我可以偏移目標C中的觸摸點嗎？

Question

是否可以抵消UITouch點？我正在使用下面顯示的觸摸方法。我想通過某個數字來抵消觸摸點，以便用戶能夠看到觸摸開始和畫出的位置。如果我試圖畫線，我想看到我的指尖，就像我們用鋼筆和鉛筆做的一樣。任何幫助歡迎。

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


    // add the first touch 
    UITouch *touch = [touches anyObject]; 

    previousPoint = [touch previousLocationInView:self]; 
    currentPoint = [touch locationInView:self]; 

    // init the bezier path 
    self.currentTool = [self toolWithCurrentSettings]; 
    self.currentTool.lineWidth = self.lineWidth; 
    self.currentTool.lineColor = self.lineColor; 
    self.currentTool.lineAlpha = self.lineAlpha; 

    [self.currentTool setInitialPoint:currentPoint]; 
... 

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

    // save all the touches in the path 
    UITouch *touch = [touches anyObject]; 

    previousPoint2 = previousPoint1; 
    previousPoint1 = [touch previousLocationInView:self]; 
    currentPoint = [touch locationInView:self]; 

    //currentPoint.y += 40; 
    CGRect bounds = [(DrawingPenTool*)self.currentTool addPathPreviousPoint:previousPoint2 withPreviousPoint:previousPoint1 withCurrentPoint:currentPoint]; 

     CGRect drawBox = bounds; 
     drawBox.origin.x -= self.lineWidth * 2.0; 
     drawBox.origin.y -= self.lineWidth * 2.0; 
     drawBox.size.width += self.lineWidth * 4.0; 
     drawBox.size.height += self.lineWidth * 4.0; 

     [self setNeedsDisplayInRect:drawBox];  
     [self.currentTool moveFromPoint:previousPoint1 toPoint:currentPoint]; 
     [self setNeedsDisplay]; 
    } 

} 

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

    [self touchesMoved:touches withEvent:event]; 

     CGPoint point = [[touches anyObject] locationInView:self]; 
     [self.currentTool setInitialPoint:point]; 


     } 

} 

Answer 1

可以使用的UIEvent predictedTouches和UITouch estimatedProperties就可以知道下一個觸摸可能會是。通過這種方式，您可以繼續繪製「前方」用戶。這正是這個功能的用途。