【Android进阶】怎样使用文件来保存程序中的数据

在程序中。有非常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;
}