UniApp写入读取android本地文件，不会被清除

       项目背景，我们是用uniapp编写的收银程序，然后打包到Android工程，再打包成apk包安装到用户的收银机上，收银机是android系统。由于项目需求，每次升级我们收银系统版本后，之前连接的打印机和LED显示屏的缓存数据都会被重新清除，因为升级相当于重新安装apk。所以把这几个配置写入到本地文件里面，登入时自动读取配置，再自动连接。下面直接贴代码

       一、在common目录下新建convertFORMat.js

// 读取json文件function getJsonData(path) { //path:路径return new Promise(resolve => { plus.io.requestFileSystem(plus.io.PUBLIC_DOWNLOADS, fs => { //请求文件系统fs.root.getFile(path, {   create: true //当文件不存在时创建}, fileEntry => {fileEntry.file(function(file) {let fileReader = new plus.io.FileReader(); //new一个可以用来读取文件的对象fileReaderfileReader.readAsText(file, "utf-8"); //读文件的格式fileReader.onerror = e => { //读文件失败// console.log("获取文件失败", fileReader.error);// plus.nativeUI.toast("获取文件失败,请重启应用", {// background: "#ffa38c",// });return;};fileReader.onload = e => { //读文件成功// console.log("读取文件成功");let txtData = e.target.result;resolve(txtData);    // 回调函数内的值想返回到函数外部  就用promise+resolve来返回出去};});}, error => {// console.log("2新建获取文件失败", error);// plus.nativeUI.toast("获取文件失败,请重启应用", {// background: "#ffa38c",// });return;});},e => {// console.log("1请求文件系统失败", e.message);// plus.nativeUI.toast("请求系统失败,请重启应用", {// background: "#ffa38c",// });return;});});};// 写入josn文件function changeData(path, seek, writeData) { //参数1：上传路径，参数2：seek方法可设置文件操作指定位置，参数3：写入的json数据plus.nativeUI.showWaiting("正在保存信息");return new Promise(resolve => {plus.io.requestFileSystem(plus.io.PUBLIC_DOWNLOADS, fs => {fs.root.getFile(path, {create: true}, fileEntry => {fileEntry.file(file => {fileEntry.createWriter(writer => {//plus.nativeUI.showWaiting("正在保存信息");writer.seek(seek); //覆盖文件const writeDataTemp = JSON.stringify(writeData, null,"\r").replace(/[\r]/g, "");writer.write(writeDataTemp); // 整个文件重写writer.onerror = function() {//console.log("4写入文件失败", writer.error.message);plus.nativeUI.closeWaiting();plus.nativeUI.toast("修改信息失败,请重新操作", {background: "#ffa38c",});return;};writer.onsuccess = function() { //填写文件成功plus.nativeUI.closeWaiting();// plus.nativeUI.toast("填写文件成功", {// background: "rgba(255, 255, 255, 0.6)",// });resolve("1");};},error => {// console.log("3创建creactWriter失败", error);// plus.nativeUI.toast("保存文件失败,请重新操作", {// background: "#ffa38c",// });return;});});},error => {// console.log("2获取文件失败", error);// plus.nativeUI.toast("保存文件失败,请重新操作", {// background: "#ffa38c",// });return;});}, e => {//console.log("1请求文件系统失败", e.message);plus.nativeUI.toast("请求系统失败,请重新操作", {background: "#ffa38c",});return;});});}async function saveFile(url, file, newfilename) {let c = await creatDirs(url)let isokm = moveDirectyOrFile(file, url + "/", newfilename);return isokm}//循环创建目录 url:"_doc/...."  _doc开头async function creatDirs(url) {let urllist = url.split("/");console.log(urllist)//创建文件夹let u = "";for (let i = 0; i < urllist.length - 1; i++) {let j = i;if (i == 0) {u = urllist[i];} else {u = u + "/" + urllist[i];}console.log(i + "-------------------")console.log(u)console.log(urllist[j + 1])await CreateNewDir(u, urllist[j + 1]);}}//重命名目录或文件名function moveDirectyOrFile(srcUrl, dstUrl, newName) { //srcUrl需要移动的目录或文件，dstUrl要移动到的目标目录（父级）plus.io.resolveLocalFileSystemURL(srcUrl, function(srcEntry) {//console.log(111)plus.io.resolveLocalFileSystemURL(dstUrl, function(dstEntry) {//console.log(222)if (srcEntry.isDirectory) {//console.log(33)srcEntry.moveTo(dstEntry, newName, function(entry) {//console.log("New Path: " + entry.fullPath);return true;}, function(e) {return e;//console.log(e.message);});} else {srcEntry.moveTo(dstEntry, newName, function(entry) {//console.log("New Path: " + entry.fullPath);return true;}, function(e) {return e;//console.log(e.message);});}}, function(e) {uni.showToast({title: '获取目标目录失败:' + e.message,duration: 2000,icon: 'none'});});}, function(e) {uni.showToast({title: '获取目录失败:' + e.message,duration: 2000,icon: 'none'});});}//创建一个新目录function CreateNewDir(url, dirName) {//url值可支持相对路径URL、本地路径URLreturn new Promise((resolver, reject) => {plus.io.resolveLocalFileSystemURL(url, function(entry) {entry.getDirectory(dirName, {create: true,exclusive: false}, function(dir) {resolver(true)}, function(error) {reject(error.message)uni.showToast({title: dirName + '目录创建失败:' + error.message,duration: 2000,icon: 'none'});});}, function(e) {reject(error.message)uni.showToast({title: '获取目录失败:' + e.message,duration: 2000,icon: 'none'});});})}function copyFileTo(url, newUrl, dirName, newName) {if (url.length >= 7 && "file://" == url.substring(0, 7)) {url = url.substring(7)}let tempUrl = url.substring(0, url.lastIndexOf('/'));let addUrl = newUrl + '/' + dirName;console.log(addUrl, tempUrl)if (addUrl == tempUrl) {return url;}console.log(newUrl, dirName, newName)return new Promise((resolve, reject) => {plus.io.resolveLocalFileSystemURL(url, async (entry) => {if (entry.isFile) {let c = await CreateNewDir(newUrl, dirName)let u = await getDirsys(addUrl)entry.copyTo(u, newName, en => {resolve(en.fullPath);}, e => {console.log(e);reject('错误：复制时出现错误')uni.showModal({title: "错误",content: "复制时出现错误"})})} else {reject('错误：路径必须是文件')uni.showModal({title: "错误",content: "路径必须是文件"})}}, (e) => {console.log(e);reject(e)uni.showModal({title: "错误",content: "打开文件系统时出错"})});})}//获取目录对象function getDirsys(url) {return new Promise((resolve, reject) => {plus.io.resolveLocalFileSystemURL(url, (entry) => {resolve(entry)}, (e) => {reject(e)console.log(e);});})}//将这些方法暴露出去export {getJSONData,changeData,saveFile,creatDirs,moveDirectyOrFile,copyFileTo,getDirsys,};

   二、写入

import {changeData,getJsonData} from '@/common/convertFormat.js';    //写在对应的方法上       let ledData = {serialPortIndex : this.serialPortIndex,serialBaudrate: this.serialBaudrate  }    //绝对路径，以"file://"开头。加粗样式 // /sdcard–>为根目录const pathUrl = 'file:///sdcard/records/led.txt';changeData(pathUrl, 0,ledData);

三、读取

import {getJsonData} from '@/common/convertFormat.js';        async initFile (){//获取配置文件中的打印机配置和led配置，赋值到缓存中const pathUrl = 'file:///sdcard/records/led.txt';let ledData = await getJsonData(pathUrl);ledData = JSON.parse(ledData); if (ledData){ uni.setStorageSync('serialPortIndex',ledData.serialPortIndex) uni.setStorageSync('serialBaudrate',ledData.serialBaudrate)  }const printUrl = 'file:///sdcard/records/print.txt';let printData = await getJsonData(printUrl);printData = JSON.parse(printData)if (printData){ uni.setStorageSync('vendorId',printData.vendorId) }},

  这样每次升级后，这个文件都会在，你也可以用android的文件管理工具，找到生成的这几个文件。路径 首页/ records/

如果有遇到权限问题则加 AndroidManifest.xml

来源地址：https://blog.csdn.net/qq_33278354/article/details/129436986