[Slider] Material theme needs to be explicitly defined to render Slider in preview mode

Description: Without explicitly specifying a theme, the Slider class fails to instantiate in the layout preview mode. The activity inherits from AppTheme, AppTheme inherits from Theme.MaterialComponents.Light.NoActionBar.

It builds and runs fine on the device, just that in the preview mode it never gets rendered.

java.lang.IllegalArgumentException: The style on this component requires your app theme to be Theme.AppCompat (or a descendant).   at com.google.android.material.internal.ThemeEnforcement.checkTheme(ThemeEnforcement.java:243)

Expected behavior: Renders in preview mode, doesn’t require extra theme

Source code:

<style name="AppTheme" parent="Theme.MaterialComponents.Light.NoActionBar">

  <com.google.android.material.slider.Slider
            android:id="@+id/slider"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:value="20"
            android:valueFrom="5.0"
            android:valueTo="100.0"
            app:labelBehavior="gone"
            app:trackColorActive="@color/icon_primary"
            app:trackColorInactive="@color/ui_dark"/>

To fix this, I had to add android:theme="@style/AppTheme" to the xml.

Android API version: 29

Material Library version: 1.2.0-alpha05

Device: API28 Samsung A70

[c5inco]

Looks like it! I was able to repro the issue in 4.0 Beta 3. I can ask the team if it’s possible to backport the fix to 3.6 and 4.0. Thanks for investigating!

[carstenhag]

Just tried it out with the newest Canary version and it works just fine. So it’s probably some Android Studio problem then which was already solved?

Android Studio 4.1 Canary 4 Build #AI-193.6494.35.41.6325121, built on March 23, 2020 Runtime version: 1.8.0_242-release-1644-b3-6222593 x86_64 VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o macOS 10.14.6 GC: ParNew, ConcurrentMarkSweep Memory: 1979M Cores: 12 Registry: ide.new.welcome.screen.force=true Non-Bundled Plugins: org.jetbrains.kotlin