将 Parse.Query 中的对象分配给全局变量

Question

我正在尝试通过解析访问查询中的变量，但它在查询完成时被销毁。正如您在下面的代码中看到的，我将它输出到控制台并且它确实有效，但是如果我尝试将它分配给一个变量然后使用它 returns 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，您的问题似乎是您运行一个异步查询并试图在该查询返回之前访问该变量。

以下是如何设置代码以延迟使用变量，直到您可以合理地确定您有实际使用的值：

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...
    }
}

将 Parse.Query 中的对象分配给全局变量

Assigning an object from Parse.Query to a global variable

java

variables

android

object

parse-platform