HarmonyOS 文件创建/写入后，无法立刻读出，需要关闭后重新创建fs对象吗？

let savePath: string = getContext().filesDir;
let filePath = savePath + '/test2.txt';
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
let str: string = 'hello, world';
let arrayBuffer = new ArrayBuffer(4096);
fs.write(file.fd, str).then((writeLen: number) => {
  console.log(`fs IO test: fd = ${file.fd} write ${str}, size = ${writeLen}`)
  // fs.closeSync(file)
  // file = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
  fs.read(file.fd, arrayBuffer, (err, readLen: number) => {
    if(err) {
      console.log(`fs IO test: read failed`)
    } else {
      console.log(`fs IO test: fd = ${file.fd} read ${buffer.from(arrayBuffer, 0, readLen).toString()} size = ${readLen}`)
    }
    fs.closeSync(file)
  })
}).catch(() => {
  console.log(`fs IO test: write failed`)
})

代码如上，可以创建文件并写入文件，读出的文件内容为空；取消中间注释后可以读出文件内容，请问是什么原理？