Detailed explanation of the Android Support Library View Page framework technical principles of the Java library Ass Libraries)

The ViewPager framework in Android Support Library is a powerful tool for achieving page sliding switching effects.It allows users to navigate between different pages by sliding gestures and support custom page conversion animation.This article will explain in detail the technical principles of Android Support Library ViewPager framework, and provide some Java code examples to help readers better understand. The technical principles of Android Support Library ViewPager can be divided into the following aspects: 1. Layout structure: ViewPage is a view component that is used to display multiple sub -views and support horizontally sliding for navigation.It is based on Framelayout, allowing sub -views to be superimposed together, and switch the displayed sub -view by sliding gestures.ViewPage needs to be defined in the XML layout file and provides sub -views through adapter. The following is an example of a simple ViewPager layout: <android.support.v4.view.ViewPager android:id="@+id/viewPager" android:layout_width="match_parent" android:layout_height="match_parent" /> 2. adapter mode: ViewPager needs to use Adapter to provide sub -views.The Adapter class is responsible for providing data sources to ViewPages and created and binded data for each sub -view when needed.Adapter is also responsible for managing the number and location of the sub -view. The following is a simple adapter example: public class MyAdapter extends PagerAdapter { private List<View> views; public MyAdapter(List<View> views) { this.views = views; } @Override public int getCount() { return views.size(); } @Override public boolean isViewFromObject(View view, Object object) { return view == object; } @Override public Object instantiateItem(ViewGroup container, int position) { View view = views.get(position); container.addView(view); return view; } @Override public void destroyItem(ViewGroup container, int position, Object object) { container.removeView((View) object); } } 3. Page switching: ViewPager supports navigation between different pages by sliding gestures.When the user touches the screen and slides, the ViewPager will calculate the target page based on the sliding distance and speed, and use the animation effect to switch the page to the specified position. ViewPageer uses GESTUREDETECTOR to detect the sliding gesture and use Scroller to achieve a smooth sliding effect.Specifically, after receiving the sliding gesture, ViewPage calls scroller to calculate the offset of sliding, and use the attribute animation to achieve smooth transition effect. The following is a simple page switch example: ViewPager viewPager = findViewById(R.id.viewPager); MyAdapter adapter = new MyAdapter(views); viewPager.setAdapter(adapter); Summarize: Through the ViewPager framework of Android Support Library, developers can easily achieve page sliding switching effects, and also support the custom page conversion animation.This article explains the technical principles of ViewPager in detail and provides some Java code examples to help readers better understand the working principle of this framework.By learning and applied to ViewPager, developers can add smoother and interactive user interface to Android applications.