Since android 6.0, the sdcard path is no longer "/storage/sdcard1/", "/storage/sdcard-ext/" or something.
The path depends on the phone instead. If I use Nexus 5x AVD, the path is "/storage/1D15-3A1B/". When I use Nexus 6p AVD, the path is "/storage/4679-1802/". So how can I dynamically write the sdcard path in program to locate the file in external sdcard?