Toast在調用方法之前運行

Question

我有以下代碼來獲取整數數據計數。 getData(NewsSettings)方法返回3.當我點擊按鈕，應用程序顯示我No new news found。

爲什麼它在getData之前運行敬酒？

修訂

我已經加入了完整的onCreate和getData方法。當我運行，它讓我No new news found然後Inside Response然後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

它返回正確的值，即小於或等於0.爲什麼？因爲，當你點擊按鈕時，它會調用getData()方法，其中包含一個異步網絡調用方法Retrofit。其中data[0]變量會在您調用onResponse()方法後獲得值。

因此，同時程序遊標完成了它的第一次執行，當你點擊某個按鈕時，遊標就開始執行。

你可以像這樣修改你的代碼。

@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); 
    } 

} 

而在你getData()方法刪除int返回類型和使用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(); 
     } 
    }); 

} 

並創建一個名爲displayDataCount()這樣，您可以顯示數據統計

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(); 

} 

Answer 2

確保如果返回值dataCount是greater than 0。調試它或刪除if-else，並使用單個makeToast方法顯示dataCount。