Android studio 里实现轮播图详细代码

在 Android Studio 中实现轮播图可以使用 ViewPager+Fragment 的方式来实现。下面是详细的代码实现步骤：

1. 创建一个包含图片的数据源

public class ImageData {
    private int imageRes;

    public ImageData(int imageRes) {
        this.imageRes = imageRes;
    }

    public int getImageRes() {
        return imageRes;
    }
}

public class ImageDataUtils {
    public static List<ImageData> getImageDataList() {
        List<ImageData> imageDataList = new ArrayList<>();
        imageDataList.add(new ImageData(R.drawable.image1));
        imageDataList.add(new ImageData(R.drawable.image2));
        imageDataList.add(new ImageData(R.drawable.image3));
        imageDataList.add(new ImageData(R.drawable.image4));
        return imageDataList;
    }
}

2. 创建一个 Fragment 来展示图片

public class ImageFragment extends Fragment {
    private ImageData imageData;

    public ImageFragment() {
    }

    public static ImageFragment newInstance(ImageData imageData) {
        ImageFragment fragment = new ImageFragment();
        fragment.imageData = imageData;
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_image, container, false);
        ImageView imageView = view.findViewById(R.id.image_view);
        imageView.setImageResource(imageData.getImageRes());
        return view;
    }
}

3. 创建一个 FragmentPagerAdapter 来管理 Fragment

public class ImagePagerAdapter extends FragmentPagerAdapter {
    private List<ImageData> imageDataList;

    public ImagePagerAdapter(FragmentManager fm, List<ImageData> imageDataList) {
        super(fm);
        this.imageDataList = imageDataList;
    }

    @Override
    public Fragment getItem(int position) {
        return ImageFragment.newInstance(imageDataList.get(position));
    }

    @Override
    public int getCount() {
        return imageDataList.size();
    }
}

4. 在布局文件中添加 ViewPager 和指示器

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="200dp"/>

    <LinearLayout
        android:id="@+id/dot_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="10dp"
        android:gravity="center_horizontal"
        android:orientation="horizontal"/>

</RelativeLayout>

5. 在 Activity 中初始化 ViewPager

public class MainActivity extends AppCompatActivity {
    private ViewPager viewPager;
    private LinearLayout dotLayout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewPager = findViewById(R.id.view_pager);
        dotLayout = findViewById(R.id.dot_layout);

        List<ImageData> imageDataList = ImageDataUtils.getImageDataList();
        ImagePagerAdapter adapter = new ImagePagerAdapter(getSupportFragmentManager(), imageDataList);
        viewPager.setAdapter(adapter);

        // 添加指示器
        for (int i = 0; i < imageDataList.size(); i++) {
            ImageView dotView = new ImageView(this);
            dotView.setImageResource(R.drawable.dot_selector);
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                    LinearLayout.LayoutParams.WRAP_CONTENT,
                    LinearLayout.LayoutParams.WRAP_CONTENT);
            params.leftMargin = 10;
            params.rightMargin = 10;
            dotLayout.addView(dotView, params);
        }

        // 设置 ViewPager 的页面切换监听器，用于更新指示器
        viewPager.addOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                super.onPageSelected(position);
                for (int i = 0; i < imageDataList.size(); i++) {
                    ImageView dotView = (ImageView) dotLayout.getChildAt(i);
                    dotView.setSelected(i == position);
                }
            }
        });
    }
}

其中，dot_selector 是一个选择器文件，用于设置指示器的选中和未选中状态：

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/dot_selected" android:state_selected="true"/>
    <item android:drawable="@drawable/dot_unselected"/>
</selector>

这样就可以实现一个简单的轮播图了。