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[操作系统]iOS 监听控件某个属性的改变observeValueForKeyPath


 

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"];    // 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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