NullPointerException in Floating Action Button in Fragment

Question

can you help me with this error:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.design.widget.FloatingActionButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
                                                                    at com.sadface.tutorapp.FirstFragment.onCreateView(FirstFragment.java:23)

I want to handle FAB in fragment, so here's code:

FirstFragment.class

public class FirstFragment extends Fragment {

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.fragment_first,
            container, false);
    FloatingActionButton fab = (FloatingActionButton) view.findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
    return view;
}

}

And fragment_first.xml :

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/holo_green_dark">

<TextView
    android:id="@+id/textView3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:text="First Fragment"
    android:textAppearance="?android:attr/textAppearanceLarge"/>

<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom|end"
    android:layout_margin="@dimen/fab_margin"
    app:srcCompat="@android:drawable/ic_input_add" /></RelativeLayout>

I read on stackoverflow, that i have use view.findById, but it isn't work, i don't understand what's a problem?

You are having null pointer exception, means that either your id of fab isn't correct or its just define in another layout. — Abdul Kawee, May 21 '17 at 14:33
Yes. The method findViewById is returning null because cant find the element — IgniteCoders, May 21 '17 at 14:37

score 0 · Answer 1 · answered May 21 '17 at 14:41

0

Add this to your FAB in xml:

android:onClick:"nameOfMethod"

And in your fragment:

    public void nameofMethod(View v){
     //button Clicked
}

answered May 21 '17 at 14:41

Haris ali

773
1
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never add listeners in XML. You will burn in hell for that. – Vladyslav Matviienko May 21 '17 at 14:46
1

And why is that ? – Haris ali May 21 '17 at 14:50
because they get lost by developer immediately after you change at least small peace of code related to them. http://stackoverflow.com/a/18267474/1568530 https://www.google.com.ua/search?q=android+setting+onclick+in+xml+is+bad&oq=android+setting+onclick+in+xml+is+bad&aqs=chrome..69i57j69i64.7603j0j7&sourceid=chrome&ie=UTF-8 – Vladyslav Matviienko May 21 '17 at 14:54
I always use them and I never had a problem. Who knows why... – Phantômaxx May 21 '17 at 14:55
I got your point but then y did they made it in the first place ! – Haris ali May 21 '17 at 15:00
they do alot of stuped things. This is one of them for sure. Maibe they wanted to easen the Android development learning for people who used HTML development before? – Vladyslav Matviienko May 21 '17 at 15:06

score 0 · Accepted Answer · answered May 21 '17 at 14:43

It seems that your code is right. I find FloatingActionButton says:Android floating action button which reacts on scrolling events. Becomes visible when an attached target is scrolled up and invisible when scrolled down.

Maybe you should use some layouts which can scroll. Here is the official example:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
         xmlns:fab="http://schemas.android.com/apk/res-auto"
         android:layout_width="match_parent"
         android:layout_height="match_parent">

<ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

<com.melnykov.fab.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:layout_margin="16dp"
        android:src="@drawable/ic_action_content_new"
        fab:fab_colorNormal="@color/primary"
        fab:fab_colorPressed="@color/primary_pressed"
        fab:fab_colorRipple="@color/ripple" />

The official example has used a listview.

NullPointerException in Floating Action Button in Fragment

2 Answers2