android SDCARD 读写操作

代码如下所示：

package com.mzz.utils;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.http.util.EncodingUtils;

import android.os.Environment;

public class FileUtil {

	private File file = null;
	
	private final String SDCARD_PATH = Environment.getExternalStorageDirectory() + "/";
	/**
	 * 根据目录和文件名创建文件
	 * @param dir 如果为空代表在SDCARD跟目录创建新文件
	 * @param fileName 创建文件的文件名
	 * @return -1表示文件已存在 0表示创建失败 1表示创建成功
	 */
	public int createNewFile(String dir , String fileName) {
		
		if(dir.length() != 0) {
			File path = new File(SDCARD_PATH + dir);
			if(!path.exists()) {
				file = new File(SDCARD_PATH + dir);
				//创建目录
				if(file.mkdirs()) {
					//将file重新赋值为带文件名的
					file = new File(SDCARD_PATH + dir + "/" + fileName);
				}
			}
			else {
				file = new File(SDCARD_PATH + dir + "/" + fileName);
			}
		} 
		else {
			file = new File(SDCARD_PATH + fileName);
		}
		if(file.exists()) {
			return -1;
		} 
		else {
			try {
				if(file.createNewFile()) {
					return 1;
				}
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		return 0;
	}
	
	//往指定目录、指定文件中写入String对象
	public void writeString2File(String dir , String fileName, String src) {
		FileOutputStream out = null;
		if(createNewFile(dir,fileName) != 0)
		{
			try {
				out = new FileOutputStream(file);
				out.write(src.getBytes());
			} catch (FileNotFoundException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} finally {
				try {
					if(createNewFile(dir,fileName) != 0)
						out.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			
		}
	}
	
	//读指定目录、指定文件中的String数据
	public String readFile(String dir, String fileName) {
		FileInputStream input = null;
		byte[] buffer = new byte[1024 * 10];//10K
		if(createNewFile(dir, fileName) != 0) {
			try {
				input = new FileInputStream(file);
				input.read(buffer);
				return EncodingUtils.getString(buffer, "UTF-8");
			} catch (FileNotFoundException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		return null;
	}
}