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dartswitch-statementflutter
Josh Kahane
Josh Kahane

Reputation: 17169

Flutter Switch - onChanged Not Changing

When using the following Switch widget, the isOn value always returns true and never changes.

The Switch only moves position on a swipe too, a tap won't move it. How to resolve?

bool isInstructionView = false;

Switch(
    value: isInstructionView,
    onChanged: (bool isOn) {
      setState(() {
        isInstructionView = isOn;
        print(isInstructionView);
      });
    },
    activeColor: Colors.blue,
    inactiveTrackColor: Colors.grey,
    inactiveThumbColor: Colors.grey,
)

Update: For extra clarity, onChanged always returns isOn as true. Why would this be?

Upvotes: 16

Views: 28819

Answers (10)

Raghav Saxena
Raghav Saxena

Reputation: 91

I faced the same issue , the problem is your

bool isInstructionView = false;

is in same build method which will get rebuild due to change of switch to render new UI on setState()

Solution is to move it out of function Scope to Class Scope so that your variable do not change on rendering Widget again

Upvotes: 4

Cha Mildz
Cha Mildz

Reputation: 41

Use Transform when use Switch will work.

 bool isSwitched = false;

 Transform.scale(
  scale: 1.8,
  child: Switch(
    onChanged: (value) {
      setState(() {
        isSwitched = value;
      });
    },
    value: isSwitched,
  ),
 )

Upvotes: 1

Cha Mildz
Cha Mildz

Reputation: 41

Change SwitchListTile instead of Switch will work.

bool isSwitched = false;

SwitchListTile(
    title: Text("title"),
    controlAffinity: ListTileControlAffinity.leading,
    contentPadding: EdgeInsets.symmetric(),
    value: isSwitched ,
    onChanged: (bool value) {
      setState(() {
        isSwitched = value;
      });
    }
)

Upvotes: 2

srt111
srt111

Reputation: 1539

To get Switch to work , move the setState(() {}) outside of Switch in a callback function .

// Switch  Widget
    Switch( value: _toggleState,
            onChanged: _attemptChange,
            ),
    
//Callback
 void _attemptChange(bool newState) {
    setState(() {
      _toggleState = newState;
      newState ? _switchCase = 'ON' : _switchCase = 'OFF';
    });

Upvotes: 1

tipu sultan
tipu sultan

Reputation: 337

Here Is my code for toggle button

class ToggleButtonScreen extends StatefulWidget {
 @override
 _ToggleButtonScreenState createState() => _ToggleButtonScreenState();
}

class _ToggleButtonScreenState extends State<ToggleButtonScreen> {
 bool _value = false;

 @override
 Widget build(BuildContext context) {
   return Scaffold(
     body: SafeArea(
       child: Center(
         child: Container(
           decoration: BoxDecoration(
             image: DecorationImage(
               image: _value ? AssetImage("images/cnw.png") : AssetImage("images/cnw.png"),
               fit: BoxFit.cover,
             ),
           ),
           child: Padding(
             padding: EdgeInsets.all(AppDimens.EDGE_REGULAR),
             child: Column(
               children: [
                // _customSwitchButton(),
                 _normalToggleButton(),
               ],
             ),
           ),
         ),
       ),
     ),
   );
 }

Widget _normalToggleButton () {
   return Container(
     child: Transform.scale(
       scale: 2.0,
       child: Switch(
         activeColor : Colors.greenAccent,
         inactiveThumbColor: Colors.redAccent,
         value: _value,
           activeThumbImage: AssetImage("images/cnw.png"),
           inactiveThumbImage : AssetImage("images/simple_interest.png"),
           onChanged: (bool value){
            setState(() {
              _value = value;
            });
           },
       ),
     ),
   );
}
}

Upvotes: 4

Shukry Shahril
Shukry Shahril

Reputation: 169

You just need to make sure to declare the bool for the switch toggle outside Widget build to make it global and acessible for SetState method. No need to initstate and etc.

    class ExampleClass extends StatefulWidget {
     @override
     _ExampleClassState createState() => _ExampleClassState();
    }

    class _ExampleClassState extends State<ExampleClass> {

     bool isInstructionView = false;

     @override
     Widget build(BuildContext context) {

      return Container(
       child:  Switch(
       value: isInstructionView,
       onChanged: (isOn) {

         setState(() {
           isInstructionView = isOn
         });

         print(isInstructionView);

        },
        ...
      ),
     );
    }
   }

Upvotes: 11

Hiren
Hiren

Reputation: 686

I have also got the same problem while I was implementing CupertinoSwitch. I was able to turn it ON but wasn't able to turn it OFF.

According to this example, I tried to put my Switch inside the widget called 'Semantics' and magically it started working.

Below is the code:

body: Column(
    children: <Widget>[
      SizedBox(height: 50.0,),
      Semantics(
        container: true,
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          children: <Widget>[
            CupertinoSwitch(
              value: _switchValue,
              onChanged: (bool value){
                setState(() {
                  _switchValue = value;
                  _animating = value;
                });
              },
            ),

            Text(
              "${_switchValue ? "On" : "Off"}",
              style: TextStyle(fontSize: 20.0,
                              fontWeight: FontWeight.bold),
            ),
          ],  
        ),
        ),
        SizedBox(
          height: 50.0,
        ),
        Visibility(
            child: CupertinoActivityIndicator(
            animating: _animating,
            radius: 30.0,
          ),
          visible: _animating,
        ),
    ],

  ),

Hope it helps.

Upvotes: -1

Francis Manoj Fernnado
Francis Manoj Fernnado

Reputation: 262

You need to rebuild the widget when the state changes. refer the documentation https://docs.flutter.io/flutter/material/Switch/onChanged.html

Upvotes: 2

Bilal Şimşek
Bilal Şimşek

Reputation: 5943

I added additional code chunks according to @Zulfiqar 's answer. I didn't test this code but I m using similar codes in my project. if you want to save it and use in another class or if you want to show latest state for everytime you load you can save the state in a global variable and call it when you load the class. hope it will help..

class Tab_b extends StatefulWidget {

  @override
  State<StatefulWidget> createState() => new _TabsPageState();
}

class _TabsPageState extends State<Tab_b>{
  bool isInstructionView;
  @override
  void initState() {
    isInstructionView = Global.shared.isInstructionView;
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: new AppBar(
        title: new Text("add data"),
      ),
      body: new Container(
        child:  Switch(
          value: isInstructionView,
          onChanged: (bool isOn) {
            print(isOn);
            setState(() {
             isInstructionView = isOn;
             Global.shared.isInstructionView = isOn;
             isOn =!isOn;
              print(isInstructionView);
            });
          },
          activeColor: Colors.blue,
          inactiveTrackColor: Colors.grey,
          inactiveThumbColor: Colors.grey,
        ),
      ),
    );
  }
}
class Global{
  static final shared =Global();
  bool isInstructionView = false;
}

Upvotes: 8

Sher Ali
Sher Ali

Reputation: 5793

class Tab_b extends StatefulWidget {

bool isInstructionView = false;
@override
State<StatefulWidget> createState() => new _TabsPageState();
}

class _TabsPageState extends State<Tab_b>{

@override
Widget build(BuildContext context) {

return Scaffold(
    appBar: new AppBar(
    title: new Text("add data"),
),
body: new Container(
  child:  Switch(
    value: widget.isInstructionView,
    onChanged: (bool isOn) {
      print(isOn);
      setState(() {
        widget.isInstructionView = isOn;
        print(widget.isInstructionView);
      });
    },
    activeColor: Colors.blue,
    inactiveTrackColor: Colors.grey,
    inactiveThumbColor: Colors.grey,
  ),
),
);
}

Upvotes: 4

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