ios - 转动轮子？

Question

我已经在这里阅读了一些相关示例，但无法使其发挥作用。我有一些名为 Wheel 的 UIView ，我想在其中触摸和拖动时旋转。它应该像真正的轮子一样工作，所以如果我触摸某个点，它不会旋转到该点，只有当我拖动手指时，我才会旋转。

我尝试过这个，但是我所做的每一个小 Action 都会得到一个完整的旋转。我想将天使添加到 View 中，而不是旋转到新天使..

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

    UITouch *touch = [[event allTouches] anyObject];
    CGPoint touchPoint = [touch locationInView:self];

    CGPoint center=wheel.center;

    float xLeg = fabs(center.x - touchPoint.x);
    float yLeg = fabs(center.y-touchPoint.y);
    float angle = atan(xLeg / yLeg);


    NSLog(@"%f",angle);
      wheel.transform = CGAffineTransformMakeRotation( angleInDegree );

}

Answer 1

这应该可以解决问题。请注意我如何将第一个接触点存储在 touchesBegan:withEvent: 中。这使我可以从拖动时获得的每个触摸点中减去第一个触摸点，从而为我提供需要旋转的真实角度。

编辑

我做了一些调整，现在即使在多次触摸之后它也变得平滑和规则。

演示

WheelViewController.m

@interface WheelViewController () {
    CGPoint startPoint;
    CGFloat startAngle;
    CGFloat endAngle;
}

@end

@implementation WheelViewController

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [[event allTouches] anyObject];
    startPoint = [touch locationInView:self.view];
    startAngle = [self angleForTouchPoint:startPoint] - endAngle;

    NSLog(@"\r\nStart angle: %f", startAngle);
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [[event allTouches] anyObject];
    CGPoint touchPoint = [touch locationInView:self.view];
    CGFloat touchAngle = [self angleForTouchPoint:touchPoint];

    NSLog(@"Touch angle: %f", touchAngle);

    self.wheel.transform = CGAffineTransformMakeRotation(fmodf(touchAngle - startAngle, 2 * M_PI));
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [[event allTouches] anyObject];
    CGPoint touchPoint = [touch locationInView:self.view];
    endAngle = [self angleForTouchPoint:touchPoint] - startAngle;

    NSLog(@"End angle: %f", endAngle);
}

- (CGFloat)angleForTouchPoint:(CGPoint)touchPoint {
    CGPoint center = self.wheel.center;

    float xLeg = touchPoint.x - center.x;
    float yLeg = touchPoint.y - center.y;

    float angle = fmodf(atan(yLeg/xLeg), (2 * M_PI));

    if (xLeg < 0) {
        angle += M_PI;
    }

    return angle;
}