iphone - 如何在iPhone的速度计中旋转图像

Question

以下是在触摸事件上旋转箭头(uiimage)的代码。在这种情况下，我减去了先前和当前两个触摸的位置，但是问题是箭头(uiimage)有时会沿触摸的相反方向移动。

- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
    UITouch *touch = [touches anyObject];        
    NSLog(@"%@",[touch view]);   
    if ([touch view] == ImgViewArrowImage) 
    {
    CGPoint currentLocation = [touch locationInView:touch.view];
    CGPoint pastLocation = [touch previousLocationInView:touch.view];

    CGPoint d1 = CGPointMake(currentLocation.x-touch.view.center.x, currentLocation.y-touch.view.center.y);   
    CGPoint d2 = CGPointMake(pastLocation.x-touch.view.center.x, pastLocation.y-touch.view.center.y);

    CGFloat angle1 = atan2(d1.y, d1.x); 
    CGFloat angle2 = atan2(d2.y, d2.x); 
    [[ImgViewArrowImage layer] setAnchorPoint:CGPointMake(0.0, 0.5)];
    [[ImgViewArrowImage layer] setPosition:CGPointMake(159,211)];

    ImgViewArrowImage.transform = CGAffineTransformRotate(ImgViewArrowImage.transform, angle1-angle2);
  } 
}

Answer 1

我只是从我的代码中删除了两行，我的代码现在正在工作，所以最终代码是

- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
    UITouch *touch = [touches anyObject];        
    NSLog(@"%@",[touch view]);   
    if ([touch view] == ImgViewArrowImage) 
    {
    CGPoint d1 = [touch locationInView:touch.view];
    CGPoint d2 = [touch previousLocationInView:touch.view];


    CGFloat angle1 = atan2(d1.y, d1.x); 
    CGFloat angle2 = atan2(d2.y, d2.x); 
    [[ImgViewArrowImage layer] setAnchorPoint:CGPointMake(0.0, 0.5)];
    [[ImgViewArrowImage layer] setPosition:CGPointMake(159,211)];

    ImgViewArrowImage.transform = CGAffineTransformRotate(ImgViewArrowImage.transform, angle1-angle2);
  } 
}