[android] How to know if a Fragment is Visible?

I'm using the support library v4 and my questions are, How to know if a Fragment is Visible? and How can I change the propierties of the Layout inflated in the Fragment? Thanks in advance.

---Edit---

I'm using fragments like in the android developers tutorial with a FragmentActivity

Try this if you have only one Fragment

if (getSupportFragmentManager().getBackStackEntryCount() == 0) {
                    //TODO: Your Code Here
                }

Adding some information here that I experienced:

fragment.isVisible is only working (true/false) when you replaceFragment() otherwise if you work with addFragment(), isVisible always returns true whether the fragment is in behind of some other fragment.

If you want to know when use is looking at the fragment you should use

yourFragment.isResumed()

instead of

yourFragment.isVisible()

First of all isVisible() already checks for isAdded() so no need for calling both. Second, non-of these two means that user is actually seeing your fragment. Only isResumed() makes sure that your fragment is in front of the user and user can interact with it if thats whats you are looking for.

ArticleFragment articleFrag = (ArticleFragment)
            getSupportFragmentManager().findFragmentById(R.id.article_fragment);

    if (articleFrag != null && articleFrag.isVisible()) {

        // Call a method in the ArticleFragment to update its content
        articleFrag.updateArticleView(position);
    }

see http://developer.android.com/training/basics/fragments/communicating.html

you can try this way:

Fragment currentFragment = getFragmentManager().findFragmentById(R.id.fragment_container);

or

Fragment currentFragment = getSupportFragmentManager().findFragmentById(R.id.fragment_container);

In this if, you check if currentFragment is instance of YourFragment

if (currentFragment instanceof YourFragment) {
     Log.v(TAG, "your Fragment is Visible");
}

getUserVisibleHint() comes as true only when the fragment is on the view and visible

Both isVisible() and isAdded() return true as soon as the Fragment is created, and not even actually visible. The only solution that actually works is:

if (isAdded() && isVisible() && getUserVisibleHint()) {
    // ... do your thing
}

This does the job. Period.

NOTICE: getUserVisibleHint() is now deprecated. be careful.

You can override setMenuVisibility like this:

@Override
public void setMenuVisibility(final boolean visible) {
   if (visible) {
      //Do your stuff here
   }

   super.setMenuVisibility(visible);
}

None of the above solutions worked for me. The following however works like a charm:-

override fun setUserVisibleHint(isVisibleToUser: Boolean)

One thing to be aware of, is that isVisible() returns the visible state of the current fragment. There is a problem in the support library, where if you have nested fragments, and you hide the parent fragment (and therefore all the children), the child still says it is visible.

isVisible() is final, so can't override unfortunately. My workaround was to create a BaseFragment class that all my fragments extend, and then create a method like so:

public boolean getIsVisible()
{
    if (getParentFragment() != null && getParentFragment() instanceof BaseFragment)
    {
        return isVisible() && ((BaseFragment) getParentFragment()).getIsVisible();
    }
    else
    {
        return isVisible();
    }
}

I do isVisible() && ((BaseFragment) getParentFragment()).getIsVisible(); because we want to return false if any of the parent fragments are hidden.

This seems to do the trick for me.

Just in case you use a Fragment layout with a ViewPager (TabLayout), you can easily ask for the current (in front) fragment by ViewPager.getCurrentItem() method. It will give you the page index.

Mapping from page index to fragment[class] should be easy as you did the mapping in your FragmentPagerAdapter derived Adapter already.

int i = pager.getCurrentItem();

You may register for page change notifications by

ViewPager pager = (ViewPager) findViewById(R.id.container);
pager.addOnPageChangeListener(this);

Of course you must implement interface ViewPager.OnPageChangeListener

public class MainActivity 
    extends AppCompatActivity
    implements ViewPager.OnPageChangeListener
{
    public void onPageSelected (int position)
    {
        // we get notified here when user scrolls/switches Fragment in ViewPager -- so
        // we know which one is in front.
        Toast toast = Toast.makeText(this, "current page " + String.valueOf(position), Toast.LENGTH_LONG);
        toast.show();
    }

    public void onPageScrolled (int position, float positionOffset, int positionOffsetPixels) {
    }

    public void onPageScrollStateChanged (int state) {
    }
}

My answer here might be a little off the question. But as a newbie to Android Apps I was just facing exactly this problem and did not find an answer anywhere. So worked out above solution and posting it here -- perhaps someone finds it useful.

Edit: You might combine this method with LiveData on which the fragments subscribe. Further on, if you give your Fragments a page index as constructor argument, you can make a simple amIvisible() function in your fragment class.

In MainActivity:

private final MutableLiveData<Integer> current_page_ld = new MutableLiveData<>();
public LiveData<Integer> getCurrentPageIdx() { return current_page_ld; }

public void onPageSelected(int position) {
    current_page_ld.setValue(position);
}

public class MyPagerAdapter extends FragmentPagerAdapter
{
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page: But only on first
        // creation -- not on restore state !!!
        // see: https://stackoverflow.com/a/35677363/3290848
        switch (position) {
            case 0:
                return MyFragment.newInstance(0);
            case 1:
                return OtherFragment.newInstance(1);
            case 2:
                return XYFragment.newInstance(2);
        }
        return null;
    }
}

In Fragment:

    public static MyFragment newInstance(int index) {
        MyFragment fragment = new MyFragment();
        Bundle args = new Bundle();
        args.putInt("idx", index);
        fragment.setArguments(args);
        return fragment;
    }

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mPageIndex = getArguments().getInt(ARG_PARAM1);
        }
        ...
    }
    
    public void onAttach(Context context)
    {
        super.onAttach(context);
        MyActivity mActivity = (MyActivity)context;

        mActivity.getCurrentPageIdx().observe(this, new Observer<Integer>() {
            @Override
            public void onChanged(Integer data) {
                if (data == mPageIndex) {
                    // have focus
                } else {
                    // not in front
                }
            }
        });
    }