depth property Null safety
An integer that is guaranteed to be greater than the parent's, if any. The element at the root of the tree must have a depth greater than 0.
Implementation
int get depth {
assert(() {
if (_lifecycleState == _ElementLifecycle.initial) {
throw FlutterError('Depth is only available when element has been mounted.');
}
return true;
}());
return _depth;
}