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

Answer 1

For all android versions use this code.

I tried R. Zagórski's answer, but I am not able to run this code on Pie. However, I have updated their code in my answer.

PowerButtonService:

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");
                    Intent intent = new Intent(Intent.ACTION_CALL);
                    intent.setData(Uri.parse("tel:" + "9690008019"));
                    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    intent.addFlags(Intent.FLAG_FROM_BACKGROUND);
                    startActivity(intent);
                } 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);

      **// here I done with EDIT** 

        int LAYOUT_FLAG;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
            LAYOUT_FLAG = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
        } else {
            LAYOUT_FLAG = WindowManager.LayoutParams.TYPE_PHONE;
        }
        View mView = LayoutInflater.from(this).inflate(R.layout.service_layout, mLinear);
        WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);

        //params
        WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.WRAP_CONTENT,
                LAYOUT_FLAG,
                WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
                PixelFormat.TRANSLUCENT);
        params.gravity = Gravity.LEFT | Gravity.CENTER_VERTICAL;
        wm.addView(mView, params);
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
}

and service_layout: