title: How to position button in stack
body: <p>I'm trying to create an UI in flutter recently. I created a stack which has several widgets(graphs, sub-graphs, etc.).  The last widget I wanted to show is a raised button. Which must be placed like image below. I used a card widget which has stack with several widgets in it. I put my button in this stack for showing it under the card. But the button must be overflow the card as shown in image below:</p>
  <p><a href="https://i.stack.imgur.com/X61DP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/X61DP.png" alt="enter image description here" /></a></p>
  <p>The code I used for card widget:</p>
  <pre><code>Widget _buildCard(BuildContext context) {
      return Center(
        child: Card(
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(15),
            side: BorderSide(color: Colors.blueGrey, width: 0.5),
          ),
          child: Container(
            height: MediaQuery.of(context).size.height * .65,
            width: MediaQuery.of(context).size.width * .80,
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.center,
              mainAxisSize: MainAxisSize.max,
              children: &lt;Widget&gt;[
                Padding(
                  padding: const EdgeInsets.all(8.0),
                  child: Text(
                    &quot;Genel Durum&quot;,
                    style: TextStyle(
                      fontSize: 20,
                      color: Colors.black,
                      letterSpacing: 0.3,
                    ),
                  ),
                ),
                Divider(
                  color: Colors.grey,
                  thickness: 0.3,
                  endIndent: 10,
                  indent: 10,
                ),
                Stack(
                  children: [
                    Expanded(
                      child: _buildChart(dataList),
                    ),
                  ],
                ),
                SizedBox(
                  height: 20,
                ),
                _buildSubGraph(),
                SizedBox(
                  height: 40,
                ),
                Positioned(top: 50, left: 50, child: _buildDetailsButton()),
              ],
            ),
          ),
        ),
      );
    }
  </code></pre>
  <p>The code I used for the button:</p>
  <pre><code>Widget _buildDetailsButton() {
      return Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Expanded(
            child: ButtonTheme(
              height: 50,
              minWidth: 100,
              child: RaisedButton(
                onPressed: () {},
                color: Colors.white24,
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.circular(30),
                ),
                child: Text(&quot;Detayları Gör&quot;),
              ),
            ),
          ),
        ],
      );
    }
  </code></pre>
  <p>Here is what I get when I tried to debug my app:</p>
  <pre><code>══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
  The following assertion was thrown while applying parent data.:
  Incorrect use of ParentDataWidget.
  The ParentDataWidget Expanded(flex: 1) wants to apply ParentData of type FlexParentData to a
  RenderObject, which has been set up to accept ParentData of incompatible type StackParentData.
  Usually, this means that the Expanded widget has the wrong ancestor RenderObjectWidget. Typically,
  Expanded widgets are placed directly inside Flex widgets.
  The offending Expanded is currently placed inside a Stack widget.
  The ownership chain for the RenderObject that received the incompatible parent data was:
    CustomPaint ← AnimatedCircularChart ← Container ← Expanded ← Stack ← Column ← ConstrainedBox ←
  Container ← Semantics ← DefaultTextStyle ← ⋯
  When the exception was thrown, this was the stack:
  </code></pre>
  <p><strong>EDIT</strong>: Still can not achieve my goal at the moment. I can not create necessary image on the image. When my button tries to overflow my card it gives error because of overflowing again. Here's new code that I used:</p>
  <pre><code>Widget _buildCard(BuildContext context) {
      return Center(
        child: Card(
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(15),
            side: BorderSide(color: Colors.blueGrey, width: 0.5),
          ),
          child: Container(
            height: MediaQuery.of(context).size.height * .65 + 10,
            width: MediaQuery.of(context).size.width * .80,
            child: Stack(
              fit: StackFit.expand,
              overflow: Overflow.visible,
              children: [
                Column(
                  crossAxisAlignment: CrossAxisAlignment.center,
                  mainAxisSize: MainAxisSize.min,
                  children: &lt;Widget&gt;[
                    Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Text(
                        &quot;Genel Durum&quot;,
                        style: TextStyle(
                          fontSize: 20,
                          color: Colors.black,
                          letterSpacing: 0.3,
                        ),
                        textAlign: TextAlign.center,
                      ),
                    ),
                    Divider(
                      color: Colors.grey,
                      thickness: 0.3,
                      endIndent: 10,
                      indent: 10,
                    ),
                    _buildChart(dataList),
                    SizedBox(
                      height: 20,
                    ),
                    _buildSubGraph(),
                    SizedBox(
                      height: 30,
                    ),
                    Positioned(right: 0, left: 0, bottom: -1,child: Expanded(child: _buildDetailsButton())),
                  ],
                ),
              ],
            ),
          ),
        ),
      );
    }
  </code></pre>