package com.example.f01_sdcard01;

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

import android.os.Environment;

public class FileUtiles {
	// 在向sd卡写入数据时要记得向mainifest清单中增加一个 <uses-permission
	// android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
	// 传递两个参数，一个为文件名，一个为写入的数据
	public void fileSave(String fileName, byte[] data) {

		FileOutputStream fileOutputStream = null;
		String state = Environment.getExternalStorageState();
		if (Environment.MEDIA_MOUNTED.equals(state)) {
			// 创建sdcard目录
			File file = new File(Environment.getExternalStorageDirectory()
					.getAbsolutePath() + "/txt");
			// 如果目录不存在，就创建一个文件
			if (!file.exists()) {
				file.mkdirs();
			}
			try {
				// 将数据写入指定文件中
				fileOutputStream = new FileOutputStream(
						new File(file, fileName));
				try {
					fileOutputStream.write(data, 0, data.length);
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			} catch (FileNotFoundException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} finally {
				if (fileOutputStream != null) {
					try {
						fileOutputStream.close();
					} catch (IOException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				}
			}

		}

	}

}public String readSdcard(String fileName){
        //读取指定文件的数据
		
    if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
			
			File file = new File(Environment.getExternalStorageDirectory()
					.getAbsolutePath() + "/txt/");
			// 如果目录不存在，就创建一个文件
			if (file.exists()) {
				File file2=new File(file, fileName);
				InputStream inputStream=null;
				ByteArrayOutputStream arrayOutputStream=new ByteArrayOutputStream();
				try {
					inputStream = new FileInputStream(file2);
					byte[] data=new byte[1024];
					int len=0;
					try {
						while((len=inputStream.read(data))!=-1){
							arrayOutputStream.write(data, 0, len);
						}
						return new String(arrayOutputStream.toByteArray()); 
					} catch (IOException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				} catch (FileNotFoundException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}finally{
					if(inputStream!=null){
						try {
							inputStream.close();
						} catch (IOException e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						}
					}
				}
				
					
				}
				
			}
		
		
		
		return null;
		
	}
Android之sdcard写入数据（源代码分享）,布布扣,bubuko.com
Android之sdcard写入数据（源代码分享）