JakeWharton/butterknife · error · IllegalStateException

@BindBool field type must be 'boolean'. (

Error message

@BindBool field type must be 'boolean'. (

What it means

@BindBool reads a boolean resource with Resources.getBoolean, so parseBindBool requires the field's type to be the primitive boolean. A Boolean (boxed), int, or any other type throws this IllegalStateException at bind time. The compiler flavor enforces the identical rule during annotation processing.

Source

Thrown at butterknife-reflect/src/main/java/butterknife/ButterKnife.java:446

    return Unbinder.EMPTY;
  }

  private static @Nullable Unbinder parseBindBool(Object target, Field field, View source) {
    BindBool bindBool = field.getAnnotation(BindBool.class);
    if (bindBool == null) {
      return null;
    }
    validateMember(field);

    int id = bindBool.value();
    Resources resources = source.getContext().getResources();

    Object value;
    Class<?> fieldType = field.getType();
    if (fieldType == boolean.class) {
      value = resources.getBoolean(id);
    } else {
      throw new IllegalStateException("@BindBool field type must be 'boolean'. ("
          + field.getDeclaringClass().getName()
          + '.'
          + field.getName()
          + ')');
    }
    trySet(field, target, value);

    return Unbinder.EMPTY;
  }

  private static @Nullable Unbinder parseBindColor(Object target, Field field, View source) {
    BindColor bindColor = field.getAnnotation(BindColor.class);
    if (bindColor == null) {
      return null;
    }
    validateMember(field);

    int id = bindColor.value();

View on GitHub (pinned to fcdebedf32)

Solutions

1. Change the field to primitive boolean: `@BindBool(R.bool.is_tablet) boolean isTablet;`
2. In Kotlin, use a non-null `Boolean` property so the backing field is primitive

Example fix

// before
@BindBool(R.bool.is_tablet)
Boolean isTablet; // boxed

// after
@BindBool(R.bool.is_tablet)
boolean isTablet;

if (field.getType() != boolean.class) {
  throw new IllegalStateException("@BindBool field must be primitive boolean: " + field);
}

static boolean isPrimitiveBooleanField(Field f) {
  return f.getType() == boolean.class;
}

When it happens

Trigger: `@BindBool(R.bool.is_tablet) Boolean isTablet;` (boxed wrapper instead of primitive); Kotlin properties whose backing field resolves to Boolean; annotating an int flag field with @BindBool.

Common situations: Kotlin `var isTablet: Boolean = false` with the annotation landing on a boxed context; Java developers using the wrapper type out of habit; nullable boolean fields.

Related errors

• @BindView fields must extend from View or be an interface. (
• @BindViews must be a List or array. (
• @BindViews List or array type must extend from View or be an
• @BindAnim field type must be 'Animation'. (
• @BindArray field type must be one of: String[], int[], CharS

AI-assisted analysis of JakeWharton/butterknife@fcdebedf32 (2026-08-14). Data as JSON: /api/errors/67d70b1cf4961ca9. Report an issue: GitHub.