如何在 Firefox 45+ 的附加组件中读取本地文件

Question

我花了 4 个小时试图找到将文件加载到我的 Firefox 插件中的解决方案。但是，没有成功（（（。

我的代码：

const {TextDecoder, OS} = Cu.import("resource://gre/modules/osfile.jsm", {});
var decoder = new TextDecoder();
var promise = OS.File.read("C:\\test.txt");
promise = promise.then(function onSuccess(array) {
    alert(decoder.decode(array));
});

上面的代码无法强制运行（（（。我做错了什么？

Answer 1

您拥有的代码基本上可以按照编写的方式工作。但是，这假定已定义 alert() 并且在您尝试读取文件时没有错误。但是，alert() 通常不会被定义，除非您在代码中的其他地方定义了它。如果您查看Browser Console（Ctrl-Shift-J，或 Cmd-Shift-J 在 OSX 上）。很遗憾，您没有在问题中包含该信息。

参考资料：

• OSFile.jsm
• OS.File for the main thread
• OS.File.read()
• Promise: Handling errors and common pitfalls

下面是一个完整的 Firefox Add-on SDK 扩展，它两次读取并输出到控制台B:\testFile.txt 的文件。下面包含的示例文本文件在控制台中的输出是：

read-text-file:readTextFile: This is a text file line 1
Line 2
read-text-file:readUtf8File: This is a text file line 1
Line 2

index.js：

var {Cu} = require("chrome");
//Open the Browser Console (Used in testing/developmenti to monitor errors/console)
var utils = require('sdk/window/utils');
activeWin = utils.getMostRecentBrowserWindow();
activeWin.document.getElementById('menu_browserConsole').doCommand();
var buttons     = require('sdk/ui/button/action');
var button = buttons.ActionButton({
    id: "doAction",
    label: "Do Action",
    icon: "./myIcon.png",
    onClick: doAction
});
//Above this line is specific to the Firefox Add-on SDK
//Below this line will also work for Overlay/XUL and bootstrap/restartless add-ons
//const Cu = Components.utils; //Uncomment this line for Overlay/XUL and bootstrap add-ons
const { TextDecoder, OS } = Cu.import("resource://gre/modules/osfile.jsm", {});
function doAction(){
    var fileName = 'B:\\textFile.txt'
    //Read the file and log the contents to the console.
    readTextFile(fileName).then(console.log.bind(null,'readTextFile:'))
                          .catch(Cu.reportError);
    //Do it again, using the somewhat shorter syntax for a utf-8 encoded file
    readUtf8File(fileName).then(console.log.bind(null,'readUtf8File:'))
                          .catch(Cu.reportError);
}
function readTextFile(fileName){
    var decoder = new TextDecoder();
    return OS.File.read(fileName).then(array => decoder.decode(array));
}
function readUtf8File(fileName){
    //Using the somewhat shorter syntax for a utf-8 encoded file
    return OS.File.read(fileName, { encoding: "utf-8" }).then(text => text);
}

package.json：

{
    "title": "Read a text file",
    "name": "read-text-file",
    "version": "0.0.1",
    "description": "Reads a text file in two different ways.",
    "main": "index.js",
    "author": "Makyen",
    "engines": {
        "firefox": ">=38.0a1",
        "fennec": ">=38.0a1"
    },
    "license": "MIT",
    "keywords": [
        "jetpack"
    ]
}

textFile.txt：

This is a text file line 1
Line 2