Flutter - How do I toggle the color of a RaisedButton upon click?

问题

I am trying to toggle the color of a raised button. Initially the button should be blue and when it is pressed it turns to grey. Right now I have a bool value called pressAttention and it is set to false. I am using this to initially set this the false. When the button is pressed it toggles the pressAttention bool, but it seems that the widget is never updated again.

new RaisedButton(
                  child: new Text("Attention"),
                  textColor: Colors.white,
                  shape: new RoundedRectangleBorder(borderRadius: new BorderRadius.circular(30.0)),
                  color: pressAttention?Colors.grey:Colors.blue,
                  onPressed: () => doSomething("Attention"),
                )

void doSomething(String buttonName){
if(buttonName == "Attention"){
  if(pressAttention = false){
    pressAttention = true;
  } else {
    pressAttention = false;
  }
}

}

回答1:

This button will need to be created in the build of a State of a StatefulWidget, and the State must have a member variable bool pressAttention = false;. As Edman suggests, you need to make state changes in a setState callback for the Widget to redraw.

new RaisedButton(
  child: new Text('Attention'),
  textColor: Colors.white,
  shape: new RoundedRectangleBorder(
    borderRadius: new BorderRadius.circular(30.0),
  ),
  color: pressAttention ? Colors.grey : Colors.blue,
  onPressed: () => setState(() => pressAttention = !pressAttention),
);

回答2:

Or you can use rxdart:

import 'package:rxdart/rxdart.dart';

...

bool presssedFavorite = false;
final _pressAttention = BehaviorSubject<bool>();
Observable<bool> get coursesStream => _pressAttention.stream;

...

StreamBuilder(stream: _pressAttention,
builder: (BuildContext context, AsyncSnapshot<bool> snapshot) {
if (snapshot.hasData)
  presssedFavorite = snapshot.data;

  return RawMaterialButton(
      onPressed: (){
        _addToFavorites(context);
      },
      child: Padding(
        padding: EdgeInsets.all(5),
        child: Icon(
          presssedFavorite ? Icons.favorite : Icons.favorite_border,
          color: Colors.red,
          size: 17,
        ),
      ),
    );
  },
),

void _addToFavorites(BuildContext context) async{
  //my code...
  _pressAttention.sink.add(!presssedFavorite);
}

It is more complicated, but you can use this solution also with web services, firestore, db... And you can use with StatelessWidget and StatefulWidget.

回答3:

If you want the button to change color for the pressed state you just need to use the "highlightColor" property in RaisedButton

       RaisedButton(
          onPressed: () {},
          child: Text("Test"),
          highlightColor: YOUR_PRESSED_COLOR, //Replace with actual colors
          color: IDLE_STATE_COLOR,
        ),

来源：https://stackoverflow.com/questions/50863681/flutter-how-do-i-toggle-the-color-of-a-raisedbutton-upon-click

标签

android

button

dart

widget

Flutter