自己简单封装了一个带hint的轮播ViewPager，用来展示app首页的Banner，先看效果图吧。

ezgif-1-437f7aee24.gif

具体源码及demo地址

• dependencies（依赖）

compile 'com.coldmoqiuli:banners:1.0.0'

使用起来非常方便~~2至3行代码就能实现上述效果，只要传入一个list就可以（其中是你需要展示的ImageView），当然也可以自己在这基础上添加各种Transform动画。

        bannerView = (BannerView) findViewById(R.id.banner);
        bannerView.setViewList(viewList);
        bannerView.startLoop(true);

实现原理相信大家应该都知道，就是可能懒得去封装这种东西。

具体思路：

• 1. 继承自FrameLayout，在下层填充一个ViewPager

• 2.根据ViewPager的itemCount去动态生成底部hint小圆点

           if (mLinearPosition.getChildCount() != viewSize) {
                int diffCnt = mLinearPosition.getChildCount() - viewSize;
                boolean needAdd = diffCnt < 0;
                diffCnt = Math.abs(diffCnt);
                for (int i = 0; i < diffCnt; i++) {
                    if (needAdd) {
                        ImageView img = new ImageView(getContext());
                        LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                        layoutParams.rightMargin = getResources().getDimensionPixelOffset(R.dimen.dimen_9dp);
                        img.setLayoutParams(layoutParams);
                        img.setBackgroundResource(R.drawable.banner_point);
                        mLinearPosition.addView(img);
                    } else {
                        mLinearPosition.removeViewAt(0);
                    }
                }
            }

• 3.通过Handler去控制轮播的频率，重新设置ViewPager的currentItem以及hint小圆点的背景

private static class BannerHandler extends Handler {
        private WeakReference<BannerView> weakReference = null;

        public BannerHandler(BannerView bannerView) {
            super(Looper.getMainLooper());
            this.weakReference = new WeakReference<BannerView>(bannerView);
        }

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if (this.weakReference == null) {
                return;
            }
            BannerView bannerView = this.weakReference.get();
            if (bannerView == null || bannerView.mViewPager == null || bannerView.mViewPager.getAdapter() == null || bannerView.mViewPager.getAdapter().getCount() <= 0) {
                sendEmptyMessageDelayed(MSG_LOOP, LOOP_INTERVAL);
                return;
            }
            int curPos = bannerView.mViewPager.getCurrentItem();
            curPos = (curPos + 1) % bannerView.mViewPager.getAdapter().getCount();
            bannerView.mViewPager.setCurrentItem(curPos);
            sendEmptyMessageDelayed(MSG_LOOP, LOOP_INTERVAL);
        }
    }

• 4.具体细节，如无限轮播adapter的创建，handler中的弱引用，启动销毁loop等等