How to use conditional statements/ternary inside a flutter widget

Question

I need to know is it possible to use ternary/if else inside flutter widgets.

I'm trying to create a buttonCreator widget which will take few parameters, one of which will be the background. I need to check whether the widget has background enabled or not. What i have is this but i have no idea how to use it in real dart code.

Container buildButton(String text, bool bg){
  return new Container(
    decoration: new BoxDecoration(
      border: new Border.all(color: Colors.white),
      if (bg != true ? color: Colors.white : '')
    ),
    padding: new EdgeInsets.all(15.0),
    margin: new EdgeInsets.symmetric(horizontal: 10.0, vertical: 5.0),
    child: new Center(
      child: new Text(
        text, style: new TextStyle(color: Colors.white, fontFamily: 'Monsterrat')
      )
    ),
  );
};

Possible duplicate of How to use conditional statement within child atribute of a Flutter Widget (Center Widget) — Shady Aziza
– Shady Aziza, Commented Apr 8, 2018 at 17:01
This is not a duplicate, i need to return a object with the value not only the value itself. — Sewer
– Sewer, Commented Apr 8, 2018 at 17:13

Shady Aziza · Accepted Answer · 2018-04-08 17:42:30Z

I think this is what your question is actually about ?

import 'package:flutter/material.dart';

void main() => runApp(new MaterialApp(
  home: new Home(),
));


class Home extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new Flexible(
                          child: new MyContainer(
                color: Colors.red,
              ),
            ),
            new Flexible(
                          child: new MyContainer(
                img: "http://www.clker.com/cliparts/F/v/O/6/E/c/cartoon-rubber-duck-hi.png",
              ),
            )
          ],
        ),
      ),
    );
  }
}

class MyContainer extends StatelessWidget {
  String img;
  Color color;
  MyContainer ({this.img,this.color});
  @override
  Widget build(BuildContext context) {
    return this.img!=null? new Container(
      decoration: new BoxDecoration(
        image:new DecorationImage(
          image: new NetworkImage(this.img)
        ) 
      ),
    ): new Container(
      decoration: new BoxDecoration(
        color: this.color
      ),
    );
  }
}

BambinoUA · Accepted Answer · 2019-07-11 10:42:42Z

2

Container buildButton(String text, bool bg){
  return new Container(
    decoration: new BoxDecoration(
      border: new Border.all(color: Colors.white),
      color: bg ? Colors.white : null, // you can use ternary operator here
    ),
    padding: new EdgeInsets.all(15.0),
    margin: new EdgeInsets.symmetric(horizontal: 10.0, vertical: 5.0),
    child: new Center(
      child: new Text(
        text, style: new TextStyle(color: Colors.white, fontFamily: 'Monsterrat')
      )
    ),
  );
};

answered Jul 11, 2019 at 10:42

BambinoUA

7,2835 gold badges43 silver badges64 bronze badges

Comments

user3739779 · Accepted Answer · 2020-05-29 01:29:55Z

1

decoration: new BoxDecoration(
    border: new Border.all(color: Colors.white),
    color: bg ? Colors.transparent : Colors.red, // you can use ternary operator here
),

Modified from AleksTi's answer. color property cannot be null.

answered May 29, 2020 at 1:29

user3739779

1832 silver badges6 bronze badges

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