javascript - React -- Canvas 不会绘制图像

Question

这里有点挣扎。如果我只是在 Canvas 上填充或做任何其他事情——没问题。我得到没有外部图像的 div。尝试了本地镜像文件以及 URL...谢谢!

import React, { Component, PropTypes } from 'react';

export default class CanvasCreator extends Component {

componentDidMount() {
    this.updateCanvas();
}

updateCanvas() {
    const ctx = this.refs.canvas.getContext('2d');

    var imageObj1 = new Image();
    imageObj1.src = 'https://s-media-cache-ak0.pinimg.com/236x/d7/b3/cf/d7b3cfe04c2dc44400547ea6ef94ba35.jpg'
    ctx.drawImage(imageObj1,0,0);

}
render() {
    return (


        <canvas ref="canvas" width={300} height={300}> </canvas>

    );
 }
};

Answer 1

您缺少 onload 方法。这对你有用:

   updateCanvas() {
    const ctx = this.refs.canvas.getContext('2d');

    var imageObj1 = new Image();
    imageObj1.src = 'https://s-media-cache-ak0.pinimg.com/236x/d7/b3/cf/d7b3cfe04c2dc44400547ea6ef94ba35.jpg'
 imageObj1.onload = function() {
        ctx.drawImage(imageObj1,0,0);
}

}