I got a new android device recently.
When i use it for developing. i found that i can not print out logs by Log.d(), the only way i can do is System.out.println.
I found the solution for this:
Dial this: *#*#2846579#*#*
Service menu will appear.
Go to "ProjectMenu" -> "Background Setting" -> "Log Setting" Open "Log switch" and set it to ON. Open "Log level setting" and set the log level you wish.
Reboot the phone.