Android 文件读写的例子

 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import org.apache.http.util.EncodingUtils; 

 public class MyLogFile {
       private static FileOutputStream fout;
       public MyLogFile() {
       } 

       public static void createFile(){
            try {
                 fout = new FileOutputStream("/mnt/sdcard/zyrPad.txt");
                 // fout = openFileOutput("/mnt/sdcard/zyrPad.txt",Mode);
           } catch (FileNotFoundException e) {
                 e.printStackTrace();
           }
      } 

      //写在/mnt/sdcard/目录下面的文件
      public static void writeFileSdcard(String message){
            try{
                  //FileOutputStream fout = openFileOutput(fileName, MODE_PRIVATE);
                 message= message+"\n";
                 byte [] bytes = message.getBytes();
                 fout.write(bytes);
            } catch(Exception e){
                 e.printStackTrace();
            }
       }

       //读在/mnt/sdcard/目录下面的文件
       public String readFileSdcard(String fileName){
             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;
       } 

       /** * 关闭文件流 */
       public static void closeFile(){
             try {
                  fout.close();
             } catch (IOException e) {
                  e.printStackTrace();
             }
       }
 } 

调用的时候很简单：
MyLogFile.createFile();//创建文件
MyLogFile.writeFileSdcard("------------写文字到文件中----------------");

使用完后，记得关闭：
MyLogFile.closeFile()