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Volley—简单迅捷的Android网络模块范例

2014-6-20 10:55| 发布者: joejoe0332| 查看: 6384| 评论: 0|原作者: zerob13|来自: 伯乐在线

摘要: olley 是一个提供给 Android 应用非常易用的网络库，更好的是这个库还加快了网络访问速度。本文会总览Volley库的主要功能，包括工作原理、常见工作模式以及如何使用该库从网络上并行加载缩略图到应用ListView中的流 ...

第五步： 在 activity_main.xml 中添加一个 ListView

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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity">
 
    <ListView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/listView"
            android:layout_alignParentTop="true" android:layout_alignParentLeft="true"/>
</RelativeLayout>


第六步： 为 ListView 的行布局新建一个“row_listview.xml”

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<?xml version="1.0" encoding="utf-8"?>
 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="100dp">
 
    <TextView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:text="Large Text"
            android:id="@+id/txtTitle" android:layout_gravity="left|center_vertical"/>
    <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceMedium"
            android:text="Medium Text"
            android:id="@+id/txtDesc" android:layout_gravity="left|center_vertical" android:textColor="#929292"
            android:minLines="2" android:ellipsize="end" android:maxLines="2"/>
    <TextView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:text="Small Text"
            android:id="@+id/txtDate" android:layout_gravity="left|center_vertical" android:textColor="#d6d6d6"/>
</LinearLayout>


第七步： 把如下代码添加到 MainActivity.java 文件中
通过 Volley 去请求网络需要分三步。
1、通过 Volley 类来新建一个新的请求队列：

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private RequestQueue mRequestQueue;
.
.
.
mRequestQueue = Volley.newRequestQueue(this);


2、新建一个 JsonObjectRequest 对象，并且设置好各项具体参数，比如url、http method以及监听结果的listeners

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JsonObjectRequest jr = new JsonObjectRequest(Request.Method.GET,url,null,new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
                Log.i(TAG,response.toString());
                parseJSON(response);
                va.notifyDataSetChanged();
                pd.dismiss();
;            }
        },new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.i(TAG,error.getMessage());
            }
        });


3、将JsonObjectRequest添加到 JsonObjectRequest中：

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mRequestQueue.add(jr);

下面的代码是带有Adapter，以及Model的完整代码，为了方便阅读我把所有的类都放到了一个Java文件中。

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package com.kpbird.volleytest;
 
import android.app.ProgressDialog;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.Volley;
import org.json.JSONArray;
import org.json.JSONObject;
 
import java.util.ArrayList;
 
public class MainActivity extends Activity {
 
    private String TAG = this.getClass().getSimpleName();
    private ListView lstView;
    private RequestQueue mRequestQueue;
    private ArrayList<NewsModel> arrNews ;
    private LayoutInflater lf;
    private VolleyAdapter va;
    private ProgressDialog pd;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lf = LayoutInflater.from(this);
 
 
        arrNews = new ArrayList<NewsModel>();
        va = new VolleyAdapter();
 
        lstView = (ListView) findViewById(R.id.listView);
        lstView.setAdapter(va);
        mRequestQueue =  Volley.newRequestQueue(this);
        String url = "http://pipes.yahooapis.com/pipes/pipe.run?_id=giWz8Vc33BG6rQEQo_NLYQ&_render=json";
        pd = ProgressDialog.show(this,"Please Wait...","Please Wait...");
        try{
            Thread.sleep(2000);
        }catch(Exception e){
 
            }
        JsonObjectRequest jr = new JsonObjectRequest(Request.Method.GET,url,null,new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
                Log.i(TAG,response.toString());
                parseJSON(response);
                va.notifyDataSetChanged();
                pd.dismiss();
;            }
        },new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.i(TAG,error.getMessage());
            }
        });
        mRequestQueue.add(jr);
 
 
 
    }
 
    private void parseJSON(JSONObject json){
        try{
            JSONObject value = json.getJSONObject("value");
            JSONArray items = value.getJSONArray("items");
            for(int i=0;i<items.length();i++){
 
                    JSONObject item = items.getJSONObject(i);
                    NewsModel nm = new NewsModel();
                    nm.setTitle(item.optString("title"));
                    nm.setDescription(item.optString("description"));
                    nm.setLink(item.optString("link"));
                    nm.setPubDate(item.optString("pubDate"));
                    arrNews.add(nm);
            }
        }
        catch(Exception e){
            e.printStackTrace();
        }
 
 
    }
 
 
    class NewsModel{
        private String title;
        private String link;
        private String description;
        private String pubDate;
 
        void setTitle(String title) {
            this.title = title;
        }
 
        void setLink(String link) {
            this.link = link;
        }
 
        void setDescription(String description) {
            this.description = description;
        }
 
        void setPubDate(String pubDate) {
            this.pubDate = pubDate;
        }
 
        String getLink() {
            return link;
        }
 
        String getDescription() {
            return description;
        }
 
        String getPubDate() {
            return pubDate;
        }
 
        String getTitle() {
 
            return title;
        }
    }
 
 
    class VolleyAdapter extends BaseAdapter{
 
        @Override
        public int getCount() {
            return arrNews.size();
        }
 
        @Override
        public Object getItem(int i) {
            return arrNews.get(i);
        }
 
        @Override
        public long getItemId(int i) {
            return 0;
        }
 
        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {
            ViewHolder vh ;
           if(view == null){
               vh = new ViewHolder();
               view = lf.inflate(R.layout.row_listview,null);
               vh.tvTitle = (TextView) view.findViewById(R.id.txtTitle);
               vh.tvDesc = (TextView) view.findViewById(R.id.txtDesc);
               vh.tvDate = (TextView) view.findViewById(R.id.txtDate);
               view.setTag(vh);
          }
            else{
               vh = (ViewHolder) view.getTag();
           }
 
            NewsModel nm = arrNews.get(i);
            vh.tvTitle.setText(nm.getTitle());
            vh.tvDesc.setText(nm.getDescription());
            vh.tvDate.setText(nm.getPubDate());
            return view;
        }
 
         class  ViewHolder{
            TextView tvTitle;
             TextView tvDesc;
             TextView tvDate;
 
        }
 
    }
}

你也可以从 Github 上获取完整代码： https://github.com/kpbird/volley-example


原文链接： kpbird   翻译： 伯乐在线 - zerob13
译文链接： http://blog.jobbole.com/71078/
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