UIAlertController属性

自iOS8起，苹果就建议告警框使用UIAlertController来代替UIAlertView和UIActionSheel。下面总结了一些常见的用法：
注意：
书写代码的时候，如果在viewDidLoad方法中，需要通过GCD在开启一个线程，使用dispatch_async，而写在viewDidAppear方法中，就不需要开线程了。可以参考我之前写的UIAlertController_whose view is not in the window hierarchy!问题这篇文章

1 简单的应用 （同时按钮响应Handler使用的闭包函数）

效果图

Snip20160818_1.png
代码

import UIKit

class AlertViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        let alertController = UIAlertController(title: "系统提示",message: "您确定要离开此界面吗？", preferredStyle: .Alert)
        let cancelAction = UIAlertAction(title: "取消", style: .Cancel, handler: nil)
        let okAction = UIAlertAction(title: "好的", style: .Default,handler: { action in
            print("点击了确定")
        })
        alertController.addAction(cancelAction)
        alertController.addAction(okAction)
        self.presentViewController(alertController, animated: true, completion: nil)
    }
}

2 除了弹出，还可以使用从底部向上滑出的样式

注意：

• 如果上拉菜单中有“取消”按钮的话，那么它永远都会出现在菜单的底部，不管添加的次序是如何
• 按钮使用“Destructive”样式，文字颜色变红，用来来警示用户

效果图

Snip20160818_3.png

class AlertViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        let alertController = UIAlertController(title: "保存或删除数据", message: "删除数据将不可恢复", preferredStyle: .ActionSheet)
        let cancelAction = UIAlertAction(title: "取消", style: .Cancel, handler: nil)
        let deleteAction = UIAlertAction(title: "删除", style: .Destructive, handler: nil)
        let archiveAction = UIAlertAction(title: "保存", style: .Default, handler: nil)
        alertController.addAction(cancelAction)
        alertController.addAction(deleteAction)
        alertController.addAction(archiveAction)
        self.presentViewController(alertController, animated: true, completion: nil)
    }
}

3 添加任意数量文本输入框（比如可以用来实现个登陆框）

效果图

Snip20160818_5.png
代码

import UIKit

class AlertViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let alertController = UIAlertController(title: "系统登陆", message: "请输入用户名和密码", preferredStyle: .Alert)
        alertController.addTextFieldWithConfigurationHandler { (textField: UITextField!) in
            textField.placeholder = "用户名"
        }
        alertController.addTextFieldWithConfigurationHandler { (textField: UITextField!) in
            textField.placeholder = "密码"
            textField.secureTextEntry = true
        }
        let cancelAction = UIAlertAction(title: "取消", style: .Cancel, handler: nil)
        let okAction = UIAlertAction(title: "好的", style: .Default) { (action) in
        //也可以用下标的形式获取textField let login = alertController.textFields![0]
            let login = (alertController.textFields?.first!)! as UITextField
            let password = (alertController.textFields?.last)! as UITextField
            print("用户名:\(login.text) 密码:\(password.text)")
        }
        alertController.addAction(cancelAction)
        alertController.addAction(okAction)
        //        self.presentViewController(alertController, animated: animated, completion: nil)
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
            //在另外一个线程中处理这些操作，然后通知主线程更新界面。
            dispatch_async(dispatch_get_main_queue(), {
                self.presentViewController(alertController, animated: true, completion: nil)
            })
        }
    }
    
    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        let alertController = UIAlertController(title: "系统登陆", message: "请输入用户名和密码", preferredStyle: .Alert)
        alertController.addTextFieldWithConfigurationHandler { (textField: UITextField!) in
            textField.placeholder = "用户名"
        }
        alertController.addTextFieldWithConfigurationHandler { (textField: UITextField!) in
            textField.placeholder = "密码"
            textField.secureTextEntry = true
        }
        let cancelAction = UIAlertAction(title: "取消", style: .Cancel, handler: nil)
        let okAction = UIAlertAction(title: "好的", style: .Default) { (action) in
        //也可以用下标的形式获取textField let login = alertController.textFields![0]
            let login = (alertController.textFields?.first!)! as UITextField
            let password = (alertController.textFields?.last)! as UITextField
            print("用户名:\(login.text) 密码:\(password.text)")
        }
        alertController.addAction(cancelAction)
        alertController.addAction(okAction)
        self.presentViewController(alertController, animated: animated, completion: nil)
    }
}

4 使用代码移除提示框

self.presentedViewController?.dismissViewControllerAnimated(false, completion: nil)