How do I update a TextView without causing the app to crash?

Question

In a certain Activity have a TextView variable named timeText, which needs to be changed after 3 seconds have passed after the Activity was opened.

This is the code I wrote:

TextView timeText = (TextView) findViewById(R.id.tvTimeText);
Thread timer = new Thread() {
        public void run() {
            try {
                sleep(3000);
                timeText.setText("3");
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
};
timer.start();

However this gave me this error: "Cannot refer to a non-final variable timeText inside an inner class defined in a different method"

So I changed the modifier of the TextView to final and tried again. However, now the application crashes when this activity is started.

Answer 1

Cannot update ui from a non ui thrad

 timeText.setText("3");

Use runOnUiThread or Handler.

runOnUiThread(new Runnable() {

        public void run() {
            timeText.setText("3");

        }
    });

You can declare timeText as a instance variable and you need not have final modifier.

TextView timerText;
protectected void onCreate(Bundle savedInstanceState)
{
  super.onCreate(savedInstanceState);
  setContentView(R.layout.mylayout);
  timeText = (TextView) findViewById(R.id.tvTimeText);

Answer 2

Use a handler and a runnable:

final Runnable runnable = new Runnable() {
    public void run() {
        timeText.setText("3");        
    }
};

Handler handler = new Handler();
handler.postDelayed(runnable , 3000);