How to automatically size Icons in Flutter to be as big as possible

Question

At the moment, I am using the following bit of code :

   body: new Container(
            child: new Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                children: <Widget>[
              new MaterialButton(
                height: 120.0,
                child: new Column(
                  children: <Widget>[
                    new Icon(
                      Icons.av_timer,
                      size: 100.0,
                    ),
                    new Text('TIMER'),
                  ],
                ),
                onPressed: null,
              ),
              new MaterialButton(
                height: 120.0,
                child: new Column(
                  children: <Widget>[
                    new Icon(Icons.alarm_add, size: 100.0),
                    new Text('ALARM'),
                  ],
                ),
                onPressed: null,
              )
            ])));

However, I have had to "hardcode" the Icon size to 100.0 and the height of the MaterialButton to 120.0.

I would like the MaterialButton to take as much space as possible (50% of the screen for each), and I would like the Icons to "fit nicely" in that space, ideally along with the Text scaling as well.

I haven't found the way to do that in Flutter yet. If it's not a good idea to try to do this (I would like it to use the entire space of the screen on any device) please let me know why ?

Answer 1

You can use LayoutBuilder to dynamically get the parent size during build.

A working example :

void main() {
  runApp(new MaterialApp(
    home: new TestIcon(),
  ));
}

class TestIcon extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Container(
      color: Colors.white,
      child: new LayoutBuilder(builder: (context, constraint) {
        return new Icon(Icons.access_alarms, size: constraint.biggest.height);
      }),
    );
  }
}

Answer 2

Screenshot:

---

Use FittedBox:

SizedBox.fromSize(
  size: Size.fromRadius(200),
  child: FittedBox(
    child: Icon(Icons.add),
  ),
)

Answer 3

As for the text sizing, I couldn't find a better way than using some kind of ratio based on the available biggest height.

I don't have the rights to comment yet, so I'll post it here : You can use the minimum between the biggest height and the biggest width.

It will do something similar to BoxFit.contain

Answer 4

As improvement of @CopsOnRoad answer I can suggest use FittedBox with SizedBox.expand like this:

SizedBox.expand(
    child: FittedBox(
        child: Icon(Icons.add),
    ),
)

Answer 5

Thanks to Darky, I ended up using the LayoutBuilder, along with the Expanded Widget, the Column Widget, and the use of the flex parameter to give the right proportions. As for the text sizing, I couldn't find a better way than using some kind of ratio based on the available biggest height.

body: new Container(
            child: new Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                children: <Widget>[
              new Expanded(
                  child: new MaterialButton(
                      child: new Column(
                        children: <Widget>[
                          new Expanded(
                            flex: 4,
                            child: new LayoutBuilder(
                                builder: (context, constraint) {
                              return new Icon(
                                Icons.timer,
                                size: constraint.biggest.height,
                              );
                            }),
                          ),
                          new Expanded(child:
                              new LayoutBuilder(builder: (context, constraint) {
                            return new Text('TIMER',
                                style: DefaultTextStyle.of(context).style.apply(fontSizeFactor: constraint.biggest.height/30.0));
                          })),
                        ],
                      ),
                      onPressed: () {
                        showTimePicker(
                          context: context,
                          initialTime: new TimeOfDay.now(),
                        );
                      })),
              new Expanded(
                  child: new MaterialButton(
                      child: new Column(
                        children: <Widget>[
                          new Expanded(
                            flex: 4,
                            child: new LayoutBuilder(
                                builder: (context, constraint) {
                                  return new Icon(
                                    Icons.alarm,
                                    size: constraint.biggest.height,
                                  );
                                }),
                          ),
                          new Expanded(child:
                          new LayoutBuilder(builder: (context, constraint) {
                            return new Text('ALARM',
                                style: DefaultTextStyle.of(context).style.apply(fontSizeFactor: constraint.biggest.height/30.0));
                          })),
                        ],
                      ),
                      onPressed: () {
                        showTimePicker(
                          context: context,
                          initialTime: new TimeOfDay.now(),
                        );
                      })),
            ]))