[Android] 利用Download Manager 下載檔案

http://androidgill.blogspot.tw/2011/12/android-downloadmanager.html

http://fecbob.pixnet.net/blog/post/36000039-android-%E6%AA%94%E6%A1%88%E4%B8%8B%E8%BC%89

http://www.edumobile.org/android/android-development/download-manager-in-android-programming/