Question

所以我正在研究汽车的快速动画，我希望轮胎旋转并向前翻转......但由于某种原因，它们向前滑动但后来我添加了旋转它们的代码，现在它们旋转了它来回跳跃随机x位置，这是非常令人困惑的，我不知道发生了什么......我是否遗漏了一个必要的框架或什么？

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    frame = [NSTimer scheduledTimerWithTimeInterval:1/40.f
                                                   target:self
                                                 selector:@selector(enterFrame)
                                                 userInfo:nil
                                                  repeats:YES];


}


-(void)enterFrame {

    //spin += +0.5;
    spin = 0.5;

    //wheel.center = CGPointMake(wheel.center.x+0.5, wheel.center.y);
    wheel.center = CGPointMake(wheel.center.x+spin, wheel.center.y);

    //wheel.transform = CGAffineTransformMakeRotation(spin);        
    wheel.transform = CGAffineTransformRotate(wheel.transform, spin);

}

Answer 1

绕任意点（即不是原点）旋转：

将原点移动到任意点
进行轮换。
将原点移回原位。

（以下链接指向所涉及的数学：http://www.euclideanspace.com/maths/geometry/affine/aroundPoint/matrix2d/）

请尝试以下代码，这可能会解决您的问题：

//translate the origin to the center of the wheel                                           
wheel.transform = CGAffineTransformTranslate(CGAffineTransformIdentity, wheel.center.x, wheel.center.y);   

//rotate the wheel
wheel.transform = CGAffineTransformRotate(wheel.transform, spin);   

//translate the origin back
wheel.transform = CGAffineTransformTranslate(wheel.transform,-wheel.center.x,-wheel.center.y);  

//Move the wheel 
wheel.transform = CGAffineTransformTranslate(wheel.transform,wheel.center.x+spin, wheel.center.y);

Answer 2

尝试传递角度，而不管其当前的转换如下：

wheel.transform = CGAffineTransformMakeRotation( spin/180*M_PI );

使用NSTimer旋转和翻译UIImageView

2 个答案: