Android Volley framework (I), androidvolley

Android Volley framework (I), androidvolley
Use of the Android Volley framework (1)

As this part contains a lot of content, I plan to write it into several parts. This article mainly introduces the basic use of the Volley framework as a whole;

Why use the Volley framework?

Network operations are often required to develop android applications. The Android SDK providesHttpClientAndHttpUrlConnectionThe two methods are used to process network operations, but when the application is complicated, we need to write a lot of code to process a lot of things: Image caching, request scheduling, and so on;

The Volley framework was born to solve these problems. It was proposed at the Google I/O conference in 2013: Making network operations for Android applications more convenient and convenient; abstract implementation details such as the underlying Http Client, allowing developers to focus more on and generate RESTful requests. In addition, Volley asynchronously executes all requests on different threads to avoid blocking the main thread.

What are the characteristics of Volley?

• Automatically schedule network requests
• Multiple concurrent Network Connections
• Use the standard HTTP cache mechanism to ensure the disk and memory response are consistent.
• Supported Request priority
• Supports powerful APIs for canceling requests. You can cancel a single request or multiple APIs.
• Easy to customize
• Robustness: easy to correctly update the UI and obtain data
• Debugging and tracing tools

How to Use Volley

Obtain Volley:
-Git cloneHttps://android.googlesource.com/platform/frameworks/volley
Or https://github.com/mcxiaoke/android-volley
You can also download volley. jar directly.
-If you useGit cloneTo generatevoller.jarRun the following command in the volley directory:

android update project -pant jar

Add Volley to the project:
-Setvolley.jarPaste inlibsFolder, right-clickvolley.jarFile, selectAdd as Library

RequestQueue and Request in Volley

It is not difficult to see the literal meaning.

• RequestQueueRequest queue used to execute requests
• RequestUsed to construct a request object
• Request objectThere are mainly the following types:
  
  • StringRequestThe response body is a string
  • JsonArrayRequestJSON array for sending and receiving
  • JsonObjectRequestSend and receive JSON objects
  • ImageRequestSend and receive images

Basic use of Volley

First, we need to createRequestQueue reqQueueAnd then buildXXRequest req, And then passreqQueue.add(req); Add the request to the Request queue;

Build RequestQueue

RequestQueue requestQueue = Volley. newRequestQueue (this); // here this refers to Context

Create Request(Take JsonObjectRequest as an example)

Private final String url = "http://www.xxx.com/person.json" // required url JsonObjectRequest req = new JsonObjectRequest (url, null, new Response. listener <JsonObject> () {@ Override public void onResponse (JsonObject response) {// Add your own response logic, }}, new ResponseError. listener () {@ Override public void onResponseError (VollerError error) {// handle the error Log. d ("Error Message:", "Error is" + error );}});

Add request to requestQueue

    requestQueue.add(req);

In buildingJsonObjectRequestFour parameters are required.

JsonObjectRequest req = new JsonObjectRequest (String url, Request. Method. GET (or POST), new Response. Listener (), new ResponseError. Listener ()),

The second parameter indicates the http method. The third and fourth parameters are the response listener and the response error listener, which must be overwritten respectively.onResponse()AndonResponseError()Method;RequestQueueThe request will be executed and the response callback will be made.onResponse()Method, so you need to implement your own business logic in the onResponse () method;

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