我想在 BeginContact 事件上设置一个新的 body 位置,但它仍然不起作用。它是用 JavaSript 编写的,可以绘制到画布上,但对于 Box2d 来说并不重要。在正文中的 HTML 文件中只有空画布,没有别的。这是我的代码:
在 JS 文件的开头只声明了一些变量。
Vec2 = Box2D.Common.Math.b2Vec2;
BodyDef = Box2D.Dynamics.b2BodyDef;
Body = Box2D.Dynamics.b2Body;
FixtureDef = Box2D.Dynamics.b2FixtureDef;
Fixture = Box2D.Dynamics.b2Fixture;
World = Box2D.Dynamics.b2World;
PolygonShape = Box2D.Collision.Shapes.b2PolygonShape;
DebugDraw = Box2D.Dynamics.b2DebugDraw;
var player;
紧随其后的是一个在开始时调用的设置函数。
function setup()
{
canvas = document.getElementById("collisionCanvas");
context = canvas.getContext('2d');
document.getElementsByTagName('body')[0].style.backgroundColor = "black";
canvas.style.backgroundColor = "white";
canvas.width = 320;
canvas.height = 320;
world = new World(new Vec2(0, 10), false);
//Point of the problem!!!
//setting contact listener
var listener = new Box2D.Dynamics.b2ContactListener;
listener.BeginContact = function(contact)
{
var body1 = contact.GetFixtureA().GetBody();
var body2 = contact.GetFixtureB().GetBody();
if(body1.GetUserData().type == "player")
{
body1.SetPosition({x:5, y:5});
}
else
{
body2.SetPosition({x:5, y:5});
}
}
world.SetContactListener(listener);
var fixDef = new FixtureDef;
fixDef.density = 1.0;
fixDef.friction = 0.5;
fixDef.restitution = 0.2;
var bodyDef = new BodyDef;
//creating ground
bodyDef.type = Body.b2_staticBody;
bodyDef.position.x = convertPixelsToMeters(160);
bodyDef.position.y = convertPixelsToMeters(320-32/2);
bodyDef.userData = {type: "static"};
fixDef.shape = new PolygonShape;
fixDef.shape.SetAsBox(convertPixelsToMeters(canvas.width/2), convertPixelsToMeters(32/2));
world.CreateBody(bodyDef).CreateFixture(fixDef);
//creating player
bodyDef.type = Body.b2_dynamicBody;
bodyDef.fixedRotation = true;
bodyDef.position.x = convertPixelsToMeters(160);
bodyDef.position.y = convertPixelsToMeters(160);
bodyDef.userData = {type: "player"};
fixDef.shape = new PolygonShape;
fixDef.shape.SetAsBox(convertPixelsToMeters(16), convertPixelsToMeters(16));
player = world.CreateBody(bodyDef);
player.CreateFixture(fixDef);
//setup debug draw
var debugDraw = new DebugDraw();
debugDraw.SetSprite(document.getElementById("collisionCanvas").getContext("2d"));
debugDraw.SetDrawScale(32.0);
debugDraw.SetFillAlpha(0.3);
debugDraw.SetLineThickness(1.0);
debugDraw.SetFlags(DebugDraw.e_shapeBit | DebugDraw.e_jointBit);
world.SetDebugDraw(debugDraw);
window.setInterval(update, 1000 / 60);
}
最后只有更新功能,一个帮助功能,仅此而已。
function update()
{
world.Step(
1 / 60 //frame-rate
, 10 //velocity iterations
, 10 //position iterations
);
world.DrawDebugData();
world.ClearForces();
}
function convertPixelsToMeters(x)
{
return x*0.03125;
}
$(function(){
setup();
})
重要的是只有中间代码是 BeginContact 事件,其中调用了不起作用的 SetPosition 函数。
我尝试在其他地方更改位置,例如在 KeyDown 事件中,它是正确的,所以我可以理解为什么它不起作用。