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onCreate() is called to do initial creation of the fragment. onCreateView() is called by Android once the Fragment should inflate a view. onViewCreated() is called after onCreateView() and ensures that the fragment's root view is non-null .
onCreate is called on initial creation of the fragment. You do your non graphical initializations here. It finishes even before the layout is inflated and the fragment is visible. onCreateView is called to inflate the layout of the fragment i.e graphical initialization usually takes place here.
If you were using Fragment extended to your class and have written onCreateView() method, then it would have been called only twice after your onAttach() and onDestroyView() if you are still on same fragment.
onCreateView():You can assign your View variables and do any graphical initialisations. You are expected to return a View from this method, and this is the main UI view, but if your Fragment does not use any layouts or graphics, you can return null (happens by default if you don't override).
We face some crashes initializing view in onCreateView.
You should inflate your layout in
onCreateViewbut shouldn't initialize other views usingfindViewByIdinonCreateView.
Because sometimes view is not properly initialized. So always use findViewById in onViewCreated(when view is fully created) and it also passes the view as parameter.
onViewCreated is a make sure that view is fully created.
onViewCreated android Documentation
Called immediately after onCreateView(android.view.LayoutInflater, android.view.ViewGroup, android.os.Bundle) has returned, but before any saved state has been restored in to the view. This gives subclasses a chance to initialize themselves once they know their view hierarchy has been completely created. The fragment's view hierarchy is not however attached to its parent at this point.
onViewCreated is called immediately after onCreateView (the method you initialize and create all your objects, including your TextView), so it's not a matter of performance.
From the developer site:
onViewCreated(View view, Bundle savedInstanceState)
Called immediately after onCreateView(LayoutInflater, ViewGroup, Bundle) has returned, but before any saved state has been restored in to the view. This gives subclasses a chance to initialize themselves once they know their view hierarchy has been completely created. The fragment's view hierarchy is not however attached to its parent at this point.
Source: Fragment#onViewCreated
It's better to do any assignment of subviews to fields in onViewCreated. This is because the framework does an automatic null check for you to ensure that your Fragment's view hierarchy has been created and inflated (if using an XML layout file) properly.
Code snippet from: FragmentManger.java
// This calls onCreateView()
f.mView = f.performCreateView(f.getLayoutInflater(f.mSavedFragmentState), null, f.mSavedFragmentState);
// Null check avoids possible NPEs in onViewCreated
// It's also safe to call getView() during or after onViewCreated()
if (f.mView != null) {
f.mView.setSaveFromParentEnabled(false);
if (f.mHidden) f.mView.setVisibility(View.GONE);
f.onViewCreated(f.mView, f.mSavedFragmentState);
}
onCreateView() is the Fragment equivalent of onCreate() for Activities and runs during the View creation.onViewCreated() runs after the View has been created.
should I use one over the other for performance? NO. There's no evidence of a performance boost.
There is actually an onCreate() method in Fragments too, but it's rarely used (I do never use it, nor find a good use case for it).
I always use onCreateView() in Fragments as a replacement for onCreate().
And I'm happy with that.
onCreateView returns the inflated view. OnViewCreated is called just after onCreateView and get has parameter the inflated view. Its return type is void
The docs for Fragment.onCreateView() now says:
It is recommended to only inflate the layout in this method and move logic that operates on the returned View to onViewCreated(View, Bundle).
No need for us to understand why; we just need to do as the docs says, but it would be interesting to know why this recommendation exists. My best guess is separation of concern, but IMHO this makes it a little bit more complicated than it has to be.
i think the main different between these is when you use kotlin.in onCreateView() every Time you want to access to view in your xml file you should use findViewById but in onViewCreated you can simply access to your view just by calling the id of it.
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