小球向一个方向持续运动的Demo

HelloWorldScene.h

......//设置一个protected的属性protected:    cocos2d::Vec2 _vec;......

HelloWorldScene.cpp

//这个是通过随机数设置向量的方向_vec.set(random(-0.1f, 1.0f), random(-1.0f, 1.0f));//通过normalize这个标准化函数，能够使得向量的大小为1_vec.normalize();auto dot = DrawNode::create();dot -> drawDot(Vec2(0, 0), 5, Color4F(1.0f,1.0f,1.0f,1.0f));addChild(dot);dot -> setPosition(origin.x + visibleSize.width/2,origin.y + visibleSize.height/2);schedule([dot,this,origin,visibleSize](float f){    Vec2 nowVec = dot -> getPosition();    //判断小球碰壁反弹运动    if (nowVec.x<origin.x || nowVec.x>origin.x+visibleSize.width) {        _vec.x *= -1;    }    if (nowVec.y<origin.y || nowVec.y>origin.y+visibleSize.height) {        _vec.y *= -1;    }    dot->setPosition(nowVec+_vec*10);}, "Test");

Cocos2d入门--3-- 向量的应用