Android中实现下载URL地址的网络资源的实例分享

通过URL来获取网络资源并下载资源简单实例：

package com.android.xiong.urltest;

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

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.widget.ImageView;

public class MainActivity extends Activity {
 ImageView show;
 Bitmap bitmap;
 Handler handler = new Handler() {

@Override
   public void handleMessage(Message msg) {
     if (msg.what == 0x123) {
       // 使用ImageView显示该图片
       show.setImageBitmap(bitmap);

}
   }

};

@Override
 protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_main);
   show = (ImageView) findViewById(R.id.show);

new Thread() {

@Override
     public void run() {
       // 定义一个URL对象
       URL url;
       try {
         url = new URL(
             "http://img1.gtimg.com/news/pics/hv1/37/195/1468/95506462.jpg");
         // 打开该URL的资源输入流
         InputStream is = url.openStream();
         // 从InputStream中解析出图片
         bitmap = BitmapFactory.decodeStream(is);
         // 发送消息
         handler.sendEmptyMessage(0x123);
         is.close();
         // 再次打开RL对应的资源输入流
         is = url.openStream();
         // 打开手机文件对应的输出流
         OutputStream os = openFileOutput("KEQIANG.JPG", MODE_APPEND);
         byte[] buff = new byte[1024];
         int hasRead = 0;
         // 将URL资源下载到本地
         while ((hasRead = is.read(buff)) > 0) {
           os.write(buff, 0, hasRead);
         }
         is.close();
         os.close();
       } catch (MalformedURLException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
       } catch (IOException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
       }

}

}.start();
 }

@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;
 }

}

<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"
 tools:context=".MainActivity" >

<ImageView  
   android:id="@+id/show"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:contentDescription="@string/hello_world"/>

</LinearLayout>

网络资源多线程下载：

package com.example.threaddown;

import java.util.Timer;
import java.util.TimerTask;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;

public class MainActivity extends Activity {

EditText url;
 EditText target;
 Button downBn;
 ProgressBar bar;
 DownUtil downUtil;
 private int mDownStatus;

@Override
 protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_main);
   // 获取程序界面中的三个界面控制
   url = (EditText) findViewById(R.id.url);
   target = (EditText) findViewById(R.id.target);
   downBn = (Button) findViewById(R.id.downBn);
   bar = (ProgressBar) findViewById(R.id.br);
   // 创建一个Handler对象
   final Handler handler = new Handler() {

@Override
     public void handleMessage(Message msg) {
       if (msg.what == 0x123) {
         bar.setProgress(mDownStatus);
       }
     }

};
   downBn.setOnClickListener(new OnClickListener() {

@Override
     public void onClick(View v) {
       // 初始化DownUtil对象
       downUtil = new DownUtil(url.getText().toString(), target
           .getText().toString(), 6);
       new Thread() {

@Override
         public void run() {
           try {
             // 开始下载
             downUtil.download();

} catch (Exception e) {
             e.printStackTrace();
           }
           // 定义每秒调度获取一次系统的完成进度
           final Timer timer = new Timer();
           timer.schedule(new TimerTask() {

@Override
             public void run() {
               // 获取下载任务的完成比例
               double completeRate = downUtil
                   .getCompleteRate();
               mDownStatus = (int) (completeRate * 1000);
               // 发送消息通知届满更新的进度条
               handler.sendEmptyMessage(0x123);
               // 下载完成之后取消任务进度
               if (mDownStatus >= 100) {
                 timer.cancel();
               }
             }
           }, 0, 1000);
         }

}.start();
     }
   });
 }

@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.threaddown;

import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class DownUtil {

// 定义下载资源的路径
 private String path;
 // 指定所下载的文件的保存位置
 private String targetFile;
 // 定义需要使用多少线程下载资源
 private int threadNum;
 // 定义下载的线程对象
 private DownThread[] threads;
 // 定义下载的文件总大小
 private int fileSize;

public DownUtil(String path, String targetFile, int threadNum) {
   this.path = path;
   this.targetFile = targetFile;
   this.threadNum = threadNum;
 }

public void download() throws IOException {
   URL url = new URL(path);
   HttpURLConnection conn = (HttpURLConnection) url.openConnection();
   conn.setConnectTimeout(5000);
   conn.setRequestMethod("GET");
   conn.setRequestProperty("Accept", "*/*");
   conn.setRequestProperty("Accept-Language", "zh-CN");
   conn.setRequestProperty("Charset", "UTF-8");
   conn.setRequestProperty("Connection", "Keep-Alive");
   // 得到文件的大小
   fileSize = conn.getContentLength();
   conn.disconnect();
   int currentPartsSize = fileSize / threadNum + 1;
   RandomAccessFile file = new RandomAccessFile(targetFile, "rw");
   // 设置本地文件的大小
   file.setLength(fileSize);
   file.close();
   for (int i = 0; i < threadNum; i++) {
     // 计算每条线程的下载位置
     int startPos = i * currentPartsSize;
     // 每个线程使用一个RandomAccessFile进行下载
     RandomAccessFile current = new RandomAccessFile(targetFile, "rw");
     // 定义该线程的下载位置
     current.seek(startPos);
     // 创建下载线程
     threads[i] = new DownThread(startPos, currentPartsSize, current);
     // 启动线程下载
     threads[i].start();
   }

}

// 获取下载的完成百分比
 public double getCompleteRate() {
   // 统计多条线程已经下载的总大小
   int sumSize = 0;
   for (int i = 0; i < threadNum; i++) {
     sumSize += threads[i].length;
   }
   return sumSize * 1.0 / fileSize;
 }

private class DownThread extends Thread {
   // 定义当前线程下载的位置
   private int startPos;
   // 定义当前线程下载文件的大小
   private int currentPartsSize;
   // 当前线程下载的文件块
   private RandomAccessFile currentPart;
   // 定义该线程已下载的字节数
   private int length;

public DownThread(int startPos, int currentPartsSize,
       RandomAccessFile currentPart) {
     this.startPos = startPos;
     this.currentPart = currentPart;
     this.currentPartsSize = currentPartsSize;

}

@Override
   public void run() {
     try {
       URL url = new URL(path);
       HttpURLConnection conn = (HttpURLConnection) url
           .openConnection();
       conn.setConnectTimeout(5000);
       conn.setRequestMethod("GET");
       conn.setRequestProperty("Accept", "*/*");
       conn.setRequestProperty("Accept-Language", "zh-CN");
       conn.setRequestProperty("Charset", "UTF-8");
       conn.setRequestProperty("Connection", "Keep-Alive");
       InputStream in = conn.getInputStream();
       in.skip(startPos);
       int hasRead = 0;
       byte[] buffer = new byte[1024];
       // 读取网络数据，并写入本地文件
       while (length < currentPartsSize
           && (hasRead = in.read(buffer)) > 0) {
         currentPart.write(buffer, 0, hasRead);
         // 累计该线程下载的总大小
         length += hasRead;
       }
       currentPart.close();
       in.close();

} catch (Exception e) {
       e.printStackTrace();
     }

}

}

}

<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"
 tools:context=".MainActivity" >

<EditText
   android:id="@+id/url"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:text="http://ksoap2-android.googlecode.com/svn/m2-repo/com/google/code/ksoap2-android/ksoap2-android-assembly/3.1.0/ksoap2-android-assembly-3.1.0-jar-with-dependencies.jar" />

<EditText
   android:id="@+id/target"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"  
   android:text="/mnt/sdcard/"/>

<Button
   android:id="@+id/downBn"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:text="down" />

<ProgressBar
   android:id="@+id/br"
   style="?android:attr/progressBarStyleHorizontal"
   android:layout_width="match_parent"
   android:layout_height="wrap_content" />

</LinearLayout>

<!-- 在SD卡中创建与删除文件的权限 -->
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<!-- 在SD开中写入数据的权限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<!-- 访问网路的权限 -->
<uses-permission android:name="android.permission.INTERNET" />