In -depth analysis of the technical principles of the ViewPager2 framework in the Java class library

In -depth analysis of the technical principles of the ViewPager2 framework in the Java class library introduction: ViewPager2 is a powerful Java class library framework that is used to achieve the function of sliding page in Android applications.It is an upgraded version of ViewPager in Android Support Library, which has better performance and richer features.This article will in -depth analysis of the technical principles of the ViewPager2 framework and discuss the underlying mechanism of the sliding page function. 1. Overview of viewpager2 ViewPager2 is part of the Jetpack library, which provides a simple and flexible way to achieve multi -page sliding user interface.It allows users to switch between different pages by sliding gestures or programs.Compared to ViewPager, the advantage of ViewPager2 is better stability, higher performance and richer features. Second, the working principle of viewpager2 1. Layout structure The core of ViewPager2 is a RecyclerView, which shows multiple pages in a vertical or horizontal manner.Each page is represented by a frame or a view, and these pages are placed in different positions in RecyclerView.Through RecyclerView's rolling mechanism, users can slide the page to implement page switching. 2. Adapter (adapter) ViewPager2 uses an adapter to provide the content of the page.The adapter is responsible for binding the data source with the pages in RecyclerView.Users can customize the adapter to achieve different types of page display.The adapter should inherit from the RecyclerView.adapter to achieve necessary methods, such as creating pages and binding data. 3. Page switch ViewPager2 supports multiple methods of page switching, including sliding gestures and program control.When the user slides the ViewPager2, it will trigger the RollerView rolling event.ViewPager2 will calculate the target position of the page switching based on the distance and speed of the sliding, and implement the smooth switch between the page through the RECLERView rolling animation.Users can also switch the program control page by calling ViewPager2's setcurrentity method. 4. Life cycle ViewPager2 is closely related to the life cycle between Fragment or View.When the page of ViewPager2 changes, such as the page is destroyed or re -created, ViewPager2 will automatically call the life cycle method of the page, including onCreate, onResume, and onDestroy. 3. Java code example Here are a simple Java code example to demonstrate how to use the ViewPager2 framework to create a sliding page application: // 1. Create the Fragment of the page public class PageFragment extends Fragment { @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View view = inflater.inflate(R.layout.fragment_page, container, false); // UI components of the initialization page // ... return view; } } // 2. Create an adapter public class PagerAdapter extends FragmentStateAdapter { public PagerAdapter(FragmentManager fragmentManager, Lifecycle lifecycle) { super(fragmentManager, lifecycle); } @Override public Fragment createFragment(int position) { // Create the corresponding page Fragment according to the location return new PageFragment(); } @Override public int getItemCount() { // Return to the number of pages return 3; } } // 3. Use ViewPager2 in Activity public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ViewPager2 viewPager = findViewById(R.id.viewPager); PagerAdapter pagerAdapter = new PagerAdapter(getSupportFragmentManager(), getLifecycle()); viewPager.setAdapter(pagerAdapter); } } The above code demonstrates the Fragment, adapter and the process of using ViewPager2.By setting the adapter, the page can be binded with the recyclerview to achieve the function of the sliding page. in conclusion: Through in -depth analysis of the technical principles of the ViewPager2 framework, we understand its working principles and underlying mechanisms in sliding page functions.The powerful function and flexibility of ViewPager2 allows developers to easily achieve multi -page sliding user interface.I hope this article will be able to understand the technical principles of ViewPager2.