ios 添加监听

创建一个测试的UIButton

#import "ViewController.h"

@interface ViewController ()

@property(nonatomic, strong)UIButton *button;

@end

@implementation ViewController

- (void)viewDidLoad { [super viewDidLoad]; self.button = [[UIButton alloc] initWithFrame:CGRectMake(30, 50, 50, 30)]; [self.button setTitle:@"测试" forState:UIControlStateNormal]; [self.button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal]; self.button.layer.borderWidth = 1.0f; [self.view addSubview:self.button]; //注册监听button的enabled状态 [self.button addObserver:self forKeyPath:@"enabled" options:NSKeyValueObservingOptionNew context:@"test_button"];

//监听self.panel.button的enable属性，addObserver 添加的是拥有者self NSKeyValueObservingOptionNew 是新值
[self.panel.button addObserver:self forKeyPath:@"enabled" options:NSKeyValueObservingOptionNew context:@"test_button"];
 //  3秒钟后改变当前button的enabled状态 dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0f * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ self.button.enabled = YES; });
}

添加监听观察者

/**
 *  监听按钮状态改变的方法
 *
 *  @param keyPath 按钮改变的属性
 *  @param object  按钮
 *  @param change  改变后的数据
 *  @param context 注册监听时context传递过来的值
 */
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { UIButton *button = (UIButton *)object; if (self.button == button && [@"enabled" isEqualToString:keyPath]) { NSLog(@"self.button的enabled属性改变了%@",[change objectForKey:@"new"]); }
}

log输出

2015-06-30 11:48:32.001 监听控件某个属性的改变[34212:570638] self.button的enabled属性改变了1

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