public class MainActivity extends Activity {

        Handler handler;
        TextView tvTest;
        int cnt = 0;

        @Override
        protected void onCreate(Bundle savedInstanceState) {

                super.onCreate(savedInstanceState);
                setContentView(R.layout.main);

                tvTest = (TextView) findViewById(R.id.tvTest);

                handler = new MyHandler(this);
                handler.sendEmptyMessageDelayed(0, 1000);
        }

        void someMethod() {
                tvTest.setText("Count = " + cnt++);
                handler.sendEmptyMessageDelayed(0, 1000);
        }

        @Override
        protected void onDestroy() {
                if (handler != null)
                        handler.removeCallbacksAndMessages(null);
                super.onDestroy();
        }

        static class MyHandler extends Handler {

                WeakReference<MainActivity> wrActivity;

                public MyHandler(MainActivity activity) {
                        wrActivity = new WeakReference<MainActivity>(activity);
                }

                @Override
                public void handleMessage(Message msg) {
                        super.handleMessage(msg);
                        MainActivity activity = wrActivity.get();
                        if (activity != null)
                                activity.someMethod();
                }
        }
}