[android] Creating a system overlay window (always on top)

by using service you can achieve this :

public class PopupService extends Service{

    private static final String TAG = PopupService.class.getSimpleName();
    WindowManager mWindowManager;
    View mView;
    String type ;

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

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
//        registerOverlayReceiver();
        type = intent.getStringExtra("type");
        Utils.printLog("type = "+type);
        showDialog(intent.getStringExtra("msg"));
        return super.onStartCommand(intent, flags, startId);
    }

    private void showDialog(String aTitle)
    {
        if(type.equals("when screen is off") | type.equals("always"))
        {
            Utils.printLog("type = "+type);
            PowerManager pm = (PowerManager) getApplicationContext().getSystemService(Context.POWER_SERVICE);
            WakeLock mWakeLock = pm.newWakeLock((PowerManager.SCREEN_DIM_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP), "YourServie");
            mWakeLock.acquire();
            mWakeLock.release();
        }

        mWindowManager = (WindowManager) getSystemService(WINDOW_SERVICE);
        mView = View.inflate(getApplicationContext(), R.layout.dialog_popup_notification_received, null);
        mView.setTag(TAG);

        int top = getApplicationContext().getResources().getDisplayMetrics().heightPixels / 2;

        LinearLayout dialog = (LinearLayout) mView.findViewById(R.id.pop_exit);
//        android.widget.LinearLayout.LayoutParams lp = (android.widget.LinearLayout.LayoutParams) dialog.getLayoutParams();
//        lp.topMargin = top;
//        lp.bottomMargin = top;
//        mView.setLayoutParams(lp);

        final EditText etMassage = (EditText) mView.findViewById(R.id.editTextInPopupMessageReceived);

        ImageButton imageButtonSend = (ImageButton) mView.findViewById(R.id.imageButtonSendInPopupMessageReceived);
//        lp = (LayoutParams) imageButton.getLayoutParams();
//        lp.topMargin = top - 58;
//        imageButton.setLayoutParams(lp);
        imageButtonSend.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                Utils.printLog("clicked");
//                mView.setVisibility(View.INVISIBLE);
                if(!etMassage.getText().toString().equals(""))
                {
                    Utils.printLog("sent");
                    etMassage.setText("");
                }
            }
        });

        TextView close = (TextView) mView.findViewById(R.id.TextViewCloseInPopupMessageReceived);
        close.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                hideDialog();   
            }
        });

        TextView view = (TextView) mView.findViewById(R.id.textviewViewInPopupMessageReceived);
        view.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                hideDialog();   
            }
        });

        TextView message = (TextView) mView.findViewById(R.id.TextViewMessageInPopupMessageReceived);
        message.setText(aTitle);

        final WindowManager.LayoutParams mLayoutParams = new WindowManager.LayoutParams(
        ViewGroup.LayoutParams.MATCH_PARENT,
        ViewGroup.LayoutParams.MATCH_PARENT, 0, 0,
        WindowManager.LayoutParams.TYPE_SYSTEM_ERROR,
        WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
                | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD
//                | WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
                | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON ,
        PixelFormat.RGBA_8888);

        mView.setVisibility(View.VISIBLE);
        mWindowManager.addView(mView, mLayoutParams);
        mWindowManager.updateViewLayout(mView, mLayoutParams);

    }

    private void hideDialog(){
        if(mView != null && mWindowManager != null){
            mWindowManager.removeView(mView);
            mView = null;
        }
    }
}