Android不同api调用显示的路径
Environment.getExternalStorageState:mounted
Environment.getDownloadCacheDirectory().getPath():/cache
Environment.getDataDirectory().getPath():/data
Environment.getExternalStorageDirectory().getPath():/mnt/sdcard
Environment.getExternalStoragePublicDirectory().getPath():/mnt/sdcard/Pictures
Environment.getRootDirectory().getPath():/system