UITouch touchesMoved手指方向和速度

Question

如何獲得touchmoved功能中手指運動的速度和方向？

我想獲取手指速度和手指方向，並將其應用於UIView類的方向移動和動畫速度。

我看了這個鏈接，但我不明白的答案，除了它沒有解釋如何檢測方向：

UITouch movement speed detection

到目前爲止，我試過這段代碼：

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    UITouch *anyTouch = [touches anyObject]; 
    CGPoint touchLocation = [anyTouch locationInView:self.view]; 
    //NSLog(@"touch %f", touchLocation.x); 
    player.center = touchLocation; 
    [player setNeedsDisplay]; 
    self.previousTimestamp = event.timestamp;  
} 

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    UITouch *touch = [touches anyObject]; 
    CGPoint location = [touch locationInView:self.view]; 
    CGPoint prevLocation = [touch previousLocationInView:self.view]; 
    CGFloat distanceFromPrevious = [self distanceBetweenPoints:location :prevLocation]; 
    NSTimeInterval timeSincePrevious = event.timestamp - previousTimestamp; 

    NSLog(@"diff time %f", timeSincePrevious); 
} 

Answer 1

方向將根據touchesMoved中的「location」和「prevLocation」的值確定。具體而言，位置將包含觸摸的新點。例如：

if (location.x - prevLocation.x > 0) { 
    //finger touch went right 
} else { 
    //finger touch went left 
} 
if (location.y - prevLocation.y > 0) { 
    //finger touch went upwards 
} else { 
    //finger touch went downwards 
} 

現在touchesMoved將爲給定的手指移動調用多次。代碼的關鍵是比較手指第一次觸摸屏幕時的初始值和運動最終完成時的CGPoint值。

Answer 2

爲什麼不只是下面作爲obuseme的響應變化

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

     UITouch *aTouch = [touches anyObject]; 
     CGPoint newLocation = [aTouch locationInView:self.view]; 
     CGPoint prevLocation = [aTouch previousLocationInView:self.view]; 

     if (newLocation.x > prevLocation.x) { 
       //finger touch went right 
     } else { 
       //finger touch went left 
     } 
     if (newLocation.y > prevLocation.y) { 
       //finger touch went upwards 
     } else { 
       //finger touch went downwards 
     } 
}