Github: https://github.com/saitjr/MasonryDemo

#import "ViewController4.h"
#import "Masonry.h"
 
@interface ViewController4 ()
 
@property (strong, nonatomic) UITextField *textField;
 
@end
 
@implementation ViewController4
 
- (void)dealloc {
     
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}
 
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
     
    _textField = [UITextField new];
    _textField.backgroundColor = [UIColor redColor];
    [self.view addSubview:_textField];
     
    [_textField mas_makeConstraints:^(MASConstraintMaker *make) {
        make.left.mas_equalTo(10);
        make.centerX.equalTo(self.view);
        make.bottom.mas_equalTo(0);
        make.height.mas_equalTo(40);
    }];
     
    // 注册键盘通知
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillChangeFrameNotification:) name:UIKeyboardWillChangeFrameNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHideNotification:) name:UIKeyboardWillHideNotification object:nil];
}
 
- (void)keyboardWillChangeFrameNotification:(NSNotification *)notification {
     
    // 获取键盘基本信息（动画时长与键盘高度）
    NSDictionary *userInfo = [notification userInfo];
    CGRect rect = [userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    CGFloat keyboardHeight = CGRectGetHeight(rect);
    CGFloat keyboardDuration = [userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
     
    // 修改下边距约束
    [_textField mas_updateConstraints:^(MASConstraintMaker *make) {
        make.bottom.mas_equalTo(-keyboardHeight);
    }];
     
    // 更新约束
    [UIView animateWithDuration:keyboardDuration animations:^{
        [self.view layoutIfNeeded];
    }];
}
 
- (void)keyboardWillHideNotification:(NSNotification *)notification {
     
    // 获得键盘动画时长
    NSDictionary *userInfo = [notification userInfo];
    CGFloat keyboardDuration = [userInfo[UIKeyboardAnimationDurationUserInfoKey] doubleValue];
     
    // 修改为以前的约束（距下边距0）
    [_textField mas_updateConstraints:^(MASConstraintMaker *make) {
        make.bottom.mas_equalTo(0);
    }];
     
    // 更新约束
    [UIView animateWithDuration:keyboardDuration animations:^{
        [self.view layoutIfNeeded];
    }];
}
 
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesBegan:touches withEvent:event];
    [self.view endEditing:YES];
}
 
@end