Vfrdtyky

I'm developing my first app so I'm a newbie of Android programming.

I have a button that will turn off my screen with the command

Process su = Runtime.getRuntime().exec("su -c input keyevent 26");

but the command takes about 2 seconds to turn off de screen.
So I want that immediately after clicking on the button, before launching the screen-off command will be showed a fullscreen black image, to simulate the screen off. Maybe after launching the command, with a little delay of 5seconds I have to take the image away. How can I do?

Firstly, prepare an ImageView in your layout xml:

<?xml version="1.0" encoding="utf-8"?>

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    android:layout_width="match_parent"

    android:layout_height="match_parent">



    ...

    <ImageView

        android:id="@+id/imageView"

        android:layout_width="0dp"

        android:layout_height="0dp"

        android:visibility="gone"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintEnd_toEndOf="parent"

        app:layout_constraintStart_toStartOf="parent"

        app:layout_constraintTop_toTopOf="parent"

        app:srcCompat="@color/colorAccent" />

</android.support.constraint.ConstraintLayout>

notice set the initial visibility of ImageView is gone.

Then in the OnClickListener of button:

       yourImageView.setVisibility(View.VISIBLE);

       new Handler().postDelayed(new Runnable() {

            @Override

            public void run() {

                Process su = Runtime.getRuntime().exec("su -c input keyevent 26");

                yourImageView.setVisibility(View.GONE);

            }

        }, 5000); //after 5 seconds