[android] findViewByID returns null

First of all: yes, I read all the other threads on this topic. And not only those from this site... (you see, I'm a little frustrated)

Most of them come with the advice to use android:id instead of just id in the XML file. I did.

From others, I learned, that View.findViewById works different than Activity.findViewById. I handled that, too.

In my location_layout.xml, I use:

<FrameLayout .... >
    <some.package.MyCustomView ... />

    <LinearLayout ... >
        <TextView ...
            android:id="@+id/txtLat" />
        ...
    </LinearLayout>
</FrameLayout>

In my Activity I do:

...
setContentView( R.layout.location_layout );

and in my custom view class:

... 
TextView tv = (TextView) findViewById( R.id.txtLat );

which returns null. Doing this, my Activity works fine. So maybe it's because of the Activity.findViewById and View.findViewById differences. So I stored the context passed to the customs view constructor locally and tried:

...
TextView tv = (TextView) ((Activity) context).findViewById( R.id.txtLat );

which also returned null.

Then, I changed my custom view to extend ViewGroup instead View and changed the location_layout.xml to let the TextView be a direct child of my custom view, so that the View.findViewById should work as supposed. Suprise: it didn't solve anything.

So what the heck am I doing wrong?

I'll appreciate any comments.

I'm pretty new to Android/Eclipse, by mistake I added the UI stuff to activity_main.xml instead of fragment_main.xml. Took me some hours to figure that out...

A answer for those using ExpandableListView and run into this question based on it's title.

I had this error attempting to work with TextViews in my child and group views as part of an ExpandableListView implementation.

You can use something like the following in your implementations of the getChildView() and getGroupView() methods.

        if (convertView == null) {
            LayoutInflater inflater =  (LayoutInflater) myContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.child_layout, null);
        }

I found this here.

Make sure you don't have multiple versions of your layout for different screen densities. I ran into this problem once when adding a new id to an existing layout but forgot to update the hdpi version. If you forget to update all versions of the layout file it will work for some screen densities but not others.

In my case, I had 2 activites in my project, main.xml and main2.xml. From the beginning, main2 was a copy of main, and everything worked well, until I added new TextView to main2, so the R.id.textview1 became available for the rest of app. Then I tried to fetch it by standard calling:

TextView tv = (TextView) findViewById( R.id.textview1 );

and it was always null. It turned out, that in onCreate constructor I was instantiating not main2, but the other one. I had:

setContentView(R.layout.main);

instead of

setContentView(R.layout.main2);

I noticed this after I arrived here, on the site.

INFLATE THE LAYOUT !! (which contains the id)

In my case findViewById() returned null, because the layout in which the element was written, was not inflated...

Eg. fragment_layout.xml

<ListView
android:id="@+id/listview">

findViewById(R.id.listview) returned null, because I had not done inflater.inflate(R.layout.fragment_layout, ..., ...); before it.

Hope this answer helps some of y'all.

I had this same problem. I was using a third-party library that allows you to override their adapter for a GridView and to specify your own layout for each GridView cell.

I finally realized what was happening. Eclipse was still using the library's layout xml file for each cell in the GridView, even though it gave no indication of this. In my custom adapter, it indicated that it was using the xml resource from my own project even though at runtime, it wasn't.

So what I did was to make sure my custom xml layouts and ids were different from those still sitting in the library, cleaned the project and then it started reading the correct custom layouts that were in my project.

In short, be careful if you're overriding a third-party library's adapter and specifying your own layout xml for the adapter to use. If your layout inside your project has the same file name as that in the library, you might encounter a really difficult-to-find bug!

FindViewById can be null if you call the wrong super constructor in a custom view. The ID tag is part of attrs, so if you ignore attrs, you delete the ID.

This would be wrong

public CameraSurfaceView(Context context, AttributeSet attrs) {
        super(context);
}

This is correct

public CameraSurfaceView(Context context, AttributeSet attrs) {
        super(context,attrs);
}

    @Override
protected void onStart() {
         // use findViewById() here instead of in onCreate()
    }

In my case I had inflated the layout but the child views were returning null. Originally I had this:

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

    footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
    pbSpinner = (ProgressBar) findViewById(R.id.pbListviewFooter);
    tvText = (TextView) findViewById(R.id.tvListviewFooter);
    ...
}

However, when I changed it to the following it worked:

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

    footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
    pbSpinner = (ProgressBar) footerView.findViewById(R.id.pbListviewFooter);
    tvText = (TextView) footerView.findViewById(R.id.tvListviewFooter);
    ...
}

The key was to specifically reference the already inflated layout in order to get the child views. That is, to add footerView:

• footerView.findViewById...

In my case, I was using ExpandableListView and I had set android:transcriptMode="normal". This was causing few children in expandable group to disappear and I used to get NULL exception when ever I used scroll the list.

findViewById also can return null if you're inside a Fragment. As described here: findViewById in Fragment

You should call getView() to return the top level View inside a Fragment. Then you can find the layout items (buttons, textviews, etc)

FWIW, I don't see that anyone solved this in quite the same way as I needed to. No complaints at compile time, but I was getting a null view at runtime, and calling things in the proper order. That is, findViewById() after setContentView(). The problem turned out that my view is defined in content_main.xml, but in my activity_main.xml, I lacked this one statement:

<include layout="@layout/content_main" />

When I added that to activity_main.xml, no more NullPointer.

Alongside the classic causes, mentioned elsewhere:

• Make sure you've called setContentView() before findViewById()
• Make sure that the id you want is in the view or layout you've given to setContentView()
• Make sure that the id isn't accidentally duplicated in different layouts

There is one I have found for custom views in standard layouts, which goes against the documentation:

In theory you can create a custom view and add it to a layout (see here). However, I have found that in such situations, sometimes the id attribute works for all the views in the layout except the custom ones. The solution I use is:

1. Replace each custom view with a FrameLayout with the same layout properties as you would like the custom view to have. Give it an appropriate id, say frame_for_custom_view.

2. In onCreate:

   setContentView(R.layout.my_layout);
   FrameView fv = findViewById(R.id.frame_for_custom_layout);
   MyCustomView cv = new MyCustomView(context);
   fv.addView(cv);
   

   which puts the custom view in the frame.

I have the same problem, but I think its worth sharing with you guys. If you have to findViewById in custom layout, for example:

public class MiniPlayerControllBar extends LinearLayout {
    //code
}

you cannot get the view in constructor. You should call findViewById after view has inflated. Their is a method you can override onFinishInflate

In my particular case, I was trying to add a footer to a ListView. The following call in onCreate() was returning null.

TextView footerView = (TextView) placesListView.findViewById(R.id.footer);

Changing this to inflate the footer view instead of finding it by ID solved this issue.

View footerView = ((LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.footer_view, null, false);

For me I had two xml layouts for the same activity - one in portrait mode and one in landscape. Of course I had changed the id of an object in the landscape xml but had forgotten to make the same change in the portrait version. Make sure if you change one you do the same to the other xml or you will not get an error until you run/debug it and it can't find the id you didn't change. Oh dumb mistakes, why must you punish me so?

I was facing a similar problem when I was trying to do a custom view for a ListView.

I solved it simply by doing this:

public View getView(int i, View view, ViewGroup viewGroup) {

    // Gets the inflater
    LayoutInflater inflater = LayoutInflater.from(this.contexto);

    // Inflates the layout
    ConstraintLayout cl2 = (ConstraintLayout) 
    inflater.inflate(R.layout.custom_list_view, viewGroup, false);

    //Insted of calling just findViewById, I call de cl2.findViewById method. cl2 is the layout I have just inflated. 
     TextView tv1 = (TextView)cl2.findViewById(cl2);

Possibly, you are calling findViewById before calling setContentView? If that's the case, try calling findViewById AFTER calling setContentView

Just wanted to throw my specific case in here. Might help someone down the line.

I was using the directive in my Android UI XML like this:

Parent view:

<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:tag="home_phone"
    android:background="@color/colorPrimary">

    ...

    <include
        layout="@layout/retry_button"
        android:visibility="gone" />

Child view (retry_button):

<com.foo.RetryButton
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/retry"
    android:layout_gravity="center"
    android:orientation="vertical"
    android:layout_width="100dp"
    android:layout_height="140dp">

.findViewById(R.id.retry) would always return null. But, if I moved the ID from the child view into the include tag, it started working.

Fixed parent:

<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:tag="home_phone"
    android:background="@color/colorPrimary">

    ...

    <include
        layout="@layout/retry_button"
        android:id="@+id/retry"
        android:visibility="gone" />

Fixed child:

<com.foo.RetryButton
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_gravity="center"
    android:orientation="vertical"
    android:layout_width="100dp"
    android:layout_height="140dp">

Ways to debug and find the issue:

• Comment out all findViewById in your activity.
• Comment out everything except onCreate and setContentView
• Run the project and see if any layout is set

In my case, I was using activity_main.xml in both my app module and also my library module. So when I performed the above steps, instead of the layout which I designed in the library, the layout inside app module was inflated.

So I changed the activity_main.xml file name to activity_main_lib.xml.

So make sure you do not have any duplicate layout names in your whole project.

In my experience, it seems that this can also happen when your code is called after OnDestroyView (when the fragment is on the back stack.) If you are updating the UI on input from a BroadCastReceiver, you ought to check if this is the case.

I've tried all of the above nothing was working.. so I had to make my ImageView static public static ImageView texture; and then texture = (ImageView) findViewById(R.id.texture_back); , I don't think it's a good approach though but this really worked for my case :)

It crashed for me because one of fields in my activity id was matching with id in an other activity. I fixed it by giving a unique id.

In my loginActivity.xml password field id was "password". In my registration activity I just fixed it by giving id r_password, then it returned not null object:

password = (EditText)findViewById(R.id.r_password);

Set the activity content from a layout resource. ie.,setContentView(R.layout.basicXml);

My fix was to just clean the project.

My case is none like above, no solutions worked. I assume my view was too deep into layout hierarchy. I moved it one level up and it was not null anymore.

In my case, findViewById returned null when I moved the call from a parent object into an adapter object instantiated by the parent. After trying tricks listed here without success, I moved the findViewById back into the parent object and passed the result as a parameter during instantiation of the adapter object. For example, I did this in parent object:

 Spinner hdSpinner = (Spinner)view.findViewById(R.id.accountsSpinner);

Then I passed the hdSpinner as a parameter during creation of the adapter object:

  mTransactionAdapter = new TransactionAdapter(getActivity(),
        R.layout.transactions_list_item, null, from, to, 0, hdSpinner);

In addition of the above solutions you make sure the
tools:context=".TakeMultipleImages" in the layout is same value in the mainfest.xml file :
android:name=".TakeMultipleImages" for the same activity element. it is occur when use copy and paste to create new activity