超越Spritekit中的触感

在我正在开发的游戏中,你可以通过触摸屏幕的左/右侧来将角色从左向右移动。我想做的是,如果你触摸左侧,然后触摸右侧,角色开始向右移动,而不是向左移动;向左移动的动作被覆盖。我目前做的是让游戏是单点触摸,但覆盖上一次触摸的方法是我一直坚持的地方。我的代码:

- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch *touch = [touches anyObject];
    CGPoint location = [touch locationInNode:self];

    if (location.x < screenWidth/2){
        leftMovement = YES;
        [player runLeft];
    }
    else {
        rightMovement = YES;
        [player runRight];
    }

    self.userInteractionEnabled = NO;

}
- (void) touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    [self playerStop];
    self.userInteractionEnabled = YES;
}

- (void) update:(NSTimeInterval)currentTime {
    if (isTouched && leftMovement){
        player.physicsBody.velocity=CGVectorMake(-PLAYERSPEED,
                                player.physicsBody.velocity.dy);
    }

    else if (isTouched && rightMovement){
        player.physicsBody.velocity=CGVectorMake(PLAYERSPEED,
                              player.physicsBody.velocity.dy);
    }

}