Flutter应用昨日正常运行今日出现黑屏且无报错问题咨询

Hey there, let's get to the bottom of that black screen issue! After looking through your code, I immediately spotted the root cause.

The Core Problem #

In your main() function, you're launching a blank MaterialApp instead of your custom MyApp widget. Since the default empty MaterialApp has no content to render, you end up with a black screen—no errors because the app technically runs, just without any UI!

Quick Fix #

Update your main() function to use your MyApp component instead:

void main() { runApp(const MyApp()); }

Full Corrected Code #

Here's your code with the fix applied:

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
bool _valuehidra = true;
bool _valuelight = true;
bool _valuewebasto = true;
bool _valueusb = true;
bool _valuealter = true;
void main() { runApp(const MyApp()); } // <-- Fixed this line
class MyApp extends Stateful Widget {
  const MyApp({Key? key}) : super(key: key);
  @override
  _State createState() => _State();
}
class _State extends State<MyApp> {
  bool isSwitched = false;
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Column(
          children: [
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Container(
                  margin: const EdgeInsets.fromLTRB(10, 30, 0, 0),
                  child: Image.asset('assets/images/logoisim.png', height: 125.0, fit: BoxFit.cover,),
                ),
              ],
            ),
            Container(
              decoration: BoxDecoration(
                color: Colors.indigoAccent,
                borderRadius: BorderRadius.circular(30.0),
              ),
              width: 350,
              height: 70,
              alignment: Alignment.bottomCenter,
              margin: const EdgeInsets.only(top: 20),
              child: Row(
                children: <Widget>[
                  SizedBox(width: 200, child: Container(
                    margin: const EdgeInsets.only(left: 30),
                    alignment: Alignment.centerLeft,
                    child: const Text('AYDINLATMA', style: TextStyle(color: Colors.white, fontSize: 25,fontFamily: 'YesevaOne' )),
                  ), ),
                  Transform.scale(
                    scale: 1.3,
                    child: Container(
                      margin: const EdgeInsets.only(left:50),
                      child: CupertinoSwitch(
                        value: _valuelight,
                        onChanged: (value) {
                          setState(() {
                            _valuelight = value;
                          });
                        },
                      ),
                    ),
                  ),
                ],
              ),
            ),
            Container(
              decoration: BoxDecoration(
                color: Colors.indigo,
                borderRadius: BorderRadius.circular(30.0),
              ),
              width: 350,
              height: 70,
              alignment: Alignment.bottomCenter,
              margin: const EdgeInsets.only(top: 10),
              child: Row(
                children: <Widget>[
                  SizedBox(width: 200, child: Container(
                    margin: const EdgeInsets.only(left: 30),
                    alignment: Alignment.centerLeft,
                    child: const Text('WEBASTO', style: TextStyle(color: Colors.white, fontSize: 25,fontFamily: 'YesevaOne' )),
                  ), ),
                  Transform.scale(
                    scale: 1.3,
                    child: Container(
                      margin: const EdgeInsets.only(left:50),
                      child: CupertinoSwitch(
                        value: _valuewebasto,
                        onChanged: (value) {
                          setState(() {
                            _valuewebasto = value;
                          });
                        },
                      ),
                    ),
                  ),
                ],
              ),
            ),
            Container(
              decoration: BoxDecoration(
                color: Colors.indigoAccent,
                borderRadius: BorderRadius.circular(30.0),
              ),
              width: 350,
              height: 70,
              alignment: Alignment.bottomCenter,
              margin: const EdgeInsets.only(top: 10),
              child: Row(
                children: <Widget>[
                  SizedBox(width: 200, child: Container(
                    margin: const EdgeInsets.only(left: 30),
                    alignment: Alignment.centerLeft,
                    child: const Text('HİDRAFOR', style: TextStyle(color: Colors.white, fontSize: 25,fontFamily: 'YesevaOne' )),
                  ), ),
                  Transform.scale(
                    scale: 1.3,
                    child: Container(
                      margin: const EdgeInsets.only(left:50),
                      child: CupertinoSwitch(
                        value: _valuehidra,
                        onChanged: (value) {
                          setState(() {
                            _valuehidra = value;
                          });
                        },
                      ),
                    ),
                  ),
                ],
              ),
            ),
            Container(
              decoration: BoxDecoration(
                color: Colors.indigo,
                borderRadius: BorderRadius.circular(30.0),
              ),
              width: 350,
              height: 70,
              alignment: Alignment.bottomCenter,
              margin: const EdgeInsets.only(top: 10),
              child: Row(
                children: <Widget>[
                  SizedBox(width: 200, child: Container(
                    margin: const EdgeInsets.only(left: 30),
                    alignment: Alignment.centerLeft,
                    child: const Text('ALTERNATÖR', style: TextStyle(color: Colors.white, fontSize: 25,fontFamily: 'YesevaOne' )),
                  ), ),
                  Transform.scale(
                    scale: 1.3,
                    child: Container(
                      margin: const EdgeInsets.only(left:50),
                      child: CupertinoSwitch(
                        value: _valuealter,
                        onChanged: (value) {
                          setState(() {
                            _valuealter = value;
                          });
                        },
                      ),
                    ),
                  ),
                ],
              ),
            ),
            Container(
              decoration: BoxDecoration(
                color: Colors.indigoAccent,
                borderRadius: BorderRadius.circular(30.0),
              ),
              width: 350,
              height: 70,
              alignment: Alignment.bottomCenter,
              margin: const EdgeInsets.only(top: 10),
              child: Row(
                children: <Widget>[
                  SizedBox(width: 200, child: Container(
                    margin: const EdgeInsets.only(left: 30),
                    alignment: Alignment.centerLeft,
                    child: const Text('USB (12V)', style: TextStyle(color: Colors.white, fontSize: 25,fontFamily: 'YesevaOne' )),
                  ), ),
                  Transform.scale(
                    scale: 1.3,
                    child: Container(
                      margin: const EdgeInsets.only(left:50),
                      child: CupertinoSwitch(
                        value: _valueusb,
                        onChanged: (value) {
                          setState(() {
                            _valueusb = value;
                          });
                        },
                      ),
                    ),
                  ),
                ],
              ),
            ),
            Container(
              decoration: BoxDecoration(
                color: Colors.indigo,
                borderRadius: BorderRadius.circular(30.0),
              ),
              width: 350,
              height: 90,
              alignment: Alignment.bottomCenter,
              margin: const EdgeInsets.only(top: 10),
              child: Row(
                children: <Widget>[
                  Container(
                    margin: const EdgeInsets.only(left: 30),
                    child: Image.asset('assets/images/caravan.png', height: 40.0, fit: BoxFit.cover,),
                  ),
                  Container(
                    margin: const EdgeInsets.only(left: 10),
                    alignment: Alignment.center,
                    child: const Text('KARAVANIM', style: TextStyle(color: Colors.white, fontSize: 31,fontFamily: 'YesevaOne' )),
                  ),
                  Container(
                    margin: const EdgeInsets.only(left: 10),
                    child: Image.asset('assets/images/caravan2.png', height: 40.0, fit: BoxFit.cover,),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}

Extra Checks (If Issues Persist) #

If you still see problems after applying the fix, double-check these:

• Ensure your image assets are properly listed in your pubspec.yaml under the flutter/assets section.
• Run flutter clean and flutter pub get to clear any cached build issues.

That should get your app running with all your switches and UI elements visible again!

内容的提问来源于stack exchange，提问作者Yusuf Mermer