从Parse.Query分配一个对象到一个全局变量

Question

我试图从解析中访问一个查询内部的一个查询，但是当查询结束时它会被销毁。正如你在下面的代码中看到的那样，我将它输出到控制台，它确实有效，但是如果我尝试将它分配给一个变量，然后使用它，它将返回null。任何帮助，将不胜感激。

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，你的问题似乎是你正在运行一个异步查询，并试图在查询返回之前访问该变量。

下面是你可以设置你的代码中使用的变量推迟，直到你可以确信你有一个值，实际使用：

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... 
    } 
}