ViewPager2 framework realizes the principle analysis in the Java class library

ViewPager2 is a library in Android Jetpack, which is used to achieve sliding -available pages in Android applications.It is upgraded and reconstructed to the previous ViewPager to support more powerful functions and better performance. The implementation principle of ViewPager2 can be parsed from the following aspects: 1. Layout structure: ViewPager2 uses RecyclerView as its basic layout component.By creating a internal RecyclerView.adapter to manage all sub -view views in ViewPager2. 2. Adapter: The adapter class is the key component of the ViewPager2 view content.By inheriting the RecyclerView.adapter class, and rewriting the method is the definition adapter.The adapter is responsible for creating, binding and destroying the view of each page, and also needs to provide information about the number of pages and the relevant information of the page content. public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> { // Define the data and related methods required for the appleerate @NonNull @Override public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) { // Create viewholder } @Override public void onBindViewHolder(@NonNull MyViewHolder holder, int position) { // Bind view data } @Override public int getItemCount() { // Return to the number of pages } static class MyViewHolder extends RecyclerView.ViewHolder { // Define the view component required by viewholder public MyViewHolder(@NonNull View itemView) { super(itemView); // Initialize view components } } } 3. Manager: ViewPager2 requires a layout manager to manage the layout and rolling operation of the sub -item.Use Linearlayout or GridLayoutManager to set the layout method of sub -items.By configured the layout manager of RecyclerView, the arrangement of sub -itnes in the page can be flexibly controlled. LinearLayoutManager layoutManager = new LinearLayoutManager(this); layoutManager.setOrientation(LinearLayoutManager.VERTICAL); recyclerView.setLayoutManager(layoutManager); 4. Page switch: ViewPager2 can switch the page by calling the setcurrentity () method.This method triggers the rolling mechanism inside the RecyclerView to roll to the specified page.It can be used to define the experience of page switching by setting up rolling speed, transition effect, and monitoring page switching events. viewPager2.setCurrentItem(2); Through the above implementation principles, ViewPager2 realizes the sliding page function, and has better performance and more flexible customization capabilities.This allows developers to easily create and manage multi -page application interfaces to provide a better user experience.