使用AsyncTask后台下载图片并在UI更新进度条和现实图片

 1 public class DownloadFragment extends Fragment {
 2 
 3     Button mFetchButton;
 4     ProgressBar mProgressBar;
 5     EditText mURLEditText;
 6     ImageView mImageView;
 7 
 8     @Override
 9     public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState){
10         View v=inflater.inflate(R.layout.fragment_down,container,false);
11 
12         mFetchButton=(Button)v.findViewById(R.id.download);
13         mProgressBar=(ProgressBar)v.findViewById(R.id.progress);
14         mURLEditText=(EditText)v.findViewById(R.id.editURL);
15         mImageView=(ImageView)v.findViewById(R.id.image);
16         mFetchButton.setOnClickListener(new View.OnClickListener() {
17             @Override
18             public void onClick(View v) {
19                 String url;
20                 if((url=mURLEditText.getText().toString()).equals("")){
21                     Toast.makeText(getActivity(),"请输入网址",Toast.LENGTH_LONG).show();
22                 }else{
23                     new DownloadImageTask().execute("http://"+url);
24                 }
25             }
26         });
27         return v;
28     }
29 
30     private class DownloadImageTask extends AsyncTask<String,Integer,Void>{
31 
32         Bitmap map;
33 
34         @Override
35         protected Void doInBackground(String... params) {
36             try{
37                 URL url=new URL(params[0]);
38                 HttpURLConnection connection=(HttpURLConnection)url.openConnection();
39 
40                 /*从http头解析出下载的数据总体大小,只能解析静态页面的数据*/
41                 connection.setRequestProperty("Accept-Encoding", "identity");
42                 int total=connection.getContentLength();
43 
44                 ByteArrayOutputStream out=new ByteArrayOutputStream();
45                 InputStream in=connection.getInputStream();
46 
47                 byte[] buffer=new byte[1024];
48                 int count;
49                 int progress=0;
50                 while ((count=in.read(buffer))>0){
51                     out.write(buffer,0,count);
52                     progress += count*100/total;
53                     publishProgress(progress);
54                 }
55                 out.close();
56                 in.close();
57                 publishProgress(100);
58                 map=BitmapFactory.decodeByteArray(out.toByteArray(), 0, out.toByteArray().length);
59 //                return new String(out.toByteArray());
60             } catch (IOException e){
61                 Log.e("Download Fragment","could not open a URL",e);
62             }
63             return null;
64         }
65         @Override
66         protected void onPostExecute(Void params){
67             mImageView.setImageBitmap(map);
68         }
69 
70         @Override
71         public void onProgressUpdate(Integer...params){
72             int progress=params[0];
73             mProgressBar.setProgress(progress);
74         }
75     }
76 }