Question about drupal8 ajax form

hi, this is my form code at drupal 8

// some base code...

public function buildForm(array $form, FormStateInterface $form_state) {

    $form['title'] = [
      '#type' => 'textfield',
      '#title' => $this->t('Title'),
      '#description' => $this->t('input something.'),
      '#required' => TRUE,
    ];

    $form['actions'] = [
      '#type' => 'actions',
    ];

    $form['actions']['ajaxsubmit'] = [
      '#type' => 'submit',
      '#value' => 'Ajax Submit',
      '#ajax' => [
        'callback' => '::showinput',
        'wrapper' => 'input-wrapper',
      ],
    ];

    $form['theinput'] = [
      '#type' => 'container',
      '#attributes' => ['id' => 'input-wrapper'],
    ];

    return $form;
  }

  public function showinput(array &$form, FormStateInterface $form_state) {
    $title = $form_state->getValue('title');
    $form_state->setRebuild();
    $form['show']['yourinput'] = [
      '#markup' => 'you input:'.$title,
    ];
    return $form['wing'];
  }

// some other code...

My question is:
The ‘textfield’ first time input and submit is no problem.
But after the first input, don’t work, the ‘textfield’ $form[‘show’][‘yourinput’] markup sitll display the text i input at the first time.
How to show the text i input and ajax submit at the second time adn etc.
And how to clear the text at the ‘textfield’ after i ajax submit the text.

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/4/feed