如何制作一款HTML5 RPG游戏引擎——第三篇，利用幕布切换场景

开言：

在RPG游戏中，如果有地图切换的地方，通常就会使用幕布效果。所谓的幕布其实就是将两个矩形合拢，直到把屏幕遮住，然后再展开直到两个矩形全部移出屏幕。

为了大家做游戏方便，于是我给这个引擎加了这么一个类。

本系列文章目录：

如何制作一款HTML5 RPG游戏引擎——第一篇，地图类的实现

http://blog.csdn.net/yorhomwang/article/details/8892305

如何制作一款HTML5 RPG游戏引擎——第二篇，烟雨+飞雪效果

http://blog.csdn.net/yorhomwang/article/details/8915020

该引擎是基于lufylegend开发的，学习时请先了解lufylegend。

官方网站地址：http://lufylegend.com/lufylegend

API地址：http://lufylegend.com/lufylegend/api

今天我们先看实现后的代码：

var curtain = new LCurtainSample3();
addChild(curtain);

就两行，已经达到最简单了。那么接下来就来看看是如何实现它的。

由于有很多种幕布效果，因此我只为大家实现常用的3种作为sample，大家可以借鉴一下，写出更美观的幕布。

1，LCurtainSample1

这个是一个基础幕布，效果是左右合拢。

看看构造器中的代码：

function LCurtainSample1(speed,onClosing,onComplete){
    var s = this;
    base(s,LSprite,[]);
    if(!speed)speed = LStage.width/100;
    if(!onClosing){
        s.onClosing = function(){};
    }else{
        s.onClosing = onClosing;
    }    
    if(!onComplete){
        s.onComplete = function(){};
    }else{
        s.onComplete = onComplete;
    }
    s.mode = "close";
    s.width1 = 0;
    s.width2 = 0;
    s.isDoClosing = false;
    s.speed = speed;
    s.addEventListener(LEvent.ENTER_FRAME,s.onshow);
}

这个类是继承自LSprite类，有三个参数，分别是：幕布合拢/展开的速度，幕布合拢后调用此函数，幕布展开后调用此函数。

mode 属性顾名思义，它是用来表示接下来的工作的。当为close时说明要合拢。
我们在其中定义两个属性：width1，width2，它们分别表示两块幕布显示的宽度，通过调节宽度来实现合拢。另外定义了isDoClosing来判断是否已经合拢。用speed来保存幕布移动速度，方便以后使用。

然后我们给自身加一个时间轴事件，在时间轴事件中调用onshow方法绘画幕布。

onshow中的完整代码：

LCurtainSample1.prototype.onshow = function(s){
    s.graphics.clear();
    s.graphics.drawRect(1,"black",[0,0,s.width1,LStage.height],true,"black");
    s.graphics.drawRect(1,"black",[LStage.width-s.width2,0,s.width2,LStage.height],true,"black");
    if(s.width1 >= LStage.width/2){
        s.mode = "open";
        if(s.isDoClosing == false){
            s.onClosing();
            s.isDoClosing = true;
        }
    }
    if(s.mode == "close"){
        s.width1 += s.speed;
        s.width2 += s.speed;
    }else if(s.mode == "open"){
        s.width1 -= s.speed;
        s.width2 -= s.speed;
        if(s.width1 < 0){
            s.mode = "stop";
        }
    }else if(s.mode == "stop"){
        s.graphics.clear();
        s.removeEventListener(LEvent.ENTER_FRAME,s.onshow);
        s.onComplete();
    }
}

首先我们将我们的绘图区清空，然后画一个高为画布的高度，宽为width1的矩型。由于它是从x坐标为0，y坐标为0的地方画起，所以不需要任何处理。

接着用同样的办法画出高为画布的高度，宽为width2的矩形。但是由于是在屏幕最右边开始画，所以我们就得计算出它的x坐标，然后再来画。计算方法很简单，就是用屏幕宽度减去width2的长度就可以得到画笔起始的x坐标。

接着我们判断第一块幕布是否已经到达中点，如果是，就将mode设为"open"，表示接下来要open，判断isDoClosing是否为false，是则设为true，并且调用合拢时调用的函数。

接下来我们为了使幕布增长或缩短，我用到了判断mode的值的方法来实现。当为close时，就将宽度变大，当为open时就变小。如果移动完毕就将mode设置为stop，然后接着判断如果为stop就清屏，然后移除时间轴事件，达到停止的效果。效果如下：

虽然单独看有点丑，但是如果放在游戏中还是很不错的

2，LCurtainSample2

LCurtainSample2和LCurtainSample1差不多，只是一个是横着的，一个竖着的。

直接上代码：

/**
*LCurtainSample2.js
*/
function LCurtainSample2(speed,onClosing,onComplete){
    var s = this;
    base(s,LSprite,[]);
    if(!speed)speed = LStage.height/100;
    if(!onClosing){
        s.onClosing = function(){};
    }else{
        s.onClosing = onClosing;
    }    
    if(!onComplete){
        s.onComplete = function(){};
    }else{
        s.onComplete = onComplete;
    }
    s.mode = "close";
    s.height1 = 0;
    s.height2 = 0;
    s.isDoClosing = false;
    s.speed = speed;
    s.addEventListener(LEvent.ENTER_FRAME,s.onshow);
}
LCurtainSample2.prototype.onshow = function(s){
    s.graphics.clear();
    s.graphics.drawRect(1,"black",[0,0,LStage.width,s.height1],true,"black");
    s.graphics.drawRect(1,"black",[0,LStage.height-s.height2,LStage.width,s.height2],true,"black");
    if(s.height1 >= LStage.height/2){
        s.mode = "open";
        if(s.isDoClosing == false){
            s.onClosing();
            s.isDoClosing = true;
        }
    }
    if(s.mode == "close"){
        s.height1 += s.speed;
        s.height2 += s.speed;
    }else if(s.mode == "open"){
        s.height1 -= s.speed;
        s.height2 -= s.speed;
        if(s.height1 < 0){
            s.mode = "stop";
        }
    }else if(s.mode == "stop"){
        s.graphics.clear();
        s.removeEventListener(LEvent.ENTER_FRAME,s.onshow);
        s.onComplete();
    }
}

效果如下：

3，LCurtainSample3

LCurtainSample3是LCurtainSample1和LCurtainSample2的结合体，效果就是一起合拢展开。实现方法差不多，大家可以看看：

/**
*LCurtainSample3.js
*/
function LCurtainSample3(speed,onClosing,onComplete){
    var s = this;
    base(s,LSprite,[]);
    if(!speed)speed = LStage.width/100;
    if(!onClosing){
        s.onClosing = function(){};
    }else{
        s.onClosing = onClosing;
    }    
    if(!onComplete){
        s.onComplete = function(){};
    }else{
        s.onComplete = onComplete;
    }
    s.mode = "close";
    s.height1 = 0;
    s.height2 = 0;
    s.width1 = 0;
    s.width2 = 0;
    s.isDoClosing = false;
    s.speed = speed;
    s.addEventListener(LEvent.ENTER_FRAME,s.onshow);
}
LCurtainSample3.prototype.onshow = function(s){
    s.graphics.clear();
    s.graphics.drawRect(1,"black",[0,0,LStage.width,s.height1],true,"black");
    s.graphics.drawRect(1,"black",[0,LStage.height-s.height2,LStage.width,s.height2],true,"black");
    s.graphics.drawRect(1,"black",[0,0,s.width1,LStage.height],true,"black");
    s.graphics.drawRect(1,"black",[LStage.width-s.width2,0,s.width2,LStage.height],true,"black");
    if(s.height1 >= LStage.height/2 ){
        s.mode = "open";
        if(s.isDoClosing == false){
            s.onClosing();
            s.isDoClosing = true;
        }
    }
    if(s.mode == "close"){
        s.height1 += s.speed;
        s.height2 += s.speed;
        s.width1 += s.speed;
        s.width2 += s.speed;
    }else if(s.mode == "open"){
        s.height1 -= s.speed;
        s.height2 -= s.speed;
        s.width1 -= s.speed;
        s.width2 -= s.speed;
        if(s.height1 < 0){
            s.mode = "stop";
        }
    }else if(s.mode == "stop"){
        s.graphics.clear();
        s.removeEventListener(LEvent.ENTER_FRAME,s.onshow);
        s.onComplete();
    }
}

效果如下：

4，切换场景

上面我们实现了幕布类，接下来就要实战一下了。

首先我们找几张图片：

还有一张

接着就用到了我们的幕布类实现切换场景，代码如下：

<!DOCTYPE html>
<html lang="en">
    <head>
    <meta charset="utf-8" />
    <title>Curtain幕布</title>
    <script type="text/javascript" src="./js/lufylegend-1.7.6.min.js"></script>
    <script type="text/javascript" src="./js/lufylegendrpg-1.0.0.js"></script> 
    <script>
    init(30,"legend",600,400,main);
    var backindex = 1;
    var loadlist = [
        {name:"back1",path:"./back1.jpg"},
        {name:"back2",path:"./back2.jpg"}
    ];
    var datalist = [];
    LRPGStage.setShortcuts(true);
    LGlobal.setDebug(true);
    var backLayer;
    var loadingLayer;
    function main(){
        LEvent.addEventListener(LGlobal.window,LKeyboardEvent.KEY_DOWN,onkeydown);
        loadingLayer = new LoadingSample1(); 
        addChild(loadingLayer); 
        LLoadManage.load( 
            loadlist, 
            function(progress){ 
                loadingLayer.setProgress(progress); 
            }, 
            gameInit 
        ); 
    }
    function gameInit(result){
        datalist = result;
        backLayer = new LSprite();
        addChild(backLayer);
        addImg();
    }
    function addImg(){
        backLayer.removeAllChild();
        var bitmapdata = new LBitmapData(datalist["back"+backindex]);
        var bitmap = new LBitmap(bitmapdata);
        backLayer.addChild(bitmap);
    }
    function onkeydown(){
        var curtain = new LCurtainSample3(20,function(){
            if(backindex == 1){
                backindex = 2;
            }else if(backindex == 2){
                backindex = 1;
            }
            addImg();
        },function(){
            trace("已经切换为back"+backindex);
        });
        addChild(curtain);
    }
    </script>
    </head>
    <body>
            <div id="legend"></div>
    </body>
</html>

截图如下：

合拢时

展开完成后

嘻嘻~不错吧

5，源代码

本次开发代码虽然比较多，但都有些类似，放在下面，大家可以拿下去测试：

/**
*LCurtainSample1.js
*/
function LCurtainSample1(speed,onClosing,onComplete){
    var s = this;
    base(s,LSprite,[]);
    if(!speed)speed = LStage.width/100;
    if(!onClosing){
        s.onClosing = function(){};
    }else{
        s.onClosing = onClosing;
    }    
    if(!onComplete){
        s.onComplete = function(){};
    }else{
        s.onComplete = onComplete;
    }
    s.mode = "close";
    s.width1 = 0;
    s.width2 = 0;
    s.isDoClosing = false;
    s.speed = speed;
    s.addEventListener(LEvent.ENTER_FRAME,s.onshow);
}
LCurtainSample1.prototype.onshow = function(s){
    s.graphics.clear();
    s.graphics.drawRect(1,"black",[0,0,s.width1,LStage.height],true,"black");
    s.graphics.drawRect(1,"black",[LStage.width-s.width2,0,s.width2,LStage.height],true,"black");
    if(s.width1 >= LStage.width/2){
        s.mode = "open";
        if(s.isDoClosing == false){
            s.onClosing();
            s.isDoClosing = true;
        }
    }
    if(s.mode == "close"){
        s.width1 += s.speed;
        s.width2 += s.speed;
    }else if(s.mode == "open"){
        s.width1 -= s.speed;
        s.width2 -= s.speed;
        if(s.width1 < 0){
            s.mode = "stop";
        }
    }else if(s.mode == "stop"){
        s.graphics.clear();
        s.removeEventListener(LEvent.ENTER_FRAME,s.onshow);
        s.onComplete();
    }
}
/**
*LCurtainSample2.js
*/
function LCurtainSample2(speed,onClosing,onComplete){
    var s = this;
    base(s,LSprite,[]);
    if(!speed)speed = LStage.height/100;
    if(!onClosing){
        s.onClosing = function(){};
    }else{
        s.onClosing = onClosing;
    }    
    if(!onComplete){
        s.onComplete = function(){};
    }else{
        s.onComplete = onComplete;
    }
    s.mode = "close";
    s.height1 = 0;
    s.height2 = 0;
    s.isDoClosing = false;
    s.speed = speed;
    s.addEventListener(LEvent.ENTER_FRAME,s.onshow);
}
LCurtainSample2.prototype.onshow = function(s){
    s.graphics.clear();
    s.graphics.drawRect(1,"black",[0,0,LStage.width,s.height1],true,"black");
    s.graphics.drawRect(1,"black",[0,LStage.height-s.height2,LStage.width,s.height2],true,"black");
    if(s.height1 >= LStage.height/2){
        s.mode = "open";
        if(s.isDoClosing == false){
            s.onClosing();
            s.isDoClosing = true;
        }
    }
    if(s.mode == "close"){
        s.height1 += s.speed;
        s.height2 += s.speed;
    }else if(s.mode == "open"){
        s.height1 -= s.speed;
        s.height2 -= s.speed;
        if(s.height1 < 0){
            s.mode = "stop";
        }
    }else if(s.mode == "stop"){
        s.graphics.clear();
        s.removeEventListener(LEvent.ENTER_FRAME,s.onshow);
        s.onComplete();
    }
}
/**
*LCurtainSample3.js
*/
function LCurtainSample3(speed,onClosing,onComplete){
    var s = this;
    base(s,LSprite,[]);
    if(!speed)speed = LStage.width/100;
    if(!onClosing){
        s.onClosing = function(){};
    }else{
        s.onClosing = onClosing;
    }    
    if(!onComplete){
        s.onComplete = function(){};
    }else{
        s.onComplete = onComplete;
    }
    s.mode = "close";
    s.height1 = 0;
    s.height2 = 0;
    s.width1 = 0;
    s.width2 = 0;
    s.isDoClosing = false;
    s.speed = speed;
    s.addEventListener(LEvent.ENTER_FRAME,s.onshow);
}
LCurtainSample3.prototype.onshow = function(s){
    s.graphics.clear();
    s.graphics.drawRect(1,"black",[0,0,LStage.width,s.height1],true,"black");
    s.graphics.drawRect(1,"black",[0,LStage.height-s.height2,LStage.width,s.height2],true,"black");
    s.graphics.drawRect(1,"black",[0,0,s.width1,LStage.height],true,"black");
    s.graphics.drawRect(1,"black",[LStage.width-s.width2,0,s.width2,LStage.height],true,"black");
    if(s.height1 >= LStage.height/2 ){
        s.mode = "open";
        if(s.isDoClosing == false){
            s.onClosing();
            s.isDoClosing = true;
        }
    }
    if(s.mode == "close"){
        s.height1 += s.speed;
        s.height2 += s.speed;
        s.width1 += s.speed;
        s.width2 += s.speed;
    }else if(s.mode == "open"){
        s.height1 -= s.speed;
        s.height2 -= s.speed;
        s.width1 -= s.speed;
        s.width2 -= s.speed;
        if(s.height1 < 0){
            s.mode = "stop";
        }
    }else if(s.mode == "stop"){
        s.graphics.clear();
        s.removeEventListener(LEvent.ENTER_FRAME,s.onshow);
        s.onComplete();
    }
}

这次讲解就到这里，下一次我们就来实现必不可少的对话类，不容错过哦！！！