What is the best practice in flutter for padding,margin etc.
example:
I made a simple drawer in flutter. To make everything to position in places I want. I used padding extensively.
Now the issue is when I test it on different phone of different size. the positions are inconsistent across different devices.
From the Flutter Docs:
Design discussion Why use a Padding widget rather than a Container
with a Container.padding property? There isn't really any difference
between the two. If you supply a Container.padding argument, Container
simply builds a Padding widget for you.
Container doesn't implement its properties directly. Instead,
Container combines a number of simpler widgets together into a
convenient package. For example, the Container.padding property causes
the container to build a Padding widget and the Container.decoration
property causes the container to build a DecoratedBox widget. If you
find Container convenient, feel free to use it. If not, feel free to
build these simpler widgets in whatever combination meets your needs.
In fact, the majority of widgets in Flutter are simply combinations of
other simpler widgets. Composition, rather than inheritance, is the
primary mechanism for building up widgets.
So, no worries about padding widgets.
A good practice to get some spaces inside a Column() or Row() is using SizedBox(). Then you add an extra space setting up width or height.
Related
As we All Know Many widget can do the job for us for single task.
Example - We need a square Box to show in Flutter App we can achieve this with multiple widget
Container
SizedBox
DecoratedBox
ConstrainedBox
Elevated Button
And many more widget to perform the same task. now the question comes which is more efficient way to do the job in terms of Time and Space?
You can use any of these widgets at your own discretion. The golden rule applies here:
The more functional a widget is, the more resources are spent to build/draw it.
However, we should not forget that such minimization has a serious adversary - the programmer's time which will be spent on Wrap with... by necessary widgets. The same cannot be said for Container, which contains most of the parameters.
I'd like to add a custom showMore widget if the skills widget which has a dynamic size(width) exceeds the screen width. On clicking the showMore widget it should show all the skills in a wrap .else show less.
In flutter
Constraints go down and sizes go up
See this documentation.
Flutter uses a single pass algorithm to render your application. This is a technical choice to ensure performance but it comes with limitations.
One of them is that, when you are building the widget tree, you only have access to the constraints of the parent, and not any size of any widget (since they are not rendered yet).
So a short answer to your question is:
No, you cannot do what you are trying to do (displaying something if some widgets are not fitting on the screen) since you don't have access to any sizes in the build method.
An alternative solution would be to use Wrap to wrap your chips or use a ListView on the horizontal axis to make the list of chips horizontally scrollable.
Anyway, if you really want to do this, you can hardcode the sizes of your chip and access the device size with MediaQuery.of(context).size or by using the LayoutBuilder and using contraints.maxWidth as the parent's width. Then you can check whether or not numberOfChips * chipSize <= maxWidth. But I wouldn't recommend it as the design wouldn't be responsive:
All the chips will have the same size, so you'll end up with a big chip for "c" and maybe a long name like "python" won't fit in and you'll end up with overflow issues.
What if the user changes the font size of his device? You will also end up with overflow issues.
Consider the case that I have 3 adjacent list view with each list view having a sized widget of some height. Each list view has around 24 child items. I'm trying to scale the widget using onScaleUpdate in GestureDetector.
onScaleUpdate I want to change the height of each child item of all the 3 listviews.
Is rebuilding all child better or should I rebuild the whole widget?
As #Yeasin Sheikh pointed out, using ListView.builder is good because it builds only the needed children (the ones inside the screen and just a few ones outside as precaution). And as to actually answering your question, I'm no Flutter expert, but using ListView.builder I don't think it makes that much difference, Flutter is intelligent enough to solve this by itself.
As the below diagram shows Stateful widget covers what Stateless widget do, When I can do the same thing with Stateful widget, why Flutter designers added another widget? For increasing performance?
Please do not post the difference just answer the Why?
Would you always use a sword to do a knife's job? Given that you always have both of them available with easy access. The knife can't do everything a sword can, but would that mean that a sword should be used by default for everything, since it's more robust?
You'll have many widgets where the state of the elements will not change, and others where you will not have to use setState to update your UI either(given that you would rather not use higher level state management solutions).
Using stateless widgets as long as they can do the job, means more performent widget trees.
Please do not post the difference just answer the Why?
Knowing the difference between them is key to understanding 'why', and the differences are not just in the name less vs full. But sensing that you aren't interested, that's why.
Good Flutter code seperates the code into many small Widgets. In addition to better performance creating a StatefulWidget means that you have to write more code and add unnecessary complexity to your code.
For better performance. Stateless widgets are usually only called in one of these three situations:
1- widget is inserted in the tree.
2- Widget's parent changes its configuration
3- Inherited Widget it depends on changes.
I want to display some widgets in a Wrap, and if the widgets are too many to fit on one row, I want to display different widgets (more compact versions of the normal widgets).
How can I achieve this, without resorting to manual measurements of screen width and children? Is there any built-in way to do this with a Wrap or some other widget?
What if with the compact version, the row is still full. Do you want to display the children in multiline then or wrap them with the next line? If it's the latter, then I think it's best to use Wrap from the beginning.
Another practical way is to make the child adaptable as well, by using FittedBox or make it scrollable horizontally by using SingleChildScrollView or ListView.
There can be other scenarios when it's better to show just 4-5 children that's enough to fit a row. Then have a button allowing user to navigate to a detail screen display all the children in a grid or list.