标签：preload fs const 读取 app window js Electron 本地
Electron读取本地文件并显示，也就是暴露一个读取本地特定文件内容的接口给渲染进程调用。
主要参考：https://stackoverflow.com/questions/44391448/electron-require-is-not-defined
基于官方的快速教程示例代码进行修改，原始代码如下：
// main.js
// Modules to control application life and create native browser window
const { app, BrowserWindow } = require('electron')
const path = require('path')
function createWindow () {
// Create the browser window.
const mainWindow = new BrowserWindow({
width: 800,
height: 600,
webPreferences: {
preload: path.join(__dirname, 'preload.js')
}
})
// and load the index.html of the app.
mainWindow.loadFile('index.html')
// Open the DevTools.
// mainWindow.webContents.openDevTools()
}
// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
// Some APIs can only be used after this event occurs.
app.whenReady().then(() => {
createWindow()
app.on('activate', function () {
// On macOS it's common to re-create a window in the app when the
// dock icon is clicked and there are no other windows open.
if (BrowserWindow.getAllWindows().length === 0) createWindow()
})
})
// Quit when all windows are closed, except on macOS. There, it's common
// for applications and their menu bar to stay active until the user quits
// explicitly with Cmd + Q.
app.on('window-all-closed', function () {
if (process.platform !== 'darwin') app.quit()
})
// In this file you can include the rest of your app's specific main process
// code. You can also put them in separate files and require them here.
main.js
// preload.js
// All of the Node.js APIs are available in the preload process.
// It has the same sandbox as a Chrome extension.
window.addEventListener('DOMContentLoaded', () => {
const replaceText = (selector, text) => {
const element = document.getElementById(selector)
if (element) element.innerText = text
}
for (const dependency of ['chrome', 'node', 'electron']) {
replaceText(`${dependency}-version`, process.versions[dependency])
}
})
preload.js
<!--index.html-->
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<!-- https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP -->
<meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self'">
<meta http-equiv="X-Content-Security-Policy" content="default-src 'self'; script-src 'self'">
<title>Hello World!</title>
</head>
<body>
<h1>Hello World!</h1>
We are using Node.js <span id="node-version"></span>,
Chromium <span id="chrome-version"></span>,
and Electron <span id="electron-version"></span>.
<!-- You can also require other files to run in this process -->
<script src="./renderer.js"></script>
</body>
</html>
index.html
一、似乎不安全的办法
把nodeIntegration设置为true，contextIsolation设置为false：
// Create the browser window.
const mainWindow = new BrowserWindow({
width: 800,
height: 600,
webPreferences: {
preload: path.join(__dirname, 'preload.js'),
nodeIntegration: true,
contextIsolation: false,
}
})
这样子就可以直接在渲染器处运行Node.js代码：
// renderer.js
let fs = require("fs");
fs.readFile('local_file.txt', (err, data) => {
if (err) return console.error(err);
console.log(data.toString());
});
但是这样造成的结果是，别人有可能通过Node.js运行环境随便操控本地操作系统的文件，或者造成其它风险：
二、直接写在preload.js中
为啥一定要写在render.js里呢？直接写在preload.js里就好了。（新手的疑惑：之所以区分preload.js和render.js是一种类似于“前后端分离”的思想吗？有什么东西不能直接写在preload.js ，非得写在render.js里的呢？有说法是“通过预加载把用到的api暴露到全局，这样主进程和渲染进程都能用”；有说法是“preload.js是为了把一些原属于electron的代码 通过windows["xxxxx"] 提供给前台js调用的”）
在index.html中添加一个按钮，每按一次从本地读取一次文件：
<button id="btn1">按钮1</button>
修改preload.js：
// preload.js
// All of the Node.js APIs are available in the preload process.
// It has the same sandbox as a Chrome extension.
window.addEventListener('DOMContentLoaded', () => {
省略号
let readAndDisplay = () => {
let fs = require("fs");
fs.readFile('local_file.txt', (err, data) => {
if (err) return console.error(err);
console.log(data.toString());
let myNode = document.createTextNode(data.toString());
document.body.insertBefore(myNode, document.body.firstChild);
});
}
document.querySelector('#btn1').addEventListener("click", event => {
readAndDisplay();
})
省略号
})
标签：preload,fs,const,读取,app,window,js,Electron,本地 来源： https://www.cnblogs.com/xkxf/p/15526414.html
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