Downloadmanager使用

DownloadManager是android提供的一个下载管理器

缺点：不支持断点续传

使用方法:

创建实例:

DownloadManager manager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);

创建下载任务:

DownloadManager.Request request = new DownloadManager.Request(Uri.parse(URL));//指定保存地址request.setDestinationInExternalPublicDir("chuyi", "meizhi.apk");//设置允许下载的网络状况request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI);//设置通知栏的行为request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);//通过id唯一标识此下载任务long id = manager.enqueue(request);

删除下载任务:
```
manager.remove(id);
```

查询下载任务:

DownloadManager.Query query = new DownloadManager.Query();query.setFilterById(id);Cursor cursor = manager.query(query);if(cursor.moveToFirst()){    String filename = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME));    String fileUri = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));    Toast.makeText(context,"下载完成...name:"+filename+",uri:"+fileUri,Toast.LENGTH_SHORT).show();}else {  //TODO}cursor.close();

查询下载进度:

DownloadManager.Query query = new DownloadManager.Query().setFilterById(downloadId);Cursor c = null;try {    c = downloadManager.query(query);    if (c != null && c.moveToFirst()) {        int downloadedBytes = c.getInt(c.getColumnIndexOrThrow(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));        int totalBytes = c.getInt(c.getColumnIndexOrThrow(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));        int state = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));    }} finally {    if (c != null) {        c.close();    }}

监听下载结束通知:

可以通过接收DownloadManager.ACTION_DOWNLOAD_COMPLETE广播来监听下载结束的通知

IntentFilter filter = new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE);    mReceiver = new BroadcastReceiver(){      public void onReceive(Context c,Intent i){          long downId = i.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID,-1);      }    }    context.registerReceiver(mReceiver,filter);

监听下载进度:

主要有三种方案：1.FileReceiver 2.ContentObserver 3.定时任务

class DownloadChangeObserver extends ContentObserver {public DownloadChangeObserver(){    super(handler);}@Overridepublic void onChange(boolean selfChange) {    //查询进度}}//in activityprivate DownloadChangeObserver downloadObserver;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.download_manager_demo);……downloadObserver = new DownloadChangeObserver();}@Overrideprotected void onResume() {    super.onResume();    /** observer download change **/    getContentResolver().registerContentObserver(DownloadManagerPro.CONTENT_URI, true,                                                 downloadObserver);}@Overrideprotected void onPause() {    super.onPause();    getContentResolver().unregisterContentObserver(downloadObserver);}

上面这种做法可能对性能有些损耗，因为会不断触发onChange

推荐使用ScheduledExecutorService

public static ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(3);Runnable command = new Runnable() {    @Override    public void run() {        updateView();    }};scheduledExecutorService.scheduleAtFixedRate(command, 0, 3, TimeUnit.SECONDS);

参考资料：

http://www.trinea.cn/android/android-downloadmanager/
http://www.trinea.cn/android/android-downloadmanager/
https://github.com/Trinea/android-common/blob/master/src/cn/trinea/android/common/util/DownloadManagerPro.java

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