如何将列表值复制到颤振中的另一个列表 [英] How to copy list values to another list in flutter

问题描述

我正在尝试将一个列表的值复制到另一个，我使用三个按钮第一个将值附加到 mylist，第二个用于清除 mylist，第三个按钮将值从 mynewlist 复制到 mylist.

I am trying to copy values of one list to another, I use three buttons 1st one to append a value to mylist, second one to clear the mylist, 3rd button to copy values from mynewlist to mylist.

我试过了

List<String> mylist = [
    'Albania',
    'Andorra',
    'Armenia',
    'Austria',
    'Azerbaijan',
    'Belarus',
    'Belgium',
    'Albania',
    'Andorra',
    'Armenia',
    'Austria',
    'Azerbaijan',
    'Belarus',
    'Belgium',
  ];

  List<String> mynewlist = [
    'Albania',
    'Andorra',
    'Armenia',
    'Austria',
    'Azerbaijan',
    'Belarus',
    'Belgium',
    'Albania',
    'Andorra',
    'Armenia',
    'Austria',
    'Azerbaijan',
    'Belarus',
    'Belgium',
  ];



Padding(
                padding: const EdgeInsets.all(5.0),
                child: Row(
                  children: <Widget>[
                    Expanded(
                      child: FlatButton(
                        onPressed: () {
                          setState(() {
                            print('clicked 1st');
                            print(mylist.length);
                            print(mynewlist.length);
                            mylist.add('sdsds');
                          });
                        },
                        child: Container(
                          child: Column(
                            children: <Widget>[
                              Image.asset(
                                'images/bulb.png',
                                width: 100,
                                height: 100,
                              ),
                              Text('bulb')
                            ],
                          ),
                        ),
                      ),
                    ),
                    Expanded(
                      child: FlatButton(
                        onPressed: () {
                          setState(() {
                            print('clicked 2nd');
                            print(mylist.length);
                            print(mynewlist.length);
//after i set mylist = mynewlist; when i click this button it clears the old and new list.
                            mylist.removeRange(0, mylist.length);
                          });
                        },
                        child: Container(
                          child: Column(
                            children: <Widget>[
                              Image.asset(
                                'images/bulb.png',
                                width: 100,
                                height: 100,
                              ),
                              Text('bulb')
                            ],
                          ),
                        ),
                      ),
                    ),
                    Expanded(
                      child: FlatButton(
                        onPressed: () {
                          setState(() {
                            print('clicked 3rd');
                            print(mylist.length);
                            print(mynewlist.length);
                         mylist = mynewlist;
                          });
                        },
                        child: Container(
                          child: Column(
                            children: <Widget>[
                              Image.asset(
                                'images/bulb.png',
                                width: 100,
                                height: 100,
                              ),
                              Text('bulb')
                            ],
                          ),
                        ),
                      ),
                    ),
                  ],
                ),
              )

在我第二次单击第二个按钮时它会完美运行，它会清除 mylist 和 mynewlist.

On the initial time it works perfectly the second time i click the second button it clears the mylist and mynewlist.

如何在不清除新列表的情况下复制第二个列表的值

How can i copy the values of second list without clearing the new new list

推荐答案

使用 myList = List.from(mynewlist); 代替 mylist = mynewlist;

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