学步园

权限：

 <!-- 在SDCard中创建与删除文件权限 -->
    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
  <!-- 往SDCard写入数据权限 -->
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

serviece:

 public void saveToSDCard(String filename,String content)throws Exception{
  File file = new File(Environment.getExternalStorageDirectory(),filename);
  FileOutputStream outStream = new FileOutputStream(file);
  outStream.write(content.getBytes());
  outStream.close();
 }

MainActivity:

try {
    //判断SDCard是否存在，并且可以读写
    if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))
    {
     service.saveToSDCard("wangfeng.txt",content);
     Toast.makeText(getApplicationContext(), R.string.success, 1).show();
    }else{
     Toast.makeText(getApplicationContext(), R.string.sdcarderror, 1).show();
    }
    
   } catch (Exception e) {
    Toast.makeText(getApplicationContext(), R.string.faliue, 1).show();
   }