第一个小部件

Question

我有一个简单的表单，当按下此按钮时，它里面有CircularAvatar显示ModalBottomSheet从画廊或相机拍照之间进行选择。为了使我的小部件更紧凑，我将其分离为某些文件。

FormDosenScreen（它是主屏幕）
DosenImagePicker（这只是CircularAvatar）
ModalBottomSheetPickImage（用于显示ModalBottomSheet）

问题是，我不知道如何将值从 ModalBottomSheetPickImage 传递给 FormDosenScreen 。因为我将使用 ModalBottomSheetPickImage 中的值进行插入操作。

我只能成功地从第三小部件传递到第二小部件，但是当我再次从第二小部件传递到第一小部件时，该值为null，并且我认为问题是从第二小部件传递到第一小部件的。

如何从第三个小部件传递到第一个小部件？

第一个小部件

class FormDosenScreen extends StatefulWidget {
  static const routeNamed = '/formdosen-screen';

  @override
  _FormDosenScreenState createState() => _FormDosenScreenState();
}

class _FormDosenScreenState extends State<FormDosenScreen> {
  String selectedFile;
  @override
  Widget build(BuildContext context) {
    final detectKeyboardOpen = MediaQuery.of(context).viewInsets.bottom;
    print('trigger');
    return Scaffold(
      appBar: AppBar(
        centerTitle: true,
        title: Text('Tambah Dosen'),
        actions: <Widget>[
          PopupMenuButton(
            itemBuilder: (_) => [
              PopupMenuItem(
                child: Text('Tambah Pelajaran'),
                value: 'add_pelajaran',
              ),
            ],
            onSelected: (String value) {
              switch (value) {
                case 'add_pelajaran':
                  Navigator.of(context).pushNamed(FormPelajaranScreen.routeNamed);
                  break;
                default:
              }
            },
          )
        ],
      ),
      body: Stack(
        fit: StackFit.expand,
        children: <Widget>[
          SingleChildScrollView(
            child: Column(
              mainAxisSize: MainAxisSize.min,
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: <Widget>[
                SizedBox(height: 20),
                DosenImagePicker(onPickedImage: (file) => selectedFile = file),
                SizedBox(height: 20),
                Card(
                  margin: const EdgeInsets.symmetric(horizontal: 15, vertical: 10),
                  child: Padding(
                    padding: const EdgeInsets.all(20),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.stretch,
                      children: <Widget>[
                        TextFormFieldCustom(
                          onSaved: (value) {},
                          labelText: 'Nama Dosen',
                        ),
                        SizedBox(height: 20),
                        TextFormFieldCustom(
                          onSaved: (value) {},
                          prefixIcon: Icon(Icons.email),
                          labelText: 'Email Dosen',
                          keyboardType: TextInputType.emailAddress,
                        ),
                        SizedBox(height: 20),
                        TextFormFieldCustom(
                          onSaved: (value) {},
                          keyboardType: TextInputType.number,
                          inputFormatter: [
                            // InputNumberFormat(),
                            WhitelistingTextInputFormatter.digitsOnly
                          ],
                          prefixIcon: Icon(Icons.local_phone),
                          labelText: 'Telepon Dosen',
                        ),
                      ],
                    ),
                  ),
                ),
                SizedBox(height: kToolbarHeight),
              ],
            ),
          ),
          Positioned(
            child: Visibility(
              visible: detectKeyboardOpen > 0 ? false : true,
              child: RaisedButton(
                onPressed: () {
                  print(selectedFile);
                },
                materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
                color: colorPallete.primaryColor,
                child: Text(
                  'SIMPAN',
                  style: TextStyle(fontWeight: FontWeight.bold, fontFamily: AppConfig.headerFont),
                ),
                shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(20)),
                textTheme: ButtonTextTheme.primary,
              ),
            ),
            bottom: kToolbarHeight / 2,
            left: sizes.width(context) / 15,
            right: sizes.width(context) / 15,
          )
        ],
      ),
    );
  }
}

第二个小部件


class DosenImagePicker extends StatefulWidget {
  final Function(String file) onPickedImage;
  DosenImagePicker({@required this.onPickedImage});
  @override
  DosenImagePickerState createState() => DosenImagePickerState();
}

class DosenImagePickerState extends State<DosenImagePicker> {
  String selectedImage;
  @override
  Widget build(BuildContext context) {
    return Align(
      alignment: Alignment.center,
      child: InkWell(
        onTap: () async {
          await showModalBottomSheet(
            context: context,
            builder: (context) => ModalBottomSheetPickImage(
              onPickedImage: (file) {
                setState(() {
                  selectedImage = file;
                  widget.onPickedImage(selectedImage);
                  print('Hellooo dosen image picker $selectedImage');
                });
              },
            ),
          );
        },
        child: CircleAvatar(
          foregroundColor: colorPallete.black,
          backgroundImage: selectedImage == null ? null : MemoryImage(base64.decode(selectedImage)),
          radius: sizes.width(context) / 6,
          backgroundColor: colorPallete.accentColor,
          child: selectedImage == null ? Text('Pilih Gambar') : SizedBox(),
        ),
      ),
    );
  }
}

第三小部件


class ModalBottomSheetPickImage extends StatelessWidget {
  final Function(String file) onPickedImage;

  ModalBottomSheetPickImage({@required this.onPickedImage});

  @override
  Widget build(BuildContext context) {
    return SizedBox(
      child: Padding(
        padding: const EdgeInsets.all(15.0),
        child: Wrap(
          alignment: WrapAlignment.spaceEvenly,
          children: <Widget>[
            InkWell(
              onTap: () async {
                final String resultBase64 =
                    await commonFunction.pickImage(quality: 80, returnFile: ReturnFile.BASE64);
                onPickedImage(resultBase64);
              },
              child: CircleAvatar(
                foregroundColor: colorPallete.white,
                backgroundColor: colorPallete.green,
                child: Icon(Icons.camera_alt),
              ),
            ),
            InkWell(
              onTap: () async {
                final String resultBase64 =
                    await commonFunction.pickImage(returnFile: ReturnFile.BASE64, isCamera: false);
                onPickedImage(resultBase64);
              },
              child: CircleAvatar(
                foregroundColor: colorPallete.white,
                backgroundColor: colorPallete.blue,
                child: Icon(Icons.photo_library),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

Answer 1

最干净，最简单的方法是通过提供程序。它是状态管理解决方案之一，可用于在应用程序周围传递值以及仅重建已更改的小部件。（例如：“文本”小部件的值更改时）。这是您在方案中可以使用Provider的方式：

这是您的模型的外观：

class ImageModel extends ChangeNotifier {
  String _base64Image;
  get base64Image => _base64Image;
  set base64Image(String base64Image) {
    _base64Image = base64Image;
    notifyListeners();
  }
}

别忘了添加getter和setter，以便在有依赖于它的ui时可以使用notifyListeners（）。

以下是在用户界面中访问ImageModel的值的方法：

final model=Provider.of<ImageModel>(context,listen:false);
String image=model.base64Image; //get data
model.base64Image=resultBase64; //set your image data after you used ImagePicker

这里是如何在“文本”小部件中显示数据的方法（理想情况下，您应该使用Selector而不是Consumer，以便只有在其侦听的值发生更改时才重新构建小部件）：

@override
Widget build(BuildContext context) {
 //other widgets
 Selector<ImageModel, String>(
  selector: (_, model) => model.base64Image,
  builder: (_, image, __) {
   return Text(image);
     },
   );
  }
 )
}

Answer 2

您可以轻松实现这一目标。如果您使用的是Blocs。

将值传递给上一个小部件

第一个小部件

第二个小部件

第三小部件

2 个答案: