AsyncTask异步加载图片（显示进度条刻度）

MainActivity.java

package com.example.hasynctask;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
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 android.app.Activity;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
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 imageView;
	private ProgressDialog dialog;
	private final String PATH = "https://img1.bdstatic.com/img/image/9448718367adab44aed19135dceb11c8701a18bfbbf.jpg";	//图片地址
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);	//设置布局
		dialog = new ProgressDialog(this);
		dialog.setTitle("提示");
		dialog.setMessage("正在下载图片。。。。。。");
		dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);	//设置进度条为水平方向，默认为圆形
		button = (Button) this.findViewById(R.id.button1);	//得到按钮组件
		imageView = (ImageView) this.findViewById(R.id.imageView1);	//得到图像组件
		//为按钮添加事件
		button.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View arg0) {
				//创建任务线程并执行，传入地址参数
				new MyTask().execute(PATH);	
			}
		});
	}
	/*
	 * 创建异步任务类，执行异步下载图片.
	 * 第一个参数：接收的参数
	 * 第二个参数：进度值
	 * 第三个参数：返回的值
	 */
	class MyTask extends AsyncTask<String, Integer, byte[]>{
		//最先执行的方法
		@Override
		protected void onPreExecute() {
			super.onPreExecute();
			dialog.show();	//设置UI主线程一直显示提示框
		}
		//后台执行的方法
		@Override
		protected byte[] doInBackground(String... params) {
			byte[] result = null;
			InputStream inputStream = null;
			ByteArrayOutputStream outputStream = new ByteArrayOutputStream();	//保存下载下来的输入流
			HttpClient httpClient = new DefaultHttpClient();
			try {
				HttpGet httpGet = new HttpGet(params[0]);
				HttpResponse httpResponse = httpClient.execute(httpGet);
				//result = EntityUtils.toByteArray(httpResponse.getEntity());	//把响应的实体转换成字节数组
				long file_length = httpResponse.getEntity().getContentLength();//文件总长度
				int total_length = 0;
				byte[] data = new byte[1024];
				int len = 0;
				if(httpResponse.getStatusLine().getStatusCode()==200){
					inputStream = httpResponse.getEntity().getContent();
					while((len = inputStream.read(data))!=-1){
						total_length += len;
						publishProgress((int)((total_length/(float)file_length)*100));//更新进度
						outputStream.write(data, 0, len);
					}
				}
				result = outputStream.toByteArray();
			} catch (ClientProtocolException e) {
				e.printStackTrace();
			} catch (IOException e) {
				e.printStackTrace();
			} finally{
				httpClient.getConnectionManager().shutdown();
			}
			return result;
		}
		//在doInBackground方法中通过调用publishProgress来间接调用这个方法
		@Override
		protected void onProgressUpdate(Integer... values) {
			super.onProgressUpdate(values);
			dialog.setProgress(values[0]);
		}
		//最后执行的方法，返回doInBackground结果
		@Override
		protected void onPostExecute(byte[] result) {
			super.onPostExecute(result);
			//从字节数组到图片的转换
			Bitmap bitmap = BitmapFactory.decodeByteArray(result, 0, result.length);
			imageView.setImageBitmap(bitmap);
			dialog.dismiss();
		}
		
	}
	
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}
package com.example.hasy