want to pick random Image from drawable and move it on y-coordinates(down the screen)

I am making a simple learning app for my school kids. I don't know coding but I used a tutorial to make this app. Which will pick random fruits(images) from drawable and make them fall down the screen(Y-position += 5).

I have declared them on onCreate

    apple = (ImageView) findViewById(R.id.apple);
    banana = (ImageView) findViewById(R.id.banana);
    grapes = (ImageView) findViewById(R.id.grapes);

after that

public void changePosition(){

    appleY += 5;
    if(appleY > screenHeight ) {

        appleX = (int) Math.floor(Math.random() * (frameWidth - apple.getWidth()));
        appleY = screenHeight - (screenHeight + 50);

    }
    apple.setX(appleX);
    apple.setY(appleY);


        bananaY += 5;
        if (bananaY > screenHeight) {

            bananaX = (int) Math.floor(Math.random() * (frameWidth - banana.getWidth()));
            bananaY = screenHeight - (screenHeight + 50);

        }
        banana.setX(bananaX);
        banana.setY(bananaY);

}

this makes them fall together, which might be confusing for small kids. I want it to let one image cross the screen then other should come but randomly, like apple - banana - apple - grapes - mango - banana.

please guide me. Thank you