使用导航组件而不使用 ViewModel 时如何在后台堆栈中保留 Fragment 实例？

Question

Is there a way preserve my fragments instances so that they don't get recreates when coming back from another Fragment through navigation component?

I thought of saving the fragment's instance in a variable and using it if it's not null in onCreateView(), but it seems this is not advised can generate memory leaks.

It's my only option to refactor my app and use ViewModels in all my fragments?

Answer 1

When Fragment is recreated from back stack, first method which gets called is onCreateView while when Fragment is being created for first time, onAttach followed by onCreate is called.

So you can avoid reinitialization of variables using these one time invoked methods in order to preserve their previous states. But this is advisable for small use cases only. To preserve larger data sets, you should consider using ViewModels which are bound to fragment lifecycle and retains the data until fragment is detached & destroyed.

You can post your exact use case here if you need more help.