UIButton根据不同的状态设置layer

这需要用到KVO，监听button的highlighted属性的变化，在监听回调里根据监听到得属性值设置layer

设置监听如下

[button addObserver:self forKeyPath:@"highlighted" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL];

监听回调如下

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { UIButton * bt = (UIButton* )object;

if([keyPath isEqualToString:@"highlighted"])

{

if(bt.state == UIControlStateNormal) {

bt.layer.bordColor = [UIColor redColor].CGColor;

} else{

bt.layer.bordColor = [UIColor black].CGColor;

}

}