旋轉車輪？

Question

我在這里閱讀了一些有關此的示例，但無法使其正常工作。 我有一些名為Wheel的UIView，我想在其中觸摸和拖動時進行旋轉。 它應該像一個真正的輪子一樣工作，因此，如果我在某個點觸摸，它將不會旋轉到那個點，只有當我拖動手指時，我才會旋轉。

我試過了，但是我做的每一個小動作都會使我完全旋轉。 我想將天使添加到視圖中，而不是將其添加到新天使中。

- (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

這應該可以解決問題。 請注意，我如何將第一個接觸點存儲在touchesBegan:withEvent: 。 這使我可以從拖動時獲得的每個觸摸點中減去第一個觸摸點，從而獲得需要旋轉的真實角度。

編輯

我已經進行了一些調整，以便即使經過幾次觸摸也可以保持平滑和規則。

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;
}