UIControlEventTouchDragExit在距离UIButton 100像素时触发

Question

目前,UIControlEventTouchDragExit当我从按钮拖出100像素时,唯一的触发器.我想自定义这种行为并将该范围带到大约25像素,但我对编程相对较新,并且从未需要覆盖/自定义这样的内置方法.

我在这里读了一些其他帖子,我需要继承UIButton(或者甚至UIControl？),覆盖-(BOOL) beginTrackingWithTouch: (UITouch *) touch withEvent: (UIEvent *) event和相关的方法,但我真的不知道从哪里开始这样做.

有谁可以提供一些关于如何实现这一目标的建议？非常感激!^ _ ^

Answer 1

覆盖continueTrackingWithTouch:withEvent:像这样在默认装订线内发送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];
}

Answer 2

我发现接受的答案有两个问题.

1. 注册的操作将被调用两次:
   • 第一次是手指离开控件25个像素,这是在覆盖方法中设置的.
   • 当手指离开控件大约70个像素时,第二次被调用,这是UIControl的默认行为.
2. 第二个问题是从event参数检索的位置是(0, 0),它没有正确初始化.

我找到了另一种基于这个答案来实现这个目的的方法,基本思想是在回调中处理事件而不是覆盖该方法.有两个步骤:

注册动作:

    // to get the touch up event
    [btn addTarget:self action:@selector(btnTouchUp:withEvent:) forControlEvents:UIControlEventTouchUpInside];
    [btn addTarget:self action:@selector(btnTouchUp:withEvent:) forControlEvents:UIControlEventTouchUpOutside];
    // to get the drag event
    [btn addTarget:self action:@selector(btnDragged:withEvent:) forControlEvents:UIControlEventTouchDragInside];
    [btn addTarget:self action:@selector(btnDragged:withEvent:) forControlEvents:UIControlEventTouchDragOutside];

处理事件:

- (void)btnTouchUp:(UIButton *)sender withEvent:(UIEvent *)event {
    UITouch *touch = [[event allTouches] anyObject];
    CGFloat boundsExtension = 25.0f;
    CGRect outerBounds = CGRectInset(sender.bounds, -1 * boundsExtension, -1 * boundsExtension);
    BOOL touchOutside = !CGRectContainsPoint(outerBounds, [touch locationInView:sender]);
    if (touchOutside) {
        // UIControlEventTouchUpOutside
    } else {
        // UIControlEventTouchUpInside
    }
}

- (void)btnDragged:(UIButton *)sender withEvent:(UIEvent *)event {
    UITouch *touch = [[event allTouches] anyObject];
    CGFloat boundsExtension = 25.0f;
    CGRect outerBounds = CGRectInset(sender.bounds, -1 * boundsExtension, -1 * boundsExtension);
    BOOL touchOutside = !CGRectContainsPoint(outerBounds, [touch locationInView:sender]);
    if (touchOutside) {
        BOOL previewTouchInside = CGRectContainsPoint(outerBounds, [touch previousLocationInView:sender]);
        if (previewTouchInside) {
            // UIControlEventTouchDragExit
        } else {
            // UIControlEventTouchDragOutside
        }
    } else {
        BOOL previewTouchOutside = !CGRectContainsPoint(outerBounds, [touch previousLocationInView:sender]);
        if (previewTouchOutside) {
            // UIControlEventTouchDragEnter
        } else {
            // UIControlEventTouchDragInside
        }
    }    
}

现在所有六个事件都可以使用25像素的边界扩展来处理,您当然可以根据需要将此值设置为其他值.