使用CGAffineTransformMakeRotation時的抖動運動

我在使用CGAffineTransformMakeRotation時發生跳躍運動的問題。它似乎工作正常，直到我到達象限1和2的頂部。下面是我使用的代碼和youtube鏈接，顯示發生了什麼。任何洞察力將非常感激。使用CGAffineTransformMakeRotation時的抖動運動

我的目標是旋轉一個UIWebView裏面的svg。由於我無法輕易地在UIWebView上單獨檢測觸摸，所以我在其上放置了一個空白的UIImageView。這使我可以檢測到觸摸並防止彈出複製對話框。

http://www.youtube.com/watch?v=x_OmS0MPdEE&feature=youtu.be

- (void)touchesMoved: (NSSet *)touches withEvent:(UIEvent *)event { 
[super touchesBegan:touches withEvent:event]; 
NSArray *allTouches = [touches allObjects]; 
CGPoint location = [[allTouches objectAtIndex:0] locationInView:self.view]; 
if(selected == 1) { 
    CGFloat rads = atan2f(location.y - (grid1.frame.size.height/2),location.x - (grid1.frame.size.width/2)); 
    grid1.transform = grid1Btn.transform = CGAffineTransformMakeRotation(rads); 
} 

    } 

    - (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { 
[super touchesBegan:touches withEvent:event]; 
NSArray *allTouches = [touches allObjects]; 
CGPoint location = [[allTouches objectAtIndex:0] locationInView:self.view]; 

if(CGRectContainsPoint(grid1Btn.frame, location)) 
{ 
    selected = 1; 
} 
    } 

    - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event 
    { 
     selected = -1; 
    }

來源

2011-11-19 Jeremy Roberts