iphone - 使用物镜 C 旋转图像

Question

我正在尝试旋转图像。我正在成功地做到这一点。问题是，当我向下单击并轻轻拖动时，图像会完全旋转以到达我单击的位置，然后在我顺时针拖动图像时缓慢旋转。我很关心为什么它会完全旋转到我拖动的地方。我希望拖动从找到的位置开始，而不是旋转到我手指按下的位置，然后从那里开始。

这是我的代码:

-

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

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

        int len = [allTouches count]-1;

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

        totalRadians = theAngle;

        [self rotateImage:theAngle];

    }

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

-(void) rotateImage:(float)angleRadians{

    self.transform = CGAffineTransformMakeRotation(angleRadians);
    CATransform3D rotatedTransform = self.layer.transform;
    self.layer.transform = rotatedTransform;    
}

我做错了什么吗？

谢谢!

Answer 1

不要从触摸得到的角度创建变换，而是尝试将 totalRadians 增加与新角度的差值，然后从中创建变换。

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

        int len = [allTouches count]-1;

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

        totalRadians += fabs(theAngle - totalRadians);
        totalRadians = fmod(totalRadians, 2*M_PI);

        [self rotateImage:totalRadians];

    }