android 将数据读写到SD卡

 本篇博文实现android将字符串数据保存到SD卡上以及从SD读数据返回。上代码：

package com.example.android_file2;

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

import android.os.Environment;

public class FileService {


	/**
	 * 保存内容到SDcard
	 * 
	 * @param filename文件名称
	 * @param info文件内容
	 * @return
	 */
	public static String saveInfoToSDcard(String filename, String info) {
		String result = "false";
		File file = new File(Environment.getExternalStorageDirectory(),
				filename);
		if (Environment.MEDIA_MOUNTED.equals(Environment
				.getExternalStorageState())) {
			try {
				FileOutputStream fileOutputStream = new FileOutputStream(file);
				fileOutputStream.write(info.getBytes());
				result = "true";
				fileOutputStream.close();
			} catch (FileNotFoundException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}else{
			System.out.println("Environment");
		}
		return result;
	}

	
	
	/**
	 * 读sd卡上的数据
	 * @param filename
	 * @return
	 */
	public static String getStringFromSdcard(String filename) {
		String result = null;
		// 缓存的流，和磁盘无关，不需要关闭
		ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream();
		File file = new File(Environment.getExternalStorageDirectory(),
				filename);
		if (Environment.MEDIA_MOUNTED.equals(Environment
				.getExternalStorageState())) {
			try {
				FileInputStream fileInputStream = new FileInputStream(file);
				int len = 0;
				byte[] buffer = new byte[1024];
				while ((len = fileInputStream.read(buffer)) != -1) {
					arrayOutputStream.write(buffer, 0, len);
				}
				fileInputStream.close();
				result = new String(arrayOutputStream.toByteArray());
			} catch (FileNotFoundException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		return result;
	}
}

上面类中的方法分别实现SD卡上存取数据。

还需要在AndroidMainfest.xml中添加使用权限:  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

这样就可以实现向SD卡上存取数据了。