ios - 如何让这些方法适用于多点触控？

Question

我在教程中找到了这段代码，如果触摸在屏幕的特定一侧开始，则该代码几乎将左侧或右侧的 BOOL 设置为 YES，然后检查触摸何时移动，以查看它是否在屏幕上改变了两侧为了使另一个 BOOL 是。

所以我现在正在尝试实现多点触控，但我不确定它如何与以下代码一起使用？有人知道我会如何继续吗？

-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    touchStartPoint = [touch locationInView:self.view];
    if (touchStartPoint.x < 160.0) {
        touchLeftDown = TRUE;
    }
    else if (touchStartPoint.x > 160.0) {
        touchRightDown = TRUE;
    } 
}

-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    CGPoint currentTouchPoint = [touch locationInView:self.view];

    if (touchStartPoint.x < 160.0 && currentTouchPoint.x < 160.0) {
        touchLeftDown = TRUE;
    }
    else if (touchStartPoint.x > 160.0 && currentTouchPoint.x > 160.0)
    {
        touchRightDown = TRUE;
    }
}

-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    touchLeftDown = touchRightDown = FALSE;
}

谢谢!

编辑1:这些是 bool 值在游戏循环中所做的事情，我想要实现的目标是，如果两侧同时触摸，则 TOUCH_INCRMENT 将为 0，因为两侧的触摸将相互抵消出去。我将如何实现这一目标？无论如何，这就是我正在谈论的代码:

if (touchLeftDown == TRUE) {
        touchStep -= TOUCH_INCREMENT;
    }
    else if (touchRightDown == TRUE) {
        touchStep += TOUCH_INCREMENT;
    }
    else {
        touchStep = SLOWDOWN_FACTOR * touchStep;
    }
    touchStep = MIN(MAX(touchStep, -MAX_ABS_X_STEP), MAX_ABS_X_STEP);
    pos.x += touchStep;

Answer 1

您也许可以在没有 touchStartPoint (i)var 的情况下完成这项工作。重要的是不要使用 -anyObject 而是检查每次触摸。以下代码修改可能适合您:

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

    int leftTouches=0;
    int rightTouches=0;

    for (UITouch *touch in touches) 
    { 
        CGPoint location = [touch locationInView:touch.view];
        //just in case some code uses touchStartPoint
        touchStartPoint=location;

        if (location.x < 160.0) {
            leftTouches++;
        }
        else if (location.x > 160.0) {
            rightTouches++;
        }
    }

    //reset touch state
    touchLeftDown=FALSE;

    //set touch state if touch found
    if(leftTouches>0){
        touchLeftDown=TRUE;
    }

    touchRightDown=FALSE;
    if(rightTouches>0){
        touchRightDown=TRUE;
    }

}
-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self countTouches:touches withEvent:event];
}

-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self countTouches:touches withEvent:event];
}

-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    touchLeftDown = touchRightDown = FALSE;
}

这里我创建了一个由touchesBegan和touchesMoved调用的函数，因为它们需要实现相同的逻辑。如果代码中以某种方式使用 touchStartPoint，您可能会看到一些意想不到的副作用。