cocos2d-x学习日志(15) --公告栏的实现（文字左右移动）

公告栏用的是CClayer(层)或者node节点，锚点位置是（0,0），文字信息使用CCLabelTTF保存，锚点位置是（0,0），使用的时候将它加入到node里面就好了

文字移动的思路是：

      每次都update公告的CCLabelTTF的坐标，为了让它从右往左进行移动，右边栏出来，左边栏消失，需要设置一下CCLabelTTF的可显示区域，CCLabelTTF::setTextureRect函数正是设置Label的可显示区域，因此左右边界需要特殊处理，解决方法：

HelloWorldScene.h

#ifndef __HELLOWORLD_SCENE_H__
#define __HELLOWORLD_SCENE_H__

#include "cocos2d.h"
#include <renren-ext.h>
USING_NS_CC;

class HelloWorld : public cocos2d::CCLayer
{
public:
// Here's a difference. Method 'init' in cocos2d-x returns bool, instead of returning 'id' in cocos2d-iphone
virtual bool init();

// there's no 'id' in cpp, so we recommend returning the class instance pointer
static cocos2d::CCScene* scene();

// a selector callback
void menuCloseCallback(CCObject* pSender);
CREATE_FUNC(HelloWorld);
// implement the "static node()" method manually
virtual void update(float delta);
CCLabelTTF* adLabel;
CCLayerColor * adCClayer;
CCRect m_informRect;
float m_informScrollX;
};

#endif // __HELLOWORLD_SCENE_H__

HelloWorldScene.cpp

bool HelloWorld::init()
{
//////////////////////////////
// 1. super init first
if ( !CCLayer::init() )
{
return false;
}

CCSize visibleSize = CCDirector::sharedDirector()->getVisibleSize();
CCPoint origin = CCDirector::sharedDirector()->getVisibleOrigin();
adCClayer = CCLayerColor::create(ccc4(255,0,0,100),300,30);
adCClayer->setPosition(ccp(visibleSize.width/10, visibleSize.height/2 + origin.y));
adCClayer->setAnchorPoint(ccp(0,0));
this->addChild(adCClayer);

CCSize size = adCClayer->getContentSize();

adLabel = CCLabelTTF::create("helloworld", "Arial", 24);
adLabel->setAnchorPoint(ccp(0,0));
adLabel->setPosition(CCSize(size.width,0));
m_informScrollX = size.width;
m_informRect = adLabel->getTextureRect();
this->scheduleUpdate();

adCClayer->addChild(adLabel);

return true;
}

void HelloWorld::update(float delta)
{
CCPoint pt = adCClayer->getPosition();
CCSize size = adCClayer->getContentSize();
// 文字X轴的左边界
m_informScrollX -= 1.0f;
if (m_informScrollX < -m_informRect.size.width)
{
m_informScrollX = size.width;
adLabel->setTextureRect(CCRectMake(0, 0, m_informRect.size.width, size.height));
CCLog("helloworld");
this->unscheduleUpdate();  //滚动文字越过左边界
}

// 文字从右边出来
int expose = size.width - m_informScrollX;
if (expose < m_informRect.size.width)
{
// 文字部分未全部显示出来
adLabel->setTextureRect(CCRectMake(0, 0, expose, size.height));
}
else
{
// 文字部分已经从右边全部显示出来
adLabel->setTextureRect(CCRectMake(0, 0, m_informRect.size.width, size.height));
}

// 文字从左边消失
if (m_informScrollX <= 0)
{
float offset = fabs(m_informScrollX);
adLabel->setTextureRect(CCRectMake(offset,0,adLabel->getTextureRect().size.width-offset,size.height));

return;
}
adLabel->setPosition(CCSize(m_informScrollX,0));
}

效果图：



参考博文：http://blog.csdn.net/yeweiouyang/article/details/12075039