Display the contents of a button and make it disappear after a period

Question

I’m totally new with android studio and I’m trying to create a little memory game, the game consists of a series of buttons, a row 4x4, all buttons appear being a "?" when you click the button it displays the number stored inside it, I wanted to make the content displayed inside the button disappear after a few seconds, since it is a memory game, can help me on which function to use to achieve this?

btn1.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    btn1.setText("1");

                }
            });

The btn1.setText("1") command; this taking the contents of the button, it stays forever and does not disappear, ie it does not return to being a ?

2 Doubt, I have a START button, when I clicked on it I wanted my text view that is an Accountant, to start counting the time it would take to close the game.

Answer 1

btn1.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        btn1.setText("1");
        // O Texto do botão voltará a ser "?" em 5 segundos
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                btn1.setText("?");
            }
        }, 5000); // 5 segundos
    }
});