AsyncTask加载网络Json及其解析Json---------Thread和AsyncTask加载图片2种方式

源码 http://download.csdn.net/detail/u013210620/8955435
首先看主线程布局

activity_main.xml（里面只有一个listview）

<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"
tools:context="com.example.myasynctask.MainActivity" >

<ListView
android:id="@+id/listview"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
</ListView>

</RelativeLayout>

接下来看listview中的每个条目layout(有个图片，还有一个title,一个content内容区域)

listview_item.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="4dp" >

<ImageView
android:id="@+id/iv_imageview"
android:layout_width="64dp"
android:layout_height="64dp"
android:src="@drawable/ic_launcher" />

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="26.45"
android:gravity="center"
android:orientation="vertical"
android:paddingLeft="4dp" >

<TextView
android:id="@+id/tv_title"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="title" />

<TextView
android:id="@+id/tv_content"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="content" />
</LinearLayout>

</LinearLayout>

这里先看下慕课网的json地址http://www.imooc.com/api/teacher?type=4&num=30

以及json的大概意思---只是贴出一部分

{
"status": 1,
"data": [
{
"id": 1,
"name": "Tony老师聊shell——环境变量配置文件",
"picSmall": "http://img.mukewang.com/55237dcc0001128c06000338-300-170.jpg",
"picBig": "http://img.mukewang.com/55237dcc0001128c06000338.jpg",
"description": "为你带来shell中的环境变量配置文件",
"learner": 12312
},

接下来看本地的对象

NewsBean

package com.example.myasynctask;

public class NewsBean {

public String title;
public String content;
public String imageViewUrl;
public NewsBean(String title, String content, String imageViewUrl) {
super();
this.title = title;
this.content = content;
this.imageViewUrl = imageViewUrl;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
public String getImageViewUrl() {
return imageViewUrl;
}
public void setImageViewUrl(String imageViewUrl) {
this.imageViewUrl = imageViewUrl;
}
public NewsBean() {
super();
// TODO Auto-generated constructor stub
}

}

接下来看主布局代码

MainActivity

package com.example.myasynctask;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import org.json.JSONArray;
import org.json.JSONObject;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;

public class MainActivity extends Activity {

//获取listview控件
private ListView listView;
//慕课网的Json字符串
private String jsonUrl = "http://www.imooc.com/api/teacher?type=4&num=30";
//加载Json字符串到本地，并且解析为本地对象数组
private List<NewsBean> newBeanlist;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//初始化listview控件
listView = (ListView) findViewById(R.id.listview);
//开启异步任务，传递慕课网jsonUrl进行网络异步加载任务
new MyAsyncTask().execute(jsonUrl);
}

/**
* 创建异步任务，
* 参数：慕课网的jsonHttp地址
* Void没有进度显示为Void
* 返回本地对象集合
*
*/
class MyAsyncTask extends AsyncTask<String, Void, List<NewsBean>> {

@Override
protected List<NewsBean> doInBackground(String... params) {
//构建一个方法，进行网络json字符串获取，并且解析为本地对象集合
return getJsonData(jsonUrl);
}

@Override
protected void onPreExecute() {
super.onPreExecute();
}

@Override
protected void onPostExecute(List<NewsBean> result) {
super.onPostExecute(result);
//解析完毕后，进行适配器的数据设置填充
JsonAdapter adapter = new JsonAdapter(MainActivity.this, newBeanlist);
listView.setAdapter(adapter);
}

@Override
protected void onProgressUpdate(Void... values) {

}

}

/**
* //构建一个方法，进行网络json字符串获取，并且解析为本地对象集合
* @param jsonUrl
* @return
*/
public List<NewsBean> getJsonData(String jsonUrl) {
try {
//创建url http地址
URL httpUrl = new URL(jsonUrl);
//打开http 链接
HttpURLConnection connection = (HttpURLConnection) httpUrl
.openConnection();
//设置参数  请求为get请求
connection.setReadTimeout(5000);
connection.setRequestMethod("GET");

//connection.getInputStream()得到字节输入流，InputStreamReader从字节到字符的桥梁，外加包装字符流
BufferedReader bufferedReader = new BufferedReader(
new InputStreamReader(connection.getInputStream()));
//创建字符串容器
StringBuffer sb = new StringBuffer();
String str = "";
//行读取
while ((str = bufferedReader.readLine()) != null) {
// 当读取完毕，就添加到容器中
sb.append(str);
}
//测试是否得到json字符串
Log.e("TAG", ""+sb.toString());
//创建本地对象的集合
newBeanlist = new ArrayList<NewsBean>();
// 整体是一个jsonObject
JSONObject jsonObject = new JSONObject(sb.toString());
// 键是jsonArray数组
JSONArray jsonArray = jsonObject.getJSONArray("data");
for (int i = 0; i < jsonArray.length(); i++) {
//获取jsonArray中的每个对象
JSONObject jsonObject2 = jsonArray.getJSONObject(i);
//创建本地的newsBean对象
NewsBean newsBean = new NewsBean();
//为该对象进行属性值的设置操作
newsBean.imageViewUrl = jsonObject2
.getString("picSmall");
newsBean.title = jsonObject2.getString("name");
newsBean.content = jsonObject2.getString("description");
//添加对象，组建集合
newBeanlist.add(newsBean);

}
} catch (Exception e) {
e.printStackTrace();
}
return newBeanlist;
}
}

接下来看适配器

JsonAdapter

package com.example.myasynctask;

import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

public class JsonAdapter extends BaseAdapter {

List<NewsBean> data = new ArrayList<NewsBean>();
LayoutInflater inflater;

public JsonAdapter(Context context,List<NewsBean> data) {
super();
this.data = data;
inflater = LayoutInflater.from(context);
}

@Override
public int getCount() {
return data.size();
}

@Override
public Object getItem(int position) {
return data.get(position);
}

@Override
public long getItemId(int position) {
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder = null;
if (convertView == null) {
viewHolder = new ViewHolder();
convertView = inflater.inflate(R.layout.listview_item, null);
viewHolder.title = (TextView) convertView
.findViewById(R.id.tv_title);
viewHolder.content = (TextView) convertView
.findViewById(R.id.tv_content);
viewHolder.imageView = (ImageView) convertView
.findViewById(R.id.iv_imageview);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
String imageViewUrl = data.get(position).imageViewUrl;
//进行绑定--不会出现图片错位现象--因为viewholder是复用的，会显示复用的那个itme的图片
viewHolder.imageView.setTag(imageViewUrl);

viewHolder.title.setText(data.get(position).title);
viewHolder.content.setText(data.get(position).content);
/**
* 这个方式是通过分线程进行图片下载
*/
//		new ImageLoaderThread().showImageByThread(viewHolder.imageView, data.get(position).imageViewUrl);
/**
* 这个方式是进行异步任务方式进行图片加载
*/
new ImageLoaderAsyncTask().showImageAsyncTask(viewHolder.imageView, data.get(position).imageViewUrl);
return convertView;
}

class ViewHolder{
public TextView title,content;
public ImageView imageView;
}
}

接下来看线程下载方法

ImageLoaderThread

package com.example.myasynctask;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;

public class ImageLoaderThread {
/**
* 这里设置变量的原因是 图片需要在handler里面进行判断是不是绑定了url地址，以及进行ui更新操作 url是因为绑定的那个url地址
*/
private ImageView mImageView;
private String mUrl;
/****************************************************************
* 处理handler发送过来的消息--携带bitmap
*/
private Handler handler = new Handler() {
public void handleMessage(Message msg) {
if (mImageView.getTag().equals(mUrl)) {
// 处理消息
mImageView.setImageBitmap((Bitmap) msg.obj);

}
};
};

/**
* 创建构造器，为了调用本类的方法
*/
public ImageLoaderThread() {
super();
}

/**
* @param imageView
*            图片视图
* @param url
*            图片的url地址
*/
public void showImageByThread(ImageView imageView, final String url) {
this.mImageView = imageView;
this.mUrl = url;
// 另开线程进行服务器的图片下载
new Thread() {
public void run() {
// 通过url获取图片
Bitmap bitmap = getBitmapFromUrl(url);
Message message = Message.obtain();
message.obj = bitmap;
// 通过handler发送消息
handler.sendMessage(message);
};
}.start();
}

/**
* 通过url获取网络图片
*
* @param urlString
* @return
*/
public Bitmap getBitmapFromUrl(String urlString) {
Bitmap bitmap = null;
// 字节输入流
InputStream inputStream = null;
try {
// 一系列标准化写法，设置参数之类的
URL httpUrl = new URL(urlString);
HttpURLConnection connection = (HttpURLConnection) httpUrl
.openConnection();
// 包裹下
inputStream = new BufferedInputStream(connection.getInputStream());
// 这样的方式也可以获取一个图片
bitmap = BitmapFactory.decodeStream(inputStream);
connection.disconnect();
// 返回即可
return bitmap;

} catch (Exception e) {
} finally {
try {
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return bitmap;

}

}

接下来看异步任务下载方法

ImageLoaderAsyncTask

package com.example.myasynctask;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.widget.ImageView;

public class ImageLoaderAsyncTask {

/**
* 使用异步任务进行加载图片
*
*/
public void showImageAsyncTask(ImageView imageView, final String url) {
//讲adapter传过来的imageview和url 通过构造方法传递到异步任务中
new ImageAsyncTask(imageView,url).execute(url);
}

/**
* 开启异步任务进行下载图片
* 参数：
* 是图片的地址信息
* 没有进度显示
* 返回一个图片
* @author wyf
*
*/
class ImageAsyncTask extends AsyncTask<String, Void, Bitmap> {

/**
* 这里需要设置属性的原因是
* imageview是因为需要判断是不是绑定url，以及更新ui操作
* url需要
*/
private ImageView imageView;
private String url;
public ImageAsyncTask(ImageView imageView, String url) {
super();
this.imageView = imageView;
this.url = url;
}

@Override
protected Bitmap doInBackground(String... params) {
//多留意parm[0],因为只传过来一个url，所以就取出第一个索引值
Bitmap bitmap = getBitmapFromUrl(params[0]);

return bitmap;
}

@Override
protected void onPreExecute() {
super.onPreExecute();
}

@Override
protected void onPostExecute(Bitmap bitmap) {
super.onPostExecute(bitmap);
//判断是不是绑定的特定的url地址，防止出现图篇错乱
if (imageView.getTag().equals(url)) {
//更新ui
imageView.setImageBitmap(bitmap);
}
}

@Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}

}

/**
* 通过url获取网络图片
* 跟那个线程下载图片方式一样一样的
* @param urlString
* @return
*/
public Bitmap getBitmapFromUrl(String urlString) {
Bitmap bitmap = null;
InputStream inputStream = null;
try {
URL httpUrl = new URL(urlString);
HttpURLConnection connection = (HttpURLConnection) httpUrl
.openConnection();
inputStream = new BufferedInputStream(connection.getInputStream());
bitmap = BitmapFactory.decodeStream(inputStream);
connection.disconnect();
return bitmap;

} catch (Exception e) {
} finally {
try {
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return bitmap;

}
}