iOS键盘监听以及获取键盘高度

 1 #import "ViewController.h"
 2 
 3 @interface ViewController ()<UITextFieldDelegate>
 4 @property (weak, nonatomic) IBOutlet UITextField *inputField;
 5 // 拖线获取的视图约束对象
 6 @property (weak, nonatomic) IBOutlet NSLayoutConstraint *toBottom;
 7 
 8 @end
 9 
10 @implementation ViewController
11 
12 - (void)viewDidLoad {
13     [super viewDidLoad];
14     
15     self.inputField.delegate = self;
16  
17     // 添加通知监听见键盘弹出/退出
18     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardAction:) name:UIKeyboardWillShowNotification object:nil];
19     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardAction:) name:UIKeyboardWillHideNotification object:nil];
20 }
21 
22 // 点击非TextField区域取消第一响应者
23 - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
24     [self.inputField resignFirstResponder];
25 }
26 
27 // 点击键盘Return键取消第一响应者
28 - (BOOL)textFieldShouldReturn:(UITextField *)textField{
29     [self.inputField resignFirstResponder];
30     return  YES;
31 }
32 
33 // 点击按钮取，消第一响应者
34 - (IBAction)okAction:(UIButton *)sender {
35     [self.inputField resignFirstResponder];
36 }
37 
38 // 键盘监听事件
39 - (void)keyboardAction:(NSNotification*)sender{
40     // 通过通知对象获取键盘frame: [value CGRectValue]
41     NSDictionary *useInfo = [sender userInfo];
42     NSValue *value = [useInfo objectForKey:UIKeyboardFrameEndUserInfoKey];
43     
44     // <注意>具有约束的控件通过改变约束值进行frame的改变处理
45     if([sender.name isEqualToString:UIKeyboardWillShowNotification]){
46         self.toBottom.constant = [value CGRectValue].size.height;
47     }else{
48         self.toBottom.constant = 0;
49     }
50 }
51 
52 - (void)didReceiveMemoryWarning {
53     [super didReceiveMemoryWarning];
54 }
55 
56 @end