灰屏抖動

Question

每當我嘗試啟動應用程序時都會出現灰屏（我使用的是 Flutlab。我已在 Manifest 文件中啟用 Internet 權限。）我還刪除了 Widget 內的 Expanded()。 您能否指出可能導致此問題的原因？ 這里是版本：1.0.0+1 和環境：sdk: ">=2.12.0 <3.0.0" 這里是代碼：

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'dart:io';

import 'package:image_picker/image_picker.dart';

class MyPage extends StatefulWidget {
  @override
  _MyPageState createState() => _MyPageState();
}

class _MyPageState extends State<MyPage> {
  // Variables
  File? imageFile;
  final _formKey = GlobalKey<FormState>();
  final _widthTextController = TextEditingController();
  final _heightTextController = TextEditingController();
  final _focusWidth = FocusNode();
  final _focusHeight = FocusNode();

  /// Widget
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("Image Picker"),
        ),
        body: Container(
            child: imageFile == null
                ? Column(children: <Widget>[
                    Align(
                        alignment: Alignment.center,
                        child: Center(
                            child: Padding(
                                padding: EdgeInsets.all(8.00),
                                child: Container(
                                    decoration: BoxDecoration(color: Colors.blue),
                                    child: Column(children: <Widget>[
                                      SizedBox(height: 20.00),
                                      FractionallySizedBox(
                                          widthFactor: 0.8,
                                          heightFactor: 0.4,
                                          child: InkWell(
                                              onTap: () {
                                                _getFromGallery();
                                              },
                                              child: Container(
                                                  decoration: BoxDecoration(color: Colors.white, image: DecorationImage(image: AssetImage('images/upload.png')), border: Border.all(width: 1.00, color: Colors.black), borderRadius: BorderRadius.circular(6.00)),
                                                  child: Image.file(
                                                    imageFile!,
                                                    fit: BoxFit.cover,
                                                  )))),
                                      SizedBox(height: 10),
                                      Form(
                                          key: _formKey,
                                          child: FractionallySizedBox(
                                              widthFactor: 0.2,
                                              heightFactor: 0.4,
                                              child: Column(children: <Widget>[
                                                TextFormField(
                                                    controller: _heightTextController,
                                                    focusNode: _focusHeight,
                                                    decoration: InputDecoration(
                                                      hintText: "Height",
                                                      border: UnderlineInputBorder(borderRadius: BorderRadius.circular(6.0)),
                                                    )),
                                                SizedBox(height: 8.00),
                                                TextFormField(
                                                    controller: _widthTextController,
                                                    focusNode: _focusWidth,
                                                    decoration: InputDecoration(
                                                      hintText: "Width",
                                                      border: UnderlineInputBorder(
                                                        borderRadius: BorderRadius.circular(6.0),
                                                      ),
                                                    )),
                                                InkWell(
                                                    onTap: () {
                                                      Navigator.of(context).pushNamed('/Results');
                                                    },
                                                    child: Container(decoration: BoxDecoration(image: DecorationImage(image: AssetImage('images/submit.png'))), width: 100, height: 100, child: Container()))
                                              ])))
                                    ])))))
                  ])
                : Container(
                    child: Align(
                        alignment: Alignment.center,
                        child: Center(
                            child: Padding(
                                padding: EdgeInsets.all(8.00),
                                child: Container(
                                    decoration: BoxDecoration(color: Colors.blue),
                                    child: Column(children: <Widget>[
                                      SizedBox(height: 20.00),
                                      FractionallySizedBox(
                                          widthFactor: 0.8,
                                          heightFactor: 0.4,
                                          child: InkWell(
                                              onTap: () {
                                                _getFromGallery();
                                              },
                                              child: Container(
                                                  decoration: BoxDecoration(color: Colors.white, image: DecorationImage(image: AssetImage('images/upload.png')), border: Border.all(width: 1.00, color: Colors.black), borderRadius: BorderRadius.circular(6.00)),
                                                  child: Image.file(
                                                    imageFile!,
                                                    fit: BoxFit.cover,
                                                  )))),
                                      SizedBox(height: 10),
                                      Form(
                                          key: _formKey,
                                          child: FractionallySizedBox(
                                              widthFactor: 0.2,
                                              heightFactor: 0.4,
                                              child: Column(children: <Widget>[
                                                TextFormField(
                                                    controller: _heightTextController,
                                                    focusNode: _focusHeight,
                                                    decoration: InputDecoration(
                                                        hintText: "Height",
                                                        border: UnderlineInputBorder(
                                                          borderRadius: BorderRadius.circular(6.0),
                                                        ))),
                                                SizedBox(height: 8.00),
                                                TextFormField(
                                                    controller: _widthTextController,
                                                    focusNode: _focusWidth,
                                                    decoration: InputDecoration(
                                                      hintText: "Width",
                                                      border: UnderlineInputBorder(
                                                        borderRadius: BorderRadius.circular(6.0),
                                                      ),
                                                    )),
                                                InkWell(
                                                    onTap: () {
                                                      Navigator.of(context).pushNamed('/Results');
                                                    },
                                                    child: Container(decoration: BoxDecoration(image: DecorationImage(image: AssetImage('images/submit.png'))), width: 100, height: 100, child: Container()))
                                              ])))
                                    ]))))))));
  }

  _getFromGallery() async {
    PickedFile? pickedFile = await ImagePicker().getImage(
      source: ImageSource.gallery,
      maxWidth: 1800,
      maxHeight: 1800,
    );
    if (pickedFile != null) {
      setState(() {
        imageFile = File(pickedFile.path);
      });
    }
  }

  /// Get from Camera
  _getFromCamera() async {
    PickedFile? pickedFile = await ImagePicker().getImage(
      source: ImageSource.camera,
      maxWidth: 1800,
      maxHeight: 1800,
    );
    if (pickedFile != null) {
      setState(() {
        imageFile = File(pickedFile.path);
      });
    }
  }
}

這是錯誤的樣子在此處輸入圖像描述

Answer 1

如果imageFile上有一個空指針，請將Image.file()小部件包裝在 if 語句中

child: imageFile != null ? Image.file(
    imageFile!,
    fit: BoxFit.cover,
  ) : null,