22

即使经过大量研究，我仍然不能完全确定我如何实现由WakeLockaService开始的 a 的BroadcastReceiver方式是否正确 - 即使它似乎工作正常。广播接收器从警报中获取发送给它的意图，因此首先从以下 API 文档开始AlarmManager：

如果您的警报接收器调用了 Context.startService()，则手机可能会在请求的服务启动之前休眠。为防止这种情况，您的 BroadcastReceiver 和 Service 将需要实施单独的唤醒锁定策略，以确保手机继续运行直到服务可用。

所以，在onReceive()我做：

    Intent serviceIntent = new Intent(context, SomeService.class);
    context.startService(serviceIntent);

    if(SomeService.wakeLock == null) {
        PowerManager powerManager = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
        SomeService.wakeLock = powerManager.newWakeLock(
                PowerManager.PARTIAL_WAKE_LOCK, 
                SomeService.WAKE_LOCK_TAG);
    }
    if(! SomeService.wakeLock.isHeld()) {
        SomeService.wakeLock.acquire();
    }

在我做的服务中：

    try {
        // Do some work
    } finally {
        if(wakeLock != null) {
            if(wakeLock.isHeld()) {
                wakeLock.release();
            }
            wakeLock = null;
        }
    }

该SomeService.wakeLock字段是包私有的、静态的和易失的。

我不确定使用的是检查isHeld()- 它是否真的告诉我是否WakeLock获得了 a ，我是否需要进行此检查？

4

4 回答 4

4

我不确定使用的是检查isHeld()- 它是否真的告诉我是否WakeLock获得了 a ，我是否需要进行此检查？

实际上回答起来有点棘手。查看源代码PowerManager和PowerManager.WakeLock 这里的WakeLock.acquire()和WakeLock.acquireLocked()方法如下......

public void acquire(long timeout) {
    synchronized (mToken) {
        acquireLocked();
        mHandler.postDelayed(mReleaser, timeout);
    }
}

private void acquireLocked() {
    if (!mRefCounted || mCount++ == 0) {
        // Do this even if the wake lock is already thought to be held (mHeld == true)
        // because non-reference counted wake locks are not always properly released.
        // For example, the keyguard's wake lock might be forcibly released by the
        // power manager without the keyguard knowing.  A subsequent call to acquire
        // should immediately acquire the wake lock once again despite never having
        // been explicitly released by the keyguard.
        mHandler.removeCallbacks(mReleaser);
        try {
            mService.acquireWakeLock(mToken, mFlags, mTag, mWorkSource);
        } catch (RemoteException e) {
        }
        mHeld = true;
    }
}

...mService是一个IPowerManager接口，并且它的源不可用，因此在尝试调用acquireWakeLock(...).

在任何情况下，唯一可以捕获的异常是RemoteException块catch什么都不做。在 try/catch 之后立即mHeld设置，true不管。

简而言之，如果您在结果isHeld()之后立即调用，acquire()则始终为true.

进一步查看源代码PowerManager.WakeLock显示了类似的行为，无论发生什么，成员始终设置为的release()调用。release(int flags)mHeldfalse

总之，我建议将检查isHeld()作为最佳实践始终是一个好主意，以防更高版本的 Android 更改WakeLock方法的这种行为。

于 2011-08-24T21:42:11.153 回答
4

在单例中管理您的 wakeLock（可通过所有上下文和对象访问的唯一实例）

使用自定义类的单例实例，然后您可能会从 call 到 call 获得唤醒锁对象引用，



这是一个单例示例

class MyData {
   private static MyData mMydata= null; // unique reference ( singleton objet container)

   private PowerManager.Wakelock myobject = null; // inside the unique object container we have the unique working object to be use  by the application
   // can't make instance from outside... we want to have single instance
   // we want that outside use method "getInstance" to be able to use the object
   private MyData() {
   }

   // retrieve and/or create new unique instance
   public static MyData getInstance() {
     if (mMydata ==  null) mMyData = new MyData();
     return   mMyData;
   }

   // Works with your memory stored object
   // get...
   public PowerManager.WakeLock getMyWakelock() {
   return myobject;
   }
   // set ...
   public void setMyWakeLock(PowerManager.WakeLock obj) {
    myobject = obj;
   }
}


在您的应用程序中处理您的“唤醒锁”对象，您可以像访问它一样

// set a created wakelock
MyData.getInstance().setMyWakeLock(wl);
// get the saved wakelock object
PowerManager.WakeLock obj =  MyData.getInstance().getMyWakeLock();
于 2011-08-24T23:49:32.637 回答
3

所有这些工作都可以通过一个名为WakefulBroadcastReceiver的助手和本地类来完成

于 2016-01-21T09:45:12.427 回答
0

我认为 android.os.Messenger 可能是更好的方法

对于接收器：

public class MessengerReceiver extends BroadcastReceiver {


    private static final String TAG = "MessengerReceiver";

    private final MessengerHandler mHandler = new MessengerHandler();

    @Override
    public void onReceive(Context context, Intent intent) {
        // TODO: This method is called when the BroadcastReceiver is receiving
        // an Intent broadcast.
        mHandler.mWakeLock = ((PowerManager)context.getSystemService(Service.POWER_SERVICE)).newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "myreceiver");
        mHandler.mWakeLock.acquire();
        Log.e(TAG, "onReceive:: mHandler.mWakeLock=" + mHandler.mWakeLock + ", intent=" + intent + ", this=" + this);
        context.startService(new Intent(context, MessengerService.class).putExtra("messenger", new Messenger(mHandler)));
    }

    static class MessengerHandler extends Handler {

        WakeLock mWakeLock;
        @Override
        public void handleMessage(Message msg) {
            // TODO Auto-generated method stub
            if(mWakeLock != null){
                mWakeLock.release();
                Log.e(TAG, "handleMessage:mWakeLock=" + mWakeLock);
            }
            super.handleMessage(msg);
        }

    }
}

服务：

public class MessengerService extends Service {
    private static final String TAG = "MessengerService";
    public MessengerService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // TODO Auto-generated method stub      
        Log.e(TAG, "onStartCommand:: intent=" + intent);
        final Messenger messenger = intent.getParcelableExtra("messenger");
        try {
            messenger.send(Message.obtain());
        } catch (RemoteException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return super.onStartCommand(intent, flags, startId);
    }
}

即使服务和接收器在不同的进程中运行，此方法也能正常工作。

于 2016-08-07T16:15:46.633 回答