无法替换标签页中的片段

Question

I have 3 tab fragments in a view pager activity. Let's name it F1, F2, F3.

I want to update F1 after clicking an item from F2.

Here is what I have tried so far. In the activity:

public class UserShopActivity extends FragmentActivity implements
        ActionBar.TabListener,
        UserCategoriesFragment.OnUserCategoriesSelectedListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
       setContentView(R.layout.activity_user_profile);

        viewPager = (ViewPager) findViewById(R.id.pager);
        actionBar = getActionBar();
        mAdapter = new TabsUserShopAdapter(getSupportFragmentManager());

        viewPager.setAdapter(mAdapter);
        actionBar.setDisplayHomeAsUpEnabled(true);
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
...

}

...

    @Override
    public void onUserCategoriesSelected(String category_id, Boolean flag) {
        UserItemsFragment fragment = new UserItemsFragment();
        getSupportFragmentManager().beginTransaction()
                .replace(R.id.pager, fragment)
                .addToBackStack(null)
                .commit();
    }
...

}

In activity_user_profile.xml :

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

</android.support.v4.view.ViewPager>

My tabs Pager Adapter is a basic one, TabUserShopAdapter :

public class TabsUserShopAdapter extends FragmentStatePagerAdapter {
    static final int NUM_ITEMS = 3;

    public TabsUserShopAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int i) {
        switch (i) {
            case 0:
                // F1
                return new UserItemsFragment();
            case 1:
                // F2
                return new UserCategoriesFragment();
            case 2:
                // F3
                return new UserProfileFragment();
        }

        return null;
    }

    @Override
    public int getCount() {
        // get item count - equal to number of tabs
        return NUM_ITEMS;
    }



    @Override
    public int getItemPosition(Object object) {
        //return super.getItemPosition(object);
        return POSITION_NONE;
    }
}

However the listener to invoke F1 in the activity doesn't work. How do I replace the fragment to update F1 from F2, while leaving the tabs visible?

I'm not sure which ID to replace in the activity. Can someone point out the mistake here.

---

UPDATE :

I've added setCurrentItem for view page in the activity. It does work, but it only changes the tab from F2 to F1. Not with the info provided in the bundle.

@Override
public void onUserCategoriesSelected(String category_id) {
    UserItemsFragment fragment = new UserItemsFragment(viewPager);
    Bundle args = new Bundle();
    args.putString("category_id", category_id);
    fragment.setArguments(args);


    viewPager.setCurrentItem(0);
}

How do I pass this value to F1 (UserItemsFragment) and update F1 while obtaining the value? Does overriding any methods in F1 lifecycle works?

Keep in mind that F1 is preloaded with data. So, after user clicked an item in F2, F1 will get refreshed with new data.

Answer 1

One does not simply... replace a fragment in a pager :)

getSupportFragmentManager().beginTransaction()
            .replace(R.id.pager, fragment)
            .addToBackStack(null)
            .commit();

This would replace a fragment that you would have manually added (by code using the fragment manager)

Your fragments were added by the pager. You could easily access them by calling .getItem(int position) on the fragment.