ios - UIControlEventTouchDragExit 在距 UIButton 100 像素时触发

Question

目前，UIControlEventTouchDragExit 仅在我将按钮拖离按钮 100 像素时触发。我想自定义此行为并将该范围调整到 25 像素左右，但我对编程还比较陌生，从来不需要重写/自定义这样的内置方法。

我在这里的一些其他帖子中读到我需要子类化 UIButton(或者甚至 UIControl？)，并覆盖 -( BOOL) beginTrackingWithTouch: (UITouch *) touch withEvent: (UIEvent *) event 和相关方法，但我真的不知道从哪里开始这样做。

任何人都可以就如何实现这一目标提供一些建议吗？非常感激! ^_^

Answer 1

像这样覆盖 continueTrackingWithTouch:withEvent: 以在默认间距内发送 DragExit/DragOutside 事件:

- (BOOL)continueTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event
{
    CGFloat boundsExtension = 25.0f;
    CGRect outerBounds = CGRectInset(self.bounds, -1 * boundsExtension, -1 * boundsExtension);

    BOOL touchOutside = !CGRectContainsPoint(outerBounds, [touch locationInView:self]);
    if(touchOutside)
    {
        BOOL previousTouchInside = CGRectContainsPoint(outerBounds, [touch previousLocationInView:self]);
        if(previousTouchInside)
        {
            NSLog(@"Sending UIControlEventTouchDragExit");
            [self sendActionsForControlEvents:UIControlEventTouchDragExit];
        }
        else
        {
            NSLog(@"Sending UIControlEventTouchDragOutside");
            [self sendActionsForControlEvents:UIControlEventTouchDragOutside];
        }
    }
    return [super continueTrackingWithTouch:touch withEvent:event];
}