CODEWITHSUNDEEP
androidlistviewandroid-fragmentsnavigation-drawerback-stack
Phantom
Phantom

Reputation: 1028

Android BackStack NavigationDrawer

I have a problem that I've been dealing with for the last couple o days and don't seem to find an answer to it.

Description : I have a main activity which contains a navigation drawer. Each item of the navigation drawer (when clicked) creates a fragment. In that fragment, there is a listView of objects, which creates other fragments when clicked. In those fragments i have another listView of objects which opens other fragments. In other words, there series of fragment that open other fragment. Something like this:

http://s22.postimg.org/pddo5gsv5/backstack.png

In order to be able to get back to each fragment, I've implemented the addToBackstack("string") method.

My question is, how can I implement correct backstack for my application so that when i click a navigation Drawer item, all the fragments that have been added to backstack are cleared, without the one that the navigation Drawer item opens.

Any help would be appreciated. Thank you !

EDIT

Ok, it seems I managed to figure it out. Considering what advices i received from the replies, here's the solution I came up with:

@Override
public void onBackPressed() {
    int count = getFragmentManager().getBackStackEntryCount();
    if (count != 0) {
        FragmentManager.BackStackEntry backEntry = getFragmentManager()
                .getBackStackEntryAt(
                        getFragmentManager().getBackStackEntryCount() - 1);
        if (backEntry.getName() == NAVIGATION) {
            finish();
        } else
            getFragmentManager().popBackStack();
    } else {
        super.onBackPressed();
    }
}

To put it in words: First, i added a backstack entry even for the top level fragments, given them a specific tag. The I have overridden the Activity's back button function so that when the last backstack entry is a top-level fragment to finish the activity (so that it not simply detach the fragment from activity, living it empty). Otherwise, if the last entry isn't an top-level fragment, execute a popBackStack. PS: All non-top-level fragments are added to the backstack with a different tag then the top-level one. Also, i had to do a POP_BACK_STACK_INCLUSIVE in the navigation Drawer's click listener.

getFragmentManager().popBackStack(null,
                FragmentManager.POP_BACK_STACK_INCLUSIVE);

Thank you all for the advices and hopefully this EDIT help other users.

Upvotes: 2

Views: 897

Answers (2)

Alexios Karapetsas
Alexios Karapetsas

Reputation: 912

You can use the following code to solve your problem:

getFragmentManager().beginTransaction()
                    .replace(R.id.fragment_container, fragment)
                    .addToBackStack(fragment_tag)
                    .commit();

In order to make the code above work, you have to create the fragments dynamically. As hardcoded fragments cannot be replaced. To do that, you can create a container (FrameLayout etc.) which in our example has the id fragment_container. Then, the code above will add the fragment in the container dynamically. Finally, you have to pass as parameter in the addToBackStack method the fragment_tag. That means, that this transaction will be added in the back stack. And finally, in order to get it from the backstack you have to use the code below:

getFragmentManager().popBackStack(fragment_tag, FragmentManager.POP_BACK_STACK_INCLUSIVE));

The POP_BACK_STACK_INCLUSIVE flag, insures that "all matching entries will be consumed until one that doesn't match is found or the bottom of the stack is reached. Otherwise, all entries up to but not including that entry will be removed."

Upvotes: 2

Juanma Reyes
Juanma Reyes

Reputation: 51

You can clear the fragment backstack by using something like:

fragmentManager.popBackStack("string", FragmentManager.POP_BACK_STACK_INCLUSIVE);

and then you can addToBackstack and commit as usual. More info.

A code snippet that shows the way I normally use it in navigation drawers:

FragmentManager fragmentManager = getSupportFragmentManager();
if(clearBackStack) {
    fragmentManager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
FragmentTransaction ft = fragmentManager.beginTransaction();
ft.replace(R.id.content_frame, fragment);
if(!clearBackStack) {
    ft.addToBackStack(null);
}
ft.commit();

Upvotes: 0

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