上篇文章写到了简单的文件下载的功能，这里再简单的添加一个功能（显示下载进度）。代码方面改变不大，只是运用了AsyncTask的onProgressUpdate函数，不过下载图片的代码得要用另外一种方式写了。

package com.example.myasynctask;

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

import org.apache.http.HttpEntity;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends Activity {
	private Button button;
	private ImageView iv;
	private String path = "http://cdn.duitang.com/uploads/item/201310/17/20131017194234_eZfFU.thumb.600_0.png";
	private ProgressDialog dia;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		button = (Button) this.findViewById(R.id.bt);
		iv = (ImageView) this.findViewById(R.id.iv);

		dia = new ProgressDialog(this);
		dia.setTitle("提示信息");
		dia.setMessage("正在下载...");
		dia.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);

		button.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				new myTask().execute(path);
			}
		});
	}

	private class myTask extends AsyncTask<String, Integer, Bitmap> {
		@Override
		protected void onPreExecute() {
			// TODO Auto-generated method stub
			super.onPreExecute();
			dia.show();
		}

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

		@Override
		protected Bitmap doInBackground(String... params) {
			// TODO Auto-generated method stub
			Bitmap bitmap = null;

			ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
			InputStream inputStream = null;

			HttpClient httpClient = new DefaultHttpClient();
			HttpGet httpGet = new HttpGet(params[0]);
			try {
				HttpResponse httpResponse = httpClient.execute(httpGet);
				if (httpResponse.getStatusLine().getStatusCode() == 200) {
					long total_length = httpResponse.getEntity()
							.getContentLength();
					int has_read = 0;
					int total_read = 0;
					byte[] data = new byte[1024];
					inputStream = httpResponse.getEntity().getContent();
					while ((has_read = inputStream.read(data)) != -1) {
						total_read += has_read;
						outputStream.write(data, 0, has_read);
						int value = (int) (total_read / (float) total_length * 100);
						publishProgress(value);
					}

					byte[] result = outputStream.toByteArray();
					bitmap = 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();
			}
			return bitmap;
		}

		@Override
		protected void onPostExecute(Bitmap result) {
			// TODO Auto-generated method stub
			super.onPostExecute(result);
			iv.setImageBitmap(result);
			dia.dismiss();
		}

	}
}