教你如何自定义AlertView

前言：

系统自带的alertView界面有点呆板，动画有点单一，总之随着业务的发展，系统自带的alertView已经很难满足我们的需求，那自定义的就很有必要。本文就介绍如何自定义alertView，看完你就懂得制作属于自己的alertView了

一、创建DWAlert.swift

创建一个类名为在DWAlert.swift，在 class DWAlert: UIView 里面添加一些常量和属性

//const 常量
let kAlertWidth = 245.0
let kAlertHeight = 160.0
let kTitleYOffset = 15.0
let kTitleHeight = 25.0

let kContentOffset = 30.0
let kBetweenLabelOffset = 20.0
let kSingleButtonWidth = 160.0
let kCoupleButtonWidth = 107.0
let kButtonHeight = 40.0
let kButtonBottomOffset = 10.0

//property 属性
var alertTitleLabel: UILabel!
var alertContentLabel: UILabel!
var button: UIButton!
var backImageView: UIView!
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上面代码 const 是为了定义弹出框需要的坐标和长宽，由于是不变，所有let修饰，与OC中的常量类似

二、绘制alertView

写一个继承init的方法,把title(alert标题)，content(alert内容)，Title(按钮标题)，作为参数

convenience init(alertTitle title: String, alertContent content: String, title Title: String) {

    
    self.init()
    self.layer.cornerRadius = 5.0
    self.backgroundColor = UIColor.white
    self.alertTitleLabel = UILabel.init(frame: CGRect(x: 0, y: kTitleYOffset, width: kAlertWidth, height: kTitleHeight))
    self.alertTitleLabel.font = UIFont.boldSystemFont(ofSize: 20.0)
    self.alertTitleLabel.textColor = UIColor.init(red: 56.0/255.0, green: 64.0/255.0, blue: 71.0/255.0, alpha: 1)
    self.addSubview(self.alertTitleLabel)
    
    let contentLabelWidth = kAlertWidth - 16
    let alertContentMaxY: Double = Double(self.alertTitleLabel.frame.maxY)
    self.alertContentLabel = UILabel.init(frame: CGRect(x: (kAlertWidth - contentLabelWidth) * 0.5, y: alertContentMaxY, width: contentLabelWidth, height: 60))
    self.alertContentLabel.numberOfLines = 0
    
    self.alertTitleLabel.textAlignment = .center
    self.alertContentLabel.textAlignment = self.alertTitleLabel.textAlignment
    self.alertContentLabel.textColor = UIColor.init(red: 127/255.0, green: 127/255.0, blue: 127/255.0, alpha: 1)
    self.alertContentLabel.font = UIFont.systemFont(ofSize: 15.0)
    self.addSubview(self.alertContentLabel)
    
    // about button
    let btnFrame = CGRect(x: (kAlertWidth - kSingleButtonWidth) * 0.5, y: kAlertHeight - kButtonBottomOffset - kButtonHeight, width: kSingleButtonWidth, height: kButtonHeight)
    self.button = UIButton.init(type: UIButtonType.custom)
    self.button.frame = btnFrame
    
    self.button.backgroundColor = UIColor.init(red: 245/255.0, green: 24/255.0, blue: 42/255.0, alpha: 1)
    self.button.setTitle(Title, for: .normal)
    self.button.titleLabel?.font = UIFont.systemFont(ofSize: 14.0)
    self.button.setTitleColor(UIColor.white, for: .normal)
    self.button.addTarget(self, action: #selector(BtnClick), for: .touchUpInside)
    self.button.layer.cornerRadius = 3.0
    self.addSubview(self.button)
    
    self.alertTitleLabel.text = title
    self.alertContentLabel.text = content
    
    //cancle button
    let cancleBtn = UIButton.init(type: .custom)
    cancleBtn.setImage(UIImage.init(named: "1.png"), for: .normal)
    cancleBtn.setImage(UIImage.init(named: "2.png"), for: .highlighted)
    cancleBtn.frame = CGRect(x: kAlertWidth - 32, y: 0, width: 32, height: 32)
    self.addSubview(cancleBtn)
    cancleBtn.addTarget(self, action: #selector(dismissAlert), for: .touchUpInside)

}

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因为调用 self.init() ,所以得使用关键字 convenence ,使上述函数变成便利构造函数，具体看convenence介绍

三、alertView的显示与隐藏

1、 show 实现alertView显示

func show() {
//1
    let shareWindow = UIApplication.shared.keyWindow
//2
    self.frame = CGRect(x: (Double((shareWindow?.bounds.width)!) - kAlertWidth)*0.5, y: -kAlertHeight - 30, width: kAlertWidth, height: kAlertHeight)
//3
    shareWindow?.addSubview(self)
}
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上面代码介绍: 1、拿到当前显示的主窗口。 注意：主窗口一定得有，否则会崩。 2、设置alertView的frame 3、把alertView添加到主窗口

2、 removeFromSuperview 实现AlertView隐藏

override func removeFromSuperview() {
    //1
    self.backImageView.removeFromSuperview()
    self.backImageView = nil
    
    //2
    let shareWindow = UIApplication.shared.keyWindow
    let afterFrame = CGRect(x: (Double((shareWindow?.bounds.width)!) - kAlertWidth)*0.5, y: Double((shareWindow?.bounds.height)!), width: kAlertWidth, height: kAlertHeight)
    
    //3
    UIView.animate(withDuration: 0.35, delay: 0.0, options: .curveEaseOut, animations: { 
        self.frame = afterFrame
        let angle = M_1_PI / 1.5
        self.transform = CGAffineTransform.init(rotationAngle: CGFloat(angle))
    }) { (finished) in
        //4
        super.removeFromSuperview()
    }
}

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上面代码介绍： 1、移除掉待会讲到的 willMove(toSuperview newSuperview: UIView?) 方法中添加的 backImageView 背景蒙版 2、获取当前主窗口，并定义一个alertView的frame 3、利用 UIView.animate 对alertView进行动画操作。 注意：angle值为M_1_PI / 1.5，只是个参考，您可以换其他的值，试试效果 4、完成动画后，调用父类的 removeFromSuperview 移除alertView

四、实现alertView坠落效果

在 willMove(toSuperview newSuperview: UIView?) 里面实现，该方法会在当alertView即将加入主窗口时被系统自动调用，详情请看UIView不可不知的秘密

override func willMove(toSuperview newSuperview: UIView?) {
    if newSuperview == nil {
        return
    }
    let shareWindow = UIApplication.shared.keyWindow
    
    if self.backImageView == nil {
        self.backImageView = UIView.init(frame: (shareWindow?.bounds)!)
    }
    
    self.backImageView.backgroundColor = UIColor.black
    self.backImageView.alpha = 0.6
    shareWindow?.addSubview(self.backImageView)
    let angle = M_1_PI / 2
    self.transform = CGAffineTransform.init(rotationAngle: CGFloat(angle))
    let afterFrame = CGRect(x: (Double((shareWindow?.bounds.width)!) - kAlertWidth)*0.5, y: (Double((shareWindow?.bounds.height)!) - kAlertHeight)*0.5, width: kAlertWidth, height: kAlertHeight)
    UIView.animate(withDuration: 0.35, delay: 0.0, options: .curveEaseIn, animations: {
        self.transform = CGAffineTransform.init(rotationAngle: 0)
        self.frame = afterFrame
    }) { (finished) in
    }
    super.willMove(toSuperview: newSuperview)
}
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上面代码重点是 UIView.animate 里的，实现了坠落动画效果。 注意： self.transform = CGAffineTransform.init(rotationAngle: 0) 设置旋转角度，再设置frame。

五、使用DWAlert

在 ViewController 创建一个按钮，并添加一个点击事件 ClickMe ,在方法里面创建alertView

@IBAction func ClickMe(_ sender: Any) {
    let alert = DWAlert(alertTitle: "注意", alertContent: "流星坠落效果来了:stuck_out_tongue_closed_eyes:", title: "确定")
    alert.show()
}
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在此，该alertView已经完成，效果如下：