Flutter setstate on local variable not updating UI

Question

So I tried to dynamically update an individual listview item. I am using a function to generate each item and I created a local variable in that function. I used setstate to update that variable but the UI is not updating. If i make the same variable global it works but i changes every listview items which I dont want. Does anyone have any tips on doing that? I am new to flutter and Sorry if this has been asked multiple times. I tried searching but couldnt find any solutions. This is a similar code for the item builder function.

Widget generateListItem(){ 
    bool flag= false;
    return InkWell(
       onTap:(){
          setState((){
             flag=true;
          })
       },
       child: Text(flag? "Changed" : "Not Changed"),
    );
}

When rebuild 'generateListItem' by setState(), flag is also reset. So always flag is false. — KuKu
– KuKu, Commented Oct 20, 2020 at 2:37
Ohh.. That makes more sense now. Is there any way to update the item individually? — Bikram gurung
– Bikram gurung, Commented Oct 20, 2020 at 2:57
Make it a variable inside the State class instead of inside the method. @Bikramgurung — sameer kashyap
– sameer kashyap, Commented Oct 20, 2020 at 2:58
If I do that setstate changes every Item. I want to individually change the specific item. — Bikram gurung
– Bikram gurung, Commented Oct 20, 2020 at 2:59
You need to control that value at top parent widget re-builded. "Page(here)[Stateful widget] - build() - 'generateListItem' widget..." — KuKu
– KuKu, Commented Oct 20, 2020 at 2:59

Elriz Wiraswara · Accepted Answer · 2020-10-20 04:12:17Z

1

the flag is resetted every time you call setState, beacuse the flag is in your generateListItem() widget,

I think you must set the bool in a list, so when you called setState, the state in the list of bool not resetted,

List<bool> flag = [];  // 

Widget generateListItem(int i){ 
flag.add(false);
return InkWell(
   onTap:(){
      setState((){
         flag[i]=true;
      })
   },
   child: Text(flag[i]? "Changed" : "Not Changed"),
);}

answered Oct 20, 2020 at 4:12

Elriz Wiraswara

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1 Comment

Jerry Over a year ago

amazing! Map<String,bool> could be too.

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