的UIImageView如何跟蹤順時針或逆時針用戶運動

Question

我已經成功地實現這個職位旋轉使用此代碼一個UIImageView

iPhone - Wheel tracking finger jumps to same starting position?

我同胞的開發人員的問題是，在觸摸的用戶既可以旋轉圖像順時針和逆時針。有沒有一種方法可以檢測用戶移動視圖的方向？

它對我很重要，因爲我正在製作一個時鐘應用程序。我讓用戶將分針形式從0分鐘一直移動到60分鐘。當它到達那裏時，我將時針向上移動一次。但用戶可以逆時針旋轉分針，在這種情況下，我需要將時針向下移動一下。有任何想法嗎？

Answer 1

你可以設置一個名爲「lastPoint」的成員變量來記錄點你感動

的，你可以calc下下一次的方向

CGPoint lastPoint; 


- (void) touchedBegin:(NSSet *)touches withEvent:(UIEvent *)event { 
    lastPoint = [touch locationInView:self.view]; 
} 

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

//you can save the point , then used in next time you want 

int tInput = [allTouches count]-1; 

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

float theLastAngle = atan2(lastPoint.y-imageX.center.y, lastPoint.x-imageX.center.x); 

lastPoint = location; 

// compare theAngle & theLastAngle , so you can know it is clockwise or counterclockwise. 
}