尝试在MainActivity外部更新UI元素

Handler handler = new Handler(Looper.getMainLooper());
handler.post(new Runnable() {
    @Override
    public void run() {
        // 在此处进行UI元素的更新操作
    }
});

BroadcastReceiver receiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        // 在此处进行UI元素的更新操作
    }
};

@Override
protected void onResume() {
    super.onResume();
    IntentFilter filter = new IntentFilter("com.example.ACTION_UPDATE_UI");
    registerReceiver(receiver, filter);
}

@Override
protected void onPause() {
    super.onPause();
    unregisterReceiver(receiver);
}

Intent intent = new Intent("com.example.ACTION_UPDATE_UI");
sendBroadcast(intent);

public interface UIUpdateListener {
    void updateUI();
}

public class MainActivity extends AppCompatActivity implements UIUpdateListener {
    // ...

    @Override
    public void updateUI() {
        // 在此处进行UI元素的更新操作
    }
}

UIUpdateListener listener = (UIUpdateListener) mainActivity;
listener.updateUI();