仿转转首页Banner图

实现效果

• 当banner滚动的时候 首先会缩放当前以及上一个或下一个banner图，
• 当banner滚动时会，背景会随滚动系数变化

部分实现

1、缩放（自动滚动）

   自动滚动开始时 缩放当前cell
  @objc func automaticScroll(){
        if totalItemCount == 0{return}
        let currentIndex = self.currentIndex()  
        let targetIndex = currentIndex + 1
        
        let cell = banner.cellForItem(at: IndexPath.init(row: currentIndex, section: 0))
        UIView.animate(withDuration: 0.2, animations: {
            cell?.transform = CGAffineTransform(scaleX: 0.85, y: 0.85)
        }) { (finish) in
            self.scrollToIndex(targetIndex: targetIndex)
        }
    }
//滚动动画结束后还原 当前 以及 前后的cell
func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
        self.autoScrollIndex = self.currentIndex()
        
        let cell1 = banner.cellForItem(at: IndexPath.init(row: self.autoScrollIndex - 1 < 0 ? totalItemCount :  self.autoScrollIndex - 1, section: 0))
        
        let cell2 = banner.cellForItem(at: IndexPath.init(row: self.autoScrollIndex , section: 0))
        let cell3 = banner.cellForItem(at: IndexPath.init(row: self.autoScrollIndex + 1 > totalItemCount ? totalItemCount/2 : 0, section: 0))
        
        UIView.animate(withDuration: 0.2) {
            cell1?.transform = CGAffineTransform(scaleX: 1, y: 1)
            cell2?.transform = CGAffineTransform(scaleX: 1, y: 1)
            cell3?.transform = CGAffineTransform(scaleX: 1, y: 1)
        }
    }
  

2、缩放（拖动）

if scrollView.isDragging || scrollView.isDecelerating{
            let itemIndex = self.pageControlIndexWithCurrentCellIndex(index: draggingIndex)
            //向左
            if lastContentOffset > curretContentOffset{

                let cell1 = banner.cellForItem(at: IndexPath.init(row: self.draggingIndex, section: 0))
                let cell2 = banner.cellForItem(at: IndexPath.init(row: self.draggingIndex - 1 < 0 ? totalItemCount: self.draggingIndex - 1, section: 0))
                
                UIView.animate(withDuration: 0.1) {
                    cell1?.transform = CGAffineTransform(scaleX: 0.85, y: 0.85)
                    cell2?.transform = CGAffineTransform(scaleX: 0.85, y: 0.85)
                }
                let topIndex = itemIndex - 1 < 0 ? self.banners.count - 1 : itemIndex - 1
                let bottomIndex = itemIndex
                self.topImage.sd_setImage(with: URL.init(string: banners[topIndex].bgImg!), completed: nil)
                self.bottomImage.sd_setImage(with: URL.init(string: banners[bottomIndex].bgImg!), completed: nil)
                UIView.animate(withDuration: 0.5, animations: {
                    self.leftView.setRadius(radius: (mainW * CGFloat(self.draggingIndex) - curretContentOffset) * 2, direction: .right)
                    self.rightView.setRadius(radius: 0, direction: .left)
                })
                
            }else{
                 //向右
                let cell1 = banner.cellForItem(at: IndexPath.init(row: self.draggingIndex, section: 0))
                let cell2 = banner.cellForItem(at: IndexPath.init(row: self.draggingIndex + 1 >= totalItemCount ? totalItemCount/2 : draggingIndex + 1, section: 0))
                
                UIView.animate(withDuration: 0.1) {
                    cell1?.transform = CGAffineTransform(scaleX: 0.85, y: 0.85)
                    cell2?.transform = CGAffineTransform(scaleX: 0.85, y: 0.85)
                }
                
                let topIndex = itemIndex + 1 > self.banners.count - 1 ? 0 : itemIndex + 1
                let bottomIndex = itemIndex
                self.topImage.sd_setImage(with: URL.init(string: banners[topIndex].bgImg!), completed: nil)
                self.bottomImage.sd_setImage(with: URL.init(string: banners[bottomIndex].bgImg!), completed: nil)
                UIView.animate(withDuration: 0.5, animations: {
                    self.leftView.setRadius(radius: 0, direction: .right)
                    self.rightView.setRadius(radius: (mainW * CGFloat(self.draggingIndex) - curretContentOffset) * 2, direction: .left)
                })
            }
        }


func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        //拖动结束后
        lastContentOffset = scrollView.contentOffset.x
        self.autoScrollIndex = self.currentIndex()
        
        let cell1 = banner.cellForItem(at: IndexPath.init(row: self.autoScrollIndex - 1 < 0 ? totalItemCount :  self.autoScrollIndex - 1 , section: 0))
        let cell2 = banner.cellForItem(at: IndexPath.init(row: self.autoScrollIndex , section: 0))
        let cell3 = banner.cellForItem(at: IndexPath.init(row: self.autoScrollIndex + 1 > totalItemCount ? totalItemCount/2 : 0, section: 0))
        
        UIView.animate(withDuration: 0.2) {
            cell1?.transform = CGAffineTransform(scaleX: 1, y: 1)
            cell2?.transform = CGAffineTransform(scaleX: 1, y: 1)
            cell3?.transform = CGAffineTransform(scaleX: 1, y: 1)
        }
    }
    

2、背景动画

思路：
在view底层有两个imageView  在最上层的view加个MaskView（遮罩）MaskView 上分别添加两个view即leftView以及当banner滚动时 改变左右的圆的半径 实现动画效果

UIView.animate(withDuration: 0.5, animations: {
                    self.leftView.setRadius(radius: (curretContentOffset - mainW * CGFloat(itemIndex)) * 2, direction: .right)
                    self.rightView.setRadius(radius: 0, direction: .left)
                })

UIView.animate(withDuration: 0.5, animations: {
                    self.leftView.setRadius(radius: 0, direction: .right)
                    self.rightView.setRadius(radius: (curretContentOffset - mainW * CGFloat(self.autoScrollIndex)) * 2, direction: .left)
                })


import UIKit

enum MDBannerSrollDirection {
    case unknow
    case left
    case right
}

class MDMaskView: UIView {

    // Only override draw() if you perform custom drawing.
    // An empty implementation adversely affects performance during animation.
    
    var maskRadius:CGFloat = 0
    var direction:MDBannerSrollDirection = .unknow
    func setRadius(radius:CGFloat,direction:MDBannerSrollDirection){
        self.maskRadius = radius
        self.direction = direction
        if self.direction != .unknow{
            self.setNeedsDisplay()
        }
        
    }
    
    override func draw(_ rect: CGRect) {
        self.backgroundColor = .clear
        if direction != .unknow{
            let ctx = UIGraphicsGetCurrentContext()
            if direction == .left{
                ctx?.addArc(center: CGPoint(x: self.center.x + rect.width/2, y: self.center.y), radius: maskRadius, startAngle: 0, endAngle: .pi * 2, clockwise: false)
            }else{
                ctx?.addArc(center: CGPoint(x: self.center.x - rect.width/2, y: self.center.y), radius: maskRadius, startAngle: 0, endAngle: .pi * 2, clockwise: false)
            }
            ctx?.setFillColor(UIColor.white.cgColor)
            ctx?.fillPath()
        }
    }

}

github地址 https://github.com/daimengxiaozhi/MDShockBannerView 给个Star吧！
2018.4.27 新增OC版本 2018.5.3 新增Android版本
注：初步尝试可能会有bug，欢迎大家提出建议。

附安卓使用代码：

  classpath 'com.jfrog.bintray.gradle:gradle-bintray-plugin:1.1'
        classpath 'com.github.dcendents:android-maven-gradle-plugin:1.5'



 mBannerList = result.data;
mBOneBanner.setImages(mBannerList)
                        .setImageLoader(new GlideImageLoader()).start();
 @Override
    public void onStart() {
        super.onStart();
        mBOneBanner.stopAutoPlay();
    }

    @Override
    public void onStop() {
        super.onStop();
        //结束轮播
        mBOneBanner.stopAutoPlay();
    }
@Override
    public void OnBannerClick(int position) {
      //点击事件
    }