android读取sd卡文件的工具类

package com.guanjia.global;

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 ;

 public FileUtils() {
  //得到当前外部存储设备的目录
  SDCardRoot = Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator;
  // 获取扩展SD卡设备状态
  SDStateString = Environment.getExternalStorageState();
 }
 /**
  * 在SD卡上创建文件
  * @param dir    目录路径
  * @param fileName
  * @return
  * @throws IOException
  /
 public File createFileInSDCard(String dir ,String fileName) throws IOException {
  File file = new File(SDCardRoot+ dir + File.separator + fileName);
  file.createNewFile();
  return file;
 }

 /**
  *  在SD卡上创建目录
  * @param dir 目录路径
  * @return
  /
 public File creatSDDir(String dir) {
  File dirFile = new File(SDCardRoot + dir + File.separator);
  if( !dirFile.exists() ){
   dirFile.mkdirs();
  }
  return dirFile;
 }

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

 /***
  * 获取文件的路径
  * @param dir
  * @param fileName
  * @return
  /
 public String getFilePath(String dir,String fileName){
  return SDCardRoot + dir + File.separator + fileName;
 }

 /***
  * 获取SD卡的剩余容量,单位是Byte
  * @return
  /
 public long getSDAvailableSize(){
  if (SDStateString.equals(android.os.Environment.MEDIA_MOUNTED)) {
   // 取得sdcard文件路径
   File pathFile = android.os.Environment.getExternalStorageDirectory();
   android.os.StatFs statfs = new android.os.StatFs(pathFile.getPath());
   // 获取SDCard上每个block的SIZE
   long nBlocSize = statfs.getBlockSize();
   // 获取可供程序使用的Block的数量
   long nAvailaBlock = statfs.getAvailableBlocks();
   // 计算 SDCard 剩余大小Byte
   long nSDFreeSize = nAvailaBlock * nBlocSize ;
   return nSDFreeSize;
  }
  return 0;
 }

 /**
  * 将一个字节数组数据写入到SD卡中
  /
 public boolean write2SD(String dir,String fileName,byte[] bytes){

  if(bytes == null ){
   return false;
  }

  OutputStream output = null;
  try {
   // 拥有可读可写权限，并且有足够的容量
   if (SDStateString.equals(android.os.Environment.MEDIA_MOUNTED) && bytes.length < getSDAvailableSize() ) {
    File file = null;
    creatSDDir(dir);
    file = createFileInSDCard(dir,fileName);
    output = new BufferedOutputStream(new FileOutputStream(file));
    output.write(bytes);
    output.flush();
    return true;
   }
  } catch (IOException e1) {
   // TODO Auto-generated catch block
   e1.printStackTrace();
  }finally{
   try{
    if( output != null ){
     output.close();
    }
   }
   catch(Exception e){
    e.printStackTrace();
   }
  }
  return false;
 }

 /***
  * 从sd卡中读取文件，并且以字节流返回
  * @param dir
  * @param fileName
  * @return
  /
 public byte[] readFromSD(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 data;
  } catch (FileNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }finally{
   try {
    if( inputStream != null ){
     inputStream.close();
    }
   } catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
  }
  return null;
 }

    /**
     * 将一个InputStream里面的数据写入到SD卡中 ,从网络上读取图片
     /
    public File write2SDFromInput(String dir,String fileName,InputStream input){

     File file = null;
     OutputStream output = null;
  try {
   int size = input.available();
   // 拥有可读可写权限，并且有足够的容量
   if (SDStateString.equals(android.os.Environment.MEDIA_MOUNTED) && size < getSDAvailableSize() ) {
    creatSDDir(dir);
    file = createFileInSDCard(dir,fileName);
    output = new BufferedOutputStream(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 (IOException e1) {
   // TODO Auto-generated catch block
   e1.printStackTrace();
  }finally{
   try{
    if( output != null ){
     output.close();
    }
   }
   catch(Exception e){
    e.printStackTrace();
   }
  }
  return file;
    }

}