/** 开始拖动刚体*/
private void startDragBody(b2Body b, float x, float y)
{
if (b == null || b.GetType() != b2Body.b2_dynamicBody)
{
return;
}
if (_mj != null)
{
_world.DestroyJoint(_mj);
}
b2MouseJointDef jointDef = new b2MouseJointDef();
jointDef.bodyA = _world.GetGroundBody();
jointDef.bodyB = b;
jointDef.target.Set(x, y);
jointDef.maxForce = 1e6f;
_mj = _world.CreateJoint(jointDef) as b2MouseJoint;
}
