The underlying technical principles of the Android SUPPORT Library View Page framework

Android support Library View Pager framework underlying technical principles inquiry introduction: Android application development provides a wealth of basic libraries to support various functions and layouts.One of them is the SUPPORT LIBRARY library, which provides developers with many cross -version compatible features.View Page is a very useful component in the SUPPORT LIBRARY library. It can help us achieve a sliding user interface, similar to the effect of sliding view switching.This article will explore the underlying technical principles of Android Support Library View Page framework. 1. Introduction to View Pages: View Pages is a view container that allows us to manage multiple different frameants or views in the same Activity.Users can switch different Fragment or views through horizontally.View Pages can flexibly manage the life cycle of Fragment and cache them by using FragmentPageradapter or FragmentStatePageradapter as its adapter, thus achieving high -efficiency page switching and memory management. Second, the principles of the underlying level: 1. View container and adapter: View Page implements page management by using a view container and adapter.The view container is responsible for displaying the currently visible page and handling the user's sliding action.The adapter is responsible for obtaining the page from the storage data source (such as the Fragment list) and provided it with the view container for display.Through this mechanism, View Pages can achieve fast page switching and loading. 2. Layout and drawing: The layout of the View Page is very simple, it only needs to contain a sliding area.When the user slides the page, the View Pages will update the position of the current visible page according to the offset of sliding.When switching on the page, the View Pages get the corresponding page by calling the adapter method and draw.This mechanism allows View Pages to achieve smooth and smooth page switching effects. 3. Cache and life cycle management: In order to improve the performance of page switching, the View Pages cache a certain number of pages.At the initial load, the View Pages pre -load multiple pages according to the needs of the adapter.When the user slides to the new page, the View Page checks if you need to create a new page or reuse the existing page.In this way, View Pages can flexibly manage the life cycle of the page and improve memory utilization and performance. Third, sample code: Below is a simple example code to demonstrate how to use the View Pager to achieve the effect of switching Fragment. 1. Create an Activity layout file (Activity_main.xml): <androidx.viewpager.widget.ViewPager android:id="@+id/viewPager" android:layout_width="match_parent" android:layout_height="match_parent" /> 2. Create a adapter class to manage Fragment (MyPageradapter.java):: import androidx.fragment.app.Fragment; import androidx.fragment.app.FragmentManager; import androidx.fragment.app.FragmentPagerAdapter; public class MyPagerAdapter extends FragmentPagerAdapter { private static final int NUM_PAGES = 3; public MyPagerAdapter(FragmentManager fm) { super(fm); } @Override public Fragment getItem(int position) { return MyFragment.newInstance(position); } @Override public int getCount() { return NUM_PAGES; } } 3. Create a Fragment class to show different pages (MyFragment.java):: import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import androidx.fragment.app.Fragment; public class MyFragment extends Fragment { private static final String ARG_PAGE = "page"; private int mPage; public static MyFragment newInstance(int page) { MyFragment fragment = new MyFragment(); Bundle args = new Bundle(); args.putInt(ARG_PAGE, page); fragment.setArguments(args); return fragment; } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mPage = getArguments().getInt(ARG_PAGE); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Create the corresponding view according to the page View view = inflater.inflate(R.layout.fragment_my, container, false); // Todo: Add view content return view; } } 4. Set View Page and adapter in Activity: import androidx.appcompat.app.AppCompatActivity; import androidx.viewpager.widget.ViewPager; public class MainActivity extends AppCompatActivity { private ViewPager viewPager; private MyPagerAdapter adapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); viewPager = findViewById(R.id.viewPager); adapter = new MyPagerAdapter(getSupportFragmentManager()); viewPager.setAdapter(adapter); } } This article introduces the underlying technical principles of Android Support Library View Page framework.By understanding its implementation mechanism, we can better use View Pages to achieve the function of sliding switching and optimize performance and user experience.I hope this article can help you with some help. (Note: The above example code is a pseudo code. Please adjust and modify it according to the specific situation when used.)