javascript - 渲染从道具接收到的画布对象
问题描述
再会!
我是 React 和 html2canvas 的新手。我正在制作一个应用程序,它将使用 html2canvas 对我的 DOM 进行“截图”,然后将其存储到一组截图中,然后这些截图也将呈现在屏幕上。
我<canvas>
将从 html2canvas 承诺接收到的每个对象存储到一个数组中,然后将其传递给我的ScreenshotsContainer
组件,该组件将数组传递给Screenshots
组件。然后该Screenshots
组件会将对象数组映射<canvas>
到各个Screenshot
组件。
在 App.js 中,我调用 html2canvas 函数,然后将数组传递给 ScreenshotsContainer 组件
import React, { Component } from 'react';
import ScreenshotsContainer from './containers/ScreenshotsContainer/ScreenshotsContainer'
import html2canvas from 'html2canvas';
import './App.css';
class App extends Component {
state = {
canvasArray: []
}
getScreenshotHandler = () => {
console.log("[Canvas Array from state length:]" + this.state.canvasArray.length)
let canvasArray = this.state.canvasArray;
html2canvas(document.body).then((canvas) => {
canvasArray.push(canvas)
});
console.log("[Canvas Object value: ]" + canvasArray);
this.setState({ canvasArray: canvasArray })
}
render() {
return (
<React.Fragment>
<button onClick={this.getScreenshotHandler}>Get Screenshot</button>
<ScreenshotsContainer canvasArray={this.state.canvasArray} />
</React.Fragment>
);
}
}
export default App;
ScreenshotsContainer 组件会将接收到的数组传递给 Screenshots 组件:
import React, { Component } from 'react';
import './ScreenshotsContainer.css'
import Screenshots from '../../components/Screenshots/Screenshots';
class ScreenshotsContainer extends Component {
render() {
return (
<div className="ScreenshotsContainer">
<Screenshots canvasArray={this.props.canvasArray} />
</div>
);
}
}
export default ScreenshotsContainer;
Screenshots 组件将映射数组并将每个画布对象传递给 Screenshot 组件:
import React, { Component } from 'react';
import Screenshot from './Screenshot/Screenshot';
class Screenshots extends Component {
render() {
const screenshots = this.props.canvasArray.map(canvas => {
return (
<Screenshot
key={Math.random}
canvasObj={canvas}
/>
)
})
return (
<React.Fragment>
{screenshots}
</React.Fragment>
);
}
}
export default Screenshots;
这是屏幕截图组件
import React from 'react';
import './Screenshot.css';
const screenshot = (props) => (
<div className="Screenshot" >
<canvas ref={props.canvasObj} style={{
width: '10%',
height: '10%'
}} />
</div>
);
export default screenshot;
按下按钮时我实际得到的:
我的结果的实际截图我 想知道哪一部分出了问题。任何帮助,将不胜感激。
解决方案
这个特定的库以特定的方式工作(看起来它在幕后做了很多“魔术”——你应该在这里更具体地查看源代码,即 src 中的渲染器文件夹)
将画布保存到数组内部的状态(正确的反应做事方式)将是一个问题,因为它将它保存为具有许多方法等的复杂对象......我们无法渲染对象......这个库是没有考虑到 React 编写......
下面的代码示例是 React 中的一个简单实现...
这是一个现场演示:https ://codesandbox.io/s/9y24vwn1py
import React, { Component } from 'react';
import html2canvas from 'html2canvas';
class App extends Component {
constructor(props) {
super(props);
this.captureRef = React.createRef();
this.displayRef = React.createRef();
}
getScreenshotHandler = () => {
html2canvas(this.captureRef.current).then(canvas =>
this.displayRef.current.appendChild(canvas),
);
};
render() {
return (
<div>
<div ref={this.captureRef}>
<h2>This enitre div will be captured and added to the screen</h2>
</div>
<button onClick={this.getScreenshotHandler}>Get Screenshot!</button>
<section>
<h5>Your screenshots will be availbale below</h5>
<div ref={this.displayRef} />
</section>
</div>
);
}
}
export default App;
编辑:根据下面的评论,这里是另一种解决方法:
class App extends Component {
constructor(props) {
super(props);
this.state = { canvasArray: [] };
this.captureRef = React.createRef();
}
getScreenshotHandler = () => {
html2canvas(this.captureRef.current).then(canvas =>
this.setState({
canvasArray: [canvas.toDataURL(), ...this.state.canvasArray],
}),
);
};
renderCanvas = () => {
return this.state.canvasArray.map((canvas, i) => {
return <img key={i} src={canvas} alt="screenshot" />;
});
};
render() {
return (
<div className="wrapper">
<div ref={this.captureRef}>
<p>This enitre div will be captured</p>
</div>
<button onClick={this.getScreenshotHandler}>Get Screenshot!</button>
<section>
<h5>Your screenshots will be availbale below:</h5>
{this.renderCanvas()}
</section>
</div>
);
}
}
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