iphone - UIImageView 如何跟踪顺时针或逆时针用户运动

Question

我已经使用这篇文章中的这段代码成功地实现了旋转 uiimageview

iPhone - Wheel tracking finger jumps to same starting position?

我想问其他开发人员的问题是，触摸的用户可以顺时针和逆时针旋转图像。有什么方法可以检测用户移动 View 的方向吗？

它对我很重要，因为我正在制作一个时钟应用程序。我让用户将最小手从 0 分钟一直移动到 60 分钟。当它到达那里时，我将时针向上移动。但是用户可以逆时针旋转分针，在这种情况下我需要将时针向下移动。有什么想法吗？

Answer 1

你可以设置一个名为“lastPoint”的成员变量来记录你上次移动的点

下次可以计算方向

CGPoint lastPoint;


- (void) touchedBegin:(NSSet *)touches withEvent:(UIEvent *)event {
    lastPoint = [touch locationInView:self.view];
}

-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
NSSet *allTouches = [event allTouches];

//you can save the point , then used in next time you want

int tInput = [allTouches count]-1;

UITouch *touch =[[allTouches allObjects] objectAtIndex:tInput];
CGPoint location = [touch locationInView:self.view];
float theAngle = atan2( location.y-imageX.center.y, location.x-imageX.center.x );

<strong>float theLastAngle =  atan2( lastPoint.y-imageX.center.y, lastPoint.x-imageX.center.x );</strong>

<strong>lastPoint = location;</strong>

// compare theAngle & theLastAngle , so you can know it is clockwise or counterclockwise.
}