Download
- url: String- path: String- listener: DownloadListener
+ Download():+ download():- requset();- save();+ pause():
DownloadRunnable
- download: Download
+ run():
被观察者：Downlooad
DownloadControl
- list: List- executor: ExecutorService
+ add():+ start():+ pause():+ remove():
观察者：MainActivity
DownloadListener
+ berforeConnected():+ afterConnected():+ onProgress();+ onFinished():
MainActivity
- listView: LIstView- control: DownloadControl- listener: DownloadListerner
# onCreate():+ newDownload():+ startDownload():+ pauseDownload():
