java - Toast 在调用方法之前运行

Question

我有以下代码来获取整数数据计数。getData(NewsSettings) 方法返回 3。当我单击该按钮时，应用程序显示未找到新新闻.

为什么它在 getData 之前运行 toast？

已更新

我添加了完整的 onCreate 和 getData 方法。当我运行时，它显示 No new news found 然后是 Inside Response 然后是 Data count = 3

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_profile);
    assert getSupportActionBar() != null;
    getSupportActionBar().setTitle(R.string.action_profile);

    pref = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());

    Button button = (Button) findViewById(R.id.buttonBuilder);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            newsSettings = new NewsSettings();
            newsSettings.setPreferredCity(pref.getString("prefCity", ""));
            int dataCount = getData(newsSettings);
            if(dataCount > 0)
                Toast.makeText(getApplicationContext(), dataCount + " new news found", Toast.LENGTH_SHORT).show();
            else
                Toast.makeText(getApplicationContext(), "No new news found", Toast.LENGTH_SHORT).show();
        }
    });
}

private int getData(NewsSettings newsSettings) {
    final int[] data = {0};

    RequestInterface requestInterface = RequestHelper.getInstance().getRequest();

    ServerRequest request = new ServerRequest();
    request.setOperation("dataCount");
    request.setNewsSettings(newsSettings);

    Call <ServerResponse> response = requestInterface.operation(request);

    response.enqueue(new Callback <ServerResponse>() {
        @Override
        public void onResponse(Call <ServerResponse> call,
                               retrofit2.Response <ServerResponse> response) {
            ServerResponse resp = response.body();
            Toast.makeText(getApplicationContext(), "Inside Response", Toast.LENGTH_SHORT).show();

            if(resp.getResult().equals(Constants.SUCCESS)) {
                data[0] = resp.getNewsSettings().getDataCount();
                Toast.makeText(getApplicationContext(), "Data count = " + data[0], Toast.LENGTH_LONG).show();
            }
        }

        @Override
        public void onFailure(Call <ServerResponse> call, Throwable t) {
            Log.d(Constants.TAG,"failed");
            Toast.makeText(getApplicationContext(), t.getLocalizedMessage(), Toast.LENGTH_LONG).show();
        }
    });
    return data[0];
}

Answer 1

它返回正确的值，即小于或等于 0。为什么？因为，当您单击按钮时，它会调用 getData() 方法，该方法包含 Retrofit 的异步网络调用方法。其中 data[0] 变量在调用 get onResponse() 方法后被填充值。

因此，与此同时，程序光标完成了它的第一次执行，该执行是在您单击某个按钮时开始的。

您可以像这样修改您的代码。

@Override
protected void onCreate(Bundle savedInstanceState) {
  ....
  ....

  button.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
       newsSettings = new NewsSettings();
       newsSettings.setPreferredCity(pref.getString("prefCity", ""));

       /** here is the modification **/
       getData(newsSettings);
  }

}

并在您的 getData() 方法中删除 int 返回类型并使用 void

private void getData(NewsSettings newsSettings) {  // remove int return type

   .....
   .....

   response.enqueue(new Callback <ServerResponse>() {
      @Override
      public void onResponse(Call <ServerResponse> call,
                           retrofit2.Response <ServerResponse> response) {
          ServerResponse resp = response.body();
          Toast.makeText(getApplicationContext(), "Inside Response", Toast.LENGTH_SHORT).show();

          if(resp.getResult().equals(Constants.SUCCESS)) {
              data[0] = resp.getNewsSettings().getDataCount();

           /** here is the modification ***/
              displayDataCount(data[0]);  // call to displayCount() method

              Toast.makeText(getApplicationContext(), "Data count = " + data[0], Toast.LENGTH_LONG).show();
          }
      }

      @Override
      public void onFailure(Call <ServerResponse> call, Throwable t) {
          Log.d(Constants.TAG,"failed");
          Toast.makeText(getApplicationContext(), t.getLocalizedMessage(), Toast.LENGTH_LONG).show();
      }
  });

}

然后像这样创建另一个名为 displayDataCount() 的方法，您可以在其中显示数据计数

private void displayDataCount(int dataCount) {
   if(dataCount > 0)
      Toast.makeText(getApplicationContext(), dataCount + " new news found", Toast.LENGTH_SHORT).show();
   else
      Toast.makeText(getApplicationContext(), "No new news found", Toast.LENGTH_SHORT).show();

}