显示下载进度

  1 package com.wangzhen.tasks;
  2 
  3 import java.io.ByteArrayOutputStream;
  4 import java.io.IOException;
  5 import java.io.InputStream;
  6 
  7 import org.apache.http.HttpEntity;
  8 import org.apache.http.HttpResponse;
  9 import org.apache.http.client.ClientProtocolException;
 10 import org.apache.http.client.methods.HttpGet;
 11 import org.apache.http.impl.client.DefaultHttpClient;
 12 
 13 import android.app.ProgressDialog;
 14 import android.content.Context;
 15 import android.graphics.Bitmap;
 16 import android.graphics.BitmapFactory;
 17 import android.os.AsyncTask;
 18 import android.widget.ImageView;
 19 
 20 /**
 21  * 下载图片
 22  * 
 23  * @author Administrator
 24  * 
 25  */
 26 public class DownloadTask extends AsyncTask<String, Integer, byte[]> {
 27 
 28     Context mContext;
 29     ImageView mImageView;
 30     ProgressDialog mDialog = null;
 31 
 32     public DownloadTask(Context context, ImageView imageView) {
 33         mContext = context;
 34         mImageView = imageView;
 35     }
 36 
 37     @Override
 38     protected void onPreExecute() {
 39         // TODO Auto-generated method stub
 40         super.onPreExecute();
 41         mDialog = new ProgressDialog(mContext);
 42         mDialog.setTitle("提示信息");
 43         mDialog.setMessage("正在下载中，请稍后");
 44         mDialog.setCancelable(false);
 45         mDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
 46         mDialog.show();
 47     }
 48 
 49     @Override
 50     protected byte[] doInBackground(String... params) {
 51 
 52         HttpGet request = new HttpGet(params[0]);
 53         ByteArrayOutputStream BAOS = new ByteArrayOutputStream();
 54         try {
 55             HttpResponse response = new DefaultHttpClient().execute(request);
 56             if (response.getStatusLine().getStatusCode() == 200) {
 57                 HttpEntity entity = response.getEntity();
 58                 // 得到文件总长度
 59                 long file_length = entity.getContentLength();
 60                 // 每次读取后累加的总长
 61                 long total_length = 0;
 62                 byte[] buffer = new byte[1024];
 63                 InputStream inputStream = entity.getContent();
 64                 int length = 0;
 65                 while ((length = inputStream.read(buffer)) > 0) {
 66                     // 累加进度
 67                     total_length += length;
 68                     // 将数据写入ByteArrayOutputStream中
 69                     BAOS.write(buffer, 0, length);
 70                     // 计算进度
 71                     int progress = (int) (total_length * 100 / file_length);
 72                     publishProgress(progress);
 73                 }
 74             }
 75         } catch (ClientProtocolException e) {
 76             // TODO Auto-generated catch block
 77             e.printStackTrace();
 78         } catch (IOException e) {
 79             // TODO Auto-generated catch block
 80             e.printStackTrace();
 81         }
 82         return BAOS.toByteArray();
 83     }
 84 
 85     @Override
 86     protected void onPostExecute(byte[] result) {
 87         // TODO Auto-generated method stub
 88         super.onPostExecute(result);
 89         mDialog.dismiss();
 90         Bitmap bitmap = BitmapFactory.decodeByteArray(result, 0, result.length);
 91         mImageView.setImageBitmap(bitmap);
 92     }
 93 
 94     @Override
 95     protected void onProgressUpdate(Integer... values) {
 96         // TODO Auto-generated method stub
 97         super.onProgressUpdate(values);
 98         mDialog.setProgress(values[0]);
 99     }
100 }