How can I get Fragment from View?

I added some Fragment into a TableLayout and I want to manage them from my container Activity, so I used this:

Fragment fragment = (Fragment) tableLayout.getChildAt(i);

but getChildAt(int) returns a View and a View could NOT cast to Fragment

I don't understand why people are down-voting your question. Fragments can be very confusing at times, especially for beginners. To understand your problem, you must learn what is a Fragment and how they are used.

To start with, a View is something that has an existence on the screen. Examples include: TextView, EditText, Button, etc. They are placed inside "layouts" written in Xml or Java/Kotlin. These layouts are shown using an Activity.

Now, a Fragment is not a View. It does not have any existence on the screen at all. Instead, it's a class that simply manages a "layout" — kinda similar to an Activity. If you need the View returned by your Fragment's onCreateView(), you can directly use findViewById() within your Activity.

If you need a reference to your Fragment, there are two possible ways of doing this:

1. If you added the Fragment programmatically like this

   getFragmentManager() .beginTransaction() .replace(R.id.fragment_container_viewgroup, myFragment, FRAGMENT_TAG) .commit();

You can use:

MyFragment myFragment = (MyFragment) getFragmentManager().findFragmentByTag(FRAGMENT_TAG);

2) If you added the Fragment inside an XML layout like this:

<fragment android:name="com.example.android.fragments.HeadlinesFragment"
    android:id="@+id/fragmentContainer"
    android:layout_weight="1"
    android:layout_width="0dp"
    android:layout_height="match_parent" />

You can use this:

getFragmentManager().findFragmentById(R.id.fragmentContainer);

Basically, each Activity has a FragmentManager class that maintains all the active Fragments, and there are two ways of finding them: Using a unique TAG that you pass while showing a fragment, or passing the container view-ID where the fragment was added.

For people looking how to actually get a reference to the Fragment object from a View there is now a method in FragmentManager called findFragment(View) (reference)

//in Java 
FragmentManager.findFragment(view)

//in Kotlin there is an extension function
view.findFragment()

Be careful - it will throw an IllegalStateException if the view was not added via a fragments onCreateView.

You can not get a fragment like this. You will have to add fragment with a tag and retrieve it by that tag.

to add a fragment do following:

getFragmentManager().beginTransaction().add(R.id.container, fragment, "tagTofindFragment");

to get fragment:

fragment = getFragmentManager().findFragmentByTag("tagTofindFragment");

Here tagTofindFragment is that tag that should be unique among your fragments.