【Android进阶】如何使用文件来保存程序中的数据

来源：互联网发布：4399刷盒币软件编辑：程序博客网时间：2024/05/21 22:36

在程序中，有很多保存和获取数据的方法，本篇文章，主要介绍使用文件系统对程序中的数据进行保存和读取的操作

我直接写了一个帮助类，进行文件的写入和读取操作

/** * 用于在文件中保存程序数据 *  * @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目录下，使用DDMS可以进行查看

如下图所示：

使用DDMS将文件导出，即可查看内容

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

下面的写入到SDCard的操作

// save infomation in the SDCardpublic boolean saveToSDCard(String fileName, String content) {// judge weather the SDCard exits,and can be read and writtenif (!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;}

下面是读取位于SDCard根目录下文件的操作方法

// read the file in the SDCardpublic 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;}

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