Bug: Clicking on pre-selected tab shows empty fragment instead of base fragment

[p-fischer]

After the long awaited release, I could finally get rid of frag-nav as a locale module and include it as a dependency. Thank you for that! :)

Unfortunately, I found an issue occurring in both versions 1.1.0 and 1.2.0:

Previously I could click on a tab, which already was selected, and go back to the first fragment of the tab's stack. No matter if there were one or multiple fragments on the stack.

Now, I just see an empty fragment.

I assume this is a bug or must the library be used differently now?

[bulatgaleev]

Same.
Also it happens when i pop() while there's only 1st fragment of 1st tab in stack.

[ncapdevi]

@localhostEU This is actually intentional. Sometimes different apps do different things when you get to the bottom of the stack, and I wanted to leave the flexibility up to the user of the library. If you want to back out of the activity at the bottom of the stack, you'll want to do something like this:

    @Override
    public void onBackPressed() {
        if (mNavController.canPop()) {
            mNavController.pop();
        } else {
            super.onBackPressed();
        }
    }

[ncapdevi]

@p-fischer So sorry for the delay on things. I'm back to actively managing the project. Could you show me the code that you're using on a re-selection of the tab in order to clear the stack?

[p-fischer]

Glad, you're back on active development since I think this lib perfectly captures my desired behavior for bottom bar navigation.

This is my code. On re-selection, I'm basically just calling clearStack() - it should be equal to what you do in your sample app.

        bottomBar.setItemsFromMenu( R.menu.menu_bottombar, new OnMenuTabClickListener()
		{
			@Override
			public void onMenuTabSelected( @IdRes int menuItemId )
			{
				awaitSecondBackPress = true;

				View lastSelectedTab = findViewById( lastSelectedTabId );
				View nowSelectedTab = findViewById( menuItemId );

				if ( lastSelectedTab != null )
				{
					lastSelectedTab.setSelected( false );
				}

				if ( nowSelectedTab != null )
				{
					nowSelectedTab.setSelected( true );
				}

				lastSelectedTabId = menuItemId;

				switch ( menuItemId )
				{
					case R.id.bottombar_1:
						navController.switchTab( INDEX_1 );
						break;
					case R.id.bottombar_2:
						navController.switchTab( INDEX_2 );
						break;
					case R.id.bottombar_3
						navController.switchTab( INDEX_3 );
						break;
				}
			}

			@Override
			public void onMenuTabReSelected( @IdRes int menuItemId )
			{
				lastSelectedTabId = menuItemId;
				navController.clearStack();
			}
		} );

[ncapdevi]

Hmm, seems to be working for me. Looks like you're using an older version of bottombar library. Could you try updating to the latest version

compile 'com.roughike:bottom-bar:2.0.2'

Then your code would look like this for the re-selection

        bottomBar.setOnTabReselectListener(new OnTabReselectListener() {
            @Override
            public void onTabReSelected(@IdRes int tabId){
		lastSelectedTabId = menuItemId;
                navController.clearStack();
            }
        });

[p-fischer]

Updating to bottom-bar v2 could be the solution.

However, since my app is close to its next release I won't be able to test that immediately.

I guess your sample app using bottom-bar v1 could run into the same issue. You might want to update it too.

[ncapdevi]

@p-fischer That's a good point, I wasn't running into it with the sample app, so there must be something else going on. I need to push out a bug fix, so I'll need to release 1.2.1 sometime today anyways, I'll look into it more and see if I can find exactly what's going on. Could you show me how you're adding your fragments?

[ncapdevi]

It's strange to me that this could be happening at all. The first lines of the clearStack() method are

    public void clearStack() {
        //Grab Current stack
        Stack<Fragment> fragmentStack = mFragmentStacks.get(mSelectedTabIndex);

        // Only need to start popping and reattach if the stack is greater than 1
        if (fragmentStack.size() > 1) {}

Meaning that it will only attempt to clear the stack if it has more than one fragment on it. And you're saying if you are on a tab, and then reselect it, it's clearing it to empty?

[p-fischer]

List<Fragment> fragments = new ArrayList<>( 3 );
fragments.add( FirstFragment.newInstance( false ) );
fragments.add( SecondFragment.newInstance() );
fragments.add( ThirdFragment.newInstance( false ) )

navController = new FragNavController( savedInstanceState, getSupportFragmentManager(),
                                          R.id.container, fragments, INDEX_1 );

where INDEX_1 = 0
called from onCreate()

[ncapdevi]

Does INDEX_1 =0; or does INDEX_1 = FragNavController.TAB1; ?

[bulatgaleev]

What's v2? Theres nothing about it in description/changelogs.

[ncapdevi]

@localhostEU https://github.com/ncapdevi/FragNav/releases

[p-fischer]

@ncapdevi the second option. Does it make a difference?

@localhostEU v2 refers to this library used in the sample app: https://github.com/roughike/BottomBar

[bulatgaleev]

@ncapdevi @p-fischer Ah, that was bottom bar context :) Nvm then!

[ncapdevi]

@p-fischer It shouldn't, but the annotation processor might have been doing something weird if it was just set to 0 (since it's supposed to only allow the predefined TabIndex). That looks entirely right. I'll see if I can replicate it. Just to clarify again. If you go from Tab 1 -> Tab 2 and press Tab 2 again, it clears the stack to an empty state? and also, if you add fragments on to Tab 1, and re-select that tab, it's also clearing the stack to an empty state?

[ncapdevi]

@p-fischer One other question, are you adding fragments to the container in any way other than using the navController object?

[p-fischer]

@ncapdevi Yes I saw the "empty fragment" in both cases - with a current stack supposed to be of size 1 and with size 2 before re-selection.
However, I did not debug into the issue and look into the current stack after the re-selection.

[ncapdevi]

I'll see if I can reproduce it, but any other information would be helpful.

[p-fischer]

One other question, are you adding fragments to the container in any way other than using the navController object?

No, fragments are pushed to the stack through this method of MainActivity exclusively:

@Override
public void pushFragment( Fragment fragment )
{
	if ( navController != null )
	{
		navController.push( fragment );
	}
}

As soon as I look into it again, I'll share any information.

[p-fischer]

@ncapdevi I'm using another version of the bottom-bar lib in my project than your sample app does:
compile 'com.roughike:bottom-bar:1.3.4'

[ncapdevi]

Able to reproduce it. Will let you know when I can get and push out a fix. Thanks for your help

[ncapdevi]

@p-fischer fixed it. https://github.com/ncapdevi/FragNav/releases
@localhostEU This bug was also affecting you in the back press, but is fixed now.

compile 'com.ncapdevi:frag-nav:1.2.1'

[ncapdevi]

Just realized the issue isn't entirely fixed. It was will clear the stack, but not all the way to the bottom. I'll push out a fix again today

[ncapdevi]

Actually, the problem shouldn't affect you with the way the constructor that you are using. That being said. I've pushed out a fix.

compile 'com.ncapdevi:frag-nav:1.2.2'