尝试在keypress上移动box2dweb中的动态主体

Question

我创建了一个dynamic_body，我希望使用EventListener移动该主体。 但是，我无法访问正文，我的代码中存在ApplyImpulse()或ApplyForce()函数的问题。但我无法看到它。我错过了什么？

function init() {
    var   b2Vec2 = Box2D.Common.Math.b2Vec2
        ,  b2AABB = Box2D.Collision.b2AABB
        ,   b2BodyDef = Box2D.Dynamics.b2BodyDef
        ,   b2Body = Box2D.Dynamics.b2Body
        ,   b2FixtureDef = Box2D.Dynamics.b2FixtureDef
        ,   b2Fixture = Box2D.Dynamics.b2Fixture
        ,   b2World = Box2D.Dynamics.b2World
        ,   b2MassData = Box2D.Collision.Shapes.b2MassData
        ,   b2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape
        ,   b2CircleShape = Box2D.Collision.Shapes.b2CircleShape
        ,   b2DebugDraw = Box2D.Dynamics.b2DebugDraw
        ,  b2MouseJointDef =  Box2D.Dynamics.Joints.b2MouseJointDef
        ;

     var world = new b2World(
           new b2Vec2(0, 0)    //gravity
        ,  true                 //allow sleep
     );

     var fixDef = new b2FixtureDef;
     fixDef.density = 1.0;
     fixDef.friction = 0.5;
     fixDef.restitution = 0.2;


     var bodyDef = new b2BodyDef;
     //creating ground
     bodyDef.type = b2Body.b2_staticBody;
     fixDef.shape = new b2PolygonShape;
     fixDef.shape.SetAsBox(20, 2);
     bodyDef.position.Set(10, 500 / 30 + 1.8);
     world.CreateBody(bodyDef).CreateFixture(fixDef);
     bodyDef.position.Set(10, -1.8);
     world.CreateBody(bodyDef).CreateFixture(fixDef);
     fixDef.shape.SetAsBox(2, 14);
     bodyDef.position.Set(-1.8, 13);
     world.CreateBody(bodyDef).CreateFixture(fixDef);
     bodyDef.position.Set(25, 13);
     world.CreateBody(bodyDef).CreateFixture(fixDef);

     // creating body

     playerbody = new b2BodyDef;
     playerbody.type = b2Body.b2_dynamicBody;
     bodyfix = new b2FixtureDef;
     bodyfix.shape = new b2PolygonShape;   
     bodyfix.shape.SetAsBox(
         0.4 //half width
         ,  0.6 //half height
     );
     playerbody.position.x = 3.2;
     playerbody.position.y = 14;

     bodyfix.body = playerbody;
     bodyA = world.CreateBody(playerbody).CreateFixture(bodyfix);

     function aPressed()  { 
         var direction = new b2Vec2(-5,0);
         bodyA.ApplyImpulse( direction , bodyA.GetWorldCenter());
     }
     function dPressed() { 
         var direction = new b2Vec2(5,0);
         bodyA.ApplyImpulse( direction , bodyA.GetWorldCenter());
     }
     function spacePressed()    {
         var direction = new b2Vec2(0,5);
         bodyA.ApplyImpulse( direction , bodyA.GetWorldCenter());
     }
     function ctrlPressed(){
         var direction = new b2Vec2(0,-2);
         bodyA.ApplyImpulse( direction , bodyA.GetWorldCenter());
     }
     // keyboard controls
   document.addEventListener('keypress',function(event) { 
       var keycode = event.keyCode;
       switch (keycode){
       case 65:
           aPressed();
           break;
       case 68: 
           dPressed();
           break;
       case 32:
           spacePressed();
           break;
       case 17:
           ctrlPressed();
           break;
     }
 },false);