unbindService启动过程分析

Posted by Gityuan on May 2, 2016

基于Android 6.0的源码剖析, 分析bind service的启动流程。

/frameworks/base/core/java/android/app/ContextImpl.java
/frameworks/base/core/java/android/app/LoadedApk.java
/frameworks/base/core/java/android/app/IServiceConnection.aidl(自动生成Binder两端)

一. unbind

文章bindService启动过程分析,介绍了 bindService的过程,本文介绍其对应的另一个操作unbind。

unbind调用链:

AMP.unbindService
  AMS.unbindService
    AS.unbindServiceLocked
      AS.removeConnectionLocked
        ATP.scheduleUnbindService
          AT.scheduleUnbindService
            AT.handleUnbindService
              Service.onUnbind
        AS.bringDownServiceIfNeededLocked
          AS.bringDownServiceLocked
            ATP.scheduleUnbindService
              AT.scheduleUnbindService
            ATP.scheduleStopService
              AT.scheduleStopService

1.1 AMP.unbindService

… //省略,未完待续

二. onServiceDisconnected

当service所在进程死亡后,binderDied死亡回调后触发的。

2.1 binderDied

[-> LoadedApk.ServiceDispatcher.DeathMonitor]

private final class DeathMonitor implements IBinder.DeathRecipient
{
    DeathMonitor(ComponentName name, IBinder service) {
        mName = name;
        mService = service;
    }

    public void binderDied() {
        death(mName, mService); //【见流程2.2】
    }

    final ComponentName mName;
    final IBinder mService;
}

2.2 death

[-> LoadedApk.ServiceDispatcher]

public void death(ComponentName name, IBinder service) {
    ServiceDispatcher.ConnectionInfo old;

    synchronized (this) {
        mDied = true;
        old = mActiveConnections.remove(name);
        if (old == null || old.binder != service) {
            return;
        }
        old.binder.unlinkToDeath(old.deathMonitor, 0);
    }

    if (mActivityThread != null) {
        //【见流程2.3】
        mActivityThread.post(new RunConnection(name, service, 1));
    } else {
        doDeath(name, service);
    }
}

2.3 run

[-> LoadedApk.ServiceDispatcher.RunConnection]

private final class RunConnection implements Runnable {
    RunConnection(ComponentName name, IBinder service, int command) {
        mName = name;
        mService = service;
        mCommand = command;
    }

    public void run() {
        if (mCommand == 0) {
            doConnected(mName, mService);
        } else if (mCommand == 1) {
            doDeath(mName, mService); //【见流程2.4】
        }
    }
}

2.4 doDeath

[-> LoadedApk.ServiceDispatcher]

public void doDeath(ComponentName name, IBinder service) {
   //回调用户定义的onServiceDisconnected方法
   mConnection.onServiceDisconnected(name);
}

三. 总结

  1. unbind()是bind的逆操作,主要是清理bind相关对象,并不会回调onServiceDisconnected.
  2. 当Service进程死亡,经过Binder死亡回调,则会进入Client端进程来执行binderDied(),经过层层调用, 最终回调用户定义的onServiceDisconnected方法。

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