android: broadcast receiver for screen on and scre

问题:

I was just wondering if it is possible to register a broadcast receiver that detects Screen ON/OFF in the application manifest. The reason why I don\'t like the programmable method is that it requires the app to be running in order to detect such a thing, while: \"Applications with Broadcast Receivers registered in the manifest don’t have to be running when the Intent is broadcast for the receivers to execute\" (source: Professional Android 2 Application Development book)

My app is actually a lockscreen app which by using the programmable way needs to be running all the time :S

Is there a way around it?

I\'m trying the following in the manifest:

<receiver android:name=\".MyBroadCastReciever\">
    <intent-filter>
        <action android:name=\"android.intent.action.SCREEN_OFF\"/>
        <action android:name=\"android.intent.action.SCREEN_ON\"/>
    </intent-filter>
</receiver>

and simple MyBroadCastReciever class:

public class MyBroadCastReciever extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction().equals(Intent.ACTION_SCREEN_OFF)) {
            Log.i(\"Check\",\"Screen went OFF\");
            Toast.makeText(context, \"screen OFF\",Toast.LENGTH_LONG).show();
        } else if (intent.getAction().equals(Intent.ACTION_SCREEN_ON)) {
            Log.i(\"Check\",\"Screen went ON\");
            Toast.makeText(context, \"screen ON\",Toast.LENGTH_LONG).show();
        }
    }
}

回答1:

The two actions for screen on and off are:

android.intent.action.SCREEN_OFF
android.intent.action.SCREEN_ON

But if you register a receiver for these broadcasts in a manifest, then the receiver will not receive these broadcasts.

For this problem, you have to create a long running service, which is registering a local broadcast receiver for these intents. If you do this way, then your app will look for screen off only when your service is running which won\'t irritate user.

PS: start the service in foreground to make it running longer.

A simple code snippet will be something like this:

IntentFilter screenStateFilter = new IntentFilter();
screenStateFilter.addAction(Intent.ACTION_SCREEN_ON);
screenStateFilter.addAction(Intent.ACTION_SCREEN_OFF);
registerReceiver(mScreenStateReceiver, screenStateFilter);

Don\'t forget to unregister the receiver in the Service\'s onDestroy:

unregisterReceiver(mScreenStateReceiver);

Just in case for people who are asking why the receiver does not work with the declare broadcasts in manifest for ACTION_SCREEN_ON and ACTION_SCREEN_OFF:

https://developer.android.com/reference/android/content/Intent.html#ACTION_SCREEN_ON https://developer.android.com/reference/android/content/Intent.html#ACTION_SCREEN_OFF

You cannot receive this through components declared in manifests, only by explicitly registering for it with Context.registerReceiver().

This is a protected intent that can only be sent by the system.

回答2:

You need to create a background service to check for it. Then you can set it programmatically.