在SDcard中创建文件与读取文件

        //判断SDcard是否挂载
        if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
            //取得SDcard卡目录
            File fileDir = Environment.getExternalStorageDirectory();
            System.out.println(fileDir.getAbsolutePath());// /storage/emulated/0
            createFile(fileDir, "test2.txt");
            readFile(fileDir, "test2.txt");
        }