Question

为什么我的_image无法更新？

当用户从图库或照相机中选择新图像时，我需要更新 _image 属性，但是当用户选择新图像时，我使用setState将新值设置为 _image ，但是没有不起作用（未更新用户界面）。

我的代码在这里有问题：抱歉，我无法提供完整的源代码，因为stackoverflow的编辑器抱怨很多代码。

Statefull类：枚举ChooseMedia {相机，画廊}

  File _image;

  void getImage(ChooseMedia media) async {
    if (media == ChooseMedia.camera) {
      var image = await ImagePicker.pickImage(source: ImageSource.camera);
      var pathLocal = await getApplicationDocumentsDirectory();
      await image.copy('${pathLocal.path}/profileImage.jpg').then((_) {
        setState(() {
          _image = image;
        });
      });
    }
    if (ChooseMedia.gallery == media) {
      var image = await ImagePicker.pickImage(source: ImageSource.gallery);
      var pathLocal = await getApplicationDocumentsDirectory();

      await image.copy('${pathLocal.path}/profileImage.jpg').then((_) {
        setState(() {
          _image = image;
        });
      });
    }
  }



  @override
  Widget build(BuildContext context) {

        return PopupMenuButton(
          elevation: 5,
          shape: RoundedRectangleBorder(
              borderRadius: BorderRadius.all(Radius.circular(15))),
          onSelected: (ChooseMedia media) {
            getImage(media);
          },
          itemBuilder: (BuildContext context) => <PopupMenuEntry<ChooseMedia>>[
            const PopupMenuItem<ChooseMedia>(
              value: ChooseMedia.gallery,
              child: ListTile(
                leading: Icon(
                  Icons.picture_in_picture,
                ),
                title: Text('From galaxy'),
              ),
            ),
            const PopupMenuItem<ChooseMedia>(
              value: ChooseMedia.camera,
              child: ListTile(
                leading: Icon(Icons.camera),
                title: Text('Take picture'),
              ),
            ),
          ],
          child: Container(
              decoration: BoxDecoration(),
              padding: EdgeInsets.all(7),
              child: CircleAvatar(
                  backgroundImage: _image == null
                      ? AssetImage('assets/images/profile.jpg')
                      : FileImage(_image))),
        );
  }

Answer 1

您正在混合“等待”和“然后” 只需

var copiedImage = await image.copy('${pathLocal.path}/profileImage.jpg');
setState(() {
    _image = copiedImage;
});

为什么我在异步功能中使用setState而不是更新状态（Flutter）？

1 个答案: