Android Support Library V4: Realizing a variety of interface design in the Java class library

Android support library (SUPPORT LIBRARY) is a collection of practical tools and classes for Android developers for the Android system that is compatible with different versions.Among them, Android Support Library V4 is the most popular and widely used support library. It can achieve a variety of interface design in the low version of the Android system. In order to achieve a variety of interface design in the Java class library, we need to perform the following steps: Step 1: Configuration dependencies In the project's Build.Gradle file, add dependence on SUPPORT LIBRARY V4.The example code is as follows: dependencies { implementation 'com.android.support:support-v4:28.0.0' } This will introduce SUPPORT LIBRARY V4 so that we can use the category and tools. Step 2: Create layout files Create a new XML layout file in the Res/Layout directory to define the appearance and layout of the interface.You can use a variety of available layout components, such as Linearlayout, RelativeLayout and ConstraintLayout, and other UI elements such as buttons, text views, etc.The following is the code of a sample layout file: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Hello World!" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Click Me" /> </LinearLayout> This example layout file contains a text view and a button. Step 3: Reference layout in the java file In related Java files, the layout file is associated with the Java file with the SetContentView () method.The example code is as follows: public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } } This will be associated with the current event (Activity) in the MainActivity class. Through the above steps, we can implement a variety of interface design.You can change the layout files according to demand and add more UI components to create a unique interface. It should be noted that before using the SUPPORT LIBRARY V4, make sure it has been added to the dependence of the project so as to use the class and methods in the code.