安卓读写文件

电玩女神 2021-09-22 00:16 453阅读 0赞

1. Manifest文件添加权限声明

<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
    
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

2.代码

package com.example.android.hui_obd_monitor;
    
    import android.content.Context;
    import android.os.Environment;
    import android.util.Log;
    import java.io.*;
    
    // 参考： https://blog.csdn.net/bq1073100909/article/details/37887735?utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7Edefault-19.control&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7Edefault-19.control
    
    public class FileDo {
    
        public static final String TAG = "FileDo";
    
        // /storage/emulated/0/DCIM
        static public File m_InternalStorage = Environment.getExternalStorageDirectory(); // 内部存储 // 获取系统SD卡目录
    
        static public File m_Directory_DCIM = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM); // 相机目录
    
        private Context context;
    
        public FileDo(Context context){
            this.context=context;
        }
    
        //保存到SD卡
        static public void saveToSDCard(String fileNameString,String fileContentString) throws Exception{
            File parent = m_InternalStorage;
            Log.d(TAG, "saveToSDCard: " + parent.getAbsolutePath() + "/" + fileNameString);
            File file=new File(parent, fileNameString);
            FileOutputStream outStream=new FileOutputStream(file);
            outStream.write(fileContentString.getBytes());
            outStream.close();
        }
    
        public void save(String fileNameString,String fileContentString) throws Exception{
            //文件输出流
            //其中两个参数一个是文件名一个是文件的权限，Context.MODE_PRIVATE代表只允许本程序读写
            FileOutputStream outStream=context.openFileOutput(fileNameString,Context.MODE_PRIVATE);
            //以字节流传入
            outStream.write(fileContentString.getBytes());
            outStream.close();
        }
    
        public String read(String fileNameString)throws Exception{
            FileInputStream inStream=context.openFileInput(fileNameString);
            //内存字节数组输出流，主要先将每次读取的字节流存入到内存中然后在进行输出
            ByteArrayOutputStream outStream=new ByteArrayOutputStream();
            //每次读取1024
            byte[] buffer=new byte[1024];
            int len=0;
            while((len=inStream.read(buffer))!=-1){
                outStream.write(buffer, 0, len);
            }
            //把内存中的数据转换为字节流
            byte[] data = outStream.toByteArray();
            //转换成字符串返回
            return new String(data);
        }
    
    }