android内部培训视频_第四节(1)_异步网络操作

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);        }}

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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();            }

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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"}]}

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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;    }        }

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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);        }            }

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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;        }    }

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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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