Ok guys I\'m little stacked here. According to official documentation Google says that \"Once you\'ve defined your Drawable in XML, save the file in the res/drawable/ direct
It's is exactly like you said : you have the create the file manually. But also the XML file content has to be valid. That's all. You can show us your button_drawable.xml content so we check it.
Just add a new XML file into the res/drawable folder. The drawable file looks like next:
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<gradient
android:startColor="#FF000000"
android:centerColor="#FF000000"
android:endColor="#FF777777"
android:angle="90" />
</shape>