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" />