代碼片--Android--圖片下載進度條

public class MainActivity extends ActionBarActivity {

    Button b;
    ImageView i;
    ProgressDialog p;//進度條
    String path="http://pic.nipic.com/2007-12-23/200712231523651_2.jpg";//圖片地址

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        b = (Button) findViewById(R.id.button1);
        i = (ImageView) findViewById(R.id.imageView1);
        p = new ProgressDialog(this);
        p.setTitle("提示信息");
        p.setMessage("下載中，請稍後...");
        p.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);//設置進度樣式
        b.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                new MyTask().execute(path);//啓動AsyncTask
            }
        });

    }

//第一個參數是路徑
//第二個參數是進度刻度
//但三個參數是返回類型
    class MyTask extends AsyncTask<String, Integer, Bitmap> {

//準備階段，一般顯示進度條
        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();
            p.show();
        }
//後臺長時間跑的邏輯業務
        @Override
        protected Bitmap doInBackground(String... params) {
            // TODO Auto-generated method stub
            Bitmap bp=null;
            InputStream in=null;
            ByteArrayOutputStream bo=new ByteArrayOutputStream();
            //設置Http協議訪問
            HttpClient httpClient=new DefaultHttpClient();
            HttpGet httpGet =new HttpGet(params[0]);
            try {
                HttpResponse httpResponse=httpClient.execute(httpGet);

                //當Http請求成功返回
                if(httpResponse.getStatusLine().getStatusCode()==200){
                    in=httpResponse.getEntity().getContent();//通過流得到實體內容
                    long file_length=httpResponse.getEntity().getContentLength();//得到文件總容量
                    int len=0;//每次讀取長度
                    int total_length=0;//已讀取總長
                    byte[] data=new byte[1024];
                    while ((len=in.read(data))!=-1) {
                        total_length+=len;
                        int value= (int) ((total_length/(float)file_length)*100);
                        publishProgress(value);
                        bo.write(data, 0, len);
                    }
                    byte[] result=bo.toByteArray();
                    bp=BitmapFactory.decodeByteArray(result, 0, result.length);

                }
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
//對各種流關閉
            finally{
                if(in!=null){
                    try {
                        in.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
                if(bo!=null){
                    try {
                        bo.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }

            return bp;
        }
//時時更新UI進度條
        @Override
        protected void onProgressUpdate(Integer... values) {
            // TODO Auto-generated method stub
            super.onProgressUpdate(values);
            p.setProgress(values[0]);
        }
//doInBackground方法結束後執行此方法，對UI做最後更新
        @Override
        protected void onPostExecute(Bitmap result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
            p.dismiss();
            i.setImageBitmap(result);
        }

    }
}