应用程序注销输入事件通道

最新推荐文章于 2023-01-31 09:23:21 发布

原创

最新推荐文章于 2023-01-31 09:23:21 发布 · 878 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#android #输入系统

当Android Activity销毁时，会注销输入事件通道。本文详细分析了这一过程，包括ActivityRecord.windowsVisibleLocked()、WindowManagerService的处理、InputChannel的dispose()方法，涉及client端和server端的InputChannel注销步骤，以及在native层的操作。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

应用程序注销输入事件通道

- 应用程序注销输入事件通道

1.简介

当Activity的窗口创建时，它会向InputManagerService注册输入消息接收通道；而当Activity窗口销毁时，它就会向InputManagerService注销前面注册的输入消息接收通道。

WindowManagerService在处理处于Stopped状态的Activity窗口时，就会注销它们之前所注册的键盘消息接收通道。对于那些处于Stopped状态的Activity窗口来说，它们等待的是销毁，而不是等待可见。所以我们将从ActivityRecord的windowVisiable函数开始分析，输入消息接收通道的注销过程。

2.源码分析

2.1 ActivityRecord.windowsVisible()

final class ActivityRecord {
    .....
    static class Token extends IApplicationToken.Stub {
        @Override
        public void windowsVisible() {
            synchronized (mService) {
                ActivityRecord r = tokenToActivityRecordLocked(this);
                if (r != null) {
                    r.windowsVisibleLocked();//调用ActivityRecord的windowsVisibleLocked(),见2.2
                }
            }
        }
    }
}

2.2 ActivityRecord.windowsVisibleLocked()

void windowsVisibleLocked() {
    mStackSupervisor.reportActivityVisibleLocked(this);
    if (!nowVisible) {
        nowVisible = true;
        lastVisibleTime = SystemClock.uptimeMillis();
        if (!idle) {
            mStackSupervisor.processStoppingActivitiesLocked(false);
        } else {
            final int size = mStackSupervisor.mWaitingVisibleActivities.size();//等待可见的Activity
            if (size > 0) {
                for (int i = 0; i < size; i++) {
                    ActivityRecord r = mStackSupervisor.mWaitingVisibleActivities.get(i);//获取ActivityRecord记录
                }
                mStackSupervisor.mWaitingVisibleActivities.clear();
                mStackSupervisor.scheduleIdleLocked();//调用ActivityStackSupervisor的scheduleIdleLocked()方法，见2.3
            }
        }
        service.scheduleAppGcsLocked();
        }
    }
    ......
}

应用程序中的每一个Activity在ActivityManagerService中都有一个ActivityRecord对应，它们是以堆栈的形式组织在ActivityManagerService中的ActivityStack中。一个即将要显示，但还没有显示的Activity，它的ActivityRecord的成员变量nowVisible为false，成员变量idle为true，表示这个即将要显示的Activity窗口处于空闲状态。

2.3 ActivityStackSupervisor.scheduleIdleLocked()

final void scheduleIdleLocked() {
    mHandler.sendEmptyMessage(IDLE_NOW_MSG);//发送IDLE_NOW_MSG消息，最终调用activityIdleInternal()方法，见2.4
}

2.4 ActivityStackSupervisor.activityIdleInternalLocked()

final ActivityRecord activityIdleInternalLocked(final IBinder token, boolean fromTimeout,
        Configuration config) {
    .....
    final ArrayList<ActivityRecord> stops = processStoppingActivitiesLocked(true);
    NS = stops != null ? stops.size() : 0;
    .....
    for (int i = 0; i < NS; i++) {
        r = stops.get(i);
        final ActivityStack stack = r.task.stack;
        if (stack != null) {
            if (r.finishing) {
                stack.finishCurrentActivityLocked(r, ActivityStack.FINISH_IMMEDIATELY, false);//调用ActivityStack的finishCurrentActivityLocked()方法，见2.5
            } else {
                stack.stopActivityLocked(r);//调用ActivityStack的stopActivityLocked方法
            }
        }
    }
    .....
}

如果ActivityRecord的finishing变量为true的话，将调用ActivityStack的finishCurrentActivityLocked()方法来销毁Activity。

2.5 ActivityStack.finishCurrentActivityLocked()

final ActivityRecord finishCurrentActivityLocked(ActivityRecord r, int mode, boolean oomAdj) {

    .....
    mStackSupervisor.mStoppingActivities.remove(r);
    mStackSupervisor.mGoingToSleepActivities.remove(r);
    mStackSupervisor.mWaitingVisibleActivities.remove(r);
    ......
    final ActivityState prevState = r.state;
    r.state = ActivityState.FINISHING;
    if (mode == FINISH_IMMEDIATELY
            || (prevState == ActivityState.PAUSED
                && (mode == FINISH_AFTER_PAUSE || mStackId == PINNED_STACK_ID))
            || finishingActivityInNonFocusedStack
            || prevState == ActivityState.STOPPED
            || prevState == ActivityState.INITIALIZING) {
        r.makeFinishingLocked();
        boolean activityRemoved = destroyActivityLocked(r, true, "finish-imm");//销毁Activity，见2.6
        .....
    }else{
        .......
    }
    return r;
}

如果传进来的mode为FINISH_IMMEDIATELY，并且Activity的状态为Stopped，则销毁该Activity。

2.6 ActivityStack.destroyActivityLocked()

final boolean destroyActivityLocked(ActivityRecord r, boolean removeFromApp, String reason) {
    EventLog.writeEvent(EventLogTags.AM_DESTROY_ACTIVITY,
            r.userId, System.identityHashCode(r),