Android中的EACCESS权限被拒绝

String path="mnt/extsd/Test";

                try{
                    File myFile = new File(path,"Hello.txt");              //device.txt
                    myFile.createNewFile();
                    FileOutputStream fOut = new FileOutputStream(myFile);

                    OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
                    myOutWriter.append(txtData.getText());
                    myOutWriter.close();
                    fOut.close();
                    Toast.makeText(getBaseContext(),"Done writing SD "+myFile.getPath(),Toast.LENGTH_SHORT).show();
                } catch (Exception e) {
                    Toast.makeText(getBaseContext(),e.getMessage(),Toast.LENGTH_SHORT).show();
                    System.out.println("Hello"+e.getMessage());
                }
            }

外部存储卡的路径是mnt / extsd /.这就是为什么我无法使用Environment.getExternalStorageDirectory().getAbsolutePath()给我一个路径mnt / sdcard,这条路径是我平板电脑中的内部存储路径.请说明为什么会这样,我该如何解决这个问题