從Parse.Query分配一個對象到一個全局變量

Question

我試圖從解析中訪問一個查詢內部的一個查詢，但是當查詢結束時它會被銷燬。正如你在下面的代碼中看到的那樣，我將它輸出到控制檯，它確實有效，但是如果我嘗試將它分配給一個變量，然後使用它，它將返回null。任何幫助，將不勝感激。

ParseQuery<ParseObject> query = ParseQuery.getQuery("Hospitales"); 
      query.whereEqualTo("Codigo", id); 
      query.getFirstInBackground(new GetCallback<ParseObject>() { 
       public void done(ParseObject object, ParseException e) { 
        if (object == null) { 
         Log.d("score", "The getFirst request failed."); 
        } else { 
         Log.d("id", "Retrieved the object."); 
         String status = object.getString("Hospital"); 
         m2Status = object.getString("Hospital"); 
         System.out.println("Hospital: " + status); 
         System.out.println(status + m2Status); 
        } 
       } 
      }); 

Answer 1

所以，基本上，你的問題似乎是你正在運行一個異步查詢，並試圖在查詢返回之前訪問該變量。

下面是你可以設置你的代碼中使用的變量推遲，直到你可以確信你有一個值，實際使用：

private void runQuery() { 
    ParseQuery<ParseObject> query = ParseQuery.getQuery("Hospitales"); 
    query.whereEqualTo("Codigo", id); 
    query.getFirstInBackground(new GetCallback<ParseObject>() { 
     public void done(ParseObject object, ParseException e) { 
      if (object == null) { 
       Log.d("score", "The getFirst request failed."); 
       // You don't have a good value to use, so figure 
       // out a way to handle that scenario 
      } else { 
       Log.d("id", "Retrieved the object."); 
       String status = object.getString("Hospital"); 
       m2Status = object.getString("Hospital"); 
       System.out.println("Hospital: " + status); 
       System.out.println(status + m2Status); 
       // You have a good value to use, so 
       // now you can actually use it 
       afterQueryProcessing(); 
      } 
     } 
    }); 
} 
private void afterQueryProcessing() { 
    // You can access m2Status here reliably, 
    // assuming you only call this method 
    // as shown above, but you should still 
    // use defensive programming 
    if (m2Status != null) { 
     // Now you know you have a value to use... 
    } 
}