revise code sample for callback interface
revise code sample for callback interface

Change-Id: I8e27e2579dcc5cb84a71c74769fb89bb639e16ba

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base