How to hook into the Power button in Android?

Question

On an Android device, where the only buttons are the volume buttons and a power button, I want to make the app react to presses on the power button (long and short). How is this done?

Answer 1

You could overwrite the public boolean onKeyDown(int keyCode, KeyEvent event) and public boolean onKeyUp(int keyCode, KeyEvent event) functions in your Activity class and test if keyCode is equal to KeyEvent.KEYCODE_POWER.

I haven't tested this, but I would assume the system treats this like it does the Home key in that you cannot stop the system from receiving the key event, you can only observe that it occurs. To test this, try returning True from the above functions and see if this catches the key event.

Answer 2

Sharing a method to listen for Power button long press. Works with API 23+ permissions:

1. Asking for system permission to draw overlay (This is not a normal or vulnerable permission). This is not a user permission, so You should really know, what you are doing, by asking for it.

   public class MainActivity extends AppCompatActivity {
   
       public final static int REQUEST_CODE = 10101;
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
           if (checkDrawOverlayPermission()) {
               startService(new Intent(this, PowerButtonService.class));
           }
       }
   
       public boolean checkDrawOverlayPermission() {
           if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
               return true;
           }
           if (!Settings.canDrawOverlays(this)) {
               /** if not construct intent to request permission */
               Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
                   Uri.parse("package:" + getPackageName()));
           /** request permission via start activity for result */
               startActivityForResult(intent, REQUEST_CODE);
               return false;
           } else {
               return true;
           }
       }
   
       @Override
       @TargetApi(Build.VERSION_CODES.M)
       protected void onActivityResult(int requestCode, int resultCode, Intent data) {
           if (requestCode == REQUEST_CODE) {
               if (Settings.canDrawOverlays(this)) {
                   startService(new Intent(this, PowerButtonService.class));
               }
           }
       }
   }
   

2. Starting a service and adds a special view to WindowManager

3. Waiting for an action inside View's onCloseSystemDialogs method.

   public class PowerButtonService extends Service {
   
       public PowerButtonService() {
   
       }
   
       @Override
       public void onCreate() {
           super.onCreate();
           LinearLayout mLinear = new LinearLayout(getApplicationContext()) {
   
               //home or recent button
               public void onCloseSystemDialogs(String reason) {
                   if ("globalactions".equals(reason)) {
                       Log.i("Key", "Long press on power button");
                   } else if ("homekey".equals(reason)) {
                       //home key pressed
                   } else if ("recentapss".equals(reason)) {
                       // recent apps button clicked
                   }
               }
   
               @Override
               public boolean dispatchKeyEvent(KeyEvent event) {
                   if (event.getKeyCode() == KeyEvent.KEYCODE_BACK
                       || event.getKeyCode() == KeyEvent.KEYCODE_VOLUME_UP
                       || event.getKeyCode() == KeyEvent.KEYCODE_VOLUME_DOWN
                       || event.getKeyCode() == KeyEvent.KEYCODE_CAMERA
                       || event.getKeyCode() == KeyEvent.KEYCODE_POWER) {
                       Log.i("Key", "keycode " + event.getKeyCode());
                   }
                   return super.dispatchKeyEvent(event);
               }
           };
   
           mLinear.setFocusable(true);
   
           View mView = LayoutInflater.from(this).inflate(R.layout.service_layout, mLinear);
           WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
   
           //params
           WindowManager.LayoutParams params = new WindowManager.LayoutParams(
               100,
               100,
               WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
               WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
                       | WindowManager.LayoutParams.FLAG_FULLSCREEN
                       | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN
                       | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON,
               PixelFormat.TRANSLUCENT);
           params.gravity = Gravity.LEFT | Gravity.CENTER_VERTICAL;
           wm.addView(mView, params);
       }
   
       @Override
       public IBinder onBind(Intent intent) {
           return null;
       }
   }
   

Manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="powerbuttonpress">

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>

        <service
            android:name=".PowerButtonService"
            android:enabled="true"
            android:exported="true">
        </service>

    </application>

</manifest>

service_layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

</LinearLayout>

Answer 3

As mentioned here https://stackoverflow.com/a/15828592/1065357

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    if(!hasFocus) {
       Intent closeDialog = new Intent(Intent.ACTION_CLOSE_SYSTEM_DIALOGS);
        sendBroadcast(closeDialog);
    }
}