黑屏 - Matter.js

Question

matter.js -

这是 matter.js 的 one of the demo。它 returns 一个空白屏幕。我已经尝试了几种方法并为此花费了数小时，但仍然无法弄清楚这里出了什么问题。

我检查了括号、语法和拼写错误，但它仍然是 returns 空白屏幕。

我检查过 matter.js 是否在后台正确加载。

有好心人指出这里的错误吗？

<script>
window.addEventListener('load', function() {

//Fetch our canvas
var canvas = document.getElementById('world22');

    var Engine = Matter.Engine,
        Render = Matter.Render,
        Runner = Matter.Runner,
        Composites = Matter.Composites,
        Events = Matter.Events,
        Constraint = Matter.Constraint,
        MouseConstraint = Matter.MouseConstraint,
        Mouse = Matter.Mouse,
        World = Matter.World,
        Bodies = Matter.Bodies;

    // create engine
    var engine = Engine.create(),
        world = engine.world;

    // create renderer
    var render = Render.create({
        // element: document.body,
        canvas: canvas,
        engine: engine,
        options: {
            width: 800,
            height: 600,
            showAngleIndicator: true,
        }
    });

    Render.run(render);

    // create runner
    var runner = Runner.create();
    Runner.run(runner, engine);

    // add bodies
    var ground = Bodies.rectangle(395, 600, 815, 50, { isStatic: true }),
        rockOptions = { density: 0.004 },
        rock = Bodies.polygon(170, 450, 8, 20, rockOptions),
        anchor = { x: 170, y: 450 },
        elastic = Constraint.create({ 
            pointA: anchor, 
            bodyB: rock, 
            stiffness: 0.05
        });

    var pyramid = Composites.pyramid(500, 300, 9, 10, 0, 0, function(x, y) {
        return Bodies.rectangle(x, y, 25, 40);
    });

    var ground2 = Bodies.rectangle(610, 250, 200, 20, { isStatic: true });

    var pyramid2 = Composites.pyramid(550, 0, 5, 10, 0, 0, function(x, y) {
        return Bodies.rectangle(x, y, 25, 40);
    });

    World.add(engine.world, [ground, pyramid, ground2, pyramid2, rock, elastic]);

    Events.on(engine, 'afterUpdate', function() {
        if (mouseConstraint.mouse.button === -1 && (rock.position.x > 190 
 rock.position.y < 430)) {
            rock = Bodies.polygon(170, 450, 7, 20, rockOptions);
            World.add(engine.world, rock);
            elastic.bodyB = rock;
        }
    });

    // add mouse control
    var mouse = Mouse.create(render.canvas),
        mouseConstraint = MouseConstraint.create(engine, {
            mouse: mouse,
            constraint: {
                stiffness: 0.2,
                render: {
                    visible: false
                }
            }
        });

    World.add(world, mouseConstraint);

    // keep the mouse in sync with rendering
    render.mouse = mouse;

    // fit the render viewport to the scene
    Render.lookAt(render, {
        min: { x: 0, y: 0 },
        max: { x: 800, y: 600 }
    });


        });
  </script>

<canvas id="world22"></canvas>

Answer 1

修复：

(1) 将您的 world22 元素从 canvas 更改为 div 或任何其他合适的元素。显然 matter.js 将在容器中创建它自己的 canvas，因此无法在 canvas.

中使用 canvas 做任何事情

(2) 您的条件中缺少 ||，导致语法错误，介于 rock.position.x > 190 rock.position.y < 430 之间。不知道在粘贴到 SO 时这是否成为错别字。

(3) 在创建渲染时指定容器元素时使用属性 element。不要使用 canvas: canvas。使用 element: canvas。关于这里Render.create({ ... });

这是修改后的源代码。我想您可以安全地忽略我是如何包含 matter.js 脚本的。我不知道版本是否重要，假设您使用的是最新版本。

<!doctype html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/matter-js/0.14.2/matter.js"></script>
<script>
window.addEventListener('load', function() {

 //Fetch our canvas
 var canvas = document.getElementById('world22');

    var Engine = Matter.Engine,
        Render = Matter.Render,
        Runner = Matter.Runner,
        Composites = Matter.Composites,
        Events = Matter.Events,
        Constraint = Matter.Constraint,
        MouseConstraint = Matter.MouseConstraint,
        Mouse = Matter.Mouse,
        World = Matter.World,
        Bodies = Matter.Bodies;

    // create engine
    var engine = Engine.create(),
        world = engine.world;

    // create renderer
    var render = Render.create({
        element: canvas,
        engine: engine,
        options: {
            width: 800,
            height: 600,
            showAngleIndicator: true,
        }
    });

    Render.run(render);

    // create runner
    var runner = Runner.create();
    Runner.run(runner, engine);

    // add bodies
    var ground = Bodies.rectangle(395, 600, 815, 50, { isStatic: true }),
        rockOptions = { density: 0.004 },
        rock = Bodies.polygon(170, 450, 8, 20, rockOptions),
        anchor = { x: 170, y: 450 },
        elastic = Constraint.create({ 
            pointA: anchor, 
            bodyB: rock, 
            stiffness: 0.05
        });

    var pyramid = Composites.pyramid(500, 300, 9, 10, 0, 0, function(x, y) {
        return Bodies.rectangle(x, y, 25, 40);
    });

    var ground2 = Bodies.rectangle(610, 250, 200, 20, { isStatic: true });

    var pyramid2 = Composites.pyramid(550, 0, 5, 10, 0, 0, function(x, y) {
        return Bodies.rectangle(x, y, 25, 40);
    });

    World.add(engine.world, [ground, pyramid, ground2, pyramid2, rock, elastic]);

    Events.on(engine, 'afterUpdate', function() {
        if (mouseConstraint.mouse.button === -1 && (rock.position.x > 190 || 
 rock.position.y < 430)) {
            rock = Bodies.polygon(170, 450, 7, 20, rockOptions);
            World.add(engine.world, rock);
            elastic.bodyB = rock;
        }
    });

    // add mouse control
    var mouse = Mouse.create(render.canvas),
        mouseConstraint = MouseConstraint.create(engine, {
            mouse: mouse,
            constraint: {
                stiffness: 0.2,
                render: {
                    visible: false
                }
            }
        });

    World.add(world, mouseConstraint);

    // keep the mouse in sync with rendering
    render.mouse = mouse;

    // fit the render viewport to the scene
    Render.lookAt(render, {
        min: { x: 0, y: 0 },
        max: { x: 800, y: 600 }
    });


});
</script>


</head>
<body>
<div id="world22"></div>
</body>
<html>

我根据此处提供的最小示例进行调试 https://github.com/liabru/matter-js/wiki/Getting-started ....

起初我没有注意到 canvas 问题，但后来我使用浏览器开发工具检查了 world22 元素。 另一个 canvas 是嵌套的，所以我就是这样知道的。

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