Android开发

Android中实现下载URL地址的网络资源的实例分享

本文主要是介绍Android中实现下载URL地址的网络资源的实例分享，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

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" />
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