Stage 2 · Lesson 3 of 10
Constraints go down, sizes go up
layout follows one rule. A parent passes , a minimum and maximum width and height, down to each child. The child picks a size within them and reports it back up.
The parent then decides where to place it. A cannot choose its own position or ignore its constraints. Once this clicks, the famous errors make sense.
The yellow and black striped overflow bar means a child wanted more space than it was allowed. An "unbounded height" error means a ListView inside a was offered endless height. Read the official "Understanding constraints" page and work through its examples.
Common trapwrapping widgets in SizedBox and Container at random until the error goes away.
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Resources for this stage
Start with
- GuideFreeFlutter Documentation
Google
Do the first Flutter app codelab, then the layout, constraints and lists pages