MainActivity.java

package cn.com.uangel.asynctask;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.URI;

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

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends Activity {

	ImageView imageView01;
	TextView textView;

	@Override
	public void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.main);

		textView = (TextView) this.findViewById(R.id.textview);

		imageView01 = (ImageView) this.findViewById(R.id.imageview);

		GetImage getImage = new GetImage();

		getImage.execute("http://hi.csdn.net/attachment/201010/27/0_1288149117Yk8W.gif");
		Log.d("fff", "onCreat");
	}

	private class GetImage extends AsyncTask<Object, Integer, Object> {

		public GetImage() {

			super();

			// TODO Auto-generated constructor stub

		}

		@Override
		protected void onCancelled() {

			Log.i("fff", "onCancelled is running...");

			super.onCancelled();

		}

		@Override
		protected void onPostExecute(Object result) {

			/*
			 * 
			 * 此方法在主线程执行，任务执行的结果作为此方法的参数返回
			 */

			Log.i("fff", "onPostExecute is running...");

			Log.i("fff", "result == null ? " + (result == null));

			imageView01.setImageBitmap((Bitmap) result);

			super.onPostExecute(result);
		}

		@Override
		protected void onPreExecute() {

			/*
			 * 
			 * 执行预处理，它运行于UI线程，可以为后台任务做一些准备工作，比如绘制一个进度条控件
			 */

			Log.i("fff", "onPreExecute is running...");

			super.onPreExecute();

		}

		@Override
		protected void onProgressUpdate(Integer... values) {

			System.out.println("onProgressUpdate");
			/*
			 * 
			 * 此方法在主线程执行，用于显示任务执行的进度。
			 */

			Log.i("fff", "onProgressUpdate is running...");

			// 由publishProgress传递的值

			Log.i("fff", "values " + values[0]);

			super.onProgressUpdate(values);

		}

		@Override
		protected Object doInBackground(Object... params) {

			/*
			 * 
			 * 此方法在后台线程执行，完成任务的主要工作，通常需要较长的时间。
			 * 
			 * 在执行过程中可以调用publicProgress(Progress…)来更新任务的进度。
			 */

			Log.i("fff", "doInBackground is running...");

			try {

				Bitmap bitmap;

				HttpClient client = new DefaultHttpClient();

				// params[0]代表连接的url

				URI uri = URI.create((String) params[0]);

				HttpGet get = new HttpGet(uri);

				HttpResponse response = client.execute(get);

				HttpEntity entity = response.getEntity();

				long length = entity.getContentLength();

				Log.i("fff", "length:   " + length);

				InputStream in = entity.getContent();

				if (in != null) {

					ByteArrayOutputStream baos = new ByteArrayOutputStream();

//					
//					byte[] buf = new byte[128];
//
//					int ch = -1;
//
//					int count = 0;
//
//					while ((ch = in.read(buf)) != -1) {
//
//						baos.write(buf, 0, ch);
//
//						count += ch;
//
//						if (length > 0) {
//
//							// 如果知道响应的长度，调用publishProgress()更新进度
//
//							// onProgressUpdate读取进度
//
//							publishProgress((int) ((count / (float) length) * 100));
//
//						}
//
//						// 为了在模拟器中清楚地看到进度，让线程休眠100ms
//
//						// Thread.sleep(100);
//
//					}
					publishProgress(100);//调用onProgressUpdate()
					bitmap = BitmapFactory.decodeStream(in);

					in.close();

					baos.close();

					return bitmap;

				}

			} catch (Exception e) {

				e.printStackTrace();

			}

			return null;

		}

	}

}