Using drawable with a gradient there is visible defects on Android virtual device (emulator) because screen bit depth is 16 bpp by default. AVD bit depth can be increased in settings. Create AVD with checked box Use Host GPU, open settings file which is usually with Android image in C:\Users\username\.android\avd\4.2.avd\hardware-qemu.ini and search for line
hw.lcd.depth = 16
change to
hw.lcd.depth = 32
Then save settings file and start AVD with Wipe user data checked option. Tested on Android 4.2
