我如何在Android的onResponse之外使用变量？ [英] How do i use a variable outside the onResponse in Android?

问题描述

我创建了一个活动，将一些记录插入到mysql数据库中。我声明了一个名为 lastInsertId 的全局变量。当我尝试 println onResponse 方法中的变量时，可以正常工作，但是当我尝试 println 在方法外返回 null 。我需要在方法之外使用这个变量。可以做什么？
这里是我的代码：

I have created an activity in which i insert some records into a mysql database. I declared a global variable named lastInsertId. When i try to println the variable inside the onResponse method, works fine but when i try to println outside the method returns null. I need to use this variable also outside the method. What can be done? Here is my code:

String insertUrl = "http://localhost/file.php";
String lastInsertId;

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

    RequestQueue requestQueue = Volley.newRequestQueue(getApplicationContext());

    StringRequest request = new StringRequest(Request.Method.POST, insertUrl, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            lastInsertId = response.toString();
            System.out.println(lastInsertId); // returns the lastInsertId
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {

        }
    }) {

        @Override
        protected Map<String, String> getParams() throws AuthFailureError {
            Map<String, String> parameters = new HashMap<String, String>();

            // parameters

            return parameters;
        }
    };
    requestQueue.add(request);
    System.out.println(lastInsertId); // get's null
}

谢谢！

Thanks!

推荐答案

我弄明白了。大约一年后我回答了这个问题，因为我看到这个帖子有几百个访问者。希望我的回答能够帮助其他功能访问者从onResponse方法获取数据。这里是代码：

I figure it out. I answered this question after about a year, beacuse i saw that this post had a few hundred visitor. Hope my answer will help other feature visitors to get data out from onResponse method. Here is the code:

String insertUrl = "http://localhost/file.php";
String lastInsertId;

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

    RequestQueue requestQueue = Volley.newRequestQueue(getApplicationContext());

    StringRequest request = new StringRequest(Request.Method.POST, insertUrl, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            lastInsertId = response.toString();
            System.out.println(lastInsertId); // returns the lastInsertId
            callback.onSuccess(lastInsertId);
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {

        }
    }) {

        @Override
        protected Map<String, String> getParams() throws AuthFailureError {
            Map<String, String> parameters = new HashMap<String, String>();

            // parameters

            return parameters;
        }
    };
    requestQueue.add(request);
}

public interface VolleyCallback{
    void onSuccess(ArrayList<Data> dataArrayList);
}

这是我们在Activity中需要的代码。

And this is the code we need inside the Activity.

public void onResume(){
    super.onResume();
    getString(new VolleyCallback(){
        @Override
        public void onSuccess(String result){
            System.out.println(result); // returns the value of lastInsertId
        }
    });
}

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