Button离开高亮状态时调用方法

问题描述

我想在按钮突出显示时执行一个操作，并在它离开突出显示状态时执行另一个操作.有什么建议吗?

I want to perform a action when a button is highlighted and perform another action when it leaves the highlighted state. Any advice?

推荐答案

你可以使用KVO

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

然后

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([@"highlighted" isEqualToString:keyPath]) {

        NSNumber *new = [change objectForKey:NSKeyValueChangeNewKey];
        NSNumber *old = [change objectForKey:NSKeyValueChangeOldKey];

        if (old && [new isEqualToNumber:old]) {
            NSLog(@"Highlight state has not changed");
        } else {
            NSLog(@"Highlight state has changed to %d", [object isHighlighted]);
        }
    }
}

您只真正关心更改，并且每次状态更改时都会调用它，例如如果您移动选择，然后用手指向下拖动到按钮外

You only really care about the changes and this will be called every time the state changes e.g. if you move select and then with your finger still down drag outside of the button

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