An example WordPress plugin that shows how to create a custom field type with text input and textarea which can be repeated ans sorted.

admin-page-framework-test-text-and-textarea-field-type.php

<?php
/* Plugin Name: Admin Page Framework Test - Text and Textarea Field Type */ 

// Include the library file. Set your file path here.
$_sLibraryPath = defined( 'WP_DEBUG' ) && WP_DEBUG 
    ? dirname( dirname( __FILE__ ) ) . '/admin-page-framework/development/admin-page-framework.php'
    : dirname( dirname( __FILE__ ) ) . '/admin-page-framework/library/admin-page-framework.min.php';
if ( ! class_exists( 'AdminPageFramework' ) && ! include( $_sLibraryPath ) ) {
    return;    
}

class APF_Test_CustomFieldType extends AdminPageFramework {
    
    /**
     * Defines pages.
     */
    public function setUp() {
        
        $this->setRootMenuPage( __( 'Text and Textarea', 'admin-page-framework-test' ) );
        
        $this->addSubMenuItems(     
            array(
                'title'        => __( 'Text and Textarea', 'admin-page-framework-test' ),
                'page_slug'    => 'apf_test_text_and_textarea',
            )
        );        
    
    }
    
    /**
     * Defines form elements.
     * 
     * This method gets triggered when the `apf_test_text_and_textarea` page loads.
     */
    public function load_apf_test_text_and_textarea( $oFactory ) {
        
        if ( include( dirname( __FILE__ ) . '/TextAndTextAreaFieldType.php' ) ) {
            new TextAndTextAreaFieldType( get_class( $this ) );
        }
        
        $this->addSettingFields(
            array(
                'field_id'          => 'text_and_textarea',
                'type'              => 'text_and_textarea',
                'title'             => __( 'Text and Textarea', 'admin-page-framework-test' ),
                'label'             => array(
                    'text'      => __( 'Text', 'admin-page-framework-test' ),
                    'textarea'  => __( 'Text Area', 'admin-page-framework-test' ),
                ),
                'repeatable'        => true,
                'sortable'          => true,
            ),
            array(
                'field_id'          => 'submit',
                'type'              => 'submit',
            )
        );

    }
    
    
}

new APF_Test_CustomFieldType(
    null,                  // the option key - when null is passed the class name in this case 'APF_Test_CustomFieldType' will be used
    __FILE__               // the caller script path.
);

TextAndTextAreaFieldType.php

<?php
if ( ! class_exists( 'TextAndTextAreaFieldType' ) ) :
class TextAndTextAreaFieldType extends AdminPageFramework_FieldType {
        
    /**
     * Defines the field type slugs used for this field type.
     */
    public $aFieldTypeSlugs = array( 'text_and_textarea', );
    
    /**
     * Defines the default key-values of this field type. 
     * 
     * @remark            $_aDefaultKeys holds shared default key-values defined in the base class.
     */
    protected $aDefaultKeys = array(
    );
    

    /**
     * Loads the field type necessary components.
     */ 
    protected function setUp() {        }    

    /**
     * Returns an array holding the urls of enqueuing scripts.
     */
    protected function getEnqueuingScripts() { 
        return array(
            // array( 'src'    => dirname( __FILE__ ) . '/js/jquery.knob.js', 'dependencies'    => array( 'jquery' ) ),
        );
    }
    
    /**
     * Returns an array holding the urls of enqueuing styles.
     */
    protected function getEnqueuingStyles() { 
        return array();
    }            


    /**
     * Returns the field type specific JavaScript script.
     */ 
    protected function getScripts() { 
        return "";
    }

    /**
     * Returns IE specific CSS rules.
     */
    protected function getIEStyles() { return ''; }

    /**
     * Returns the field type specific CSS rules.
     */ 
    protected function getStyles() {
        return "
.admin-page-framework-section .form-table td         
.admin-page-framework-field-text_and_textarea .admin-page-framework-input-label-container label {
    display: block;
    clear: both;
    width: 100%;
}           
.admin-page-framework-field-text_and_textarea .admin-page-framework-input-label-container textarea {
    vertical-align: middle;
}
        ";
    }

    /**
     * Returns the output of the field type.
     */
    protected function getField( $aField ) { 
        
        $_aAttributes_Text     = array(
            'type'  => 'text',
            'id'    => $aField['attributes']['id'] . '_text',
            'name'  => $aField['attributes']['name'] . '[text]',
            'value' => isset( $aField['value']['text'] ) ? $aField['value']['text'] : null,
        ) + $aField['attributes'];
        $_aAttributes_Textarea = array(
            'type'  => null,
            'id'    => $aField['attributes']['id'] . '_textarea',
            'name'  => $aField['attributes']['name'] . '[textarea]',
        ) + $aField['attributes'];
        unset( $_aAttributes_Textarea['value'] );
        
        $_sLabel_text     = $this->getFieldElementByKey( $aField['label'], 'text' );
        $_sLabel_textarea = $this->getFieldElementByKey( $aField['label'], 'textarea' );

        return 
            $aField['before_label']
            . "<div class='admin-page-framework-input-label-container'>"                
                . "<label for='{$_aAttributes_Text['id']}'>"                    
                    . $this->getFieldElementByKey( $aField['before_input'], 'text' )
                    . ( $_sLabel_text
                        ? "<span class='admin-page-framework-input-label-string' style='min-width:" . $this->sanitizeLength( $aField['label_min_width'] ) . ";'>" . $_sLabel_text . "</span>"
                        : "" 
                    )
                    . "<input " . $this->generateAttributes( $_aAttributes_Text ) . " />" 
                    . $this->getFieldElementByKey( $aField['after_input'], 'text' )
                . "</label>"
                . "<label for='{$_aAttributes_Textarea['id']}'>"
                    . $this->getFieldElementByKey( $aField['before_input'], 'textarea' )
                    . ( $_sLabel_textarea
                        ? "<span class='admin-page-framework-input-label-string' style='min-width:" . $this->sanitizeLength( $aField['label_min_width'] ) . ";'>" . $_sLabel_textarea . "</span>"
                        : "" 
                    )
                    . "<textarea " . $this->generateAttributes( $_aAttributes_Textarea ) . " >" 
                            . esc_textarea( isset( $aField['value']['textarea'] ) ? $aField['value']['textarea'] : null )
                        . "</textarea>"            
                    . $this->getFieldElementByKey( $aField['after_input'], 'textarea' )
                . "</label>"                
                . $aField['after_input']                    
                . "<div class='repeatable-field-buttons'></div>" // the repeatable field buttons will be replaced with this element.
            . "</div>"
            . $aField['after_label'];
            
    }
    
}
endif;