Android 文件讀寫

關于Android文件的讀寫有兩種方式

一種是將txt文件當成資源文件放在res/raw或則res/asset文件夾下，raw的文件可以通過R.raw.fileName獲得，asset下的文件可以通過AssetManager am = getAssets();am.open(“FileName”);來打開文件。但是如果把文件當成資源文件存放的話，只能讀不能寫。如果要想寫入數據的話，就使用第二種方法

第二種方法從sd卡中讀寫文件，這樣首先要向AndroidManifest.xml中加入兩條權限消息

    <!-- 在SDCard中創建與刪除文件權限 -->


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

<!-- 往SDCard寫入數據權限 -->    

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


 然后將文件操作封裝在一個類中，在這里我把它命名為FileOption，先將代碼粘貼如下：
    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", "無內存卡");  
        }  
    }  






    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());  
        //換行  

        raf.write(add.getBytes());  
        raf.writeChar('\n');  
        raf.close();  
        return true;  
    }  
    /**返回一共有多少條記錄 
     * @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++;  
        }  
        //每三行代表一個數據項  
        //分別是 id title content data level  
        return count/5;  
    }  

}  </pre>