Android CustomTabs
· Chrome CustomTabs for Android demystified. Simplifies development and provides higher level classes including fallback in case Chrome isn't available on device.
Download JD-GUI to open JAR file and explore Java source code file (.class .java)
Click menu "File → Open File..." or just drag-and-drop the JAR file in the JD-GUI window android-customtabs-3.0.3.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.