下面我們來看一篇關於Swift使用SnapKit布局實現鍵盤出現後底部輸入框上浮效果，希望這篇文章可以對各位帶來幫助。

使用SnapKit布局時，如何實現鍵盤跟隨？
之前的文章中，我們頁面使用的是 Constraints 約束布局。如果頁面元素是使用 SnapKit 這個第三方布局庫來布局的話，也是可以實現鍵盤的跟隨上移效果。
實現方式同樣是監聽鍵盤通知，然後改變下約束，從而實現上移動畫效果。

效果圖如下：

代碼如下：

import UIKit
import SnapKit
 
class ViewController: UIViewController {
    
    //底部工具欄下約束
    var bottomConstraint: Constraint?
 
    //底部工具欄視圖
    var toolBar = UIView()
    
    //發送按鈕
    var sendBtn = UIButton(type: .System)
    
    //文本輸入框
    var textField = UITextField()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        //添加底部工具欄視圖
        toolBar.backgroundColor = UIColor(red: 0, green: 0, blue: 0, alpha: 0.1)
        self.view.addSubview(toolBar)
        
        //設置底部工具欄視圖約束
        toolBar.snp_makeConstraints { (make) -> Void in
            make.left.right.equalTo(self.view)
            make.height.equalTo(50)
            self.bottomConstraint = make.bottom.equalTo(self.view).constraint
        }
        
        //添加按鈕
        sendBtn.setTitle("發送", forState: .Normal)
        sendBtn.setTitleColor(UIColor.whiteColor(),forState: .Normal)
        sendBtn.backgroundColor=UIColor.orangeColor()
        sendBtn.addTarget(self,action:#selector(sendMessage(_:)),forControlEvents:.TouchUpInside)
        toolBar.addSubview(sendBtn)
        
        //設置按鈕約束
        sendBtn.snp_makeConstraints { (make) -> Void in
            make.width.equalTo(60)
            make.height.equalTo(30)
            make.centerY.equalTo(toolBar)
            make.right.equalTo(toolBar).offset(-10)
        }
        
        //添加輸入框
        textField.borderStyle = UITextBorderStyle.RoundedRect
        toolBar.addSubview(textField)
        
        //設置輸入框約束
        textField.snp_makeConstraints { (make) -> Void in
            make.left.equalTo(toolBar).offset(10)
            make.right.equalTo(sendBtn.snp_left).offset(-10)
            make.height.equalTo(30)
            make.centerY.equalTo(toolBar)
        }
        
        //監聽鍵盤通知
        NSNotificationCenter.defaultCenter().addObserver(self,
                        selector: #selector(ViewController.keyboardWillChange(_:)),
                        name: UIKeyboardWillChangeFrameNotification, object: nil)
    }
    
    //鍵盤改變
    func keyboardWillChange(notification: NSNotification) {
        if let userInfo = notification.userInfo,
            value = userInfo[UIKeyboardFrameEndUserInfoKey] as? NSValue,
            duration = userInfo[UIKeyboardAnimationDurationUserInfoKey] as? Double,
            curve = userInfo[UIKeyboardAnimationCurveUserInfoKey] as? UInt {
            
            let frame = value.CGRectValue()
            let intersection = CGRectIntersection(frame, self.view.frame)
            
            //self.view.setNeedsLayout()
            //改變下約束
            self.bottomConstraint?.updateOffset(-CGRectGetHeight(intersection))
            
            UIView.animateWithDuration(duration, delay: 0.0,
                                       options: UIViewAnimationOptions(rawValue: curve),
                                       animations: { _ in
                                        self.view.layoutIfNeeded()
                }, completion: nil)
        }
    }
    
    //發送按鈕點擊
    func sendMessage(sender: AnyObject) {
        //關閉鍵盤
        textField.resignFirstResponder()
    }
 
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}