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html5游戏中如何设置组建的运动-1

51自学网 http://www.51zixue.net

 在“游戏旋转”一章中,借助绘制组件的新方式,动作更加灵活。

如何移动对象?

向组件构造函数添加speed属性,该属性表示组件的当前速度。

 

还可以在newPos()方法中进行一些更改,以根据速度和角度计算组件的位置。

 

默认情况下,组件面朝上,通过将speed属性设置为1,组件将开始向前移动。

Example

function component(width, height, color, x, y) {
    this.gamearea = gamearea;
    this.width = width;
    this.height = height;
    this.angle = 0;
    this.speed = 1;
    this.x = x;
    this.y = y; 
    this.update = function() {
        ctx = myGameArea.context;
        ctx.save();
        ctx.translate(this.x, this.y); 
        ctx.rotate(this.angle);
        ctx.fillStyle = color;
        ctx.fillRect(this.width / -2, this.height / -2, this.width, this.height); 
        ctx.restore(); 
    }
    this.newPos = function() {
        this.x += this.speed * Math.sin(this.angle);
        this.y -= this.speed * Math.cos(this.angle);
    }
}
完整源代码:
<!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;

function startGame() {
    myGamePiece = new component(30, 30, "red", 225, 225);
    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);
    },
    stop : function() {
        clearInterval(this.interval);
    },    
    clear : function() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
}

function component(width, height, color, x, y, type) {

    this.type = type;
    this.width = width;
    this.height = height;
    this.speed = 1;
    this.angle = 0;
    this.x = x;
    this.y = y;    
    this.update = function() {
        ctx = myGameArea.context;
        ctx.save();
        ctx.translate(this.x, this.y);
        ctx.rotate(this.angle);
        ctx.fillStyle = color;
        ctx.fillRect(this.width / -2, this.height / -2, this.width, this.height);        
        ctx.restore();    
    }
    this.newPos = function() {
        this.x += this.speed * Math.sin(this.angle);
        this.y -= this.speed * Math.cos(this.angle);
    }
}

function updateGameArea() {
    myGameArea.clear();
    myGamePiece.newPos();
    myGamePiece.update();
}

</script>

<p>红色方块将向前移动。

尝试改变速度属性,你会看到红色方块将相应地移动。</p>
</body>
</html>

 
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