Question

在iOS应用中，我有两个跟随用户触摸的UI元素。问题是如果触摸移动到快速，UI元素将停止跟随。（它还确保UI元素不能移动到某些边界之外）

这是我用来移动UI元素的代码，在移动的触摸上运行：

// Move the pinch UI around
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

    UITouch *touch = [[event allTouches] anyObject];
    CGPoint touchLoc = [touch locationInView:self.view];

    CGPoint imageHeight = CGPointMake((_pinchUI_top.frame.origin.x)+(_pinchUI_top.frame.size.width/2), size_OriginalImage.height);

    // Top line
    if (CGRectContainsPoint([_pinchUI_top frame], [touch locationInView:self.view])) {

        CGPoint touchLocY = CGPointMake((_pinchUI_top.frame.origin.x)+(_pinchUI_top.frame.size.width/2), touchLoc.y);
        _pinchUI_top.center = touchLocY;

        // If outside of image, stop
        if (touchLocY.y > imageHeight.y) {
            _pinchUI_top.center = imageHeight;
        }
        else {
            pixelsFromBottom = touchLoc.y;
        }

    // Bottom line
    } else if (CGRectContainsPoint([_pinchUI_bottom frame], [touch locationInView:self.view])) {

        CGPoint touchLocY = CGPointMake((_pinchUI_bottom.frame.origin.x)+(_pinchUI_bottom.frame.size.width/2), touchLoc.y);
        _pinchUI_bottom.center = touchLocY;

        // If outside of image, stop
        if (touchLocY.y > imageHeight.y) {
            _pinchUI_bottom.center = imageHeight;
        }
        else {
            pixelsFromTop = touchLoc.y;
        }
    }
}

_pinchUI_top和_pinchUI_bottom是两个UI元素。

Answer 1

使用touchesBegan事件获取原始位置（并处理顶部或底部），因此不要在touchesMoved中进行检查，而是在触摸事件开始时执行此操作。然后在touchesMoved事件中，您可以移动相应的图像。

float topY;
float bottomY;
bool touchValid;
bool touchTop;

- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    UITouch *touch = [[event allTouches] anyObject];
    CGPoint touchLoc = [touch locationInView:self.view];

    float touchY = touchLoc.y;

    touchValid = NO;

    if (CGRectContainsPoint([_pinchUI_top frame], [touch locationInView:self.view])) {
        topY = touchY;
        touchTop = YES;
        touchValid = YES;
    } else if (CGRectContainsPoint([_pinchUI_bottom frame], [touch locationInView:self.view])){
        bottomY = touchY;
        touchTop = NO;
        touchValid = YES;
    }

}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

    UITouch *touch = [[event allTouches] anyObject];
    CGPoint touchLoc = [touch locationInView:self.view];

    CGPoint imageHeight = CGPointMake((_pinchUI_top.frame.origin.x)+(_pinchUI_top.frame.size.width/2), size_OriginalImage.height);

    if (touchValid) {

        // Top line
        if (touchTop) {

            CGPoint touchLocY = CGPointMake((_pinchUI_top.frame.origin.x)+(_pinchUI_top.frame.size.width/2), touchLoc.y);
            _pinchUI_top.center = touchLocY;

            // If outside of image, stop
            if (touchLocY.y > imageHeight.y) {
            _pinchUI_top.center = imageHeight;
            }
            else {
                pixelsFromBottom = touchLoc.y;
            }

    // Bottom line
        } else if (!touchTop) {

            CGPoint touchLocY = CGPointMake((_pinchUI_bottom.frame.origin.x)+(_pinchUI_bottom.frame.size.width/2), touchLoc.y);
            _pinchUI_bottom.center = touchLocY;

            // If outside of image, stop
            if (touchLocY.y > imageHeight.y) {
                _pinchUI_bottom.center = imageHeight;
            }
            else {
                pixelsFromTop = touchLoc.y;
            }

        }
    }
}

这应该解决它。

触摸后UI元素出现问题

1 个答案: