Shape theming ​

Material Design encourages brand expression through shapes. The Material Components library offers a shape library that can be used to create non-standard shapes using a MaterialShapeDrawable, a Drawable that can draw custom shapes while taking shadows, elevation, scale and color into account.

On top of the shape library, the Material Components library provides a mechanism with which to easily customize component shapes at the theme level. Shape theming offers a new dimension with which to customize the look and feel of your app.

Design and API Documentation ​

• Material Design 3 guidelines: Shape

How it works ​

MaterialShapeDrawable and ShapeAppearanceModel ​

MaterialShapeDrawable begins with a path generated by a ShapeAppearanceModel. A ShapeAppearanceModel is made of CornerTreatments and EdgeTreatments that combine to create a custom shape path, and is usually passed to a MaterialShapeDrawable's constructor.

The shape library provides some subclassed CornerTreatments and EdgeTreatments to make it easy to build new shapes:

• CutCornerTreatment
• RoundedCornerTreatment
• TriangleEdgeTreatment

Both CornerTreatment and EdgeTreatment can be subclassed to create custom corners and edges.

Note: When subclassing CornerTreatment or EdgeTreatment, make sure to implement the Cloneable interface to ensure that the ShapeAppearanceModel can create deep copies of the corner and edge treatments.

Theming MaterialShapeDrawables ​

Components backed by MaterialShapeDrawables can use themes across an application.

Shape styles ​

These are the shape styles providing the Material 3 shape scale. The shape families in these styles (i.e., cornerFamily) are mapped to the theme attribute ?attr/shapeCornerFamily. See the section below for more details.

Shape theme attributes ​

Theme attributes can be set at the theme level to change the shape values that components use to set their shapes.

Aside from defining these attributes in your theme, you likely will not need to reference these attributes at all; the widget styles are already mapped to the appropriate theme attribute to create a seamless shape theming experience. To change individual shapes throughout your app, you should use the shapeAppearance and shapeAppearanceOverlay attributes rather than redefining theme level attributes.

Note: There is no sanity check for the shape values mapped to these theme attributes. It is the developer's responsibility to guarantee the relative correctness, for example, "medium" is smaller than "large", etc.

Usage ​

Building a shape appearance ​

Component shapes are backed by "shape appearances", which are style references that define aspects of the shape. ShapeAppearanceModel uses the shapeAppearance style and creates corner and edge treatments out of the shapeAppearance values.

The following attributes can be used in a shapeAppearance style:

To build a shapeAppearance, you need at least a cornerSize and cornerFamily value specified for each corner.

ShapeAppearance and shapeAppearanceOverlay attributes ​

Two attributes are provided to set a component's shape style, shapeAppearance and shapeAppearanceOverlay:

The shapeAppearanceOverlay attribute is provided to override components on a case by case basis. This attribute stacks on top of the shapeAppearance attribute; the shapeAppearance is read first, and then if there is anything specified in the shapeAppearanceOverlay attribute, it overrides what’s set in the shapeAppearance.

Note: shapeAppearance styles require both cornerSize and cornerFamily to be set, while shapeAppearanceOverlay does not. This means that when defining a custom shapeAppearance style, you should either inherit from a parent if one exists, or set both cornerSize and cornerFamily. However, when defining a style to be used as a shapeAppearanceOverlay, you should generally set an empty parent by setting parent="". This is because shapeAppearanceOverlay stacks on top of shapeAppearance, so all values will be set in the shapeAppearance.

Using shapeAppearance in the theme ​

The Material Components library supports theming shapes at the application level. To apply theme shapes across your app, specify the shape theme attributes in your theme. This will allow components that support shape theming to read the customized values and change their shapes accordingly.

If you want to change the small and medium corners in your app to cut corners, define the shape theme attributes to point to custom style references that contain shape values:

<style name="Theme.MyApp" parent="Theme.Material3.Light">
  ...
  <item name="shapeAppearanceCornerSmall">@style/ShapeAppearance.MyApp.Corner.Small</item>
  <item name="shapeAppearanceCornerMedium">@style/ShapeAppearance.MyApp.Corner.Medium</item>
  ...
</style>

The shape theme attributes should point to custom shapeAppearance styles that define both cornerSize and cornerFamily. You can either define both attributes in a style from scratch or modify the corner family from a built-in shape style like this:

<style name="ShapeAppearance.MyApp.Corner.Small" parent="">
  <item name="cornerFamily">cut</item>
  <item name="cornerSize">4dp</item>
</style>

<style name="ShapeAppearance.MyApp.Corner.Medium" parent="ShapeAppearance.Material3.Corner.Medium">
  <item name="cornerFamily">cut</item>
  <item name="cornerSize">8dp</item>
</style>

Material components that support shape theming use theme attributes according to the themed shape values.

Customizing component shapes ​

Theme-wide component overrides ​

You can change a component's shape across the entire app by defining a custom shapeAppearanceOverlay in the component's style.

If you want to modify MaterialCardView so that it uses 16dp rounded corners across the entire app, define your own card style to extend from the widget's style, and set the relevant attributes to the desired theme attributes:

<style name="Widget.MyApp.CardView" parent="Widget.Material3.CardView">
  <item name="shapeAppearanceOverlay">@style/ShapeAppearanceOverlay.MyApp.CardView</item>
</style>

And define ShapeAppearanceOverlay.MyApp.CardView:

<style name="ShapeAppearanceOverlay.MyApp.CardView" parent="">
  <item name="cornerFamily">rounded</item>
  <item name="cornerSize">16dp</item>
</style>

Then make sure to set the component's style in your theme to your custom style:

<style name="Theme.MyApp" parent="Theme.Material3.Light">
  ...
  <item name="materialCardViewStyle">@style/Widget.MyApp.CardView</item>
  ...
</style>

All cards in your app should now have 16dp rounded corners.

Individual component overrides ​

You can also change an individual component's shape on a case by case basis. For example, if cards in your theme have 16dp rounded corners, but one card should have 16dp cut corners, you can change that card's cornerFamily by setting the shapeAppearanceOverlay attribute on the card in your layout.

Define a custom shapeAppearanceOverlay style with just the attribute you want to overlay on top of the existing shapeAppearance. In this case, you would set cornerFamily to cut:

<style name="ShapeAppearanceOverlay.MyApp.CardView.Cut" parent="">
  <item name="cornerFamily">cut</item>
</style>

Then, set the card's shapeAppearanceOverlay attribute to that ShapeAppearanceOverlay style in your layout:

<com.google.android.material.card.MaterialCardView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginLeft="@dimen/mtrl_card_spacing"
    android:layout_marginTop="@dimen/mtrl_card_spacing"
    android:layout_marginRight="@dimen/mtrl_card_spacing"
    app:shapeAppearanceOverlay="@style/ShapeAppearanceOverlay.MyApp.CardView.Cut">
  <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="@string/card_text"/>
</com.google.android.material.card.MaterialCardView>

The cornerFamily attribute set in the shapeAppearanceOverlay will override the cornerFamily set in the card's shapeAppearance, so the card should now have 16dp cut corners instead of 16dp rounded corners.

Supported components ​

Components that support shape theming have a shapeAppearance attribute, a shapeAppearanceOverlay attribute, and are backed by a MaterialShapeDrawable:

• Bottom Sheet
• Card
• Chip
• Date Picker
• Dialog
• Extended Floating Action Button
• Floating Action Button
• Button
• Time Picker
• Navigation Drawer
• Slider
• Snackbar
• Text Field