// 向SD卡写入数据
     private void writeSDcard(String str) {
         try {
             // 判断是否存在SD卡
             if (Environment.getExternalStorageState().equals(
                     Environment.MEDIA_MOUNTED)) {
                 // 获取SD卡的目录
                 File sdDire = Environment.getExternalStorageDirectory();
                 FileOutputStream outFileStream = new FileOutputStream(
                         sdDire.getCanonicalPath() + "/test.txt");
                 outFileStream.write(str.getBytes());
                 outFileStream.close();
                 Toast.makeText(this, "数据保存到text.txt文件了", Toast.LENGTH_LONG)
                         .show();
             }
         } catch (Exception e) {
             e.printStackTrace();
         }
     }
 
     
     // 从SD卡中读取数据
     private void readSDcard() {
         StringBuffer strsBuffer = new StringBuffer();
         try {
             // 判断是否存在SD
             if (Environment.getExternalStorageState().equals(
                     Environment.MEDIA_MOUNTED)) {
                 File file = new File(Environment.getExternalStorageDirectory()
                         .getCanonicalPath() + "/test.txt");
                 // 判断是否存在该文件
                 if (file.exists()) {
                     // 打开文件输入流
                     FileInputStream fileR = new FileInputStream(file);
                     BufferedReader reads = new BufferedReader(
                             new InputStreamReader(fileR));
                     String st = null;
                     while ((st = reads.readLine()) != null) {
                         strsBuffer.append(st);
                     }
                     fileR.close();
                 } else {
                     Toast.makeText(this, "该目录下文件不存在", Toast.LENGTH_LONG).show();
                 }
             }
         } catch (Exception e) {
             e.printStackTrace();
         }
         Toast.makeText(this, "读取到的数据是：" + strsBuffer.toString() + "",
                 Toast.LENGTH_LONG).show();
     }
 }