Flutter: Accessing Bloc data from outside a build method - flutter

Question

Can I access the data in Bloc streams from outside a build method?
For example, in the build method, I am able to access the data using snapShot.data. Like this:
return StreamBuilder(
//initialData: Colors.blue,
stream: colorBloc.colorStream,
builder: (BuildContext context, snapShot) => Container(
width: menuButtonSize,
height: menuButtonSize,
decoration: BoxDecoration(
shape: BoxShape.circle,
color: snapShot.data, //This returns the correct colour previously stored in this stream.
boxShadow: [
BoxShadow(
color: Colors.black,
blurRadius: 15,
),
],
),
),
);
But for troubleshooting another Bloc instance that I am trying to get working, I would like to be able to print out the current value of snapShot.data somehow, so I can see what it is doing and if it is updating properly, because currently it isn't working.
Current snippet of non-working Bloc:
Widget customTheme() {
return StreamBuilder(
initialData: true,
stream: customToggleBloc.customToggleStream,
builder: (BuildContext context, snapShot) => GestureDetector(
onTap: (){
snapShot.data == true ? widget?._callback('custom') : widget?._callback('clearcustom'); //Section A
},
child: Container(
width: menuButtonSize + 8,
height: menuButtonSize + 8,
decoration: BoxDecoration(
shape: BoxShape.circle,
color: AppState.brownTheme,
boxShadow: [
BoxShadow(
color: Colors.black,
blurRadius: 25,
),
],
),
child: new IconTheme(
data: new IconThemeData(
color: Colors.white,
size: 35,
),
child: snapShot.data == true ? new Icon(Icons.add_photo_alternate) : new Icon(Icons.cancel), // Section B
),
),
),
);
}
So what I would like it to do is have a button that is in one of two states at all times. 1) It displays Icons.add_photo_alternate and allows you to pick an image from the gallery; 2) It displays Icons.cancel and removes the previously selected image. Section A handles the onPress event options, and Section B handles the displayed icon.
What I actually get is Icons.add_photo_alternate at all times, and on press actually triggers BOTH of the alternative code blocks.
So I would really like to be able to access this data to see where I might be going wrong!
I am trying variations of things similar to:
print(customToggleBloc.customToggleSink.toString());
Which returns:
Instance of '_StreamSinkWrapper<bool>'
And not the value inside. Is it even possible to access this information?

Answer 1

I think this behavior is caused by your stream not returning any data, and thus relying on the initialData you provide to build its children.To be sure, you can remove the initialDate: true from your StreamBuilder and wrap the builder body with if-else to check for data existence: if data is available your GestureDetector will be built, if not a CircularProgressIndicator will be displayed in the middle. This way you will know what is going on with your stream:
Widget customTheme() {
return StreamBuilder(
//initialData: true,
stream: customToggleBloc.customToggleStream,
builder: (BuildContext context, snapShot) {
if(snapShot.hasData){
print(snapShot.data.toString());
return GestureDetector(
onTap: (){
widget?._callback(snapShot.data == true ? 'custom' : 'clearcustom') ; //Section A
},
child: Container(
width: menuButtonSize + 8,
height: menuButtonSize + 8,
decoration: BoxDecoration(
shape: BoxShape.circle,
color: AppState.brownTheme,
boxShadow: [
BoxShadow(
color: Colors.black,
blurRadius: 25,
),
],
),
child: new IconTheme(
data: new IconThemeData(
color: Colors.white,
size: 35,
),
child: Icon(snapShot.data == true ? Icons.add_photo_alternate : Icons.cancel), // Section B
),
),
);
}else{
return Center(
child: CircularProgressIndicator(),
);
}
}
);
}