Want to Access Power Button events in android

问题:

   i=0;
   public boolean onKeyDown(int keyCode, KeyEvent event) {
    System.out.println("In Key Down Method." + event.getKeyCode());
    if (event.getKeyCode() == KeyEvent.KEYCODE_POWER) {
        i++;
        System.out.println("Power button pressed.");
        if (i == 2) {
            System.out.println("Power button pressed continuoulsy 3 times.");
            Toast.makeText(MainActivity.this, "Power button pressed " + i + " times.", Toast.LENGTH_SHORT).show();
        } else {
            System.out.println("Power button pressed continuoulsy " + i + " times.");
            Toast.makeText(MainActivity.this, "Power button pressed " + i + " times.", Toast.LENGTH_SHORT).show();
        }
    }
    return super.onKeyDown(keyCode, event);
}

I am trying to access power button event using above code.Its working fine for Volume_Up and Volume_Down Key but not Working For Power/Lock Button.Why it happens? Suggest Some Example or code.

回答1:

You cannot override the power button press from your application. But when you press power button the screen turns on/off. So you can detect this using a broadcast receiver.

<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>

MyBroadCastReciever.java

public class MyBroadCastReciever extends BroadcastReceiver {

@Override
public void onReceive(Context context, Intent intent) {
    if (intent.getAction().equals(Intent.ACTION_SCREEN_OFF)) {
        //Take count of the screen off position
    } else if (intent.getAction().equals(Intent.ACTION_SCREEN_ON)) {
        //Take count of the screen on position
    }
}
}

Hope this is helpful for you.

Note:-For to keep my broadcast receiver always running in Background.I am written one Background Service which continuously start in background and give boost to my broadcast receiver.

回答2:

You should add the following permission to your manifest file:

<uses-permission android:name="android.permission.PREVENT_POWER_KEY" />