实现QQ的TabBar拖拽动效

话不多说,效果如下:

全部代码已上传至 —Github— 欢迎 Star.

使用

class HKTabBarViewController: UITabBarController {

override func viewDidLoad() {
    super.viewDidLoad()
    ...
    viewControllers = [vc0, vc1, vc2]

    /**
     * imageName 图片名称
     * title 文字
     * distance 最大的偏移距离
     * mini_x_Coef 小图x偏移系数
     * mini_y_Coef 小图y偏移系数
     */
    let item = HKTabBarModel(imageName: "recent", title: "消息", distance: 10, mini_x_Coef: 0.2, mini_y_Coef: 0.4)
    let item1 = HKTabBarModel(imageName: "buddy", title: "联系人")
    let item2 = HKTabBarModel(imageName: "qworld", title: "动态", distance: 10, mini_x_Coef: -0.2, mini_y_Coef: 0.2)

    // let tabbar = HKTabBar(items: [item, item1, item2])
    // tabbar.hk_delegate = self

    let tabbar = HKTabBar(items: [item, item1, item2]) { (btn, index) in
        print(btn?.title ?? "title")
        self.selectedIndex = index
    }

        self.setValue(tabbar, forKey: "tabBar")
    }
}

//extension HKTabBarViewController: HKTabBarDelegate {
//    func hk_tabBar(_ tabBar: HKTabBar, didSelect item: HKDragButton, index: Int) {
//         self.selectedIndex = index
//    }
//}

分析

我们分析动画效果可以猜出,QQ的TabBar 是在按钮上放置了两张图片.在拖拽时两张图片分别有着不同的偏移量.(在QQ的资源包里发现了,这样的图片,证实确实是两张图片而成).

工作
所以呢,实现这个效果有几个重点(重点不是难点 都很简单),

1.让按钮响应拖拽(pan)手势,并能根据手指的位置计算两张图片应有的偏移
代码如下

        //distance 最大偏移量
        // dragButton_x  & dragButton_y 需要偏移的量
        //
         var point = pan.location(in: self)
         point = CGPoint(x: point.x - bounds.size.width * 0.5, y:  point.y - bounds.size.height * 0.5)
         let X = point.x
         let Y = point.y
         let R = sqrt(pow(X , 2) + pow(Y , 2))
         let scale = R / distance
         self.dragButton_x = X / scale
         self.dragButton_y = Y / scale

2.更改图片位置

    //mini_x_Coef ,mini_y_Coef 是小图的偏移差异,为了造成"立体(诡异)"的效果
    private func dragIcon() {
        let x =  (bounds.size.width - imageView_big.bounds.size.width) * 0.5 + dragButton_x
        let y =  (bounds.size.height - imageView_big.bounds.size.height) * 0.5 + dragButton_y
        
        self.imageView_big.frame = CGRect(x: x,
                                          y: y,
                                          width: self.imageView_big.bounds.size.width,
                                          height: self.imageView_big.bounds.size.height
        )
        
        self.imageView_mini.frame = CGRect(x: x + self.dragButton_x * mini_x_Coef,
                                           y: y + self.dragButton_y * mini_y_Coef,
                                           width: self.imageView_big.bounds.size.width,
                                           height: self.imageView_big.bounds.size.height
        )
    }

3.放手归位

    //让计算出的偏移量位0 即可
     self.dragButton_y = 0
     self.dragButton_x = 0
     UIView.animate(withDuration: 0.3) {
        self.imageView_big.frame = CGRect(x: 0.0 , y: 0.0, width: self.itemW, height: self.itemH - 15.0)
        self.imageView_mini.frame = CGRect(x: 0.0 , y: 0.0, width: self.itemW, height: self.itemH - 15.0)
      }

4.选中动画

    //首先更改图片
      ...
    //最简单的动画
     UIView.animate(withDuration: 0.2, animations: {
            self.imageView_big.transform = CGAffineTransform(scaleX: 0.85, y: 0.85)
            self.imageView_mini.transform = CGAffineTransform(scaleX: 0.85, y: 0.85)
            
        }) { (_) in
            UIView.animate(withDuration: 0.2, animations: {
                self.imageView_big.transform = CGAffineTransform(scaleX: 1, y: 1)
                self.imageView_mini.transform = CGAffineTransform(scaleX: 1, y: 1)
            })
        }

以上便是 <实现QQ的TabBar拖拽动效> 的主要代码 Github