标签：android style blog class code java
第四节(1)：异步网络操作
一、结合asyncTask下载网络图片
1.定义下载类，继承自asyncTask，参数分别为：String(url地址）,Integer（刻度，本例没有用到），BitMap（下载成功后的图片）
public class downloadImageTask extends AsyncTask<String, Integer, Bitmap> { /** * 在线程开始之前执行 */ @Override protected void onPreExecute() { // TODO Auto-generated method stub super.onPreExecute(); dialog.setTitle("提示"); dialog.setMessage("正在下载数据,请稍候..."); dialog.show(); } /** * 异步执行耗时操作 */ @Override protected Bitmap doInBackground(String... params) {} /** * 执行完成后 */ @Override protected void onPostExecute(Bitmap result) { // TODO Auto-generated method stub super.onPostExecute(result); dialog.dismiss(); image1.setImageBitmap(result); } }
2.实现doInBackground
1) 定义HttpClient和HttpGet
HttpClient client = new DefaultHttpClient(); HttpGet get = new HttpGet(params[0]); //params[0]为主线程调用时传入的url地址
2) 利用HttpResponse取得网络返回
try { HttpResponse response = client.execute(get); if (response.getStatusLine().getStatusCode() == 200) { HttpEntity entity = response.getEntity(); byte[] data = EntityUtils.toByteArray(entity); bitmap = BitmapFactory .decodeByteArray(data, 0, data.length); } // 404/500 } catch (ClientProtocolException e) { // TODO Auto-generated catch block e.printStackTrace(); Toast.makeText(MainActivity.this, "网络请求失败", Toast.LENGTH_LONG) .show(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }
3.主线程调用
// 启用多线程访问网络下载图片 new downloadImageTask() .execute("http://image.tianjimedia.com/uploadImages/2013/287/IEOV0N9V8RR7_1000x500.jpg");
二、下载网络json数据，并绑定至listview
json内容：
{ users: [ { face: "001.jpg", headShip: "软件工程师", userName: "周瑜" }, { face: "002.jpg", headShip: "开发人员", userName: "陈风" }, { face: "003.jpg", headShip: "开发人员", userName: "季炜" }, { face: "004.jpg", headShip: "开发人员", userName: "小包" }, { face: "005.jpg", headShip: "开发人员", userName: "小裴" } ] }
1.根据json格式定义User实体
package com.cmcc.utils; public class User { private String userName; private String headShip; private String face; public User() { super(); } public String getUserName() { return userName; } public void setUserName(String userName) { this.userName = userName; } public String getHeadShip() { return headShip; } public void setHeadShip(String headShip) { this.headShip = headShip; } public String getFace() { return face; } public void setFace(String face) { this.face = face; } }
2.利用asyncTask下载数据
public class getUserTask extends AsyncTask<String, Void, List<User>>{ @Override protected void onPreExecute() { // TODO Auto-generated method stub super.onPreExecute(); dialog.setTitle("提示"); dialog.setMessage("正在下载,请稍候..."); dialog.show(); } @Override protected List<User> doInBackground(String... params) { // TODO Auto-generated method stub List<User> list = new ArrayList<User>(); HttpClient client = new DefaultHttpClient(); HttpGet get = new HttpGet(params[0]); try { HttpResponse response = client.execute(get); if(response.getStatusLine().getStatusCode() == 200){ String json = EntityUtils.toString(response.getEntity()); JSONObject jsonObj = new JSONObject(json); JSONArray jsonArray = jsonObj.getJSONArray("users"); for(int i = 0;i<jsonArray.length();i++){ JSONObject obj = jsonArray.getJSONObject(i); User user = new User(); user.setUserName(obj.getString("userName")); user.setHeadShip(obj.getString("headShip")); user.setFace(obj.getString("face")); list.add(user); } } } catch (ClientProtocolException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (JSONException e) { // TODO Auto-generated catch block e.printStackTrace(); } return list; } @Override protected void onPostExecute(List<User> result) { // TODO Auto-generated method stub super.onPostExecute(result); dialog.dismiss(); myAdapter adapter = new myAdapter(result,MainActivity.this); //自定义adapter，详见下面代码 listview1.setAdapter(adapter); } }
3.自定义baseAdapter，绑定listView
public class myAdapter extends BaseAdapter{ List<User> list; Context context; LayoutInflater inflater; public myAdapter(List<User> list,Context context) { super(); this.list = list; this.context = context; inflater = LayoutInflater.from(context); } @Override public int getCount() { // TODO Auto-generated method stub return list.size(); } @Override public Object getItem(int position) { // TODO Auto-generated method stub return list.get(position); } @Override public long getItemId(int position) { // TODO Auto-generated method stub return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { // TODO Auto-generated method stub View view; if(convertView!=null){ view = convertView; }else{ view = inflater.inflate(R.layout.user, null); } final ImageView face = (ImageView) view.findViewById(R.id.face); TextView tvUserName = (TextView) view.findViewById(R.id.tvUserName); TextView tvHeadShip = (TextView) view.findViewById(R.id.tvHeadShip); tvUserName.setText(list.get(position).getUserName()); tvHeadShip.setText(list.get(position).getHeadShip()); //头像下载，实现类详见后面代码 String imageUrl = "http://xxx.xxxx.xxxx/resources/face/"+list.get(position).getFace(); DownloadFace download = new DownloadFace(imageUrl); download.loadImageFromUrl(new downloadFaceCallBack() { @Override public void setDrawble(Drawable drawable) { // TODO Auto-generated method stub face.setImageDrawable(drawable); } }); return view; } }
三、ListView中异步下载头像
下载头像线程类
package com.cmcc.utils; import java.io.IOException; import java.net.MalformedURLException; import java.net.URL; import android.R.drawable; import android.annotation.SuppressLint; import android.graphics.drawable.Drawable; import android.os.Handler; import android.os.Message; public class DownloadFace { String faceUrl; public DownloadFace(String faceUrl) { super(); this.faceUrl = faceUrl; } @SuppressLint("HandlerLeak") public void loadImageFromUrl(final downloadFaceCallBack callback) { final Handler handler = new Handler(){ @Override public void handleMessage(Message msg) { // TODO Auto-generated method stub super.handleMessage(msg); Drawable drawable = (Drawable) msg.obj; callback.setDrawble(drawable); } }; new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub try { Drawable drawable = Drawable.createFromStream(new URL( faceUrl).openStream(), ""); Message msg = Message.obtain(); msg.obj = drawable; handler.sendMessage(msg); } catch (MalformedURLException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }).start(); } public interface downloadFaceCallBack { public void setDrawble(Drawable drawable); } }
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标签：android style blog class code java
原文地址：http://www.cnblogs.com/zhouyu629/p/3723847.html
