Android slideshow problem with

Hello All,
I am trying to make a simple android app that will display some images for a user specifiable number of milliseconds each.
But it just stays on the first one.
could you have a look and tell me what you think.

public class MainActivity extends AppCompatActivity {
    public ImageView canvas;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        canvas = findViewById(R.id.canvas);
        canvas.setWillNotCacheDrawing(true);
        canvas.setVisibility(View.VISIBLE);
    }


    public void buttonPressed(View view){
        PhdMan clock;
        setContentView(R.layout.activity_main);
        clock = new PhdMan();
        clock.delay(1000);
        canvas.setImageResource(R.drawable.c1);
        canvas.invalidate();
        clock.delay(2000);
        canvas.setImageResource(R.drawable.c2);
        canvas.invalidate();
        clock.delay(1500);
        canvas.setImageResource(R.drawable.c3);

      clock.delay(700);
        canvas.setImageResource(R.drawable.c4);
        clock.delay(3000);
        canvas.setImageResource(R.drawable.c5);
        clock.delay(1000);
        canvas.setImageResource(R.drawable.c6);
        clock.delay(1200);
    }


}

class SMan extends Thread {
    void delay(long ms){
        try{
            sleep(ms);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

}

I am open to C/C++ alternatives.
I was wishing there was a 'call kernel' function for the display.
In the future I would like to have the user be able to select or take the pictures.