参考疯狂android讲义，重点在于学习1、HttpConnection访问网络2、多线程下载文件的处理
主activity：
package com.example.multithreaddownload; import java.util.Timer;
import java.util.TimerTask; //import org.crazyit.net.R; import android.annotation.SuppressLint;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar; @SuppressLint("HandlerLeak")
public class MultiThreadDown extends Activity { EditText target;
EditText url;
Button downButton;
ProgressBar bar;
DownUtil downUtil;
private int mDownloadStatus;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); url = (EditText) findViewById(R.id.url);
target = (EditText) findViewById(R.id.target);
downButton = (Button) findViewById(R.id.down);
bar = (ProgressBar) findViewById(R.id.bar); final Handler handler = new Handler(){ public void handleMessage(Message msg)
{
if(msg.what == 0x123)
{
bar.setProgress(mDownloadStatus);
}
}
}; downButton.setOnClickListener(new OnClickListener()
{ @Override
public void onClick(View v) {
// downUtil = new DownUtil(url.getText().toString(),
target.getText().toString(),5);
try{
downUtil.download();
}catch(Exception e)
{
e.printStackTrace();
}
//设置定时器
final Timer timer = new Timer();
timer.schedule(new TimerTask()
{ @Override
public void run() {
//
double completeRate = downUtil.getCompleteRate();
mDownloadStatus = (int) (completeRate * 100);
handler.sendEmptyMessage(0x123);
if(mDownloadStatus >= 100)
{
timer.cancel();
}
} }, 0, 100);
} });
} }
package com.example.multithreaddownload; import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL; public class DownUtil { private String path;
private String targetFile;
private int threadNum;
private DownloadThread[] threads;
private int fileSize; public DownUtil(String path, String targetFile, int threadNum) {
super();
this.path = path;
this.targetFile = targetFile;
//初始化thread数组
threads = new DownloadThread[threadNum];
this.threadNum = threadNum;
} public void download() throws Exception
{
URL url = new URL(path);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();//开启http链接
connection.setRequestMethod("GET");//向服务器发送GET请求获取数据
connection.setConnectTimeout(5000);//设置连接超时为5s
// connection.setRequestProperty(
// "Accept",
// "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*");
// connection.setRequestProperty("Accept-Language", "zh-CN");
// connection.setRequestProperty("Charset", "UTF-8");
// connection.setRequestProperty(
// "User-Agent",
// "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");
// connection.setRequestProperty("Connection", "Keep-Alive"); fileSize = connection.getContentLength();//获取文件大小
connection.disconnect();//关闭http连接
int currentPartSize = fileSize / threadNum +1;//按线程数分割后文件块的大小
RandomAccessFile file = new RandomAccessFile(targetFile, "rw");//随机产生本地目标文件 file.setLength(fileSize);//根据fileSize设置本地文件大小
file.close();//关闭文件
for(int i = 0; i < threadNum; i++)
{
//计算每条线程下载的开始位置
int startPos = i * currentPartSize;
//每个线程使用一个RandomAccessFile进行下载
RandomAccessFile currentPart = new RandomAccessFile(targetFile, "rw");
//定位该线程的下载位置
currentPart.seek(startPos);
//创建下载线程
threads[i] = new DownloadThread(startPos, currentPartSize,
currentPart);
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;
}
// 返回已经完成的百分比
return sumSize * 1.0 / fileSize;
}
private class DownloadThread extends Thread{
//当前线程下载的位置
private int startPos;
//定义当前线程负责下载的文件大小
private int currentPartSize;
//定义当前线程负责的下载块
private RandomAccessFile currentPart;
//定义该线程已下载的字节数
public int length; public DownloadThread(int startPos, int currentPartSize,
RandomAccessFile currentPart) {
// super();
this.startPos = startPos;
this.currentPartSize = currentPartSize;
this.currentPart = currentPart;
} @Override
public void run() {
super.run();
try{
URL url = new URL(path);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setConnectTimeout(5000);
// connection.setReadTimeout(5000);
// connection.setRequestProperty(
// "Accept",
// "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*");
// connection.setRequestProperty("Accept-Language", "zh-CN");
// connection.setRequestProperty("Charset", "UTF-8"); InputStream in = connection.getInputStream();
//跳过startPos个字节，只下载本线程负责的文件块
in.skip(this.startPos);
byte[] buffer = new byte[1024];
int hasRead = 0;
while((length < currentPartSize) && (hasRead = in.read(buffer)) != -1)
{
currentPart.write(buffer, 0, hasRead);
length += hasRead; }
currentPart.close();
in.close(); }catch(Exception e)
{
e.printStackTrace();
}
} } }
activity_main.xml文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="要下载的资源的URL："
/>
<EditText
android:id="@+id/url"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="http://www.crazyit.org/attachment.php?aid=1093&k=4ec76aeaa41ee84acf667b420e926783&t=1297311085"
/>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="目标文件："
/>
<EditText
android:id="@+id/target"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="/mnt/sdcard/a.rar"
/>
<Button
android:id="@+id/down"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/down"
/>
<!-- 定义一个水平进度条,用于显示下载进度 -->
<ProgressBar
android:id="@+id/bar"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:max="100"
style="@android:style/Widget.ProgressBar.Horizontal"
/>
</LinearLayout>
strings.xml:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="down">下载</string>
<string name="app_name">多线程下载</string>
<string name="action_settings">Settings</string>
</resources>
AndroidManifest.xml配置文件添加以下权限：
<!-- 在SD卡中创建与删除文件权限 -->
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
<!-- 向SD卡写入数据权限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<!-- 授权访问网络 -->
<uses-permission android:name="android.permission.INTERNET"/>
运行结果：
