Auxiliary lines are added to the drawing interface, and chain dependencies are added between the controls.
Add vector illustration.
The data saved by the ViewModel can exceed the life cycle of the Activity, improving the convenience of using the data.
LiveData can add observers, and when the data changes, modify the View (UI) data.
DataBinding can directly bind data in Layout and directly use data in View (provided that ViewModel is used).
ViewModelSavedState can extend the data storage period, and can still be saved in the background.
AndroidViewModel contains the global attribute Application, which is more convenient for data persistence and storage (there is no risk of passing the Context and causing memory leaks).
Navigation realizes the switching of pages (NavHost: container; Fragment: actual page; NavController: Navi management; NavGraph: switching path and animation).
LifecycleObserver monitors the life cycle of Activity and monitors the response page cycle through OnLifecycleEvent (Lifecycle.Event.ON_PAUSE).
Room provides sqllite framework.
dagger2 provides an IOC framework.
