The AppBarDesign can't be assigned to the parameter type 'PreferredSizeWidget'

Question

Anyone please give some information why this is happening?

When I try to add a class AppBarDesign which implements appBar flutter is gi

Answer 1

If you get the error

The argument type x can't be assigned to the parameter type 'PreferredSizeWidget'.

Just wrap x in the PreferredSize widget.

Example:

appBar: AppBar(
    bottom: Column(
              children: [
                new TabBar(
                  tabs: [
                    new Tab(icon: new Icon(Icons.directions_car)),
                    new Tab(icon: new Icon(Icons.directions_transit)),
                    new Tab(
                      icon: new Icon(Icons.airplanemode_active),
                    )
                  ],
                ),
              ],
            ),

Here I get the error: The argument type 'Column' can't be assigned to the parameter type 'PreferredSizeWidget'.

Solution:

Click on Column

Click on light bulb

Choose Wrap with Widget

Replace widget with PreferredSize

Add a PreferredSize attribute, such as preferredSize: Size.fromHeight(100.0),

Result:

appBar: AppBar(
     bottom: PreferredSize(
              preferredSize: Size.fromHeight(100.0),
              child: Column(
                children: [
                  new TabBar(
                    tabs: [
                      new Tab(icon: new Icon(Icons.directions_car)),
                      new Tab(icon: new Icon(Icons.directions_transit)),
                      new Tab(
                        icon: new Icon(Icons.airplanemode_active),
                      )
                    ],
                  ),
                ],
              ),
            ),