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html游戏中如何添加多个障碍?

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 如何添加多个障碍?

 
为此,我们需要一个用于计数帧的属性,以及用于以给定帧速率执行某些东西的方法。

Example

var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.frameNo = 0;        
        this.interval = setInterval(updateGameArea, 20);
    },
    clear : function() {
        this.context.clearRect(00, this.canvas.width, this.canvas.height);
    },
    stop : function() {
        clearInterval(this.interval);
    }
}

function everyinterval(n) {
    if ((myGameArea.frameNo / n) % 1 == 0) {return true;}
    return false;
}
如果当前帧数与给定的间隔对应,则每个Interval函数返回true。

要定义多个障碍物,首先将障碍物变量声明为数组。

其次,我们需要对updateGameArea函数进行一些更改。

Example

var myGamePiece;
var myObstacles = [];

function updateGameArea() {
    var x, y;
    for (i = 0; i < myObstacles.length; i += 1) {
        if (myGamePiece.crashWith(myObstacles[i])) {
            myGameArea.stop();
            return;
        } 
    }
    myGameArea.clear();
    myGameArea.frameNo += 1;
    if (myGameArea.frameNo == 1 || everyinterval(150)) {
        x = myGameArea.canvas.width;
        y = myGameArea.canvas.height - 200
        myObstacles.push(new component(10200"green", x, y));
    }
    for (i = 0; i < myObstacles.length; i += 1) {
        myObstacles[i].x += -1;
        myObstacles[i].update();
    }
    myGamePiece.newPos(); 
    myGamePiece.update();
}
在updateGameArea函数中,我们必须循环遍历每个障碍物,看看是否有碰撞。 如果发生碰撞,updateGameArea功能将停止,并且不再进行绘图。
updateGameArea功能计量帧数,并每150帧增加一个障碍。
 
完整代码:
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
 
</head>
<body onload="startGame()">
<script>
 
var myGamePiece;
var myObstacles = [];
 
function startGame() {
    myGamePiece = new component(30, 30, "red", 10, 120);
    myGameArea.start();
}
 
var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.frameNo = 0;
        this.interval = setInterval(updateGameArea, 20);
        },
    clear : function() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    },
    stop : function() {
        clearInterval(this.interval);
    }    
}
 
function component(width, height, color, x, y) {
    this.width = width;
    this.height = height;
    this.speedX = 0;
    this.speedY = 0;    
    this.x = x;
    this.y = y;    
    this.update = function() {
        ctx = myGameArea.context;
        ctx.fillStyle = color;
        ctx.fillRect(this.x, this.y, this.width, this.height);
    }
    this.newPos = function() {
        this.x += this.speedX;
        this.y += this.speedY;        
    }    
    this.crashWith = function(otherobj) {
        var myleft = this.x;
        var myright = this.x + (this.width);
        var mytop = this.y;
        var mybottom = this.y + (this.height);
        var otherleft = otherobj.x;
        var otherright = otherobj.x + (otherobj.width);
        var othertop = otherobj.y;
        var otherbottom = otherobj.y + (otherobj.height);
        var crash = true;
        if ((mybottom < othertop) || (mytop > otherbottom) || (myright < otherleft) || (myleft > otherright)) {
            crash = false;
        }
        return crash;
    }
}
 
function updateGameArea() {
    var x, y;
    for (i = 0; i < myObstacles.length; i += 1) {
        if (myGamePiece.crashWith(myObstacles[i])) {
            myGameArea.stop();
            return;
        } 
    }
    myGameArea.clear();
    myGameArea.frameNo += 1;
    if (myGameArea.frameNo == 1 || everyinterval(150)) {
        x = myGameArea.canvas.width;
        y = myGameArea.canvas.height - 200;
        myObstacles.push(new component(10, 200, "green", x, y));
    }
    for (i = 0; i < myObstacles.length; i += 1) {
        myObstacles[i].x += -1;
        myObstacles[i].update();
    }
    myGamePiece.newPos();    
    myGamePiece.update();
}
 
function everyinterval(n) {
    if ((myGameArea.frameNo / n) % 1 == 0) {return true;}
    return false;
}
 
function moveup() {
    myGamePiece.speedY = -1; 
}
 
function movedown() {
    myGamePiece.speedY = 1; 
}
 
function moveleft() {
    myGamePiece.speedX = -1; 
}
 
function moveright() {
    myGamePiece.speedX = 1; 
}
 
function clearmove() {
    myGamePiece.speedX = 0; 
    myGamePiece.speedY = 0; 
}
</script>
<div style="text-align:center;width:480px;">
  <button onmousedown="moveup()" onmouseup="clearmove()" ontouchstart="moveup()">UP</button><br><br>
  <button onmousedown="moveleft()" onmouseup="clearmove()" ontouchstart="moveleft()">LEFT</button>
  <button onmousedown="moveright()" onmouseup="clearmove()" ontouchstart="moveright()">RIGHT</button><br><br>
  <button onmousedown="movedown()" onmouseup="clearmove()" ontouchstart="movedown()">DOWN</button>
</div>
<p>每150帧都有一个新的障碍,我们每秒钟有50帧,每隔三秒就有一个障碍!</p>
 
</body>
</html>

 
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