显示下载进度

package com.wangzhen.tasks;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.app.ProgressDialog;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.widget.ImageView;

/**
 * 下载图片
 * 
 * @author Administrator
 * 
 */
public class DownloadTask extends AsyncTask<String, Integer, byte[]> {

    Context mContext;
    ImageView mImageView;
    ProgressDialog mDialog = null;

    public DownloadTask(Context context, ImageView imageView) {
        mContext = context;
        mImageView = imageView;
    }

    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();
        mDialog = new ProgressDialog(mContext);
        mDialog.setTitle("提示信息");
        mDialog.setMessage("正在下载中，请稍后");
        mDialog.setCancelable(false);
        mDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        mDialog.show();
    }

    @Override
    protected byte[] doInBackground(String... params) {

        HttpGet request = new HttpGet(params[0]);
        ByteArrayOutputStream BAOS = new ByteArrayOutputStream();
        try {
            HttpResponse response = new DefaultHttpClient().execute(request);
            if (response.getStatusLine().getStatusCode() == 200) {
                HttpEntity entity = response.getEntity();
                // 得到文件总长度
                long file_length = entity.getContentLength();
                // 每次读取后累加的总长
                long total_length = 0;
                byte[] buffer = new byte[1024];
                InputStream inputStream = entity.getContent();
                int length = 0;
                while ((length = inputStream.read(buffer)) > 0) {
                    // 累加进度
                    total_length += length;
                    // 将数据写入ByteArrayOutputStream中
                    BAOS.write(buffer, 0, length);
                    // 计算进度
                    int progress = (int) (total_length * 100 / file_length);
                    publishProgress(progress);
                }
            }
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return BAOS.toByteArray();
    }

    @Override
    protected void onPostExecute(byte[] result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        mDialog.dismiss();
        Bitmap bitmap = BitmapFactory.decodeByteArray(result, 0, result.length);
        mImageView.setImageBitmap(bitmap);
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        // TODO Auto-generated method stub
        super.onProgressUpdate(values);
        mDialog.setProgress(values[0]);
    }
}