从 volley onResponse 获取返回值答案

【问题标题】：Getting a return value from volley onResponse从 volley onResponse 获取返回值
【发布时间】：2016-06-15 15:15:08
【问题描述】：

我正在尝试制作我的第一个真正的程序，所以请放轻松。这部分使用 Google API 和 volley 将输入的邮政编码转换为 lat/lng 坐标，但我不知道如何让 volley 函数“返回”坐标。根据我的阅读，我需要实现一些回调方法，但我不知道该怎么做。

    //Converts values in TextView to String
    locationurl = address.getText().toString();

    //RequestQueue Variable
    RequestQueue mRequestQueue;

    // Instantiate the cache and set up the network to use HttpURLConnection as the HTTP client.
    Cache cache = new DiskBasedCache(getCacheDir(), 1024 * 1024); // 1MB cap
    BasicNetwork network = new BasicNetwork(new HurlStack());

    //Instantiate the RequestQueue with the cache and network
    mRequestQueue = new RequestQueue(cache, network);

    //Start Queue
    mRequestQueue.start();

    String addressurl = "http://maps.googleapis.com/maps/api/geocode/json?address=" + location;

    //Formulate the request and handle the response
    StringRequest address = new StringRequest(Request.Method.GET, addressurl,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    coordinates = parseLocation(response);
                    if((coordinates == null && coordinates.isEmpty())||coordinates.equals("NOT_VALID_ADDRESS")) {
                        showAlert("Please Enter A Valid Zip Code");
                    } else {

                    }
                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    showAlert("Error."); //Error code display
                    //TODO: fix error handling
        }
    });
    mRequestQueue.add(address); //Add address to ResponseQueue

【问题讨论】：

new Response.Listener<String>() 是回调

标签： java android json android-volley

【解决方案1】：

将您的onResponse 方法更改为：

@Override
public void onResponse(String response) {
    coordinates = parseLocation(response);
    if((coordinates == null && coordinates.isEmpty())||coordinates.equals("NOT_VALID_ADDRESS")) {
        showAlert("Please Enter A Valid Zip Code");
    } else {
        useCoordinates(coordinates);
    }
}

然后实现使用坐标的方法：

public void useCoordinates(Location coordinates) {
    // Use the value
}

【讨论】：

【解决方案2】：

我想你想做这样的事情：

这将是你的回调类：(NetworkResponse.java)

public abstract class NetworkResponse<T> implements Response.Listener<T>, Response.ErrorListener {


    @Override
    public void onResponse(T t) {
        String coordinates = parseLocation(t);
        onCoordinatesReceived(coordinates;
    }

    @Override
    public void onErrorResponse(VolleyError volleyError) {
        onCoordinatesReceived("");
        }

    public String parseLocation(T s) {
        return null;
        //Implement parsing here.
    }

    public abstract void onCoordinatesReceived(String coordinates) ;


}

并在您现有的课程中进行以下更改：

StringRequest address = new StringRequest(Request.Method.GET, addressurl,
        new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                coordinates = parseLocation(response);
                if((coordinates == null && coordinates.isEmpty())||coordinates.equals("NOT_VALID_ADDRESS")) {
                    showAlert("Please Enter A Valid Zip Code");
                } else {

                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                showAlert("Error."); //Error code display
                //TODO: fix error handling
    }
});
mRequestQueue.add(address); //Add address to ResponseQueue

---到---

  NetworkResponse<String> networkResponse =
                      new NetworkResponse<>() {
                          @Override
                          public void onCoordinatesReceived(String coordinates){
//Here are your coordinates.
                        if((coordinates == null && coordinates.isEmpty())||coordinates.equals("NOT_VALID_ADDRESS")) {
                        showAlert("Please Enter A Valid Zip Code");
                      else {
                        //Your implementation here.
                           }
}
        StringRequest address = new StringRequest(Request.Method.GET, addressurl,
                networkResponse, networkResponse);
        mRequestQueue.add(address); //Add address to ResponseQueue

请注意：此处为您的回调类中的 NetworkResponse。

【讨论】：