Dart / Flutter-加载SQLite对象和审核Widget的正确方法

Question

I've already seen a lot of discussions regarding the subject, but haven't find a proper soultion for my problem.

What I would like to achieve is to pass Process.id from ListView to second widget, then in second widget - load the object from SQLite and update other widgets in Scaffold with Process data.

I've already managed to do that (partially), 'cause I'm struggling with loading data to ListView widget (I have to parse json String to create List and then whenever I'm trying to update ListView.builder using the List - I'm getting blank screen and exceptions). Commenting out ListView.builder - the widgets works fine... probably I'm putting the code in wrong place ...

This is how my code looks like:

1. Pass Process.id from ListView in Widget 1 ...

    ... return new ListTile( onTap: () { Navigator.push( context, MaterialPageRoute(builder: (context) => ScreenProcessDetails(processId: _newProcesses[index].id)));}, ... 

   to Widget 2 -> DONE:

    class ScreenProcessDetails extends StatefulWidget { final int processId; ScreenProcessDetails({Key key, @required this.processId}) : super(key: key); @override State createState() { return new _ScreenProcessDetailsState(); } } 

2. Loading the Process object from SQLite (using SQFlite) in Widget's 2 ScreenProcessDetails initState() -> DONE, as below:

    class _ScreenProcessDetailsState extends State<ScreenProcessDetails> { Process process; Future<Process> getProcess(int id) async { process = await _repository.getProcess(id); setState(() { }); } @override void initState() { super.initState(); getProcess(widget.processId); } @override Widget build(BuildContext context) { String defaultValue = process.defaultValue; List<dynamic> filesJson = jsonDecode(process.files); filesList = filesJson.map((i) => new Files.fromJson(i)).toList(); return new Scaffold( appBar: new AppBar(title: new Text(process.name)), body: Builder (builder: (context) => new Container( child: new Column( children: <Widget>[ new Text(process.name), new TextFormField(initialValue: defaultValue,), new ListView.builder( physics: const NeverScrollableScrollPhysics(), itemCount: filesList.length, itemBuilder: (context, int index) { return new ListTile( leading: new Icon(Icons.archive, color: Colors.amber), title: new Text(filesList[index].name), subtitle: new Text(filesList[index].guid), ); }) //skipped rest of code } 

But the filesList is not loaded - whole screen is white and I'm getting list of excepiotns (below). I wonder what I might be doing wrong ? I've already tried to use String insted of my Process object with no luck.

And one more thing - is this aproach I mean loading object from SQLite in initState() correct ? Beacause I'm seeing one exception:

2019-02-20 13:02:13.023 19208-19288/pl.itelix.documentapp I/flutter: Another exception was thrown: NoSuchMethodError: The getter 'name' was called on null.

which (as far as I understand) mean that the object was null... but the whole widget is build propely ?!

Or should I load SQLite data using Future and then start loading whole widget tree ? And one more thing - I've tried to use FutureBuilder but it gas been recreated every time I've tried to type text in TextField.

Exception lsit:

2019-02-20 12:41:07.490 19208-19288/documentapp I/flutter: Another exception was thrown: Vertical viewport was given unbounded height.
2019-02-20 12:41:07.492 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderViewport#627ff NEEDS-LAYOUT NEEDS-PAINT
2019-02-20 12:41:07.493 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderViewport#627ff NEEDS-PAINT
2019-02-20 12:41:07.496 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderIgnorePointer#e5843 relayoutBoundary=up26 NEEDS-PAINT
2019-02-20 12:41:07.500 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderSemanticsAnnotations#bb781 relayoutBoundary=up25 NEEDS-PAINT
2019-02-20 12:41:07.502 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderPointerListener#57754 relayoutBoundary=up24 NEEDS-PAINT
2019-02-20 12:41:07.503 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderSemanticsGestureHandler#54f57 relayoutBoundary=up23 NEEDS-PAINT
2019-02-20 12:41:07.505 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: _RenderScrollSemantics#1370c relayoutBoundary=up22 NEEDS-PAINT
2019-02-20 12:41:07.507 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#c4b4e relayoutBoundary=up21 NEEDS-PAINT
2019-02-20 12:41:07.508 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderCustomPaint#88d67 relayoutBoundary=up20 NEEDS-PAINT
2019-02-20 12:41:07.510 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#b4040 relayoutBoundary=up19 NEEDS-PAINT
2019-02-20 12:41:07.511 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderFlex#09183 relayoutBoundary=up18 NEEDS-PAINT
2019-02-20 12:41:07.513 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderPadding#50678 relayoutBoundary=up17 NEEDS-PAINT
2019-02-20 12:41:07.515 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: _RenderInkFeatures#de7b5 relayoutBoundary=up16 NEEDS-PAINT
2019-02-20 12:41:07.517 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderCustomPaint#05457 relayoutBoundary=up15 NEEDS-PAINT
2019-02-20 12:41:07.519 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderPhysicalShape#2b262 relayoutBoundary=up14 NEEDS-PAINT
2019-02-20 12:41:07.520 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderPadding#5eb3c relayoutBoundary=up13 NEEDS-PAINT
2019-02-20 12:41:07.522 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderSemanticsAnnotations#e3fcc relayoutBoundary=up12 NEEDS-PAINT
2019-02-20 12:41:07.524 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderFlex#8eaef relayoutBoundary=up11 NEEDS-PAINT
2019-02-20 12:41:07.525 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: _RenderSingleChildViewport#c3635 relayoutBoundary=up10 NEEDS-PAINT
2019-02-20 12:41:07.526 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderIgnorePointer#c220a relayoutBoundary=up9 NEEDS-PAINT
2019-02-20 12:41:07.529 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderSemanticsAnnotations#bf875 relayoutBoundary=up8 NEEDS-PAINT
2019-02-20 12:41:07.530 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderPointerListener#789f6 relayoutBoundary=up7 NEEDS-PAINT
2019-02-20 12:41:07.532 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderSemanticsGestureHandler#cabf4 relayoutBoundary=up6 NEEDS-PAINT
2019-02-20 12:41:07.533 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: _RenderScrollSemantics#8ab03 relayoutBoundary=up5 NEEDS-PAINT
2019-02-20 12:41:07.535 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#274a1 relayoutBoundary=up4 NEEDS-PAINT
2019-02-20 12:41:07.536 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderCustomPaint#6174f relayoutBoundary=up3 NEEDS-PAINT
2019-02-20 12:41:07.538 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#a452d relayoutBoundary=up2 NEEDS-PAINT
2019-02-20 12:41:07.539 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderPadding#8c834 relayoutBoundary=up1 NEEDS-PAINT
2019-02-20 12:41:07.543 19208-19288/documentapp I/flutter: Another exception was thrown: RenderBox was not laid out: RenderRepaintBoundary#a452d relayoutBoundary=up2 NEEDS-PAINT

ANY HELP MUCH APPRECIATED ! THANK YOU IN ADVANCE! :)

Answer 1

发现了问题-列中的ListView必须包装在Flex / Extended小部件中。