单击按钮时 setText 不会更改或更新

Question

I am trying to get random character when the user clicks in button in textView, it works but when I click again it's not updating the random character in my textView. Below is my code.

 char[] chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
StringBuilder sb = new StringBuilder(26);
Random random = new Random();

char c = chars[random.nextInt(chars.length)];
sb.append(c);
final String output = sb.toString();
    show_random.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            letters.setText(output); //only shows one time and when I click again it's not udapting
        }
    });

How do I get random character in every button click?

Answer 1

Just place generation of a random character inside the onClick() function.

 char[] chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
 StringBuilder sb = new StringBuilder(26);
 Random random = new Random();

 show_random.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        char c = chars[random.nextInt(chars.length)];
        sb.append(c);
        final String output = sb.toString();
        letters.setText(output); 
    }
});

If you want just a single character then do next:

    show_random.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        char c = chars[random.nextInt(chars.length)];
        letters.setText(Character.toString(c)); 
    }
});

You don't need StringBuilder in this code if you just want to randomly set one character.