使用导航器根据Flutter上一个屏幕返回的数据更新变量 [英] Update the variable depending on what data was returned from the previous screen in Flutter using the Navigator

问题描述

我有一个变量_PhotoName，该变量为null，但是当我拍照并在另一个屏幕上重复术语base64时，如果base64不为null，我希望变量_PhotoName为timestamp.img.这是显示此变量的代码部分，还有返回base 64的代码:

I have a variable _PhotoName, this variable is null, but when I take a photo and repeat the term base64 from another screen, I would like the variable _PhotoNameto be a timestamp.img , if base64 is not null. here is the part of the code that displays this variable, and there is also code where base 64 is returned:

              Container(
              padding: EdgeInsets.only(left: 15, right: 15, top: 5),
              color: Colors.white,
              child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                children: <Widget>[
                  Expanded(
                    child: Text(
                        "$_PhotoName",
                        style: TextStyle(color: Colors.black, fontSize: 15)

                    ),

                  ),
                  Expanded(
                    child: ButtonTheme(
                        alignedDropdown: true,
                        child: new RaisedButton.icon(
                          label: Text('Add Image'),//Добавити фото
                          onPressed: () async{
                            _imageB64 = await  Navigator.push(
                                context,
                                MaterialPageRoute(
                                builder: (context) => image.PicturePreview(camera)),
                             );

                          },

                          icon : Icon(Icons.camera_alt),
                        )
                    ),
                  ),

                ],

              ),
            ),

推荐答案

我可能不明白这个问题，但是您可以检查 base64 是否为 null ，如果是，请更新国家

I might have not understood the question but you could check if base64 is null and if so update the state

if (_imageB64 != null) {
    setState ((){
        _PhotoName = WHAT_IT_NEEDS_TO_BE_EQUAL_TO;
    });
}

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