Android 用AsyncTask下载网络图片并显示百分比

1.添加布局文件：activity_main.xml

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical" >

     <ImageView
         android:id="@+id/mImageView"
         android:layout_width="300dp"
         android:layout_height="300dp" />

     <ProgressBar
         android:id="@+id/mProgressBar"
         style="?android:attr/progressBarStyleHorizontal"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:maxHeight="10dip"
         android:minHeight="10dip" />

     <Button
         android:id="@+id/btnGetImg"
         android:layout_width="120dp"
         android:layout_height="50dp"
         android:text="Getmage" />

     <Button
         android:id="@+id/btnAbort"
         android:layout_width="120dp"
         android:layout_height="50dp"
         android:text="Abort" />

 </LinearLayout>

2.添加java文件MainActivity.java

 package com.example.loadimgfrominternet;

 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLConnection;

 import android.app.Activity;
 import android.content.Context;
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import android.os.AsyncTask;
 import android.os.Bundle;
 import android.os.SystemClock;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.ImageView;
 import android.widget.ProgressBar;

 public class MainActivity extends Activity implements OnClickListener {

     private Button btnGetImg;
     private Button btnAbort;
     private ProgressBar mProgressBar;
     private ImageView mImageView;
     private static final String ImageUrl = "https://images0.cnblogs.com/i/169207/201408/112229149526951.png";

     ImageLoader loader = null;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         initView();
     }

     private void initView() {
         btnGetImg = (Button) findViewById(R.id.btnGetImg);
         btnAbort = (Button) findViewById(R.id.btnAbort);
         mProgressBar = (ProgressBar) findViewById(R.id.mProgressBar);
         btnGetImg.setOnClickListener(this);
         btnAbort.setOnClickListener(this);

         mProgressBar.setVisibility(View.INVISIBLE);
         mImageView = (ImageView) findViewById(R.id.mImageView);
     }

     @Override
     public void onClick(View v) {
         int id = v.getId();
         if (id == R.id.btnGetImg) {
             loader = new ImageLoader();
             loader.execute(ImageUrl);
             btnGetImg.setEnabled(false);
         } else if (id == R.id.btnAbort) {
             loader.cancel(true);
             btnGetImg.setEnabled(true);
         }
     }

     class ImageLoader extends AsyncTask<String, Integer, Bitmap> {
         @Override
         protected void onPreExecute() {
             mProgressBar.setVisibility(View.VISIBLE);
             mProgressBar.setProgress();
             mImageView.setImageResource(R.drawable.noimg);
             super.onPreExecute();
         }

         @Override
         protected Bitmap doInBackground(String... params) {
             String imgUri = params[];

             try {
                 URL url = null;
                 HttpURLConnection conn = null;
                 InputStream inputStream = null;
                 OutputStream outputStream = null;
                 String filename = "local_temp_image";

                 try {

                     url = new URL(imgUri);
                     conn = (HttpURLConnection) url.openConnection();
                     conn.setDoInput(true);
                     conn.setDoOutput(false);
                     conn.setConnectTimeout( * );
                     inputStream = conn.getInputStream();
                     outputStream = openFileOutput(filename,
                             Context.MODE_PRIVATE);
                     byte[] data = new byte[];
                     int seg = ;
                     long total = conn.getContentLength();
                     long current = ;
                     while (!isCancelled()
                             && (seg = inputStream.read(data)) != -) {
                         outputStream.write(data, , seg);
                         current += seg;
                         int progress = (int) ((float) current / total * );
                         publishProgress(progress);// // 通知进度条UI更新
                         SystemClock.sleep();
                     }
                 } finally {
                     if (conn != null) {
                         conn.disconnect();
                     }
                     if (inputStream != null) {
                         inputStream.close();
                     }
                     if (outputStream != null) {
                         outputStream.close();
                     }
                 }
                 // return BitmapFactory.decodeStream(HandlerData(ImageUrl));
                 return BitmapFactory.decodeFile(getFileStreamPath(filename)
                         .getAbsolutePath());
             } catch (MalformedURLException e) {
                 e.printStackTrace();
             } catch (IOException e) {
                 e.printStackTrace();
             }
             return null;
         }

         @Override
         protected void onProgressUpdate(Integer... values) {
             if (isCancelled())
                 return;
             mProgressBar.setProgress(values[]);
             btnGetImg.setText(values[] + "%");
             super.onProgressUpdate(values);
         }

         @Override
         protected void onPostExecute(Bitmap bitmap) {
             if (bitmap != null) {
                 mImageView.setImageBitmap(bitmap);
             }
             mProgressBar.setVisibility(View.INVISIBLE);
             mProgressBar.setProgress();
             btnAbort.setEnabled(false);
             super.onPostExecute(bitmap);
         }
     }

     /* 根据URI地址读取输入流 */
     public static InputStream HandlerData(String url) {
         InputStream inStream = null;

         try {
             URL feedUrl = new URL(url);
             URLConnection conn = feedUrl.openConnection();
             conn.setConnectTimeout( * );
             inStream = conn.getInputStream();
         } catch (Exception e) {
             e.printStackTrace();
         }

         return inStream;
     }
 }

3.运行效果图如下：

4.附上项目下载地址：

http://files.cnblogs.com/_ymw/LoadImgFromInternet_%E5%8D%9A%E5%AE%A2%E9%99%84%E4%BB%B6.rar