在可可觸摸中實現基於觸摸的旋轉

Question

我想知道什麼是在我的iPhone應用程序中實現基於旋轉的拖拽動作的最佳方式。

我有一個UIView，我希望圍繞它的中心旋轉，當用戶手指觸摸視圖並移動它時。把它想象成需要用手指調整的刻度盤。

的基本問題歸結爲：

1）我應該還記得最初的角度，改造時的touchesBegan被調用，然後每touchesMoved被調用時應用新的變換，基於當前位置的看法手指，例如，像：

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

    UITouch *touch = [touches anyObject]; 
    CGPoint currentPoint = [touch locationInView:self]; //current position of touch 

if (([touch view] == self) 
    && [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS //middle is centre of view 
    && [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //will be rotation gesture 

    //remember state of view at beginning of touch 
    CGPoint top = CGPointMake(self.middle.x, 0); 
    self.initialTouch = currentPoint; 
    self.initialAngle = angleBetweenLines(self.middle, top, self.middle, currentPoint); 
    self.initialTransform = self.transform; 
} 
} 

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

    UITouch *touch = [touches anyObject]; 
    CGPoint currentPoint = [touch locationInView:self]; //current position of touch 

    if (([touch view] == self) 
    && [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS 
    && [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //a rotation gesture 

    //rotate tile 
    float newAngle = angleBetweenLines(self.middle, CGPointMake(self.middle.x, 0), self.middle, currentPoint); //touch angle 
    float angleDif = newAngle - self.initialAngle; //work out dif between angle at beginning of touch and now. 
    CGAffineTransform newTransform = CGAffineTransformRotate(self.initialTransform, angleDif); //create new transform 
    self.transform = newTransform; //apply transform. 
} 

OR

2）如果我只是記得我最後已知的位置/角度和旋轉基於對之間的角度差的觀點，現在，例如， ：

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

     UITouch *touch = [touches anyObject]; 
     CGPoint currentPoint = [touch locationInView:self]; //current position of touch 

    if (([touch view] == self) 
     && [Utility getDistance:currentPoint toPoint:self.middle] <= ROTATE_RADIUS 
     && [Utility getDistance:currentPoint toPoint:self.middle] >= MOVE_RADIUS) { //will be rotation gesture 

     //remember state of view at beginning of touch 
     CGPoint top = CGPointMake(self.middle.x, 0); 
     self.lastTouch = currentPoint; 
     self.lastAngle = angleBetweenLines(self.middle, top, self.middle, currentPoint); 
    } 
    } 

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

     UITouch *touch = [touches anyObject]; 
     CGPoint currentPoint = [touch locationInView:self]; //current position of touch 

     if (([touch view] == self) 
     && [Utility getDistance:currentPoint toPoint:middle] <= ROTATE_RADIUS 
     && [Utility getDistance:currentPoint toPoint:middle] >= MOVE_RADIUS) { //a rotation gesture 

     //rotate tile 
     float newAngle = angleBetweenLines(self.middle, CGPointMake(self.middle.x, 0), self.middle, currentPoint); //touch angle 
     float angleDif = newAngle - self.lastAngle; //work out dif between angle at beginning of touch and now. 
     CGAffineTransform newTransform = CGAffineTransformRotate(self.transform, angleDif); //create new transform 

     self.transform = newTransform; //apply transform. 
     self.lastTouch = currentPoint; 
     self.lastAngle = newAngle; 
    } 

第二個選項對我更​​有意義，但它沒有給出令人愉快的結果（鋸齒更新和非平滑旋轉）。在性能方面哪種方式最好（如果有的話）？

乾杯！

Answer 1

您考慮過使用UIRotationGestureRecognizer嗎？看起來好像已經有了邏輯，可能會讓事情變得更簡單。

Answer 2

它實際上比您嘗試的更簡單。

您需要三個數據點：

• 你的觀點的由來。
• 當前觸摸
• 之前的觸摸

傳遞給你的觸摸對象實際上包含了最後觸摸位置的位置的位置。所以你不需要跟蹤它。

所有你需要做的就是兩條線之間計算角度：

• 產地爲當前觸摸
• 原產於之前的觸摸

然後將其轉換成弧度，並使用你的CGAffineTransformRotate（）。在touchesMoved處理程序中完成所有操作。

這裏是計算你需要的只是什麼功能：

傑夫拉馬什的

static inline CGFloat angleBetweenLinesInRadians(CGPoint line1Start, CGPoint line1End, CGPoint line2Start, CGPoint line2End) { 

    CGFloat a = line1End.x - line1Start.x; 
    CGFloat b = line1End.y - line1Start.y; 
    CGFloat c = line2End.x - line2Start.x; 
    CGFloat d = line2End.y - line2Start.y; 

    CGFloat line1Slope = (line1End.y - line1Start.y)/(line1End.x - line1Start.x); 
    CGFloat line2Slope = (line2End.y - line2Start.y)/(line2End.x - line2Start.x); 

    CGFloat degs = acosf(((a*c) + (b*d))/((sqrt(a*a + b*b)) * (sqrt(c*c + d*d)))); 


    return (line2Slope > line1Slope) ? degs : -degs;  
} 

禮貌：

http://iphonedevelopment.blogspot.com/2009/12/better-two-finger-rotate-gesture.html

例子：

UITouch *touch = [touches anyObject]; 
CGPoint origin = [view center]; 
CGFloat angle = angleBetweenLinesInRadians(origin, [touch previousLocationInView:self.superview.superview], origin, [touch locationInView:self.superview.superview]);