按钮离开突出显示状态时的调用方法 [英] Call method when Button leaves Highlighted State

问题描述

我想在突出显示按钮时执行操作，并在离开突出显示状态时执行其他操作。任何建议？

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:@"new"];
        NSNumber *old = [change objectForKey:@"old"];

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

你真正关心的是变化，这将在每次状态改变时被调用，例如如果你移动选择，然后用手指按下按钮

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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