added form from ui_component not showing save button magento 2

Question

i am adding form through ui_component but not save and back button are not showing

<?xml version="1.0" encoding="UTF-8"?>
<!--
/**
 * Copyright © 2015 Magento. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../../../lib/internal/Magento/Framework/Ui/etc/ui_configuration.xsd">
    <argument name="data" xsi:type="array">
        <item name="js_config" xsi:type="array">
            <item name="provider" xsi:type="string">sampleform_form.sampleform_form_data_source</item>
            <item name="deps" xsi:type="string">sampleform_form.sampleform_form_data_source</item>
        </item>
        <item name="label" xsi:type="string" translate="true">Sample Form</item>
        <item name="layout" xsi:type="array">
            <item name="type" xsi:type="string">tabs</item>
        </item>
    </argument>

    <dataSource name="sampleform_form_data_source">
        <argument name="dataProvider" xsi:type="configurableObject">
            <argument name="class" xsi:type="string">Magento\SampleForm\Model\DataProvider</argument>
            <argument name="name" xsi:type="string">sampleform_form_data_source</argument>
            <argument name="primaryFieldName" xsi:type="string">entity_id</argument>
            <argument name="requestFieldName" xsi:type="string">id</argument>
        </argument>
        <argument name="data" xsi:type="array">
            <item name="js_config" xsi:type="array">
                <item name="component" xsi:type="string">Magento_Ui/js/form/provider</item>
            </item>
        </argument>
    </dataSource>

    <fieldset name="sample_fieldset">
        <argument name="data" xsi:type="array">
            <item name="config" xsi:type="array">
                <item name="label" xsi:type="string" translate="true">Sample Fieldset</item>
            </item>
        </argument>

        <!-- This field represents form id and is hidden -->
        <field name="entity_id">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="visible" xsi:type="boolean">false</item>
                    <item name="dataType" xsi:type="string">text</item>
                    <item name="formElement" xsi:type="string">input</item>
                    <item name="source" xsi:type="string">sampleform</item>
                </item>
            </argument>
        </field>

        <!-- This field has data type 'text' and standard 'input' form element and looks like input -->
        <field name="title">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="label" xsi:type="string">Some text</item>
                    <item name="visible" xsi:type="boolean">true</item>
                    <item name="dataType" xsi:type="string">text</item>
                    <item name="formElement" xsi:type="string">input</item>
                    <item name="source" xsi:type="string">sampleform</item>
                </item>
            </argument>
        </field>
     </fieldset>
 </form>

Answer 1

adding this in data

<argument name="data" xsi:type="array">
    <item name="js_config" xsi:type="array">
        <item name="provider" xsi:type="string">sampleform_form.sampleform_form_data_source</item>
        <item name="deps" xsi:type="string">sampleform_form.sampleform_form_data_source</item>
    </item>
    <item name="label" xsi:type="string" translate="true">Sample Form</item>
    <item name="layout" xsi:type="array">
        <item name="type" xsi:type="string">tabs</item>
    </item>
    <item name="buttons" xsi:type="array">
    <item name="back" xsi:type="string">Namespace\Modulename\Block\Adminhtml\Category\Edit\BackButton</item>
    <item name="save" xsi:type="string">Namespace\Modulename\Block\Adminhtml\Category\Edit\SaveButton</item>

    </item>
</argument>

back button block

namespace Namespace\Modulename\\Block\Adminhtml\Category\Edit;

use Magento\Framework\View\Element\UiComponent\Control\ButtonProviderInterface;

/**
 * Class BackButton
 */
class BackButton extends GenericButton implements ButtonProviderInterface
{
    /**
     * @return array
     */
    public function getButtonData()
    {
        return [
            'label' => __('Back'),
            'on_click' => sprintf("location.href = '%s';", $this->getBackUrl()),
            'class' => 'back',
            'sort_order' => 10,
            'on_click' =>''
        ];
    }

    /**
     * Get URL for back (reset) button
     *
     * @return string
     */
    public function getBackUrl()
    {
        return $this->getUrl('*/*/');
    }
}

save button block

namespace Namespace\Modulename\Block\Adminhtml\Category\Edit;

use Magento\Framework\View\Element\UiComponent\Control\ButtonProviderInterface;

/**
 * Class SaveButton
 * @package Magento\Customer\Block\Adminhtml\Edit
 */
class SaveButton extends GenericButton implements ButtonProviderInterface
{
    /**
     * @return array
     */
    public function getButtonData()
    {
        return [
            'label' => __('Save Block'),
            'class' => 'save primary',
            'data_attribute' => [
                'mage-init' => ['button' => ['event' => 'save']],
                'form-role' => 'save',
            ],
            'sort_order' => 90,
        ];
    }
}