Detailed explanation of Java class library technical principles of the Android support library Fragment framework

Detailed explanation of Java class library technical principles of the Android support library Fragment framework Android Fragment is part of the Android support library, which provides a way to manage user interface components.Fragment can be regarded as a sub -interface module in Activity, which can be nested in an Activity and has its own layout and logic.This article will introduce the JAVA -class library technical principles of the Android support library Fragment framework in detail. 1. The basic concept of fragment Fragment is a reusable component, similar to a small Activity, which is usually embedded in an Activity.Each Fragment has its own layout and logic, and can be added, removed or replaced.Fragment can have its own life cycle, can handle user interaction independently, and adapt in different devices or screen directions. 2. Fragment composition Each fragment contains the following components: -Apapter file: User interface for defining Fragment, similar to layout files in Activity. -Java code: The logical operation of the Fragment is similar to the Java code in Activity. -The life cycle method: including onCreate (), onStart (), onresume (), etc., used to manage the life cycle of Fragment. -The interaction with Activity: Obtain associated Activity by calling the getActivity () method. 3. Fragment use steps The following steps are required to use Fragment: -D definition Fragment: Create a subclass that inherit the Fragment, and implement the onCreateView () method to load the layout file and process the logical operation in Fragment. -Ad the <fragment> label in Activity: Add <fragment> tags in the Activity layout file, or add Fragment to the Java code. -E Manage Fragment: Manage Fragment through FragmentManager and FragmenttransActions, including adding, removing, replacing, hidden operations. 4. The life cycle of fragment Fragment has its own life cycle, including the following methods: -Oncreate (): Calling when Fragment was created and used to initialize some variables and resources. -OncreateView (): Call when creating a Fragment view for loading layout files. -Onstart (): Calling when Fragment can be visible but not yet obtained. -OnResume (): Calling when Fragment can be visible and obtained. -Onpause (): Call when Fragment lost focus. -Onstop (): Call when Fragment is not visible. -OnDestroyView (): Calling when the view of Fragment was destroyed. -OnDestroy (): Call when Fragment was destroyed. 5. Communication between fragments Fragment can communicate with the affiliated AAADITY, or can also communicate with other Fragment.Common communication methods include:: -GetActivity (): Get the reference to Activity of Activity, so you can call the method in Activity. -On interface callback: Define a interface, implement it in the Fragment, and institutionalized interfaces in related Activity to achieve communication between Fragment and Activity. -Sther ViewModel: Use ViewModel to share data between Fragment. 6. Example code Below is a simple example code that demonstrates how to add and replace the Fragment in Activity: Add <framelayout> to the Activity_main.xml to carry Fragment: <FrameLayout android:id="@+id/fragment_container" android:layout_width="match_parent" android:layout_height="match_parent" /> Add and replace the Fragment: add and replace the Fragment: public class MainActivity extends AppCompatActivity { private FragmentManager fragmentManager; private FragmentTransaction fragmentTransaction; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); fragmentManager = getSupportFragmentManager(); fragmentTransaction = fragmentManager.beginTransaction(); // Create and add Fragment Fragment1 fragment1 = new Fragment1(); fragmentTransaction.add(R.id.fragment_container, fragment1); // Replace Fragment Fragment2 fragment2 = new Fragment2(); fragmentTransaction.replace(R.id.fragment_container, fragment2); fragmentTransaction.commit(); } } This is a basic example, showing how to use Fragment. Through this article, we have learned in detail the Java -class library technical principles of the Android support library Fragment framework.Fragment provides a flexible way to manage user interface components, allowing developers to better handle complex UI architecture and screen adaptation.I hope this article will help you understand the use and principle of Fragment. Please note that the above example code is used as a reference only, and the actual use must be modified and expanded accordingly according to your own needs.