android读写SD卡封装的类

package com.example.filereadwrite;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.os.Environment;

public class FileUtils {
    private String SDCardRoot;
    private String SDStateString;

    /**
     * ----------------注意权限的添加----------------
     */
    public FileUtils() {
        // 得到当前外部存储设备的目录
        SDCardRoot = Environment.getExternalStorageDirectory()
                .getAbsolutePath() + File.separator;
        SDStateString = Environment.getExternalStorageState();// 获取扩展SD卡设备状态
    }

    /**
     * 在SD卡上创建文件
     * 
     * @param fileName
     * @param dir
     *            目录路径
     * @return
     * @throws IOException
     */
    public File createFileInSDCard(String fileName, String dir)
            throws IOException {
        File file = new File(SDCardRoot + dir + File.separator + fileName);
        System.out.println("file---->" + file);
        file.createNewFile();
        return file;
    }

    /**
     * 在SD卡上创建目录
     * 
     * @param dir
     *            目录路径，相当于文件夹
     * @return
     */
    public File creatSDDir(String dir) {
        File dirFile = new File(SDCardRoot + dir + File.separator);
        // System.out.println(dirFile.mkdirs());
        if (!dirFile.exists()) {
            dirFile.mkdirs();
        }
        return dirFile;
    }

    /**
     * 判断SD卡上的文件夹是否存在
     * 
     * @param fileName
     *            文件名称
     * @param path
     *            目录路径
     * @return
     */
    public boolean isFileExist(String fileName, String path) {
        File file = new File(SDCardRoot + path + File.separator + fileName);
        return file.exists();
    }

    /**
     * 将一个字节数组数据写入到SD卡中
     * 
     * @param dir
     *            目录
     * @param fileName
     * @param bytes
     * @return
     */
    public boolean writeSDCard(String dir, String fileName, byte[] bytes) {
        if (bytes == null) {
            return false;
        }
        OutputStream outputStream = null;
        if (SDStateString.equals(android.os.Environment.MEDIA_MOUNTED)) {
            // File file = null;
            creatSDDir(dir);
            try {
                File file = createFileInSDCard(fileName, dir);
                outputStream = new BufferedOutputStream(new FileOutputStream(
                        file));
                outputStream.write(bytes);
                outputStream.flush();
                return true;
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } finally {
                if (outputStream != null) {
                    try {
                        outputStream.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }

        }
        return false;
    }

    /**
     * 将一个InputStream里面的数据写入到SD卡中
     */
    public File write2SDFromInput(String path, String fileName,
            InputStream input) {

        File file = null;
        OutputStream output = null;
        try {
            creatSDDir(path);
            file = createFileInSDCard(fileName, path);
            output = new FileOutputStream(file);
            byte buffer[] = new byte[4 * 1024];
            int temp;
            while ((temp = input.read(buffer)) != -1) {
                output.write(buffer, 0, temp);
            }
            output.flush();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                output.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return file;
    }
/**
 * 读取文件
 * @param dir 所在目录
 * @param fileName
 * @return
 */
    public String loadData(String dir, String fileName) {
        File file = new File(SDCardRoot + dir + File.separator + fileName);
        if (!file.exists()) {
            return null;
        }
        InputStream inputStream = null;
        try {
            inputStream = new BufferedInputStream(new FileInputStream(file));
            byte[] data = new byte[inputStream.available()];
            inputStream.read(data);
            return new String(data);
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO: handle exception
        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
        return null;
    }
}

FileUtils fileUtils = new FileUtils();
System.out.println(fileUtils.loadData("GPS信息", "test.txt"));//前面是目录文件夹名称，后面是文件的名称

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;


public class ValueWrite {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        double[] aa = {1.52,2.36,3.52,4.21};
        double[] bb = {2.81,4.35,6.32,8.96};
        int n = aa.length;
        File file = new File("/media/stroe_room/桌面/test.txt");
        try {
            FileWriter out = new FileWriter(file);
            for (int i = 0; i < n; i++) {
                out.write(aa[i]+"\t"+bb[i]+"\r\n");//“\t”表示的是TAB，而“\r\n”表示的是回车换行
            }
            out.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        

        
    }

}