CODEWITHSUNDEEP
androidandroid-fragmentsfragment-backstack
droidpl
droidpl

Reputation: 5892

Preloading a fragment when popBackStack

I have a problem with the backstack behaviour. That is what I am doing:

add(fragment1) + addToBackStack(null)
replace(fragment2) + addToBackStack(null)

What is happening:

Now I want to change my last backstacked fragment with a new transaction which put a new backstack fragment so:

[frag1, frag2] becomes [frag1, frag3]

but this transaction made by a popBackStack + replace is making the frag1 to load by calling its onCreateView and onActivityCreated. I know this is the expected behaviour since this is how backstack works, but I am trying to find a way to avoid this preload.

Edit

In this question I am using the concept of backstack fragment for the transaction to be more clear. Every transaction here is an add+remove (which is a replace). The code for replace I am using is:

public int replaceFragment(BaseFragment newFragment, boolean addToBackStack, boolean animated, PopStackMode popMode) {
    if (popMode != null) {
        getSupportFragmentManager().popBackStack(newFragment.getFragmentTag(), popMode == PopStackMode.POP_INCLUSIVE ? FragmentManager
                .POP_BACK_STACK_INCLUSIVE : 0);
    }
    FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
    if (animated) {
        ft.setCustomAnimations(R.anim.slide_in_left, 0, R.anim.slide_out_right, 0);
    }
    ft.replace(R.id.fragment_container, newFragment, newFragment.getFragmentTag());
    if (addToBackStack) {
        ft.addToBackStack(newFragment.getFragmentTag());
    }
    return ft.commit();
}

You can see I am creating a navigation history based on the fragment backstack, as it was kind of a browser. When a "page" is added there is a fragment and a backstack transaction. In this context, I trying to:

I hope it is more clear.

Edit 2

I have filled a request feature for a flag that supports this behavior. Find it here.

Upvotes: 0

Views: 973

Answers (1)

Joao Sousa
Joao Sousa

Reputation: 4123

First, you should understand that the backstack doesn't save fragments, but it saves transactions instead. When you call popBackStack what it actually does is revert the previous transaction. More on this here.

I think that you can do this:

  1. Name your transactions by providing a unique name to your addToBackStack instead of null. i.e. addToBackStack("frag1").
  2. Don't call popBackStack + replace, but instead just call replace.
  3. Then, in your activity, override your onBackPressed and if the current fragment being displayed is Frag3 (you can check this using findFragmentByTag if you provided a tag in the replace method) you can call getSupportFragmentManager().popBackStackImmediate("frag1", FragmentManager.POP_BACK_STACK_INCLUSIVE); (otherwise call the super.onBackPressed)

Upvotes: 0

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