How to make Tree Select Box with DropdownButton in flutter

Question

I want to make a Select box with DropDownButton in Flutter. but I can not make a perfect algorithm for it. I hope to receive great help from Flutter experts. Thank you.

Screenshot of current implementation

Answer 1

I already solved this problem myself. Here is my code. But I expect a better solution of Flutter experts.

  addTaskList(){
taskChildrenList.clear();
print(selectedTaskList.length);
selectedTaskList.forEach((task){
  taskChildrenList.add(Card(
    margin: EdgeInsets.symmetric(vertical: 5),
    child: Padding(
      padding: const EdgeInsets.symmetric(horizontal: 8),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: <Widget>[
          Text("${AppLanguage.selectTaskLabel()} ${task[0].label}",style: TextStyle(fontSize: 15,fontWeight: FontWeight.bold),),
          Flexible(
            child: FittedBox(
              child: DropdownButton<JustificationTask>(
                value: selectedTasks.length==task[0].label-1?null:selectedTasks[task[0].label-1],
                icon: Icon(Icons.chevron_right),
                iconSize: 25,
                elevation: 16,
                style: TextStyle(color: Colors.black),
                underline: Container(height: 1, color: Colors.transparent,),
                onChanged: (JustificationTask value) {
                  setState(() {
                    selectedTaskList.removeRange(value.label, selectedTaskList.length);
                    selectedTasks.removeRange(value.label-1, selectedTasks.length);
                    selectedTasks.add(value);
                    if(value.children.isNotEmpty){
                      selectedTaskList.add(value.children);
                      selectedTask=null;
                    }else{
                      selectedTask=value;
                      equipment=null;
                    }
                  });
                },
                items: task.map<DropdownMenuItem<JustificationTask>>((JustificationTask value) {
                  return DropdownMenuItem<JustificationTask>(
                    value: value,
                    child: SizedBox(width:MediaQuery.of(context).size.width*0.4,child: Text("${taskName(value)}",style: TextStyle(fontSize: 20),)),
                  );
                }).toList(),
                hint: SizedBox(width:MediaQuery.of(context).size.width*0.4,child: Text(AppLanguage.task(),style: TextStyle(fontSize: 20))),
                isExpanded: false,
              ),
            ),
          ),
        ],
      ),
    ),
  ),);
});

}