> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/xamarin/guides/viewer-components/thumbnail-slider-a.md).

# Customizing thumbnail slider in Xamarin

Learn how to create a ThumbnailSlider in Xamarin.Android with this step-by-step tutorial. Customize buttons, seekbar, and appearance styles easily. The Apryse Xamarin SDK streamlines secure, serverles

{% hint style="info" %}
**This tutorial only applies to Xamarin.Android. See Xamarin.iOS equivalent here .**
{% endhint %}

[`ThumbnailSlider`](https://sdk.apryse.com/api/xamarinandroid/tools/api/pdftron.PDF.Widget.Seekbar.DocumentSlider.html) is a [`LinearLayout`](https://developer.android.com/reference/android/widget/LinearLayout.html) that contains an [`AppCompatSeekBar`](https://developer.android.com/reference/androidx/appcompat/widget/AppCompatSeekBar/) to change pages, and two [`AppCompatImageButton`](https://developer.android.com/reference/androidx/appcompat/widget/AppCompatImageButton/) on the left and right side. When sliding the seekbar, it displays a small page preview on top of the thumbnail slider.

![](https://653871032-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FgjsBtuYmcKhWOdM9VCg4%2Fuploads%2Fgit-blob-8d9a5332f5f0f19b7366a42dff2c60c5f53be78a%2F2a26a9c2e25e146ff678eb03af5c39fc52d55587-420x540.gif?alt=media)

## Show thumbnail slider

To set up your layout with the thumbnail slider, add a `<ThumbnailSlider>` element to your XML layout. For example, your layout may look like this:

{% tabs %}
{% tab title="XML" %}
{% code lineNumbers="true" %}

```xml
<com.pdftron.pdf.controls.ThumbnailSlider android:id="@+id/thumbnailSlider" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentBottom="true"/>
```

{% endcode %}
{% endtab %}
{% endtabs %}

Then, attach a [`PDFViewCtrl`](https://sdk.apryse.com/api/xamarinandroid/pdfnet/api/pdftron.PDF.PDFViewCtrl.html) to the thumbnail slider. If [`PDFViewCtrl`](https://sdk.apryse.com/api/xamarinandroid/pdfnet/api/pdftron.PDF.PDFViewCtrl.html) is in the same layout, you can set it by adding the [`app:pdfviewctrlId`](https://docs.apryse.com) attribute:

{% tabs %}
{% tab title="XML" %}
{% code lineNumbers="true" %}

```xml
<com.pdftron.pdf.controls.ThumbnailSlider android:id="@+id/thumbnailSlider" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentBottom="true" app:pdfviewctrlId="@id/pdfviewctrl"/>
```

{% endcode %}
{% endtab %}
{% endtabs %}

If [`PDFViewCtrl`](https://sdk.apryse.com/api/xamarinandroid/pdfnet/api/pdftron.PDF.PDFViewCtrl.html) is **not** in the same layout, you can programmatically set it to a thumbnail slider by calling `setPdfViewCtrl(PDFViewCtrl)`:

{% tabs %}
{% tab title="C#" %}
{% code lineNumbers="true" %}

```csharp
var thumbnailSlider = FindViewById<ThumbnailSlider>(Resource.Id.thumbnailSlider);
thumbnailSlider.SetPdfViewCtrl(mPdfViewCtrl);
```

{% endcode %}
{% endtab %}
{% endtabs %}

## Change thumbnail slider buttons

You can change the image drawable of the left menu item and right menu item buttons by adding the [`app:leftMenuItemDrawable`](https://docs.apryse.com) and [`app:rightMenuItemDrawable`](https://docs.apryse.com) attributes in your xml layout.

**Example**

{% tabs %}
{% tab title="XML" %}
{% code lineNumbers="true" %}

```xml
<com.pdftron.pdf.controls.ThumbnailSlider android:id="@+id/thumbnailSlider" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentBottom="true" app:leftMenuItemDrawable="@drawable/left_icon" app:rightMenuItemDrawable="@drawable/right_icon"/>
```

{% endcode %}
{% endtab %}
{% endtabs %}

Additionally, you can remove the left and right slider buttons by setting the drawables to null:

{% tabs %}
{% tab title="C#" %}
{% code lineNumbers="true" %}

```csharp
<com.pdftron.pdf.controls.ThumbnailSlider android:id="@+id/thumbnailSlider" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentBottom="true" app:leftMenuItemDrawable="@null" app:rightMenuItemDrawable="@null"/>
```

{% endcode %}
{% endtab %}
{% endtabs %}

You can also change the buttons programmatically by calling `setMenuItem(@DrawableRes int, @MenuItemPosition int)`. The second parameter determines the position of the button which is either `POSITION_LEFT` or `POSITION_RIGHT`.

**Example**

{% tabs %}
{% tab title="C#" %}
{% code lineNumbers="true" %}

```csharp
thumbnailSlider.SetMenuItem(Resource.Drawable.left_icon, ThumbnailSlider.PositionLeft);
```

{% endcode %}
{% endtab %}
{% endtabs %}

## Thumbnail slider listeners

### Buttons listener

You can add a menu item clicked event listener by calling [`MenuItemClicked`](https://sdk.apryse.com/api/xamarinandroid/tools/api/pdftron.PDF.Controls.NativeThumbnailSlider.html#pdftron_PDF_Controls_NativeThumbnailSlider_MenuItemClicked) to be notified when one of the left or right buttons is clicked.

{% tabs %}
{% tab title="C#" %}
{% code lineNumbers="true" %}

```csharp
thumbnailSlider.MenuItemClicked += (sender, e) =>
{
    if (e.MenuItemPosition == ThumbnailSlider.PositionLeft)
    {
        // The left button was clicked.
    }
    else
    {
        // The right button was clicked.
    }
}
```

{% endcode %}
{% endtab %}
{% endtabs %}

### Seekbar listener

You can set a thumbnail slider seekbar event listener by calling [`ThumbSliderStartTrackingTouch`](https://sdk.apryse.com/api/xamarinandroid/tools/api/pdftron.PDF.Controls.NativeThumbnailSlider.html#pdftron_PDF_Controls_NativeThumbnailSlider_ThumbSliderStartTrackingTouch) and [`ThumbSliderStopTrackingTouch`](https://sdk.apryse.com/api/xamarinandroid/tools/api/pdftron.PDF.Controls.NativeThumbnailSlider.html#pdftron_PDF_Controls_NativeThumbnailSlider_ThumbSliderStopTrackingTouch):

{% tabs %}
{% tab title="C#" %}
{% code lineNumbers="true" %}

```csharp
thumbnailSlider.ThumbSliderStartTrackingTouch += (sender, e) =>
{
    // Called when tracking on the seekbar has started
}
thumbnailSlider.ThumbSliderStopTrackingTouch += (sender, e) =>
{
    // Called when tracking on the seekbar has stopped
}
```

{% endcode %}
{% endtab %}
{% endtabs %}

## Appearance style

### Customize slider colors

You can customize the color of the left and right menu buttons as well as the seekbar by setting a custom style to the `thumbnail_slider` attribute in your apps's theme. The custom style must extend `ThumbnailSliderStyle`. For example:

{% tabs %}
{% tab title="XML" %}
{% code lineNumbers="true" %}

```xml
<style name="PDFTronAppTheme" parent="PDFTronAppThemeBase"> <item name="colorPrimary">@color/app_color_primary_day</item> <item name="colorPrimaryDark">@color/app_color_primary_dark_day</item> <item name="colorAccent">@color/app_color_accent</item> <!-- Set your custom style in your app theme --> <item name="thumbnail_slider">@style/CustomThumbnailSliderStyle</item> </style>

<style name="CustomThumbnailSliderStyle" parent="ThumbnailSliderStyle"> <!-- Change the background color of the slider--> <item name="colorBackground">@android:color/red</item> <!-- Change the color of the seekbar and seekbar icon in the slider--> <item name="seekbarColor">@android:color/black</item> <!-- Change the color of the menu button left of the slider --> <item name="leftMenuItemColor">@android:color/black</item> <!-- Change the color of the menu button right of the slider --> <item name="rightMenuItemColor">@android:color/black</item> <!-- Change the description of the menu button left of the slider --> <item name="leftMenuItemContentDescription">"LeftDescription"</item> <!-- Change the color of the menu button right of the slider --> <item name="rightMenuItemContentDescription">"RightDescription"</item> <!-- Change the icon of the menu button left of the slider --> <item name="leftMenuItemDrawable">@drawable/ic_thumbnails_grid_black_24dp</item> <!-- Change the icon of the menu button right of the slider --> <item name="rightMenuItemDrawable">@drawable/ic_list_white_24dp</item> </style>
```

{% endcode %}
{% endtab %}
{% endtabs %}

### Customize seekbar attributes

If you want to further customize the seekbar's layout attributes and appearance, such as padding and height, you can override the default seekbar style `Resource.Style.ThumbnailSliderStyle.Seekbar` by declaring the following in `Resources/Values/styles.xml`:

**Example**

For API < 21:

{% tabs %}
{% tab title="XML" %}
{% code lineNumbers="true" %}

```xml
<style name="ThumbnailSliderStyle.Seekbar" parent="Widget.AppCompat.SeekBar" > <!-- add paddingTop and paddingBottom for api < 21 here for avoiding seekbar becomes too thick--> <item name="android:paddingTop">16dp</item> <item name="android:paddingBottom">16dp</item> <item name="android:minHeight">2dp</item> <item name="android:maxHeight">2dp</item> <item name="android:layout_gravity">center</item> </style>
```

{% endcode %}
{% endtab %}
{% endtabs %}

For API >= 21:

{% tabs %}
{% tab title="XML" %}
{% code lineNumbers="true" %}

```xml
<style name="ThumbnailSliderStyle.Seekbar" parent="Widget.AppCompat.SeekBar"> <item name="android:progressTint">?attr/colorPrimary</item> <item name="android:progressBackgroundTint">?attr/colorPrimary</item> <item name="android:colorControlActivated">?attr/colorPrimary</item> <item name="android:colorControlHighlight">?attr/colorPrimary</item> <item name="android:minHeight">2dp</item> <item name="android:maxHeight">2dp</item> <item name="android:layout_gravity">center</item> </style>
```

{% endcode %}
{% endtab %}
{% endtabs %}

### Customize the thumb and progress bar

The seekbar progress bar drawable can be customized by overriding the `seek_track_material.xml` drawable file. Similarly, the seekbar thumbnail drawable can be changed by overriding the `seek_thumb.xml` drawable file. For reference, the source code for these drawables can be found in the `lib\src\PDFViewCtrlTools\res\drawable` folder of the SDK package.

## XML attributes

| Attribute                             | Description                                                                                                                               | Format    |
| ------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------- | --------- |
| `app:pdfviewctrlId`                   | Specifies the `PDFViewCtrl` view id                                                                                                       | Reference |
| `app:leftMenuItemContentDescription`  | Specifies the content description of left menu item.                                                                                      | String    |
| `app:rightMenuItemContentDescription` | Specifies the content description of right menu item.                                                                                     | String    |
| `app:leftMenuItemDrawable`            | Specifies left menu item drawable resource.                                                                                               | Reference |
| `app:rightMenuItemDrawable`           | Specifies right menu item drawable resource.                                                                                              | Reference |
| `app:colorBackground`                 | Specifies background color. Uses default system background color if not defined.                                                          | Color     |
| `app:seekbarColor`                    | Specifies seekbar progress bar and thumb color. Default value: `?attr/colorPrimary` in day mode and `@android:color/white` in night mode. | Color     |
| `app:leftMenuItemColor`               | Specifies left menu item color. Default value: `?attr/colorPrimary` in day mode and `@android:color/white` in night mode.                 | Color     |
| `app:rightMenuItemColor`              | Specifies right menu item color. Default value: `?attr/colorPrimary` in day mode and `@android:color/white` in night mode.                | Color     |
| `app:shadowEnabled`                   | Specifies whether the shadow will appear. Default value: `true`.                                                                          | Boolean   |


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