在程序，有许多方法来存储和检索数据，本文，它描述了如何使用文件系统来保存数据编程和读取操作

我直接写了一个帮助类，进行文件的写入和读取操作

/**

 * 用于在文件里保存程序数据

 *

 * @author zhaokaiqiang

 *

 */

public class FileHelper {

	private static final String TAG = "FileHelper";

	private Context mContext;

	FileHelper(Context _mContext) {

		mContext = _mContext;

	}

	// 在手机本地硬盘中保存信息

	public void save(String fileName, String content) {

		FileOutputStream fileOutputStream = null;

		try {

			fileOutputStream = mContext.openFileOutput(fileName,

					Context.MODE_PRIVATE);

			fileOutputStream.write(content.getBytes());

		} catch (FileNotFoundException e) {

			e.printStackTrace();

		} catch (IOException e) {

			e.printStackTrace();

		} finally {

			try {

				if (fileOutputStream != null) {

					fileOutputStream.close();

				}

			} catch (IOException e) {

				e.printStackTrace();

			}

		}

	}

	// 读取手机硬盘中保存的文件

	public void read(String fileName) {

		FileInputStream fileInputStream = null;

		try {

			fileInputStream = mContext.openFileInput(fileName);

			int len = 0;

			byte[] buffer = new byte[1024];

			ByteArrayOutputStream byteArrayInputStream = new ByteArrayOutputStream();

			while ((len = fileInputStream.read(buffer)) != -1) {

				byteArrayInputStream.write(buffer, 0, len);

			}

			String string = new String(byteArrayInputStream.toByteArray());

			Log.d(TAG, string);

		} catch (FileNotFoundException e) {

			e.printStackTrace();

		} catch (IOException e) {

			e.printStackTrace();

		} finally {

			if (fileInputStream != null) {

				try {

					fileInputStream.close();

				} catch (IOException e) {

					e.printStackTrace();

				}

			}

		}

	}

}

注意：使用写入操作的时候。写入的内容会将上次写入的内容进行覆盖

写入的文件保存在/data/data/package name/files文件夹下，使用DDMS能够进行查看

例如以下图所看到的：

使用DDMS将文件导出。就可以查看内容

上面这些是将数据写入到我们的手机自带的存储空间里，假设想写入我们的SDCard，那么应该怎么做呢？

以下的写入到SDCard的操作

// save infomation in the SDCard

	public boolean saveToSDCard(String fileName, String content) {

		// judge weather the SDCard exits,and can be read and written

		if (!Environment.getExternalStorageState().equals(

				Environment.MEDIA_MOUNTED)) {

			return false;

		}

		FileOutputStream fileOutputStream = null;

		File file = new File(Environment.getExternalStorageDirectory(),

				fileName);

		try {

			fileOutputStream = new FileOutputStream(file);

			fileOutputStream.write(content.getBytes());

			return true;

		} catch (FileNotFoundException e) {

			e.printStackTrace();

		} catch (IOException e) {

			e.printStackTrace();

		} finally {

			try {

				if (fileOutputStream != null) {

					fileOutputStream.close();

				}

			} catch (IOException e) {

				e.printStackTrace();

			}

		}

		return false;

	}

以下是读取位于SDCard根文件夹下文件的操作方法

// read the file in the SDCard

	public String readFromSD(String fileName) {

		FileInputStream fileInputStream = null;

		File file = new File(Environment.getExternalStorageDirectory(),

				fileName);

		try {

			fileInputStream = new FileInputStream(file);

			int len = 0;

			byte[] buffer = new byte[1024];

			ByteArrayOutputStream byteArrayInputStream = new ByteArrayOutputStream();

			while ((len = fileInputStream.read(buffer)) != -1) {

				byteArrayInputStream.write(buffer, 0, len);

			}

			String string = new String(byteArrayInputStream.toByteArray());

			return string;

		} catch (FileNotFoundException e) {

			e.printStackTrace();

		} catch (IOException e) {

			e.printStackTrace();

		} finally {

			if (fileInputStream != null) {

				try {

					fileInputStream.close();

				} catch (IOException e) {

					e.printStackTrace();

				}

			}

		}

		return null;

	}