纯粹是个人学习总结，如有不对的地方请吐槽。

一、资源文件的读取：

1. 从resource的raw中读取文件数据：
   String res = "";
   try{
   //得到资源中的Raw数据流
   InputStream in = getResources().openRawResource(R.raw.test);
   //得到数据的大小
   int length = in.available();
   byte [] buffer = new byte[length];
   //读取数据
   in.read(buffer);
   //依test.txt的编码类型选择合适的编码，如果不调整会乱码
   res = EncodingUtils.getString(buffer, "BIG5");
   //关闭
   in.close();
   }catch(Exception e){
   e.printStackTrace();
   }

2. 从resource的asset中读取文件数据
   String fileName = "test.txt"; //文件名字
   String res="";
   try{
   //得到资源中的asset数据流
   InputStream in = getResources().getAssets().open(fileName);
   int length = in.available();
   byte [] buffer = new byte[length];
   in.read(buffer);
   in.close();
   res = EncodingUtils.getString(buffer, "UTF-8");
   }catch(Exception e){
   e.printStackTrace();
   }

二、读写/data/data/<应用程序名>目录上的文件

//写数据
public void writeFile(String fileName,String writestr) throws IOException{
try{
FileOutputStream fout =openFileOutput(fileName, MODE_PRIVATE);
byte [] bytes = writestr.getBytes();
fout.write(bytes);
fout.close();
}
catch(Exception e){
e.printStackTrace();
}
}

//读数据
public String readFile(String fileName) throws IOException{
String res="";
try{
FileInputStream fin = openFileInput(fileName);
int length = fin.available();
byte [] buffer = new byte[length];
fin.read(buffer);
res = EncodingUtils.getString(buffer, "UTF-8");
fin.close();
}
catch(Exception e){
e.printStackTrace();
}
return res;
}

三、读写SD卡中的文件。也就是/mnt/sdcard/目录下面的文件

//写数据到SD中的文件
public void writeFileSdcardFile(String fileName,String write_str) throws IOException{
try{

FileOutputStream fout = new FileOutputStream(fileName);
byte [] bytes = write_str.getBytes();

fout.write(bytes);
fout.close();
}

catch(Exception e){
e.printStackTrace();
}
}

//读SD中的文件
public String readFileSdcardFile(String fileName) throws IOException{
String res="";
try{
FileInputStream fin = new FileInputStream(fileName);
int length = fin.available();
byte [] buffer = new byte[length];
fin.read(buffer);
res = EncodingUtils.getString(buffer, "UTF-8");
fin.close();
}
catch(Exception e){
e.printStackTrace();
}
return res;
}

四、使用File类进行文件的读写

//读文件
public String readSDFile(String fileName) throws IOException {
File file = new File(fileName);
FileInputStream fis = new FileInputStream(file);
int length = fis.available();
byte [] buffer = new byte[length];
fis.read(buffer);
res = EncodingUtils.getString(buffer, "UTF-8");
fis.close();
return res;
}

//写文件
public void writeSDFile(String fileName, String write_str) throws IOException{
File file = new File(fileName);
FileOutputStream fos = new FileOutputStream(file);
byte [] bytes = write_str.getBytes();
fos.write(bytes);
fos.close();
}
参考地址：http://blog.csdn.net/ztp800201/article/details/7322110