fix: Correct boolean fields display

examples/bootstrap4/app.py

@@ -26,6 +26,7 @@ class User(db.Model):
     id = db.Column(db.Integer, primary_key=True)
     name = db.Column(db.Unicode(64))
     email = db.Column(db.Unicode(64))
+    active = db.Column(db.Boolean, default=True)
 
     def __unicode__(self):
         return self.name

flask_admin/templates/bootstrap4/admin/lib.html

@@ -120,7 +120,7 @@
   {% set prepend = kwargs.pop('prepend', None) %}
   {% set append = kwargs.pop('append', None) %}
   <div class="form-group {{ kwargs.get('column_class', '') }}">
-    <label for="{{ field.id }}" class="control-label">{{ field.label.text }}
+    <label for="{{ field.id }}" class="control-label" {% if field.widget.input_type == 'checkbox' %}style="display: block"{% endif %}>{{ field.label.text }}
         {% if h.is_required_form_field(field) %}
           <strong style="color: red">&#42;</strong>
         {%- else -%}
@@ -135,7 +135,11 @@
       </div>
       {%- endif -%}
     {% endif %}
+      {% if field.widget.input_type == 'checkbox' %}
+        {% set _class = kwargs.setdefault('class', 'form-control-lg') %}
+      {% else %}
         {% set _class = kwargs.setdefault('class', 'form-control') %}
+      {% endif %}
       {%- if direct_error %} {% set _ = kwargs.update({'class': kwargs['class'] ~ ' is-invalid'}) %} {% endif -%}
       {{ field(**kwargs) | safe }}
       {%- if append -%}