如何改变Fragment的TextView内容

public class MainActivity extends Activity {

private int index;
private TextView mTextView;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mTextView = new TextView(this);
setContentView(mTextView);
new DataThread().start();
}

private String getWebData() {
return String.valueOf(++index);
}

private Handler mHandler = new Handler() {
public void handleMessage(android.os.Message msg) {
mTextView.setText((String)msg.obj);
};
};

private class DataThread extends Thread {
@Override
public void run() {

for(int i = 0; i < 4; i++) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}

final String data = getWebData();
// 只能在主线程中修改ui控件
mHandler.sendMessage(mHandler.obtainMessage(0, data));
}
}
}
}