Android自定义轮播控件

Android自定义轮播控件可以使用ViewPager和Handler实现：

1. 首先创建一个自定义的ViewPager类，并重写onTouchEvent()方法，实现手势滑动效果。

public class MyViewPager extends ViewPager {
    private float startX;
    private float startY;
    private OnItemClickListener onItemClickListener;

    public MyViewPager(Context context) {
        super(context);
    }

    public MyViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                startX = ev.getX();
                startY = ev.getY();
                break;
            case MotionEvent.ACTION_UP:
                float endX = ev.getX();
                float endY = ev.getY();
                if (startX == endX && startY == endY) {
                    if (onItemClickListener != null) {
                        onItemClickListener.onItemClick(getCurrentItem());
                    }
                }
                break;
        }
        return super.onTouchEvent(ev);
    }

    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }

    public interface OnItemClickListener {
        void onItemClick(int position);
    }
}

2. 创建一个自定义的轮播控件类，继承自LinearLayout，并在该类中初始化ViewPager和指示器，并设置自动轮播。

public class MyBanner extends LinearLayout {

    private Context mContext;
    private MyViewPager mViewPager;
    private LinearLayout mIndicatorLayout;
    private List<ImageView> mIndicatorViews;
    private List<String> mImageUrls;
    private int mCurrentItem = 0;
    private Handler mHandler = new Handler();

    public MyBanner(Context context) {
        super(context);
        initView(context);
    }

    public MyBanner(Context context, AttributeSet attrs) {
        super(context, attrs);
        initView(context);
    }

    private void initView(Context context) {
        mContext = context;
        View view = LayoutInflater.from(mContext).inflate(R.layout.my_banner_layout, this);
        mViewPager = (MyViewPager) view.findViewById(R.id.viewpager);
        mIndicatorLayout = (LinearLayout) view.findViewById(R.id.indicator_layout);
    }

    public void setImageUrls(List<String> imageUrls) {
        mImageUrls = imageUrls;
        initIndicator();
        mViewPager.setAdapter(new MyBannerAdapter());
        mViewPager.setCurrentItem(Integer.MAX_VALUE / 2 - (Integer.MAX_VALUE / 2 % mImageUrls.size()));
        startAutoScroll();
    }

    private void initIndicator() {
        mIndicatorViews = new ArrayList<>();
        for (int i = 0; i < mImageUrls.size(); i++) {
            ImageView indicatorView = new ImageView(mContext);
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                    LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
            params.rightMargin = 20;
            indicatorView.setLayoutParams(params);
            if (i == 0) {
                indicatorView.setImageResource(R.drawable.indicator_selected);
            } else {
                indicatorView.setImageResource(R.drawable.indicator_normal);
            }
            mIndicatorLayout.addView(indicatorView);
            mIndicatorViews.add(indicatorView);
        }
    }

    private void startAutoScroll() {
        mHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
                mViewPager.setCurrentItem(mViewPager.getCurrentItem() + 1);
                mHandler.postDelayed(this, 2000);
            }
        }, 2000);
    }

    private class MyBannerAdapter extends PagerAdapter {

        @Override
        public int getCount() {
            return Integer.MAX_VALUE;
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == object;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView((View) object);
        }

        @Override
        public Object instantiateItem(ViewGroup container, final int position) {
            ImageView imageView = new ImageView(mContext);
            imageView.setScaleType(ImageView.ScaleType.FIT_XY);
            Glide.with(mContext).load(mImageUrls.get(position % mImageUrls.size())).into(imageView);
            container.addView(imageView);
            imageView.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(mContext, "点击了第" + (position % mImageUrls.size() + 1) + "张图片", Toast.LENGTH_SHORT).show();
                }
            });
            return imageView;
        }
    }
}

3. 在布局文件中使用自定义的轮播控件。

<com.example.myapplication.MyBanner
    android:id="@+id/banner"
    android:layout_width="match_parent"
    android:layout_height="200dp" />

4. 在代码中设置轮播的图片地址。

List<String> imageUrls = new ArrayList<>();
imageUrls.add("http://img2.imgtn.bdimg.com/it/u=202085641,1798154443&fm=27&gp=0.jpg");
imageUrls.add("http://img5.imgtn.bdimg.com/it/u=2746360890,4221331673&fm=27&gp=0.jpg");
imageUrls.add("http://img0.imgtn.bdimg.com/it/u=3054917406,3471798182&fm=27&gp=0.jpg");
mBanner.setImageUrls(imageUrls);