一般游戏的主界面按钮的摆放，都是中心垂直对齐，如果弄得稍微炫一点，就是下面的这种效果，也就是本篇要讲解的内容：
先分析一下功能需求：
1、一共四个按钮，只有点击了最前面的按钮，按钮的响应事件才能触发，点击了其他按钮，则旋转到最前面。
2、点击了除最前面的按钮外的动画效果，和左右滑动时的动画效果。（大小，透明度，运动轨迹）
3、左右滑动到途中时松手时的动画调整。
4、按钮Z序的调整
5、滑动区域的限制
接下来看看代码怎么写：
定义一个类BtnTurn，来看头文件
#ifndef __BTN_TURN_H__
#define __BTN_TURN_H__
#include cocos2d.h
USING_NS_CC;
enum BtnPos
{
Pos_Bottom = 1,
Pos_Left,
Pos_Top,
Pos_Right,
};
class BtnTurn : public cocos2d::Layer
{
public:
BtnTurn();
~BtnTurn();
virtual bool init();
CREATE_FUNC(BtnTurn)
protected:
virtual bool onTouchBegan(Touch* touch, Event* pEvent);
virtual void onTouchMoved(Touch *pTouch, Event *pEvent);
virtual void onTouchEnded(Touch *pTouch, Event *pEvent);
//点击按钮之后的动画
void runTouchedAmt(Sprite * btn);
//滑动界面的动画
void runSlidedAmt(bool isLeft,float ratio,float judgePosX);
private:
Sprite * m_btn1;
Sprite * m_btn2;
Sprite * m_btn3;
Sprite * m_btn4;
Vec2 m_posBottom;
Vec2 m_posLeft;
Vec2 m_posTop;
Vec2 m_posRight;
Point m_firstPos;
Size m_winSize;
bool m_valid;//先点击有效区域
bool m_invalid;//先点击无效区域
};
#endif
这里最主要的核心代码就是沿椭圆轨迹旋转效果，之前有篇文章讲解了沿椭圆运动的动画，可以像用系统的MoveTo等使用runAction，参考地址：
http://blog.csdn.net/sharing_li/article/details/43268877
本篇将不采用链接中说的方法来实现。
首先，我们定义一些全局数据：
const float RUNTIME = 0.3; //动画运行时间
float A;//椭圆长半径
float Bd;//下椭圆短半径
float Bu;//上椭圆短半径
float Cx;//椭圆中心X坐标
float Cy;//椭圆中心Y坐标
再来看看我们的初始化函数：
m_winSize = Director::getInstance()->getWinSize();
m_posBottom = Vec2(0,0);
m_posLeft = Vec2(-m_winSize.width * 0.24,m_winSize.height * 0.15);
m_posTop = Vec2(0,m_winSize.height * 0.24);
m_posRight = Vec2(m_winSize.width * 0.24,m_winSize.height * 0.15);
A = m_posBottom.x - m_posLeft.x;
Bu = m_posTop.y - m_posLeft.y;
Bd = m_posLeft.y - m_posBottom.y;
Cx = m_posBottom.x;
Cy = m_posLeft.y;
Texture2D * pTt2d = Director::getInstance()->getTextureCache()->addImage(BtnTurn/btn.png);
m_btn1 = Sprite::createWithTexture(pTt2d);
m_btn1->setPosition(m_posBottom);
m_btn1->setTag(Pos_Bottom);
this->addChild(m_btn1,4);
m_btn2 = Sprite::createWithTexture(pTt2d);
m_btn2->setPosition(m_posLeft);
m_btn2->setScale(0.75);
m_btn2->setOpacity(100);
m_btn2->setTag(Pos_Left);
this->addChild(m_btn2,3);
m_btn3 = Sprite::createWithTexture(pTt2d);
m_btn3->setPosition(m_posTop);
m_btn3->setScale(0.5);
m_btn3->setOpacity(50);
m_btn3->setTag(Pos_Top);
this->addChild(m_btn3,2);
m_btn4 = Sprite::createWithTexture(pTt2d);
m_btn4->setPosition(m_posRight);
m_btn4->setScale(0.75);
m_btn4->setOpacity(100);
m_btn4->setTag(Pos_Right);
this->addChild(m_btn4,3);
auto listenerT = EventListenerTouchOneByOne::create();
listenerT->onTouchBegan = CC_CALLBACK_2(BtnTurn::onTouchBegan,this);
listenerT->onTouchMoved = CC_CALLBACK_2(BtnTurn::onTouchMoved,this);
listenerT->onTouchEnded = CC_CALLBACK_2(BtnTurn::onTouchEnded,this);
listenerT->setSwallowTouches(false);
Director::getInstance()->getEventDispatcher()->addEventListenerWithSceneGraphPriority(listenerT,this);
return true;
这里，初始化全局变量，和四个按钮的初始位置。可以发现这里的按钮并不是按钮，而是sprite，因为只有显示在最前面的按钮才能响应函数，所以定义成sprite方便处理。我们通过判断点击开始和点击结束，这两个点是否是同一个点来确定是否点击了按钮，然后根据按钮的Zorder来判断是否响应函数。我们还给每个按钮设置了tag值，这个tag值并不是不变的，因为按钮的位置会改变，所以tag的值也会改变，以确保我们通过getChildByTag函数，能够正确获取到相应tag值的按钮，比如getChildByTag(Pos_Top)，函数返回的一定是处于最上面位置的那个按钮。
我们来看看onTouchBegan函数：
bool BtnTurn::onTouchBegan(Touch* touch, Event* pEvent)
{
m_firstPos = touch->getLocation();
return true;
}
很简单，就两行代码，获取点击开始的按钮。然后看看onTouchMoved
void BtnTurn::onTouchMoved(Touch *pTouch, Event *pEvent)
{
auto movePos = pTouch->getLocation();
auto judgePos = this->convertToNodeSpace(movePos);
auto box = Rect(-m_winSize.width * 0.5,-m_winSize.height * 0.1,m_winSize.width,m_winSize.height * 0.4);
//优化，不能全屏都可以滑,并判断是先点击有效还是无效区域
if (!box.containsPoint(judgePos))
{
if (!m_valid)
{
m_invalid = true;
}
return ;
}
if (!m_invalid)
{
m_valid = true;
}
else
{
return ;
}
//根据滑动方向来运动
auto ratio = fabsf(movePos.x - m_firstPos.x) * 2 / m_winSize.width;
if (ratio >= 1)
{
return ;
}
this->runSlidedAmt(movePos.x - m_firstPos.x < 0,ratio,fabsf(m_firstPos.x - movePos.x));
}
上面代码中box是可以滑动的有效区域，m_valid和m_invalid是用来判断开始触摸屏幕，是点击了有效区域，还是无效区域。
然后根据滑动的方向，来调用动画实现函数runSlidedAmt：
void BtnTurn::runSlidedAmt(bool isLeft,float ratio,float judgePosX)
{
auto btnTop = this->getChildByTag(Pos_Top);
auto btnLeft = this->getChildByTag(Pos_Left);
auto btnRight = this->getChildByTag(Pos_Right);
auto btnBottom = this->getChildByTag(Pos_Bottom);
auto deltPosDown = m_posRight - m_posBottom;
auto deltPosUp = m_posTop - m_posLeft;
//判断是否需要调换Z顺序
if (judgePosX > m_winSize.width / 4)
{
btnTop->setZOrder(3);
btnLeft->setZOrder(isLeft ? 2 : 4);
btnRight->setZOrder(isLeft ? 4 : 2);
btnBottom->setZOrder(3);
}
auto B1 = isLeft ? Bu : Bd;//判断左边的button沿哪个椭圆运动
auto B2 = isLeft ? Bd : Bu;//判断右边的button沿哪个椭圆运动
int temp = isLeft ? (m_posBottom.x - deltPosDown.x * ratio) : (m_posBottom.x + deltPosDown.x * ratio);
btnBottom->setPosition(Vec2(temp,sin(-acos((temp - Cx)/A)) * Bd + Cy));
btnBottom->setScale(1 - 0.25 * ratio);
btnBottom->setOpacity(255 - 155 * ratio);
temp = isLeft ? (m_posLeft.y + deltPosUp.y * ratio) : (m_posLeft.y - deltPosDown.y * ratio);
btnLeft->setPosition(Vec2(-cos(asin((temp - Cy)/B1)) * A + Cx,temp));
btnLeft->setScale(0.75 - (isLeft ? 0.25 * ratio : -0.25 * ratio));
btnLeft->setOpacity(100 - (isLeft ? 50 * ratio : -155 * ratio));
temp = m_posTop.x + (isLeft ? (deltPosUp.x * ratio) : (-1 * deltPosUp.x * ratio));
btnTop->setPosition(Vec2(temp,sin(acos((temp - Cx)/A)) * Bu + Cy));
btnTop->setScale(0.5 + 0.25 * ratio);
btnTop->setOpacity(50 + 50 * ratio);
temp = m_posRight.y + (isLeft ? (-1 * deltPosDown.y * ratio) : (deltPosUp.y * ratio));
btnRight->setPosition(Vec2(cos(asin((temp - Cy)/B2)) * A + Cx,temp));
btnRight->setScale(0.75 + 0.25 * (isLeft ? ratio : -ratio));
btnRight->setOpacity(100 + (isLeft ? 155 * ratio : -50 * ratio));
}
这里，我们通过椭圆的非标准方程，根据已知的x坐标或者y坐标，求出对应的y坐标或x坐标。假如椭圆的圆心坐标为(Cx,Cy)，那么根据方程：
x = A * cosβ + Cx；y = B * sinβ + Cy；
然后根据数学函数库的反三角函数等，就可以求出相应的值了。这里需要注意的是三角函数和反三角函数的值域。
接着，我们来看看onTouchEnded函数：
void BtnTurn::onTouchEnded(Touch *pTouch, Event *pEvent)
{
if (m_invalid)
{
m_invalid = false;
return;
}
auto endPos = pTouch->getLocation();
auto delX = endPos.x - m_firstPos.x;
auto delY = endPos.y - m_firstPos.y;
//如果是点击操作
if (fabsf(delX) < 0.0001 && fabsf(delY) < 0.0001)
{
endPos = this->convertToNodeSpace(endPos);
auto box1 = m_btn1->getBoundingBox();
auto box2 = m_btn2->getBoundingBox();
auto box3 = m_btn3->getBoundingBox();
auto box4 = m_btn4->getBoundingBox();
if (box1.containsPoint(endPos))
{
if (m_btn1->getZOrder() == 4)
{
log(******************Btn1 CallBack***************);
}
else
{
this->runTouchedAmt(m_btn1);
}
}
else if (box2.containsPoint(endPos))
{
if (m_btn2->getZOrder() == 4)
{
log(******************Btn2 CallBack***************);
}
else
{
this->runTouchedAmt(m_btn2);
}
}
else if (box3.containsPoint(endPos))
{
if (m_btn3->getZOrder() == 4)
{
log(******************Btn3 CallBack***************);
}
else
{
this->runTouchedAmt(m_btn3);
}
}
else if (box4.containsPoint(endPos))
{
if (m_btn4->getZOrder() == 4)
{
log(******************Btn4 CallBack***************);
}
else
{
this->runTouchedAmt(m_btn4);
}
}
}
else//滑动操作
{
auto adjustPos = pTouch->getLocation();
//判断滑动方向
if (adjustPos.x - m_firstPos.x < 0)//向左滑动
{
auto tmpBtn = (Sprite *)this->getChildByTag(Pos_Right);
this->runTouchedAmt(tmpBtn);
}
else if (adjustPos.x - m_firstPos.x > 0)
{
auto tmpBtn = (Sprite *)this->getChildByTag(Pos_Left);
this->runTouchedAmt(tmpBtn);
}
}
m_valid = false;
}
首先判断是否是点击操作，如果是，再来判断点击了哪个button，如果是最前面的button，就响应函数，如果不是则调用动画效果；如果不是点击操作，那就是滑动操作，然后根据滑动方向调用调整动画。我们来看看runTouchedAmt函数：
void BtnTurn::runTouchedAmt(Sprite * btn)
{
auto tag = btn->getTag();
switch (tag)
{
case Pos_Left :
{
btn->runAction(Spawn::create(ScaleTo::create(RUNTIME,1),
Sequence::createWithTwoActions(MoveTo::create(RUNTIME / 2,m_posBottom),
MoveTo::create(RUNTIME / 2,m_posBottom)),
FadeIn::create(RUNTIME),NULL));
btn->setZOrder(4);
auto topBtn = (Sprite *)(this->getChildByTag(Pos_Top));
topBtn->runAction(Spawn::create(ScaleTo::create(RUNTIME,0.75),
MoveTo::create(RUNTIME,m_posLeft),
FadeTo::create(RUNTIME,100),NULL));
topBtn->setZOrder(3);
auto rightBtn = (Sprite *)this->getChildByTag(Pos_Right);
rightBtn->runAction(Spawn::create(ScaleTo::create(RUNTIME,0.5),
MoveTo::create(RUNTIME,m_posTop),
FadeTo::create(RUNTIME,50),NULL));
rightBtn->setZOrder(2);
auto bottomBtn = (Sprite *)this->getChildByTag(Pos_Bottom);
bottomBtn->runAction(Spawn::create(ScaleTo::create(RUNTIME,0.75),
MoveTo::create(RUNTIME,m_posRight),
FadeTo::create(RUNTIME,100),NULL));
bottomBtn->setZOrder(3);
btn->setTag(Pos_Bottom);
topBtn->setTag(Pos_Left);
rightBtn->setTag(Pos_Top);
bottomBtn->setTag(Pos_Right);
}
break;
case Pos_Top :
{
btn->runAction(Spawn::create(ScaleTo::create(RUNTIME,1),
Sequence::createWithTwoActions(MoveTo::create(RUNTIME/2,m_posLeft),MoveTo::create(RUNTIME/2,m_posBottom)),
FadeIn::create(0.2),NULL));
btn->setZOrder(4);
auto rightBtn = (Sprite *)this->getChildByTag(Pos_Right);
rightBtn->runAction(Spawn::create(Sequence::createWithTwoActions(ScaleTo::create(RUNTIME/2,0.5),ScaleTo::create(RUNTIME/2,0.75)),
Sequence::createWithTwoActions(MoveTo::create(RUNTIME/2,m_posTop),MoveTo::create(RUNTIME/2,m_posLeft)),
Sequence::createWithTwoActions(FadeTo::create(RUNTIME/2,50),FadeTo::create(RUNTIME/2,100)),NULL));
rightBtn->setZOrder(3);
auto bottomBtn = (Sprite *)this->getChildByTag(Pos_Bottom);
bottomBtn->runAction(Spawn::create(ScaleTo::create(RUNTIME,0.5),
Sequence::createWithTwoActions(MoveTo::create(RUNTIME/2,m_posRight),MoveTo::create(RUNTIME/2,m_posTop)),
FadeTo::create(RUNTIME,50),NULL));
bottomBtn->setZOrder(2);
auto leftBtn = (Sprite *)this->getChildByTag(Pos_Left);
leftBtn->runAction(Spawn::create(Sequence::createWithTwoActions(ScaleTo::create(RUNTIME/2,1),ScaleTo::create(RUNTIME/2,0.75)),
Sequence::createWithTwoActions(MoveTo::create(RUNTIME/2,m_posBottom),MoveTo::create(RUNTIME/2,m_posRight)),
Sequence::createWithTwoActions(FadeIn::create(RUNTIME/2),FadeTo::create(RUNTIME/2,100)),NULL));
leftBtn->setZOrder(3);
btn->setTag(Pos_Bottom);
leftBtn->setTag(Pos_Right);
rightBtn->setTag(Pos_Left);
bottomBtn->setTag(Pos_Top);
}
break;
case Pos_Right :
{
btn->runAction(Spawn::create(ScaleTo::create(RUNTIME,1),
MoveTo::create(RUNTIME,m_posBottom),
FadeIn::create(RUNTIME),NULL));
btn->setZOrder(4);
auto topBtn = (Sprite *)this->getChildByTag(Pos_Top);
topBtn->runAction(Spawn::create(ScaleTo::create(RUNTIME,0.75),
MoveTo::create(RUNTIME,m_posRight),
FadeTo::create(RUNTIME,100),NULL));
topBtn->setZOrder(3);
auto leftBtn = (Sprite *)this->getChildByTag(Pos_Left);
leftBtn->runAction(Spawn::create(ScaleTo::create(RUNTIME,0.5),
MoveTo::create(RUNTIME,m_posTop),
FadeTo::create(RUNTIME,50),NULL));
leftBtn->setZOrder(2);
auto bottomBtn = (Sprite *)this->getChildByTag(Pos_Bottom);
bottomBtn->runAction(Spawn::create(ScaleTo::create(RUNTIME,0.75),
MoveTo::create(RUNTIME,m_posLeft),
FadeTo::create(RUNTIME,100),NULL));
bottomBtn->setZOrder(3);
btn->setTag(Pos_Bottom);
topBtn->setTag(Pos_Right);
leftBtn->setTag(Pos_Top);
bottomBtn->setTag(Pos_Left);
}
break;
}
}
代码好像有点多，其实也就是分别处理点击了除最前面按钮的动画效果。这里简单起见，没有用椭圆效果，用的moveto函数。
