筆記風(fēng)格借鑒Knight_SJ

需求點(diǎn)：

通過觸發(fā)鍵盤實(shí)現(xiàn)更新視圖約束的動(dòng)畫效果，網(wǎng)上有很多通過Masonry實(shí)現(xiàn)動(dòng)畫更新約束的教程西疤，本人用Swift簡單實(shí)現(xiàn)了下。
效果如下：

效果圖.gif

特點(diǎn)：
獲取鍵盤彈出和回收時(shí)間，實(shí)時(shí)更新約束拉宗，實(shí)現(xiàn)彈出或回收鍵盤與更新約束動(dòng)畫時(shí)間同步。

更新約束一共分為三個(gè)步驟：

1. 創(chuàng)建鍵盤彈出和隱藏系統(tǒng)通知
2. 實(shí)現(xiàn)通知方法
3. 通過調(diào)用needsUpdateConstraints及updateConstraintsIfNeeded實(shí)現(xiàn)動(dòng)畫更新

示例Demo：

觸發(fā)彈出或回收鍵盤通知方法中改變約束

1、首先創(chuàng)建鍵盤彈出和隱藏系統(tǒng)通知

// 鍵盤將要彈出
NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow(notification:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
        
// 鍵盤將要回彈
NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide(notification:)), name: NSNotification.Name.UIKeyboardWillHide, object: nil)

2旦事、實(shí)現(xiàn)通知方法

    // MARK: - 鍵盤將要彈出
    func keyboardWillShow(notification: Notification) {
        let userInfo = notification.userInfo
        let aValue = userInfo?[UIKeyboardAnimationDurationUserInfoKey]
        SLLog("彈出\(aValue!)")
        
        // 判斷是否是第一次觸發(fā)開始編輯魁巩，如果是第一次則改變約束
        if isUpdataExpand == false {
            updateWithExpand(isExpanded: true, animated: true, duration: aValue! as! TimeInterval)
            isUpdataExpand = true
        }
    }
    
    // MARK: - 鍵盤將要回收
    func keyboardWillHide(notification: Notification) {
        let userInfo = notification.userInfo
        let aValue = userInfo?[UIKeyboardAnimationDurationUserInfoKey]
        SLLog("回收\(aValue!)")
        updateWithExpand(isExpanded: false, animated: true, duration: aValue! as! TimeInterval)
        // 回收把isUpdataExpand設(shè)置為false
        isUpdataExpand = false
    }

3.更新約束

    // MARK: - 更新約束
    func updateWithExpand(isExpanded:Bool, animated:Bool, duration:TimeInterval = 0.25) {
        // 重要：更新約束需要調(diào)用updateConstraints閉包
        soolifeImg.snp.updateConstraints { (make) in
            if isExpanded == false{
                make.centerX.equalTo(self)
                make.width.equalTo(SCREEN_W/4)
                make.top.equalTo(self.snp.top).offset(AD_HEIGHT(90))
                make.height.equalTo(AD_HEIGHT(120))
            }else{
                make.centerX.equalTo(self)
                make.width.equalTo(SCREEN_W/5)
                make.top.equalTo(self.snp.top).offset(AD_HEIGHT(50))
                make.height.equalTo(AD_HEIGHT(80))
            }
        }
        
        accountIT.snp.updateConstraints { (make) in
            make.left.equalTo(self.snp.left).offset(AD_WIDTH(15))
            make.right.equalTo(self.snp.right).offset(AD_WIDTH(-15))
            make.height.equalTo(AD_HEIGHT(45))
            if isExpanded == false{
                make.top.equalTo(soolifeImg.snp.bottom).offset(AD_HEIGHT(60))
            }else{
                make.top.equalTo(soolifeImg.snp.bottom).offset(AD_HEIGHT(40))
            }
        }
        
        passwordIT.snp.updateConstraints { (make) in
            make.left.equalTo(self.snp.left).offset(AD_WIDTH(15))
            make.right.equalTo(self.snp.right).offset(AD_WIDTH(-15))
            make.height.equalTo(AD_HEIGHT(45))
            make.top.equalTo(accountIT.snp.bottom).offset(AD_HEIGHT(5))
        }
        
        loginBtn.snp.updateConstraints { (make) in
            make.top.equalTo(passwordIT.snp.bottom).offset(AD_HEIGHT(40))
            make.left.equalTo(self.snp.left).offset(AD_WIDTH(20))
            make.right.equalTo(self.snp.right).offset(AD_WIDTH(-20))
            make.height.equalTo(AD_HEIGHT(40))
        }
        
        
        if animated == true {
            // 告訴self.view約束需要更新
            self.needsUpdateConstraints()
            // 調(diào)用此方法告訴self.view檢測是否需要更新約束，若需要?jiǎng)t更新姐浮，下面添加動(dòng)畫效果才起作用
            self.updateConstraintsIfNeeded()
            // 更新動(dòng)畫
            UIView.animate(withDuration: duration, animations: {
                self.layoutIfNeeded()
            })
        }
    }

完整Demo

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