I've done all the basics of C language, Java, and HTML,,, I'm really confused starting from the third lecture. It's been over a month since I took the Android class, so I'm a beginner, but I thought I knew the very basics, but I can't follow this lecture. It seems that there's almost no explanation,,,, Those who have learned a little about Android will probably understand. Those who have never learned Android will probably have a hard time.