最近刚入手学习IOS，第一个教程用的是《让不懂编程的人爱上iPhone开发(2013 iOS7版)，其中当选择在IOS 9.x deploy的时候，教程中UIAlertView已经不再适用，提示要用UIAlertController替代，所以学习了一下，特在此记录。

这次学习主要参考了：
Ammar 的 简书文章
一篇博客：博客

#import"ViewController.h"
@interfaceViewController()
- (IBAction)showAlert:(id)sender;
@end
- (IBAction)showAlert:(id)sender {
//下面内容的代码是放置在这里的
}

UIAlertControllerStyle有两种：Alert(对话框), Sheet(上拉菜单)

UIAlertControllerStyleAlert 和 UIAlertControllerStyleActionSheet

UIAlertActionStyle 有三种：Default(常规), Cancel(取消), Destructive(警示)

UIAlertActionStyleDefault, UIAlertActionStyleCancel, UIAlertActionStyleDestructive

现在看下面枚举的组合例子：

1 UIAlertControllerStyleAlert (对话框) 添加常规（okAction) 和 取消（cancelAction) 按钮：

UIAlertController* alert = [UIAlertController alertControllerWithTitle:@"Hi, Warrior!" message:@"Welcome To The Drag World" preferredStyle:UIAlertControllerStyleAlert];

UIAlertAction* okAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:nil];

UIAlertAction* cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleDestructive handler:nil];

[alert addAction: okAction];

[alert addAction: cancelAction];
//呈现视图
[self presentViewController:alert animated:YES completion:nil];

default & cancel

2 UIAlertControllerStyleAlert (对话框) 添加常规(okAction) 和警示(destructiveAction) 按钮：

只需要在上面代码中把UIAlertActionStyleCancel 替换成 UIAlertActionStyleDestructive.

default & destructive

3 UIAlertControllerStyleActionSheet (上拉菜单)添加常规，取消和警示按钮， 其中UIAlertActionStyleCancel 的UIAlertAction对象只能有一个，从显示中可以明显看出来：

UIAlertController* alert = [UIAlertControlleralertControllerWithTitle:@"Hi, Warrior!"message:@"Welcome To The Drag World"preferredStyle:UIAlertControllerStyleActionSheet];

UIAlertAction* okAction = [UIAlertActionactionWithTitle:@"OK"style:UIAlertActionStyleDefaulthandler:nil];

UIAlertAction* cancelAction = [UIAlertActionactionWithTitle:@"Cancel"style:UIAlertActionStyleCancelhandler:nil];

UIAlertAction* destructiveAction = [UIAlertActionactionWithTitle:@"Cancel"style:UIAlertActionStyleDestructivehandler:nil];

[alertaddAction: cancelAction];

[alertaddAction: okAction];

[alertaddAction: destructiveAction];

[self presentViewController:alert animated:YES completion:nil];

sheet

4 带文本输入框的对话框: 使用addTextFieldWithConfigurationHandler
例如：

UIAlertController* alert = [UIAlertController alertControllerWithTitle:@"Hi, Warrior!" message:@"Welcome To The Drag World" preferredStyle:UIAlertControllerStyleAlert];
    [alert addTextFieldWithConfigurationHandler:^(UITextField *textField){
        //配置输入框内的占位符
        textField.placeholder=@"Username";
        //设置输入框的背景颜色，其中这里RGB参数的设置范围不是0-255，而是0.0-1.0, alpha 是指背景透明度，0.0为全透明，1.0不透明
        textField.backgroundColor = [UIColor colorWithRed:111.0/255 green:206.0/255 blue:250.0/255 alpha:0.5];
}];
    [alert addTextFieldWithConfigurationHandler:^(UITextField *textFiled){
        textFiled.placeholder=@"Password";
        //设置密码的使用安全文本输入
        textFiled.secureTextEntry=YES;}];
    
    UIAlertAction *okAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
            }];
    UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:nil];
    UIAlertAction *deleteAction = [UIAlertAction actionWithTitle:@"Delete" style:UIAlertActionStyleDestructive handler:nil];
    
    [alert addAction: okAction];
    [alert addAction: cancelAction];
    [alert addAction: deleteAction];
    
    [self presentViewController:alert animated:YES completion:nil ];

带输入框的对话框