How is the user interface display process implemented in Android applications?

In Android, the user interface is displayed through the View and ViewGroup system. Typically, the UI is described in XML layout files, which are loaded into an Activity or Fragment using the setContentView() or inflate() methods.

When an Activity is launched, the system parses the XML, creates and hierarchically arranges View elements, which are then rendered on the screen. Components involved in this process include the LayoutInflater, which converts XML into View objects, and the measurement and layout mechanism, which determines the size and position of elements.

Example of loading a layout in an Activity:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main); // loads the XML layout
}

Thus, the display process involves loading and creating a View hierarchy from XML or code, measuring, positioning, and rendering it on the screen.