Dcat Admin编辑saving事件修改boolean字段不生效？

Report模型文件

protected $fillable = [
    'title',
    'summary',
    'total_page',
    'generated_at',
    'is_show',
    'is_top',
    'review_count',
];

protected $casts = [
    'generated_at' => 'datetime',
    'is_show' => 'boolean',
];

ReportController文件

protected function form()
{
    return Form::make(new Report(), function (Form $form) {
    $form->text('title')->required()->rules('required|max:255');
    $form->textarea('summary')->rows(5)->required();
    $form->radio('is_show')->default(false);
    $form->switch('is_top')->default(false);
    $form->text('review_count')->default(0)->readOnly();
    $form->datetime('created_at')->default(now());
    $form->hidden('admin_user_id');
    $form->hidden('total_page');
    $form->hidden('generated_at');

    $form->disableDeleteButton();
    $form->disableCreatingCheck();
    $form->disableEditingCheck();
    $form->disableViewCheck();

$form->saving(function (Form $form) {
    if($form->isCreating()) {
        //  后台管理员admin_user_id
        $form->admin_user_id = Admin::user()->id;
    }else {
        $form->admin_user_id = $form->model()->admin_user_id;
        //  判断报告文件是否有修改
        if($form->file_path != $form->model()->file_path) {
            $form->total_page = null;
            $form->generated_at = null;
            $form->is_show = false;
        }
    }
});
});
}