Android文件读写实例代码

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Android文件读写实例代码
1.Manifest文件中权限的声明

为了能对sdcard进行读写操作，即可创建文件或目录，需要在AndroidManifest.xml中添加权限的声明：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

2.创建目录及目标文件，并以"utf-8"编码格式对文件写入

首先可在目标文件开头定义一下目录及文件名常量，方便创建文件时用

final static String FOLDER = "/sample/";
final static String FILENAME = "sample";
final static String SUFFIX = ".txt"; // suffix could be replaced on demand

writeFile函数按命名创建目录和文件并写入字串

private void writeFile(StringBuilder sb) {
String foldername = Environment.getExternalStorageDirectory().getPath()
+ FOLDER;
File folder = new File(foldername);
if (folder != null && !folder.exists()) {
if (!folder.mkdir() && !folder.isDirectory())
{
Log.d(TAG, "Error: make dir failed!");
return;
}
}

String stringToWrite = sb.toString();
String targetPath = foldername + FILENAME + SUFFIX;
File targetFile = new File(targetPath);
if (targetFile != null) {
if (targetFile.exists()) {
targetFile.delete();
}

OutputStreamWriter osw;
try{
osw = new OutputStreamWriter(
new FileOutputStream(targetFile),"utf-8");
try {
osw.write(stringToWrite);
osw.flush();
osw.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (UnsupportedEncodingException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
}

注意在new FileOutputStream时用到编码方式为"utf-8",即以"utf-8"格式来保存这个，如果想用别的格式来保存，可换成"GB2312","Big5"等。

此外，待写入的字串可以将字串样式先用StringBuilder构造好，直接用StringBuilder变量；也可以直接传入String类型的变量。

3.以"utf-8"解码格式读入文

private String readFile(String filepath) {
String path = filepath;
if (null == path) {
Log.d(TAG, "Error: Invalid file name!");
return null;
}

String filecontent = null;
File f = new File(path);
if (f != null && f.exists())
{

FileInputStream fis = null;
try {
fis = new FileInputStream(f);
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
Log.d(TAG, "Error: Input File not find!");
return null;
}

CharBuffer cb;
try {
cb = CharBuffer.allocate(fis.available());
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
Log.d(TAG, "Error: CharBuffer initial failed!");
return null;
}

InputStreamReader isr;
try {
isr = new InputStreamReader(fis, "utf-8");
try {
if (cb != null) {
isr.read(cb);
}
filecontent = new String(cb.array());
isr.close();
} catch (IOException e) {
e.printStackTrace();
}
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Log.d(TAG, "readFile filecontent = " + filecontent);
return filecontent;
}