在uniapp中使用Native.js 使用字节流读写文件工具类封装

分类：Native.js

/**

@description: gpb文件读写工具采用Native.js
@author: Marco
@email: wtz_xupt@126.com
*/
export default class GpbFileUtil {
/**
- 单例模式获取实例
  */
  static getIntance(){
  if(!GpbFileUtil.instance){
  GpbFileUtil.instance = new GpbFileUtil()
  }
  
  return GpbFileUtil.instance
  }
  
  /**
- 构造函数
  */
  constructor(){
  this.init()
  }
  
  /**
- 初始化
  */
  init(){
  //导入类需要时间，统一导入提高效率
  this.main = plus.android.runtimeMainActivity()
  this.Environment = plus.android.importClass('android.os.Environment')
  this.File = plus.android.importClass('java.io.File')
  this.FileInputStream = plus.android.importClass("java.io.FileInputStream")
  this.FileOutputStream = plus.android.importClass('java.io.FileOutputStream')
  }
  
  /**
- 判断有没有插入sdcard
  */
  checkSDCardExist(){
  if(this.Environment.getExternalStorageState() !== this.Environment.MEDIA_MOUNTED){
  return false
  }
  return true
  }
  
  /**
- 获取sdcard根路径
  */
  getSDCardRoot(){
  return this.Environment.getExternalStorageDirectory()
  }
  
  /**
- 判断sdcard 文件是否存在
- @param {Object} filePath
- @param {Object} fileName
  */
  checkSDCardFileExist(filePath,fileName){
  let fileFullPath = this.getSDCardRoot() + this.File.separator + filePath + this.File.separator + fileName
  let file = new this.File(fileFullPath)
  return file.exists()
  }
  
  /**
- 删除sdcard中的文件
- @param {Object} filePath 文件路径
- @param {Object} fileName 文件名称
  */
  deleteSDCardFile(filePath,fileName){
  let fileFullPath = this.getSDCardRoot() + this.File.separator + filePath + this.File.separator + fileName
```
 let file = new this.File(fileFullPath)  
 if(file.exists()){  
     file.delete()  
 }  
```
  }
  
  /**
- 读取sdcard中文件内容
- @param {Object} filePath 文件路径
- @param {Object} fileName 文件名称
  */
  readFileFromSDCard(filePath,fileName){
  if(!this.checkSDCardFileExist(filePath,fileName)){
  plus.nativeUI.toast(fileName + '文件不存在！')
  return;
  }
  let fileFullPath = this.getSDCardRoot() + this.File.separator + filePath + this.File.separator + fileName
  
  let file = new this.File(fileFullPath)
  
  let fis = new this.FileInputStream(file)
  
  let bytes = new Uint8Array(fis.available())
  try{
  let index = 0
  let byte
  while((byte = fis.read()) !== -1){
  bytes[index] = byte
  ++index
  }
  
  }catch(e){
  //TODO handle the exception
  console.log('读取sd文件' + fileName + '失败:' + e.message)
  }finally{
  try{
  if(fis !== null){
  fis.close()
  }
  }catch(ex){
  //TODO handle the exception
  console.log('关闭文件输入流失败:' + ex.message)
  }
  }
  
  return bytes
  }
  
  /**
- 向sdcard中写文件
- @param {Object} filePath 文件路径
- @param {Object} fileName 文件名称
- @param {Object} fileContentBytes 文件内容字节数组
  */
  writeFileToSDCard(filePath,fileName,fileContentBytes){
  this.deleteSDCardFile()
  let fileFullPath = this.getSDCardRoot() + this.File.separator + filePath + this.File.separator + fileName
  let file = new this.File(fileFullPath)
  let fos = new this.FileOutputStream(file)
  try{
  let index = 0
  while(index < fileContentBytes.length){
  fos.write(fileContentBytes[index])
  ++index
  }
  //fos.write(fileContentBytes) //java byte数组在nativejs中写入不了，只能循环一个一个字节写入
  fos.flush()
  }catch(e){
  //TODO handle the exception
  console.log('写入sd文件' + fileName + '失败:' + e.message)
  }finally{
  try{
  if(fos !== null){
  fos.close()
  }
  }catch(ex){
  //TODO handle the exception
  console.log('关闭文件输出流失败:' + ex.message)
  }
  }
  }
}