在UIPanGestureRecognizer函数中调用ApplyLinearImpulse时不起作用

问题描述

我正在使用Box2d和Cocos2d开发iPhone游戏。我在屏幕中央有一个球，它具有使用固定装置等创建的简单边界。我想要做的是添加功能，以便用户可以滑动球以施加力并基本上在屏幕上轻拂它。 / p>

我正在使用以下代码来实现此目的：

  b2Vec2 force = b2Vec2（30，30）; 
 _body-> ApplyLinearImpulse（force，_ballBodyDef-> position）; 
  

如果我在init函数中施加线性脉冲，则球会朝正确的方向发射并表现为它应该做。但是，如果我将其放入 handlePan 函数（当用户完成手势时调用该函数），它什么也不会做。以下是该功能的完整代码：（请注意， NSLog 会写出正确的信息。

 -（void）handlePanFrom：（UIPanGestureRecognizer *）recognizer {
 if（recognizer.state == UIGestureRecognizerStateEnded）{
 CGPoint velocity = [recognizer velocityInView：recognizer.view]; 
 
 NSLog（@ Vel：％f，newPos：％f，velocity.x，velocity.y）; 
 
 b2Vec2 force = b2Vec2（30，30）; 
 _body-> ApplyLinearImpulse（force，_ballBodyDef-> position）; 
} 
} 
  

解决方案

您在handlePanFrom中施加的力始终为b2Vec2（30，30）。它永远不会随着您当前的代码而改变，因此不会移动您的方向。

I am using Box2d and Cocos2d to develop an iPhone game. I have a ball in the center of the screen with a simple boundary created using fixtures etc. What I want to do is add the functionality so that a user can "swipe" the ball to apply force and basically flick it across the screen.

I am using the following code to achieve this:

b2Vec2 force = b2Vec2(30, 30);
_body->ApplyLinearImpulse(force, _ballBodyDef->position);

If I apply a linear impulse during the init function the ball fires off in the correct direction and behaves as it should do. It doesnt do anything, however, if I put it into the handlePan function that is called when a gesture is done by the user. Here is the full code for the function: (Note that the NSLog writes out the correct information.

- (void)handlePanFrom:(UIPanGestureRecognizer *)recognizer {
    if (recognizer.state == UIGestureRecognizerStateEnded) {
            CGPoint velocity = [recognizer velocityInView:recognizer.view];

            NSLog(@"Vel: %f, newPos: %f",velocity.x,velocity.y);

            b2Vec2 force = b2Vec2(30, 30);
            _body->ApplyLinearImpulse(force, _ballBodyDef->position);
    }
}

解决方案

The force you are applying in handlePanFrom is always b2Vec2(30, 30). It will never change with your current code, and is therefore not going to move in your direction.

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