recents.java_解析Android 8.0中SystemUI Recents的task是如何启动的

前言

最近任务需求，特殊模式下任务管理界面 不能打开某个APK

任务分析

任务管理界面下单个task的onClick或者onTouch

首先找到Recents 源码 位于systemui 中

这里我们直接打开RecentsActivity.java 文件

在RecentsActivity 的oncreate中发现setContentView为recents资源文件

这里我们看到代码及注释，说明是一个自定义view - RecentsView

我们可以看到RecentsView是继承 FrameLayout的一个自定义View

RecentsView 中 有三个view 一个TaskStackView 两个Textview

public RecentsView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {

super(context, attrs, defStyleAttr, defStyleRes);

setWillNotDraw(false);

SystemServicesProxy ssp = Recents.getSystemServices();

mTransitionHelper = new RecentsTransitionHelper(getContext());

mDividerSize = ssp.getDockedDividerSize(context);

mTouchHandler = new RecentsViewTouchHandler(this);

mFlingAnimationUtils = new FlingAnimationUtils(context, 0.3f);

mScrimAlpha = Recents.getConfiguration().isGridEnabled

? GRID_LAYOUT_SCRIM_ALPHA : DEFAULT_SCRIM_ALPHA;

mBackgroundScrim = new ColorDrawable(

Color.argb((int) (mScrimAlpha * 255), 0, 0, 0)).mutate();

LayoutInflater inflater = LayoutInflater.from(context);

if (RecentsDebugFlags.Static.EnableStackActionButton) {

mStackActionButton = (TextView) inflater.inflate(R.layout.recents_stack_action_button,

this, false);

mStackActionButton.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

EventBus.getDefault().send(new DismissAllTaskViewsEvent());

}

});

addView(mStackActionButton);

}

mEmptyView = (TextView) inflater.inflate(R.layout.recents_empty, this, false);

addView(mEmptyView);

}

mStackActionButton即全部清除按钮，mEmptyView 即当TaskStack(Task的集合) 数量为空时显示的TextView，因此我们平时见到的APP的任务管理应该是在TaskStackView中的

然后分析TaskStackView 发现

TaskStackViewTouchHandler 这个应该是和Touch事件有关，因此我们进入 TaskStackViewTouchHandler中

可以看到上面的注释  说明它是 处理TaskStackView 触摸事件的类

TaskStackViewTouchHandler 中有onInterceptTouchEvent和onTouchEvent 看到它都调用到了 handleTouchEvent

下面是整个handleTouchEvent的代码

private boolean handleTouchEvent(MotionEvent ev) {

// Short circuit if we have no children

if (mSv.getTaskViews().size() == 0) {

return false;

}

final TaskStackLayoutAlgorithm layoutAlgorithm = mSv.mLayoutAlgorithm;

int action = ev.getAction();

switch (action & MotionEvent.ACTION_MASK) {

case MotionEvent.ACTION_DOWN: {

// Stop the current scroll if it is still flinging

mScroller.stopScroller();

mScroller.stopBoundScrollAnimation();

mScroller.resetDeltaScroll();

cancelNonDismissTaskAnimations();

mSv.cancelDeferredTaskViewLayoutAnimation();

// Save the touch down info

mDownX = (int) ev.getX();

mDownY = (int) ev.getY();

mLastY = mDownY;

mDownScrollP = mScroller.getStackScroll();

mActivePointerId = ev.getPointerId(0);

mActiveTaskView = findViewAtPoint(mDownX, mDownY);

Log.e("zhuwww"," mActiveTaskView \n");

// Initialize the velocity tracker

initOrResetVelocityTracker();

mVelocityTracker.addMovement(ev);

break;

}

case MotionEvent.ACTION_POINTER_DOWN: {

final int index = ev.getActionIndex();

mActivePointerId = ev.getPointerId(index);

mDownX = (int) ev.getX(index);

mDownY = (int) ev.getY(index);

mLastY = mDownY;

mDownScrollP = mScroller.getStackScroll();

mScroller.resetDeltaScroll();

mVelocityTracker.addMovement(ev);

break;

}

case MotionEvent.ACTION_MOVE: {

int activePointerIndex = ev.findPointerIndex(mActivePointerId);

int y = (int) ev.getY(activePointerIndex);

int x = (int) ev.getX(activePointerIndex);

if (!mIsScrolling) {

int yDiff = Math.abs(y - mDownY);

int xDiff = Math.abs(x - mDownX);

if (Math.abs(y - mDownY) > mScrollTouchSlop && yDiff > xDiff) {

mIsScrolling = true;

float stackScroll = mScroller.getStackScroll();

List taskViews = mSv.getTaskViews();

for (int i = taskViews.size() - 1; i >= 0; i--) {

layoutAlgorithm.addUnfocusedTaskOverride(taskViews.get(i).getTask(),

stackScroll);

}

layoutAlgorithm.setFocusState(TaskStackLayoutAlgorithm.STATE_UNFOCUSED);

// Disallow parents from intercepting touch events

final ViewParent parent = mSv.getParent();

if (parent != null) {

parent.requestDisallowInterceptTouchEvent(true);

}

MetricsLogger.action(mSv.getContext(), MetricsEvent.OVERVIEW_SCROLL);

mLastY = mDownY = y;

}

}

if (mIsScrolling) {

// If we just move linearly on the screen, then that would map to 1/arclength

// of the curve, so just move the scroll proportional to that

float deltaP = layoutAlgorithm.getDeltaPForY(mDownY, y);

// Modulate the overscroll to prevent users from pulling the stack too far

float minScrollP = layoutAlgorithm.mMinScrollP;

float maxScrollP = layoutAlgorithm.mMaxScrollP;

float curScrollP = mDownScrollP + deltaP;

if (curScrollP < minScrollP || curScrollP > maxScrollP) {

float clampedScrollP = Utilities.clamp(curScrollP, minScrollP, maxScrollP);

float overscrollP = (curScrollP - clampedScrollP);

float overscrollX = Math.abs(overscrollP) / MAX_OVERSCROLL;

float interpX = OVERSCROLL_INTERP.getInterpolation(overscrollX);

curScrollP = clampedScrollP + Math.signum(overscrollP) *

(interpX * MAX_OVERSCROLL);

}

mDownScrollP += mScroller.setDeltaStackScroll(mDownScrollP,

curScrollP - mDownScrollP);

mStackViewScrolledEvent.updateY(y - mLastY);

EventBus.getDefault().send(mStackViewScrolledEvent);

}

mLastY = y;

mVelocityTracker.addMovement(ev);

break;

}

case MotionEvent.ACTION_POINTER_UP: {

int pointerIndex = ev.getActionIndex();

int pointerId = ev.getPointerId(pointerIndex);

if (pointerId == mActivePointerId) {

// Select a new active pointer id and reset the motion state

final int newPointerIndex = (pointerIndex == 0) ? 1 : 0;

mActivePointerId = ev.getPointerId(newPointerIndex);

mDownX = (int) ev.getX(pointerIndex);

mDownY = (int) ev.getY(pointerIndex);

mLastY = mDownY;

mDownScrollP = mScroller.getStackScroll();

}

mVelocityTracker.addMovement(ev);

break;

}

case MotionEvent.ACTION_UP: {

mVelocityTracker.addMovement(ev);

mVelocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);

int activePointerIndex = ev.findPointerIndex(mActivePointerId);

int y = (int) ev.getY(activePointerIndex);

int velocity = (int) mVelocityTracker.getYVelocity(mActivePointerId);

if (mIsScrolling) {

if (mScroller.isScrollOutOfBounds()) {

mScroller.animateBoundScroll();

} else if (Math.abs(velocity) > mMinimumVelocity) {

float minY = mDownY + layoutAlgorithm.getYForDeltaP(mDownScrollP,

layoutAlgorithm.mMaxScrollP);

float maxY = mDownY + layoutAlgorithm.getYForDeltaP(mDownScrollP,

layoutAlgorithm.mMinScrollP);

mScroller.fling(mDownScrollP, mDownY, y, velocity, (int) minY, (int) maxY,

mOverscrollSize);

mSv.invalidate();

}

// Reset the focused task after the user has scrolled, but we have no scrolling

// in grid layout and therefore we don't want to reset the focus there.

if (!mSv.mTouchExplorationEnabled && !mSv.useGridLayout()) {

mSv.resetFocusedTask(mSv.getFocusedTask());

}

} else if (mActiveTaskView == null) {

// This tap didn't start on a task.

maybeHideRecentsFromBackgroundTap((int) ev.getX(), (int) ev.getY());

}

mActivePointerId = INACTIVE_POINTER_ID;

mIsScrolling = false;

recycleVelocityTracker();

break;

}

case MotionEvent.ACTION_CANCEL: {

mActivePointerId = INACTIVE_POINTER_ID;

mIsScrolling = false;

recycleVelocityTracker();

break;

}

}

return mIsScrolling;

}

分析发现，在handleTouchEvent 中 当MotionEvent.ACTION_DOWN时 通过mActiveTaskView = findViewAtPoint(mDownX, mDownY);得到了一个TaskView

findViewAtPoint实现

这里我们直接进入TaskView.java中查看 看到这里有实现点击事件的代码，这里我们加个Log打印，验证点击视图时是否经过这里

通过打印验证

的确是走的这个地方，那么我们这里可以看到主要是通过eventBus发送了一个LaunchTaskEvent事件

EventBus.getDefault().send(new LaunchTaskEvent(this, mTask, null, INVALID_STACK_ID,

screenPinningRequested));

LaunchTaskEvent源码

因此我们直接在recents中搜索哪个地方的方法用到了LaunchTaskEvent

这里看到只在TaskStackView和RecentsView中有使用到LaunchTaskEvent，其余的都是eventBus发送事件，所以我们就不用管了

然后下面看TaskStackView中的实现，很明显不是的，因此我们可以先确定是在RecentsView中的方法中

如下图所示，这个我们看它用的方法，通过mTransitionHelper去launchTaskFromRecents。这里从字面意思应该不难看出，地方已经找对了 launchTaskFromRecents即从recents中运行一个task。

然后我们在launchTaskFromRecents方法中发现有一个startTaskActivity方法

public void launchTaskFromRecents(final TaskStack stack, @Nullable final Task task,

final TaskStackView stackView, final TaskView taskView,

final boolean screenPinningRequested, final int destinationStack) {

final ActivityOptions.OnAnimationStartedListener animStartedListener;

final AppTransitionAnimationSpecsFuture transitionFuture;

if (taskView != null) {

// Fetch window rect here already in order not to be blocked on lock contention in WM

// when the future calls it.

final Rect windowRect = Recents.getSystemServices().getWindowRect();

transitionFuture = getAppTransitionFuture(

() -> composeAnimationSpecs(task, stackView, destinationStack, windowRect));

animStartedListener = () -> {

// If we are launching into another task, cancel the previous task's

// window transition

EventBus.getDefault().send(new CancelEnterRecentsWindowAnimationEvent(task));

EventBus.getDefault().send(new ExitRecentsWindowFirstAnimationFrameEvent());

stackView.cancelAllTaskViewAnimations();

if (screenPinningRequested) {

// Request screen pinning after the animation runs

mStartScreenPinningRunnable.taskId = task.key.id;

mHandler.postDelayed(mStartScreenPinningRunnable, 350);

}

};

} else {

// This is only the case if the task is not on screen (scrolled offscreen for example)

transitionFuture = null;

animStartedListener = () -> {

// If we are launching into another task, cancel the previous task's

// window transition

EventBus.getDefault().send(new CancelEnterRecentsWindowAnimationEvent(task));

EventBus.getDefault().send(new ExitRecentsWindowFirstAnimationFrameEvent());

stackView.cancelAllTaskViewAnimations();

};

}

final ActivityOptions opts = ActivityOptions.makeMultiThumbFutureAspectScaleAnimation(mContext,

mHandler, transitionFuture != null ? transitionFuture.future : null,

animStartedListener, true /* scaleUp */);

if (taskView == null) {

// If there is no task view, then we do not need to worry about animating out occluding

// task views, and we can launch immediately

startTaskActivity(stack, task, taskView, opts, transitionFuture, destinationStack);

} else {

LaunchTaskStartedEvent launchStartedEvent = new LaunchTaskStartedEvent(taskView,

screenPinningRequested);

if (task.group != null && !task.group.isFrontMostTask(task)) {

launchStartedEvent.addPostAnimationCallback(new Runnable() {

@Override

public void run() {

startTaskActivity(stack, task, taskView, opts, transitionFuture,

destinationStack);

}

});

EventBus.getDefault().send(launchStartedEvent);

} else {

EventBus.getDefault().send(launchStartedEvent);

startTaskActivity(stack, task, taskView, opts, transitionFuture, destinationStack);

}

}

Recents.getSystemServices().sendCloseSystemWindows(

StatusBar.SYSTEM_DIALOG_REASON_HOME_KEY);

}

关键代码  ssp.startActivityFromRecents 从Recents 中启动activity

private void startTaskActivity(TaskStack stack, Task task, @Nullable TaskView taskView,

ActivityOptions opts, AppTransitionAnimationSpecsFuture transitionFuture,

int destinationStack) {

SystemServicesProxy ssp = Recents.getSystemServices();

ssp.startActivityFromRecents(mContext, task.key, task.title, opts, destinationStack,

succeeded -> {

if (succeeded) {

// Keep track of the index of the task launch

int taskIndexFromFront = 0;

int taskIndex = stack.indexOfStackTask(task);

if (taskIndex > -1) {

taskIndexFromFront = stack.getTaskCount() - taskIndex - 1;

}

EventBus.getDefault().send(new LaunchTaskSucceededEvent(taskIndexFromFront));

} else {

// Dismiss the task if we fail to launch it

if (taskView != null) {

taskView.dismissTask();

}

// Keep track of failed launches

EventBus.getDefault().send(new LaunchTaskFailedEvent());

}

});

if (transitionFuture != null) {

mHandler.post(transitionFuture::precacheSpecs);

}

}

至此，已经找到了任务管理中启动task的地方，我们这里只需要在RecentsView.java的onBusEvent方法中拦截即可

比如任务管理中不能打开相册

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