设置三个按钮等宽分布

效果图：

思路：(self为自定义的View，里面有三个按钮和两个分隔线)

一、按钮约束：使三个按钮等宽分布

1、按钮一：上、左、下和self对齐，宽和“按钮二”对齐

2、按钮二：上、下和self对齐，宽和“按钮三”对齐，左和“按钮二”右对齐

3、按钮三：上、右、下和self对齐，左和“按钮二”右对齐

二、竖线约束：

1、分隔线一：CenterY和self对齐，CenterX和“按钮一”右对齐

2、分隔线二：CenterY和self对齐，CenterX和“按钮二”右对齐

private func setupUI(){
        // 添加三个按钮
        let retweetButton = addChildButton(imageName: "timeline_icon_retweet",title: "转发")
        let commentButton = addChildButton(imageName: "timeline_icon_comment",title: "评论")
        let unlikeButton = addChildButton(imageName: "timeline_icon_unlike",title: "赞")
        
        // 添加两个分隔线
        let firstLineView = addChildLineView()
        let secondLineView = addChildLineView()
        
        // 设置三个按钮的约束
        retweetButton.snp_makeConstraints { (make) in
            make.top.leading.bottom.equalTo(self)
            make.width.equalTo(commentButton)
        }
        commentButton.snp_makeConstraints { (make) in
            make.top.bottom.equalTo(self)
            make.leading.equalTo(retweetButton.snp_trailing)
            make.width.equalTo(unlikeButton)
        }
        unlikeButton.snp_makeConstraints { (make) in
            make.top.trailing.bottom.equalTo(self)
            make.leading.equalTo(commentButton.snp_trailing)
        }
        
        // 设置两个分隔线约束
        firstLineView.snp_makeConstraints { (make) in
            make.centerX.equalTo(retweetButton.snp_trailing)
            make.centerY.equalTo(self)
        }
        secondLineView.snp_makeConstraints { (make) in
            make.centerX.equalTo(commentButton.snp_trailing)
            make.centerY.equalTo(self)
        }
    }
    
    // 创建button按钮
    private func addChildButton(imageName:String,title:String) -> UIButton{
        let button = UIButton()
        button.setImage(UIImage(named:imageName), for: .normal)
        button.setTitle(title, for: .normal)
        button.titleLabel?.font = UIFont.systemFont(ofSize: 14)
        button.setTitleColor(UIColor.darkGray, for: .normal)
        button.setBackgroundImage(UIImage(named:"timeline_card_bottom_background"), for: .normal)
        button.adjustsImageWhenHighlighted = false
        addSubview(button)
        return button
    }
    
    // 创建竖线视图
    private func addChildLineView() -> UIImageView{
        let imageView = UIImageView(image:UIImage(named:"timeline_card_bottom_line"))
        addSubview(imageView)
        return imageView
    }