简单的画布动画 [英] Simply canvas animation

问题描述

我有一个简单的画布动画：两个矩形在两个不同的方向移动。然而，我觉得这可以更简化。

I have a simple canvas animation: two rectangles move in two different directions. However, I feel this could be simplified more.

http://jsfiddle.net/tmyie / R5wx8 / 6 /

var canvas = document.getElementById('canvas'),
    c = canvas.getContext('2d'),
    x = 10,
    y = 15,

    a = 20,
    b = 50;

function move() {
    c.clearRect(0, 0, 500, 300);

    c.fillRect(0, y, 5, 5),
    c.fillRect(b, 5, 15, 15);


    x++;
    y++;
    b++

    if (y > canvas.height || x > canvas.width) {
        y = 0;
        x = 0;
    }
}

setInterval(move, 100);

例如，如果我想创建另外三个形状，会发生什么？现在，我必须为每个坐标创建更多的变量：

For example, what happens if I wanted to create another three shapes? At the moment, I'd have to create more variables for each coordinate:

    x++;
    y++;
    b++

有没有办法将每个矩形转换成自己的对象？ p>

Is there a way I could turn each rectangle into its own object?

推荐答案

您可以将它们转换成对象，例如：

You can certainly turn them into objects, for example:

function Rect(x, y, w, h, dltX, dltY, color) {

    var me = this;

    this.x = x;
    this.y = y;
    this.width = w;
    this.height = h;

    this.deltaX = dltX || 0;       /// and deltas can be optional
    this.deltaY = dltY || 0;
    this.color = color || '#000';  /// color is optional

    this.update = function(ctx) {
        me.x += me.deltaX;
        me.y += me.deltaY;

        ctx.fillStyle = me.color;
        ctx.fillRect(me.x, me.y, me.width, me.height);
    }    
}

deltaX 和 deltaY 是您要为每个更新移动矩形的数量。如果将这些设置为例如1，则 x 和 y 将每次增加1， update（）被调用。

The deltaX and deltaY are how much you want to move the rectangle for each update. If you set these to for example 1 then x and y will be increased with 1 each time update() is called.

使用deltas可以简单地通过逆转delta值来创建bounces 。 delta = -delta ）以及诸如加速度，变速速度之类的东西，你可以通过三角函数使它们在特定的角度移动。

Using deltas makes it easy to create bounces (see demo below) by simply reversing the delta value (ie. delta = -delta) as well as things such as acceleration, variate speed, you can feed them through trigonometric functions to have the object move in a specific angle and so forth.

你可以使用固定值，如果你愿意，但你会发现deltas长期有利（参考注释：它实际上是一个非常经典的方法第一个Pong游戏:-)）。

You can used fixed values if you desire but you will discover that deltas are beneficial in the long run (ref. comment: it's actually a very classic method used in for instance the first Pong games :-) ).

现在我们已经定义了对象，我们可以简单地创建它的实例并将它们存储在数组中：

Now that we have defined the object we can simply create instances of it and store them in an array:

var rects = [
    new Rect(10, 10, 100, 100, 1, -2),
    new Rect(100, 1, 50, 50, 2, 1, '#f00'),
    ...
]

b $ b

从这里，它只是一个迭代数组更新每个对象的问题：

From here it's simply a matter of iterating the array to update each object:

function move() {
    ctx.clearRect(0, 0, width, height);

    for(var i = 0, r; r = rects[i]; i++) {
        /// check any conditions here
        r.update(ctx);
    }
    requestAnimationFrame(move);
}

requestAnimationFrame(move); /// start loop

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