Android working with Volley Library

Volley提供了优美的框架,使得Android应用程序网络访问更容易和更快。Volley抽象实现了底层的HTTP Client库,让你不关注HTTP Client细节,专注于写出更加漂亮、干净的RESTful HTTP请求。另外,Volley请求会异步执行,不阻挡主线程。

Volley提供的功能

简单的讲,提供了如下主要的功能:

1、封装了的异步的RESTful 请求API;

2、一个优雅和稳健的请求队列;

3、一个可扩展的架构,它使开发人员能够实现自定义的请求和响应处理机制;

4、能够使用外部HTTP Client库;

5、缓存策略;

6、自定义的网络图像加载视图(NetworkImageView,ImageLoader等);

 

为什么使用异步HTTP请求?

Android中要求HTTP请求异步执行,如果在主线程执行HTTP请求,可能会抛出android.os.NetworkOnMainThreadException  异常。阻塞主线程有一些严重的后果,它阻碍UI渲染,用户体验不流畅,它可能会导致可怕的ANR(Application Not Responding)。要避免这些陷阱,作为一个开发者,应该始终确保HTTP请求是在一个不同的线程。

 

怎样使用Volley

这篇博客将会详细的介绍在应用程程中怎么使用volley,它将包括一下几方面:

1、安装和使用Volley库

2、使用请求队列

3、异步的JSON、String请求

4、取消请求

5、重试失败的请求,自定义请求超时

6、设置请求头(HTTP headers)

7、使用Cookies

8、错误处理

安装和使用Volley库

引入Volley非常简单,首先,从git库先克隆一个下来:

git clone https://android.googlesource.com/platform/frameworks/volley

然后编译为jar包,再把jar包放到自己的工程的libs目录。

 

Creating Volley Singleton class

import info.androidhive.volleyexamples.volley.utils.LruBitmapCache;
import android.app.Application;
import android.text.TextUtils;
 
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.Volley;
 
public class AppController extends Application {
 
    public static final String TAG = AppController.class
            .getSimpleName();
 
    private RequestQueue mRequestQueue;
    private ImageLoader mImageLoader;
 
    private static AppController mInstance;
 
    @Override
    public void onCreate() {
        super.onCreate();
        mInstance = this;
    }
 
    public static synchronized AppController getInstance() {
        return mInstance;
    }
 
    public RequestQueue getRequestQueue() {
        if (mRequestQueue == null) {
            mRequestQueue = Volley.newRequestQueue(getApplicationContext());
        }
 
        return mRequestQueue;
    }
 
    public ImageLoader getImageLoader() {
        getRequestQueue();
        if (mImageLoader == null) {
            mImageLoader = new ImageLoader(this.mRequestQueue,
                    new LruBitmapCache());
        }
        return this.mImageLoader;
    }
 
    public <T> void addToRequestQueue(Request<T> req, String tag) {
        // set the default tag if tag is empty
        req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
        getRequestQueue().add(req);
    }
 
    public <T> void addToRequestQueue(Request<T> req) {
        req.setTag(TAG);
        getRequestQueue().add(req);
    }
 
    public void cancelPendingRequests(Object tag) {
        if (mRequestQueue != null) {
            mRequestQueue.cancelAll(tag);
        }
    }
}

 

 

1、Making json object request

String url = "";
         
ProgressDialog pDialog = new ProgressDialog(this);
pDialog.setMessage("Loading...");
pDialog.show();     
         
        JsonObjectRequest jsonObjReq = new JsonObjectRequest(Method.GET,
                url, null,
                new Response.Listener<JSONObject>() {
 
                    @Override
                    public void onResponse(JSONObject response) {
                        Log.d(TAG, response.toString());
                        pDialog.hide();
                    }
                }, new Response.ErrorListener() {
 
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        VolleyLog.d(TAG, "Error: " + error.getMessage());
                        // hide the progress dialog
                        pDialog.hide();
                    }
                });
 
// Adding request to request queue
AppController.getInstance().addToRequestQueue(jsonObjReq, tag_json_obj);

 

2、Making json array request

// Tag used to cancel the request
String tag_json_arry = "json_array_req";
 
String url = "http://api.androidhive.info/volley/person_array.json";
         
ProgressDialog pDialog = new ProgressDialog(this);
pDialog.setMessage("Loading...");
pDialog.show();     
         
JsonArrayRequest req = new JsonArrayRequest(url,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        Log.d(TAG, response.toString());        
                        pDialog.hide();             
                    }
                }, new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        VolleyLog.d(TAG, "Error: " + error.getMessage());
                        pDialog.hide();
                    }
                });
 
// Adding request to request queue
AppController.getInstance().addToRequestQueue(req, tag_json_arry);

 

3、Making String request

// Tag used to cancel the request
String  tag_string_req = "string_req";
 
String url = "http://api.androidhive.info/volley/string_response.html";
         
ProgressDialog pDialog = new ProgressDialog(this);
pDialog.setMessage("Loading...");
pDialog.show();     
         
StringRequest strReq = new StringRequest(Method.GET,
                url, new Response.Listener<String>() {
 
                    @Override
                    public void onResponse(String response) {
                        Log.d(TAG, response.toString());
                        pDialog.hide();
 
                    }
                }, new Response.ErrorListener() {
 
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        VolleyLog.d(TAG, "Error: " + error.getMessage());
                        pDialog.hide();
                    }
                });
 
// Adding request to request queue
AppController.getInstance().addToRequestQueue(strReq, tag_string_req);

 

4、Adding post parameters

// Tag used to cancel the request
String tag_json_obj = "json_obj_req";
 
String url = "http://api.androidhive.info/volley/person_object.json";
         
ProgressDialog pDialog = new ProgressDialog(this);
pDialog.setMessage("Loading...");
pDialog.show();     
         
        JsonObjectRequest jsonObjReq = new JsonObjectRequest(Method.POST,
                url, null,
                new Response.Listener<JSONObject>() {
 
                    @Override
                    public void onResponse(JSONObject response) {
                        Log.d(TAG, response.toString());
                        pDialog.hide();
                    }
                }, new Response.ErrorListener() {
 
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        VolleyLog.d(TAG, "Error: " + error.getMessage());
                        pDialog.hide();
                    }
                }) {
 
            @Override
            protected Map<String, String> getParams() {
                Map<String, String> params = new HashMap<String, String>();
                params.put("name", "Androidhive");
                params.put("email", "abc@androidhive.info");
                params.put("password", "password123");
 
                return params;
            }
 
        };
 
// Adding request to request queue
AppController.getInstance().addToRequestQueue(jsonObjReq, tag_json_obj);

 

5、Adding request headers

// Tag used to cancel the request
String tag_json_obj = "json_obj_req";
 
String url = "http://api.androidhive.info/volley/person_object.json";
         
ProgressDialog pDialog = new ProgressDialog(this);
pDialog.setMessage("Loading...");
pDialog.show();     
         
        JsonObjectRequest jsonObjReq = new JsonObjectRequest(Method.POST,
                url, null,
                new Response.Listener<JSONObject>() {
 
                    @Override
                    public void onResponse(JSONObject response) {
                        Log.d(TAG, response.toString());
                        pDialog.hide();
                    }
                }, new Response.ErrorListener() {
 
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        VolleyLog.d(TAG, "Error: " + error.getMessage());
                        pDialog.hide();
                    }
                }) {
 
            /**
             * Passing some request headers
             * */
            @Override
            public Map<String, String> getHeaders() throws AuthFailureError {
                HashMap<String, String> headers = new HashMap<String, String>();
                headers.put("Content-Type", "application/json");
                headers.put("apiKey", "xxxxxxxxxxxxxxx");
                return headers;
            }
 
        };
 
// Adding request to request queue
AppController.getInstance().addToRequestQueue(jsonObjReq, tag_json_obj);

 

 

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Android working with Volley Library

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