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

index out of range

Error message

index out of range

What it means

IllegalArgumentException thrown synchronously by setFocusedThumbIndex(int) when the index is negative or >= values.size(). The focused thumb is the one highlighted and driven by keyboard/a11y interaction, so it must reference an existing thumb.

Source

Thrown at lib/java/com/google/android/material/slider/BaseSlider.java:1168

    int originalHeight = drawable.getIntrinsicHeight();
    if (originalWidth == -1 && originalHeight == -1) {
      drawable.setBounds(0, 0, width, thumbHeight);
    } else {
      float scaleRatio = (float) max(width, thumbHeight) / max(originalWidth, originalHeight);
      drawable.setBounds(
          0, 0, (int) (originalWidth * scaleRatio), (int) (originalHeight * scaleRatio));
    }
  }

  /** Returns the index of the currently focused thumb */
  public int getFocusedThumbIndex() {
    return focusedThumbIdx;
  }

  /** Sets the index of the currently focused thumb */
  public void setFocusedThumbIndex(int index) {
    if (index < 0 || index >= values.size()) {
      throw new IllegalArgumentException("index out of range");
    }
    focusedThumbIdx = index;
    accessibilityHelper.requestKeyboardFocusForVirtualView(focusedThumbIdx);
    postInvalidate();
  }

  protected void setActiveThumbIndex(int index) {
    activeThumbIdx = index;
  }

  /** Returns the index of the currently active thumb, or -1 if no thumb is active */
  public int getActiveThumbIndex() {
    return activeThumbIdx;
  }

  /**
   * Registers a callback to be invoked when the slider changes. On the RangeSlider implementation,
   * the listener is invoked once for each value.

View on GitHub (pinned to ac7e18efee)

Solutions

1. Bound-check before calling: 0 <= index < slider.getValues().size().
2. Re-apply focus after setValues(), not before, since values.size() may have changed.
3. Skip the call (or clamp to size-1) instead of passing -1 when 'no thumb' is desired.

Example fix

// before
slider.setFocusedThumbIndex(savedIndex); // crashes if thumb count shrank

// after
if (savedIndex >= 0 && savedIndex < slider.getValues().size()) {
  slider.setFocusedThumbIndex(savedIndex);
}

if (index >= 0 && index < slider.getValues().size()) {
  slider.setFocusedThumbIndex(index);
}

When it happens

Trigger: Calling setFocusedThumbIndex(1) on a single-value slider; caching a focus index across a call to setValues() that reduces the thumb count; passing -1 as 'no focus' (use clearFocusedThumbIndex-equivalent behavior or skip the call instead).

Common situations: Restoring UI state after process death when the number of thumbs changed; accessibility flows that remember the last focused thumb; index math based on a stale values list.

Related errors

• At least one value must be set
• The continuousModeTickCount(%s) must be greater than or equa
• The stepSize(%s) must be 0, or a factor of the valueFrom(%s)
• There must be a keyline marked as focal.
• No color resources provided for harmonization.

AI-assisted analysis of material-components/material-components-android@ac7e18efee (2026-08-14). Data as JSON: /api/errors/59125cdc8c3d93b1. Report an issue: GitHub.