, Rect bounds) {    task.mResizeable = true;    final ActivityStack currentStack = task.stack;    if (currentStack.isHomeStack()) {        // Can't move task off the home stack. Sorry!        return;    }    // 找到给定区域相同的栈    final int matchingStackId = mWindowManager.getStackIdWithBounds(bounds);    if (matchingStackId != -1) {        // There is already a stack with the right bounds!        if (currentStack != null &&                     currentStack.mStackId == matchingStackId) {            // Nothing to do here. Already in the right stack...            return;        }        // Move task to stack with matching bounds.        moveTaskToStackLocked(task.taskId, matchingStackId, true);        return;    }    // 栈里只有一个task，直接resize栈    if (currentStack != null && currentStack.numTasks() == 1) {        // Just resize the current stack since this is the task in it.        resizeStackLocked(currentStack.mStackId, bounds);        return;    }    // 挪动task到新的栈    // Create new stack and move the task to it.    final int displayId =             (currentStack != null && currentStack.mDisplayId != -1)            ? currentStack.mDisplayId : Display.DEFAULT_DISPLAY;    ActivityStack newStack = createStackOnDisplay(getNextStackId(), displayId);    if (newStack == null) {        Slog.e(TAG, "resizeTaskLocked: Can't create stack for task=" + task);        return;    }    moveTaskToStackLocked(task.taskId, newStack.mStackId, true);    resizeStackLocked(newStack.mStackId, bounds);}

分屏的核心是task跟bound，需要看一下task是怎么裂变的