material-components/material-components-android · error · IllegalArgumentException

The view is not associated with ExpandableBehavior

Error message

The view is not associated with ExpandableBehavior

What it means

ExpandableBehavior.from(view, klass) (ExpandableBehavior.java:174) second check: the view is a CoordinatorLayout child, but the LayoutParams' behavior is either null or not an ExpandableBehavior. Behaviors are declared per-child via app:layout_behavior or set programmatically with CoordinatorLayout.LayoutParams.setBehavior(); without one, there is nothing to retrieve and the cast cannot proceed, so IllegalArgumentException is thrown.

Source

Thrown at lib/java/com/google/android/material/transformation/ExpandableBehavior.java:174

  }

  /**
   * A utility function to get the {@link ExpandableBehavior} attached to the {@code view}.
   *
   * @param view The {@link View} that the {@link ExpandableBehavior} is attached to.
   * @param klass The expected {@link Class} of the attached {@link ExpandableBehavior}.
   * @return The {@link ExpandableBehavior} attached to the {@code view}.
   */
  @Nullable
  public static <T extends ExpandableBehavior> T from(@NonNull View view, @NonNull Class<T> klass) {
    ViewGroup.LayoutParams params = view.getLayoutParams();
    if (!(params instanceof CoordinatorLayout.LayoutParams)) {
      throw new IllegalArgumentException("The view is not a child of CoordinatorLayout");
    }
    CoordinatorLayout.Behavior<?> behavior =
        ((CoordinatorLayout.LayoutParams) params).getBehavior();
    if (!(behavior instanceof ExpandableBehavior)) {
      throw new IllegalArgumentException("The view is not associated with ExpandableBehavior");
    }
    return klass.cast(behavior);
  }
}

View on GitHub (pinned to ac7e18efee)

Solutions

1. Add app:layout_behavior pointing to your ExpandableBehavior subclass on the view, e.g. app:layout_behavior="com.google.android.material.transformation.ExpandableTransformationBehavior".
2. Or set it in code: ((CoordinatorLayout.LayoutParams) view.getLayoutParams()).setBehavior(new FabTransformationBehavior());
3. Check the fully-qualified class string for typos — an unresolvable behavior string silently leaves no behavior set.

Example fix

<!-- before -->
<View android:id="+id/card"
    android:layout_width="match_parent" android:layout_height="200dp" />

<!-- after -->
<View android:id="+id/card"
    android:layout_width="match_parent" android:layout_height="200dp"
    app:layout_behavior="com.google.android.material.transformation.FabTransformationBehavior" />

boolean hasExpandableBehavior(View v) {
  ViewGroup.LayoutParams p = v.getLayoutParams();
  return p instanceof CoordinatorLayout.LayoutParams
      && ((CoordinatorLayout.LayoutParams) p).getBehavior() instanceof ExpandableBehavior;
}
ExpandableBehavior b = hasExpandableBehavior(v) ? ExpandableBehavior.from(v, ExpandableBehavior.class) : null;

@Nullable
static ExpandableBehavior resolveIfExpandable(@NonNull View v) {
  if (!(v.getLayoutParams() instanceof CoordinatorLayout.LayoutParams)) return null;
  CoordinatorLayout.Behavior<?> behavior =
      ((CoordinatorLayout.LayoutParams) v.getLayoutParams()).getBehavior();
  return behavior instanceof ExpandableBehavior ? (ExpandableBehavior) behavior : null;
}

When it happens

Trigger: Calling from() on a CoordinatorLayout child that has no app:layout_behavior attribute; a behavior set via setBehavior() with a non-ExpandableBehavior type (e.g. BottomSheetBehavior, AppBarLayout.ScrollingViewBehavior); typo in the app:layout_behavior class string so the default null/other behavior resolves.

Common situations: Adding a view inside CoordinatorLayout (fixing error 182) but forgetting to declare app:layout_behavior on it; copy-pasting a layout_behavior string from another component (e.g. bottom sheet) instead of the expandable transformation behavior class.

Related errors

• The view is not a child of CoordinatorLayout
• The view is not a child of CoordinatorLayout
• The view is not associated with SideSheetBehavior
• This behavior cannot be attached to a GONE view. Set the vie
• secondaryIconGravity cannot have the same alignment as iconG

AI-assisted analysis of material-components/material-components-android@ac7e18efee (2026-08-14). Data as JSON: /api/errors/9e4fb2925b69c3ca. Report an issue: GitHub.