======== Exception caught by rendering library ===================================================== The following assertion was thrown during paint(): RenderBox was not laid out: RenderRepaintBoundary#77511 NEEDS-LAYOUT NEEDS-PAINT 'package:flutter/src/rendering/box.dart': Failed assertion: line 2001 pos 12: 'hasSize' Either the assertion indicates an error in the framework itself, or we should provide substantially more information in this error message to help you determine and fix the underlying cause. In either case, please report this assertion by filing a bug on GitHub: https://github.com/flutter/flutter/issues/new?template=2_bug.md The relevant error-causing widget was: Column Column:file:///C:/Users/Eddy/StudioProjects/itwi/lib/pages/editor_page.dart:86:15 When the exception was thrown, this was the stack: #2 RenderBox.size (package:flutter/src/rendering/box.dart:2001:12) #3 RenderBox.paintBounds (package:flutter/src/rendering/box.dart:2666:41) #4 PaintingContext._repaintCompositedChild (package:flutter/src/rendering/object.dart:154:56) ...parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size) ... constraints: BoxConstraints(unconstrained) ... size: Size(60.0, 42.0) ... additionalConstraints: BoxConstraints(w=60.0, 0.0<=h<=Infinity) ... child: RenderDecoratedBox#ef499 relayoutBoundary=up4 ... parentData: (can use size) ... constraints: BoxConstraints(w=60.0, 0.0<=h<=Infinity) ... size: Size(60.0, 42.0) ... decoration: BoxDecoration ... border: Border.all(BorderSide(Color(0xffffffff), 1.0, BorderStyle.solid)) ...NEEDS-PAINT ... needs compositing ... parentData: offset=Offset(0.0, 0.0); flex=null; fit=null ... constraints: MISSING ... size: MISSING ... child: RenderSemanticsAnnotations#722e3 NEEDS-LAYOUT NEEDS-PAINT ... parentData: ... constraints: MISSING ... size: MISSING ====================================================================================================

Solution

Specify a width or height for the widget (ListView, etc.) inside a row or column.