小编Biu*_*Biu的帖子

请在这件事上给予我帮助。我创建了一个进度条，并在应用程序启动后每隔 100 毫秒以编程方式更新其进度（是的，这听起来很奇怪，但只是为了搞乱目的）。但每次运行它时，我都会收到 NullPointerException。有人可以帮我解决这个问题吗？日志表明 NullPointerException 发生在“custom_handler.sendMessage(message);”处 在下面。太感谢了。

private Handler custom_handler, main_handler;
private int progress = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //TextView to display the
    text_view = (TextView)findViewById(R.id.text_view); progress

    progress_bar = (ProgressBar)findViewById(R.id.progress_bar);

    //Instantiate a new worker thread
    //but somehow its handler is not instantiated
    //by the time the compiler reaches the "custom_handler.sendMessage(message);"
    //at all, keep getting NullPointerException
    //please look at the comment below the next code block.
    new MyThread().start();

    main_handler = new Handler(Looper.getMainLooper()) {
        public void handleMessage(Message …