Android Support Library v4: Introduction to the framework in the Java class library
Android Support Library v4: Introduction to the framework in the Java class library
Android Support Library V4 is an open source Java class library designed for the development of Android applications.It provides many commonly used functions and components that can help developers quickly build high -quality Android applications.
Android Support Library V4 contains many submissions, and each submuni provides specific functions and components.The following will introduce a few commonly used sub -libraries:
1. AppCompat sub -library:
The AppCompat sub -library provides support for the latest Android characteristics for the old version of Android devices.It ensures that applications have consistent appearance and behavior on various Android devices.If you are developing applications that support the old version of Android devices, the AppCompat sub -library is essential.
2. RecyclerView submark:
RecyclerView subdires provides a highly customized view component for the list and grid layout.It replaces the old version of ListView and GridView, and provides a faster and more flexible list and grid layout function.RecyclerView Sub -Library can help you build efficient lists and grid layouts, and support interactive effects such as rolling, drag and drop, and animation.
3. ViewPager subsidiaries:
The ViewPager sub -library provides a simple way to achieve the function of sliding interface.It allows you to create applications with multiple pages, and users can switch between pages by sliding gestures.ViewPager subwelling is widely used to create interactive interfaces such as picture browsers, guidance pages, tabs and other interactive interfaces.
In addition to the above -mentioned sub -libraries, Android Support Library V4 also provides many other functions and components, including animation, fragments, loading images, new features compatible with backwards, and so on.These functions and components can help developers quickly solve common development problems and improve development efficiency.
The following is a sample code, demonstrating how to use Android Support Library V4 ViewPager subwelling to create a simple picture browser:
1. Configure the built.gradle file to ensure that your project has added Android Support Library v4 dependence:
gradle
dependencies {
implementation 'com.android.support:support-v4:28.0.0'
}
2. Add ViewPager component to the XML layout file:
<android.support.v4.view.ViewPager
android:id="@+id/viewPager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
3. Initialize ViewPager in the Java code and set the adapter:
ViewPager viewPager = findViewById(R.id.viewPager);
MyPagerAdapter adapter = new MyPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(adapter);
4. Create an adapter class and implement the necessary methods in it:
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 the corresponding frame according to the position
return MyFragment.newInstance(position);
}
@Override
public int getCount() {
// Return to the total page number
return NUM_PAGES;
}
}
5. Create the Fragment class and display the picture in it:
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) {
View view = inflater.inflate(R.layout.fragment_my, container, false);
ImageView imageView = view.findViewById(R.id.imageView);
// Set different pictures according to the page
if (mPage == 0) {
imageView.setImageResource(R.drawable.image1);
} else if (mPage == 1) {
imageView.setImageResource(R.drawable.image2);
} else if (mPage == 2) {
imageView.setImageResource(R.drawable.image3);
}
return view;
}
}
Through the above code, you can use the ViewPager submnic in Android Support Library V4 to quickly create a simple picture browser.
Summary: Android Support Library V4 is a very powerful and commonly used Java class library. It provides many common functions and components to help developers quickly build high -quality Android applications.By using these sub -libraries, developers can effectively solve some common development problems and improve development efficiency.
