为什么总是newInstance或片段的对象

Question

I need to know why do we always instantiate a new object of fragment using either A.newInstance() or A() if we know there is already an instance exists. Does it not increase memory uses by the app in Android?

In my case I have an activity and multiple fragments which are opened by menus present in drawer fragment. These fragments further might open other fragments which are not listed in drawer menu. So I am wondering if is it normal to create new instances of secondary fragments by top fragment each time. The same is true for top level fragments. My flow is explained below:

1. Fragment A (new instance first time)
2. Fragment B (lower level fragment/new instance, instantiated by A)
3. Back to A (by pressing up arrow)
4. Fragment B (lower level fragment/again new instance, instantiated by A)
5. Back to A (by pressing up arrow)
6. Fragment X (new instance first time/top level fragment/from drawer menu)
7. Fragment A (again new instance of A/top level fragment/from drawer menu)

Is it correct to have multiple instances of fragments A (top level / point 7) and B (lower level / point 4)? As I am using this strategy?

Answer 1

You shouldn't instantiate new fragments everytime you "toggle between pages"

You should add them into the FragmentManager when needed with a tag (an optional string parameter), then find them using that tag ( findFragmentByTag ) , and replace the current shown Fragment if you could find the other. Otherwise, you can instantiate a new one.

You'll also need to place Fragments on the back stack ( addToBackStack ) , I think, so they are held onto by the FragmentManager