使用系统自带的下载功能

package com.hebaijun.downloadtest;

import java.io.File;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;

import android.app.Activity;
import android.app.DownloadManager;
import android.app.DownloadManager.Request;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.preference.PreferenceManager;
import android.util.Log;
import android.webkit.MimeTypeMap;

public class DownloadTestActivity extends Activity {
private DownloadManager downloadManager;
private SharedPreferences prefs;
private static final String DL_ID = "downloadI24d3222222";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
downloadManager = (DownloadManager)getSystemService(DOWNLOAD_SERVICE);
prefs = PreferenceManager.getDefaultSharedPreferences(this);
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
unregisterReceiver(receiver);
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
if(!prefs.contains(DL_ID)) {
String url = "http://down.angeeks.com/c/d2/d10129/10129003.apk";
//开始下载
Uri resource = Uri.parse(encodeGB(url));
DownloadManager.Request request = new DownloadManager.Request(resource);
request.setAllowedNetworkTypes(Request.NETWORK_MOBILE | Request.NETWORK_WIFI);
request.setAllowedOverRoaming(false);
//设置文件类型
MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();
String mimeString = mimeTypeMap.getMimeTypeFromExtension(MimeTypeMap.getFileExtensionFromUrl(url));
request.setMimeType(mimeString);
//在通知栏中显示
request.setShowRunningNotification(true);
request.setVisibleInDownloadsUi(true);
//sdcard的目录下的download文件夹
request.setDestinationInExternalPublicDir("/download/", "G5223.apk");
request.setTitle("移动G3广告");
long id = downloadManager.enqueue(request);
//保存id
prefs.edit().putLong(DL_ID, id).commit();
} else {
//下载已经开始，检查状态
queryDownloadStatus();
}

registerReceiver(receiver, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
}

/**
* 如果服务器不支持中文路径的情况下需要转换url的编码。
* @param string
* @return
*/
public String encodeGB(String string)
{
//转换中文编码
String split[] = string.split("/");
for (int i = 1; i < split.length; i++) {
try {
split[i] = URLEncoder.encode(split[i], "GB2312");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
split[0] = split[0]+"/"+split[i];
}
split[0] = split[0].replaceAll("\\+", "%20");//处理空格
return split[0];
}

private BroadcastReceiver receiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
//这里可以取得下载的id，这样就可以知道哪个文件下载完成了。适用与多个下载任务的监听
Log.v("intent", ""+intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, 0));
queryDownloadStatus();
}
};

private void queryDownloadStatus() {
DownloadManager.Query query = new DownloadManager.Query();
query.setFilterById(prefs.getLong(DL_ID, 0));
Cursor c = downloadManager.query(query);
if(c.moveToFirst()) {
int status = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
switch(status) {
case DownloadManager.STATUS_PAUSED:
Log.v("down", "STATUS_PAUSED");
case DownloadManager.STATUS_PENDING:
Log.v("down", "STATUS_PENDING");
case DownloadManager.STATUS_RUNNING:
//正在下载，不做任何事情
Log.v("down", "STATUS_RUNNING");
break;
case DownloadManager.STATUS_SUCCESSFUL:
//完成
Log.v("down", "下载完成");
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
String installPath = Environment.getExternalStorageDirectory()+ "/download/G5223.apk";
intent.setDataAndType(Uri.fromFile(new File(installPath)),"application/vnd.android.package-archive");
startActivity(intent);
break;
case DownloadManager.STATUS_FAILED:
//清除已下载的内容，重新下载
Log.v("down", "STATUS_FAILED");
downloadManager.remove(prefs.getLong(DL_ID, 0));
prefs.edit().clear().commit();
break;
}
}
}
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.hebaijun.downloadtest"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk android:minSdkVersion="8" />

<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:label="@string/app_name"
android:name=".DownloadTestActivity" >
<intent-filter >
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.DOWNLOAD_WITHOUT_NOTIFICATION"/>
</manifest>