Flutter - Unidentified cause for pixel overflow

Question

I've been trying to transplant some code from this flutter project into into this boilerplate sample and am running into some pixel overflow issues that I can't seem to fix.

This is the error thrown in the VSCode debug console;

flutter: ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
flutter: The following assertion was thrown during performLayout():
flutter: 'package:flutter/src/rendering/object.dart': Failed assertion: line 1514 pos 12:
flutter: '!_debugDoingThisLayout': is not true.

And this is the code I'm using the stimulate the error;

home_page.dart

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:cryptick_nice_ui/data/crypto_data.dart';
import 'package:cryptick_nice_ui/modules/crypto_presenter.dart';
import 'background.dart';
import 'package:cryptick_nice_ui/dependency_injection.dart';

void main() async {
  runApp(new MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      theme: new ThemeData(
          primarySwatch: Colors.pink,
          primaryColor: defaultTargetPlatform == TargetPlatform.iOS
              ? Colors.grey[100]
              : null),
      debugShowCheckedModeBanner: false,
      home: new HomePage(),
    );
  }
}


class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => new _HomePageState();
}

class _HomePageState extends State<HomePage> implements CryptoListViewContract {
  CryptoListPresenter _presenter;
  List<Crypto> _currencies;
  bool _isLoading;
  final List<MaterialColor> _colors = [Colors.blue, Colors.indigo, Colors.red];





  _HomePageState() {
    _presenter = new CryptoListPresenter(this);
  }

  @override
  void initState() {
    super.initState();
    _isLoading = true;
    _presenter.loadCurrencies();
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          title: new Text(".",
          style: new TextStyle(
            fontFamily: 'PlayfairDisplay',
            letterSpacing: 0.8,
            color: const Color(0xFF273A48),
          )
          ),
          backgroundColor: const Color(0xFF273A48),
          elevation: 0.0,
        ),
        body: _isLoading
            ? new Center(
          child: new CircularProgressIndicator(),
        )
            : _cryptoWidget()
      );
  }

    Widget _cryptoWidget() {
    final _width1 = MediaQuery.of(context).size.width;
    final _height1 = MediaQuery.of(context).size.height;
    return new Container(
      decoration: new BoxDecoration(
      color: const Color(0xFF273A48),
    ),
        child: new Column(
          children: <Widget>[
            new CustomPaint(
            size: new Size(_width1, _height1),
            painter: new Background(),
          ),
            new Flexible(
              child: new ListView.builder(
                itemCount: _currencies.length,
                itemBuilder: (BuildContext context, int index) {
                  final int i = index ~/ 2;
                  final Crypto currency = _currencies[i];
                  final MaterialColor color = _colors[i % _colors.length];
                  if (index.isOdd) {
                    return new Divider();
                  }
                  return _getListItemUi(context, currency, color);
                },
              ),
            )
          ],
        )
      );
  }



  Widget _getListItemUi(BuildContext context, Crypto currency, MaterialColor color) {
    final _width2 = MediaQuery.of(context).size.width;
    final _height2 = MediaQuery.of(context).size.height;
    _presenter.loadCurrencies();
    final headerList = new ListView.builder(
      itemBuilder: (context, index) {
        EdgeInsets padding = index == 0?const EdgeInsets.only(
            left: 20.0, right: 10.0, top: 4.0, bottom: 30.0):const EdgeInsets.only(
            left: 10.0, right: 10.0, top: 4.0, bottom: 30.0);

        return new Padding(
          padding: padding,
          child: new InkWell(
            onTap: () {
              print('Card selected');
            },
            child: new Container(
              decoration: new BoxDecoration(
                borderRadius: new BorderRadius.circular(10.0),
                color: Colors.lightGreen,
                boxShadow: [
                  new BoxShadow(
                      color: Colors.black.withAlpha(70),
                      offset: const Offset(3.0, 10.0),
                      blurRadius: 15.0)
                ],
                image: new DecorationImage(
                  image: new ExactAssetImage(
                      ''),
                  fit: BoxFit.fitHeight,
                ),
              ),
//                                    height: 200.0,
              width: 200.0,
              child: new Stack(
                children: <Widget>[
                  new Align(
                    alignment: Alignment.bottomCenter,
                    child: new Container(
                        decoration: new BoxDecoration(
                            color: const Color(0xFF273A48),
                            borderRadius: new BorderRadius.only(
                                bottomLeft: new Radius.circular(10.0),
                                bottomRight: new Radius.circular(10.0))),
                        height: 30.0,
                        child: new Row(
                          mainAxisAlignment: MainAxisAlignment.center,
                          children: <Widget>[
                            new Text(
                              'hi',
                              style: new TextStyle(color: Colors.white),
                            )
                          ],
                        )),
                  )
                ],
              ),
            ),
          ),
        );
      },
      scrollDirection: Axis.horizontal,
      itemCount: _currencies.length,
    );

    final body = new Scaffold(
      appBar: new AppBar(
        title: new Text('cryp'),
        elevation: 0.0,
        backgroundColor: Colors.transparent,
        actions: <Widget>[
          new IconButton(icon: new Icon(Icons.shopping_cart, color: Colors.white,), onPressed: (){})
        ],
      ),
      backgroundColor: Colors.transparent,
      body: new Container(
        child: new Stack(
          children: <Widget>[
            new Padding(
              padding: new EdgeInsets.only(top: 10.0),
              child: new Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                mainAxisSize: MainAxisSize.max,
                mainAxisAlignment: MainAxisAlignment.start,
                children: <Widget>[
                  new Align(
                    alignment: Alignment.centerLeft,
                    child: new Padding(
                        padding: new EdgeInsets.only(left: 8.0),
                        child: new Text(
                          'Trending News',
                          style: new TextStyle(
                            color: Colors.white70,
                            fontSize: 15.0,
                            ),
                        )),
                  ),
                  new Container(
                      height: 300.0, width: _width2, child: headerList),
                  new Expanded(child:
                  ListView.builder(itemBuilder: (context, index) {
                    return new ListTile(
                      title: new Column(
                        children: <Widget>[
                          new Row(
                            crossAxisAlignment: CrossAxisAlignment.start,
                            children: <Widget>[
                              new Container(
                                height: 72.0,
                                width: 72.0,
                                decoration: new BoxDecoration(
                                    color: Colors.lightGreen,
                                    boxShadow: [
                                      new BoxShadow(
                                          color:
                                          Colors.black.withAlpha(70),
                                          offset: const Offset(2.0, 2.0),
                                          blurRadius: 2.0)
                                    ],
                                    borderRadius: new BorderRadius.all(
                                        new Radius.circular(12.0)),
                                    image: new DecorationImage(
                                      image: new ExactAssetImage(
                                        "cryptoiconsBlack/"+currency.symbol.toLowerCase()+"@2x.png",
                                      ),
                                      fit: BoxFit.cover,
                                    )),
                              ),
                              new SizedBox(
                                width: 8.0,
                              ),
                              new Expanded(
                                  child: new Column(
                                    mainAxisAlignment:
                                    MainAxisAlignment.start,
                                    crossAxisAlignment:
                                    CrossAxisAlignment.start,
                                    children: <Widget>[
                                      new Text(
                                        'My item header',
                                        style: new TextStyle(
                                            fontSize: 14.0,
                                            color: Colors.black87,
                                            fontWeight: FontWeight.bold),
                                      ),
                                      new Text(
                                        'Item Subheader goes here\nLorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry',
                                        style: new TextStyle(
                                            fontSize: 12.0,
                                            color: Colors.black54,
                                            fontWeight: FontWeight.normal),
                                      )
                                    ],
                                  )),
                              new Icon(
                                Icons.shopping_cart,
                                color: const Color(0xFF273A48),
                              )
                            ],
                          ),
                          new Divider(),
                        ],
                      ),
                    );
                  }))
                ],
              ),
            ),
          ],
        ),
      ),
    );

    return new Container(
      decoration: new BoxDecoration(
        color: const Color(0xFF273A48),
      ),
      child: new Stack(
        children: <Widget>[
          new CustomPaint(
            size: new Size(_width2, _height2),
            painter: new Background(),
          ),
          body,
        ],
      ),
    );
  }



  Widget _getSubtitleText(String priceUSD, String percentageChange) {
    TextSpan priceTextWidget = new TextSpan(
        text: "\$$priceUSD\n", style: new TextStyle(color: Colors.black));
    String percentageChangeText = "1 hour: $percentageChange%";
    TextSpan percentageChangeTextWidget;

    if (double.parse(percentageChange) > 0) {
      percentageChangeTextWidget = new TextSpan(
          text: percentageChangeText,
          style: new TextStyle(color: Colors.green));
    } else {
      percentageChangeTextWidget = new TextSpan(
          text: percentageChangeText, style: new TextStyle(color: Colors.red));
    }

    return new RichText(
        text: new TextSpan(
            children: [priceTextWidget, percentageChangeTextWidget]));
  }



  @override
  void onLoadCryptoComplete(List<Crypto> items) {
    // TODO: implement onLoadCryptoComplete

    setState(() {
      _currencies = items;
      _isLoading = false;
    });
  }

  @override
  void onLoadCryptoError() {
    // TODO: implement onLoadCryptoError
    }
  }

And this is the background.dart file I'm using to create a grey/white pallet.

import 'package:flutter/material.dart';

class Background extends CustomPainter{
  @override
  void paint(Canvas canvas, Size size) {
    // TODO: implement paint
    _drawPentagone(canvas,  size);
  }

  _drawPentagone(Canvas canvas, Size size){
    var path = new Path();
    path.addPolygon([
      new Offset(size.width, size.height/5),
      new Offset(size.width, size.height),
      new Offset(0.0, size.height),
      new Offset(0.0, size.height/2.5),

    ], true);
    path.close();
    canvas.drawPath(path, new Paint()..color = Colors.white);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    // TODO: implement shouldRepaint
    return false;
  }

}

This is what I get in simulator, at the bottom it says BOTTOM OVERFLOWED BY 100 PIXELS

Answer 1

The problem is that you are making your background widget as large as the screen:

final _width1 = MediaQuery.of(context).size.width;
final _height1 = MediaQuery.of(context).size.height;

// ...

new CustomPaint(
  size: new Size(_width1, _height1),
  painter: new Background(),
),

The AppBar at the top probably takes 100 pixels of space, and _cryptoWidget() is only uses the space below the AppBar -

You don't need MediaQuery to create a screen-filling widget, just use a Container without any dimensions.

it's also strange that your background widget is wrapped in a Column with another Flexible below. If the background is screen-filling, how would the Flexible fit below?

Are you trying to create a scrollable view? Or do you want to draw the background widget behind the content?

Answer 2

Use this code and inside Scaffold whatever you want can add

        Widget build(BuildContext context) {
          final width = MediaQuery.of(context).size.width;
          final height = MediaQuery.of(context).size.height;
          return new Container(
            child: new Stack(
              children: <Widget>[
                new CustomPaint(
                  painter: new Background(),
                  size: new Size(width, height),
                ),
                new Scaffold(
                    appBar: new AppBar(
                      title: new Text("Custom Background"),
                      backgroundColor: Colors.transparent,
                    ),
                    backgroundColor: Colors.transparent,
                    body: new Center(
                      child: new Text("Hello how are You? :)"),
                    ))
              ],
            ),
          );
        }