Downloadmanager in android

Downloadmanager使用

DownloadManager是android提供的一個下載管理器

缺點：不支持斷點續傳

使用方法:

創建實例:

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

創建下載任務:

DownloadManager.Request request = new DownloadManager.Request(Uri.parse(URL));
//指定保存地址
request.setDestinationInExternalPublicDir(chuyi, meizhi.apk);
//設置允許下載的網絡狀況
request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI);
//設置通知欄的行為
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
//通過id唯一標識此下載任務
long id = manager.enqueue(request);

刪除下載任務:

manager.remove(id);

查詢下載任務:

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,下載完成...name:+filename+,uri:+fileUri,Toast.LENGTH_SHORT).show();
}else {
  //TODO
}
cursor.close();

查詢下載進度:

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();
    }
}

監聽下載結束通知:

可以通過接收DownloadManager.ACTION_DOWNLOAD_COMPLETE廣播來監聽下載結束的通知

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);

監聽下載進度:

主要有三種方案：1.FileReceiver 2.ContentObserver 3.定時任務

class DownloadChangeObserver extends ContentObserver {

public DownloadChangeObserver(){
    super(handler);
}

@Override
public void onChange(boolean selfChange) {
    //查詢進度
}

}
//in activity
private DownloadChangeObserver downloadObserver;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.download_manager_demo);
……
downloadObserver = new DownloadChangeObserver();
}

@Override
protected void onResume() {
    super.onResume();
    /** observer download change **/
    getContentResolver().registerContentObserver(DownloadManagerPro.CONTENT_URI, true,
                                                 downloadObserver);
}

@Override
protected void onPause() {
    super.onPause();
    getContentResolver().unregisterContentObserver(downloadObserver);
}

上面這種做法可能對性能有些損耗，因為會不斷觸發onChange

推薦使用ScheduledExecutorService

public static ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(3);
Runnable command = new Runnable() {

    @Override
    public void run() {
        updateView();
    }
};
scheduledExecutorService.scheduleAtFixedRate(command, 0, 3, TimeUnit.SECONDS);