Android DownloadManager的用法

DownloadManager是Android为开发者提供的一个后台应用组件，它通过Http层进行文件的下载任务.

一、直接操作Content Provider中的Downloads表实现！

1：使用
首先要在AndroidManifest.xml中申请访问DownloadManager的权限
<permission android:name="android.permission.ACCESS_DOWNLOAD_MANAGER"/>
添加一个下载任务：
ContentValues values = new ContentValues();
values.put(Downloads.URI, url);//指定下载地址
values.put(Downloads.COOKIE_DATA, cookie);//如果下载Server需要cookie,设置cookie
values.put(Downloads.VISIBILITY,Downloads.VISIBILITY_HIDDEN);//设置下载提示是否在屏幕顶部显示
values.put(Downloads.NOTIFICATION_PACKAGE, getPackageName());//设置下载完成之后回调的包名
values.put(Downloads.NOTIFICATION_CLASS, DownloadCompleteReceiver.class.getName());//设置下载完成之后负责接收的Receiver，这个类要继承BroadcastReceiver
values.put(Downloads.DESTINATION,save_path);//设置下载到的路径，这个需要在Receiver里自行处理
values.put(Downloads.TITLE,title);//设置下载任务的名称
this.getContentResolver().insert(Downloads.CONTENT_URI, values);//将其插入到DownloadManager的数据库中，数据库会触发修改事件，启动下载任务

2：如何为DownloadManager设置代理，比如Wap
values.put(Downloads.PROXY_HOST,"10.0.0.172");
values.put(Downloads.PROXY_PORT,"80");

3:如何在下载过程中监听下载任务
可以通过监听数据库来实现
DownloadsChangeObserver mDownloadObserver=new DownloadsChangeObserver(Downloads.CONTENT_URI);
private class DownloadsChangeObserver extends ContentObserver {
public DownloadsChangeObserver(Uri uri) {
super(new Handler());
}
@Override
public void onChange(boolean selfChange) {
//查询需要监听的字段
//比如要监听实时下载进度，查看当前下载状态：是否已经断开，或者下载失败等等
StringBuilder wherequery = new StringBuilder(Downloads.TITLE);
wherequery.append("=");
wherequery.append("'");
wherequery.append(mTitle);
wherequery.append("'");

mDownloadCursor =mContext.getContentResolver().query(Downloads.CONTENT_URI, new String[] {Downloads.TITLE, Downloads.STATUS, Downloads.CURRENT_BYTES，}, wherequery.toString(), null,orderBy)；
int mSizeColunmId=mDownloadCursor.getColumnIndexOrThrow(Downloads.CURRENT_BYTES);
mDownloadCursor.moveToFirst();
int size=mDownloadCursor.getInt(mSizeColunmId);
｝
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4：如何删除下载记录
private void deleteHistory(String title)//删除掉指定名称的下载记录
{
StringBuilder whereDelete = new StringBuilder(Downloads.TITLE);
whereDelete.append("=");
whereDelete.append("'");
whereDelete.append(str);
whereDelete.append("'");
this.getContentResolver().delete(Downloads.CONTENT_URI,whereDelete.toString(), null);

}

二、利用API提供的DownloadManager类实现(Since API 9)：

 DownloadManger mgr=(DownloadManager)getSystemService(DOWNLOAD_SERVICE); // 加入到下载队列：                     Requestdwreq=newDownloadManager.Request(uri);
dwreq.setTitle("Demo");
dwreq.setDescription("android-ndk-r6-linux-x86.tar.bz2");
dwreq.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,"android-ndk-r6-linux-x86.tar.bz2");
dwreq.setNotificationVisibility(0); 
dwreq.setShowRunningNotification(true);
lastDownload=mgr.enqueue(dwreq);

// 查询下载的状态

publicvoidqueryDownloadStatus(Viewv){
RunnablequeryRunable=newRunnable(){
longtotalsize=0;
longdowsize=0;
booleandownok=false;
Cursorc=null;
publicvoidrun(){
//查询下载文件总大小
totalsize=c.getLong(c.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));
Messagemsg_packsize=newMessage();
msg_packsize.what=MSG_DWPACKSIZE;
msg_packsize.arg1=(int)totalsize;
handler.sendMessage(msg_packsize);
while(downok==false){
c=mgr.query(newDownloadManager.Query().setFilterById(lastDownload));
if(c==null){
//tvdwsize.setText("query=null");
}
else{
c.moveToFirst();
//查询已经下载的大小
dowsize=c.getLong(c.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
if(totalsize==dowsize)downok=true;
}
Messagemsg=newMessage();
msg.what=MSG_DWSIZE;
msg.arg1=(int)dowsize;
handler.sendMessage(msg);
try{
Thread.sleep(5000);
}catch(InterruptedExceptione){
//TODOAuto-generatedcatchblock
e.printStackTrace();
}
c.close();
}
}//run
};
Threadbackground=newThread(queryRunable);
background.start();
}
publicvoiddelDownloads(Viewview){
Toast.makeText(this,"delDownloads",Toast.LENGTH_LONG).show();
mgr.remove(lastDownload);
}

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