1. The rules of function names: When I
first learned Android, I really felt that function names were very long. It was difficult to remember when it was capitalized and lowercase. Android development uses the Java language as a development tool, so the naming convention of Java is also applicable to Android, and classes in Java are capitalized. The first letter of the method name (function name) is lowercase. If there are multiple words, the first letter of each word must be capitalized-camel case nomenclature
2. The components defined in the program must be registered in AndroidManifest.xml before they can be used.
If there are multiple activities in the same project, the <activity>intent-filter needs to be established in the startup activity . Other activities that do not declare the intent-filter cannot be run directly, but can be jumped by the activity. In fact, multiple intent-filters can also be declared, but usually through jumps.