setBackgroundResource doesn't set the image

Question

    Handler hnd = new Handler() {

    @Override
    public void handleMessage(Message msg) {

        int id = sequence.get(msg.arg1);

        if(msg.arg1 % 2 == 0         


        

Answer 1

Because the resource changes in the UI thread and you are sleeping your background thread. The UI thread is running normally. Use handlers:

public class MainActivity extends Activity {

Button b;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    b = (Button) findViewById(R.id.button1);
}
Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg) {

        if (msg.arg1 % 2 == 0) {
            b.setBackgroundResource(R.drawable.analytic_icon);
        } else {
            b.setBackgroundResource(R.drawable.ic_launcher);
        }
    }
};

@Override
public void onResume() {
    super.onResume();

    Thread background = new Thread(new Runnable() {
        public void run() {
            try {
                for (int i = 0; i < 20; i++) { 
                    Thread.sleep(2000);
                    Message msg = handler.obtainMessage(); 
                    msg.arg1 = i;
                    msg.sendToTarget();
                }
            } catch (Throwable t) {
                // just end the background thread
            }
        }
    });

    background.start();
}
}