Android 文件读写详解编程语言

关于Android文件的读写有两种方式

一种是将txt文件当成资源文件放在res/raw或则res/asset文件夹下，raw的文件可以通过R.raw.fileName获得，asset下的文件可以通过AssetManager am = getAssets();am.open(“FileName”);来打开文件。但是如果把文件当成资源文件存放的话，只能读不能写。如果要想写入数据的话，就使用第二种方法

第二种方法从sd卡中读写文件，这样首先要向AndroidManifest.xml中加入两条权限消息

    <!-- 在SDCard中创建与删除文件权限 -->     
         
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>     
         
    <!-- 往SDCard写入数据权限 -->     
         
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>    

然后将文件操作封装在一个类中，在这里我把它命名为FileOption，先将代码粘贴如下：

    package com.example.littleapplication;   
       
    import java.io.BufferedReader;   
    import java.io.File;   
    import java.io.FileInputStream;   
    import java.io.FileNotFoundException;   
    import java.io.IOException;   
    import java.io.InputStreamReader;   
    import java.io.RandomAccessFile;   
    import java.util.Vector;   
       
    import android.os.Environment;   
    import android.util.Log;   
       
    public class FileOption {   
        private String fileName;   
        private File targetFile;   
        private File sdCardDir;   
           
        public FileOption(String fileName) throws IOException {   
            // TODO Auto-generated constructor stub   
            boolean mark = Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);   
            if(mark)   
            {   
                this.fileName = fileName;   
                this.sdCardDir = Environment.getExternalStorageDirectory();   
                this.targetFile = new File(this.sdCardDir.getCanonicalPath()+this.fileName);       
                if(this.targetFile.exists()==false)   
                {   
                    this.targetFile.createNewFile();   
                }   
            }   
            else{   
                Log.e("SDK", "无内存卡");   
            }   
        }   
       
               
               
               
           
       
        public Vector read() throws FileNotFoundException, IOException {   
               
            FileInputStream fis = new FileInputStream(this.sdCardDir.getCanonicalPath()+this.fileName);   
            BufferedReader br = new BufferedReader(new InputStreamReader(fis));   
            Vector res = new Vector();   
            String line = null;   
            while((line = br.readLine())!=null)   
            {   
                res.add(line);   
            }   
            br.close();   
            return res;   
            // TODO Auto-generated method stub   
        }   
        public boolean write(String add) throws IOException   
        {   
            RandomAccessFile raf = new RandomAccessFile(this.targetFile,"rw");   
            raf.seek(targetFile.length());   
            //换行   
               
            raf.write(add.getBytes());   
            raf.writeChar('/n');   
            raf.close();   
            return true;   
        }   
        /**返回一共有多少条记录  
         * @throws IOException   
         * @throws FileNotFoundException */   
        public int size() throws FileNotFoundException, IOException   
        {   
            FileInputStream fis = new FileInputStream(this.sdCardDir.getCanonicalPath()+this.fileName);   
            BufferedReader br = new BufferedReader(new InputStreamReader(fis));   
            String line = null;   
            int count = 0;   
            while((line = br.readLine())!=null)   
            {   
                count++;   
            }   
            //每三行代表一个数据项   
            //分别是 id title content data level   
            return count/5;   
        }   
       
    }