Reputation: 2941

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.

Upvotes: 291

Answers (30)

Will Buffington

Reputation: 1710

I am using Flamingo 2022.2.1 Patch 2 (Build #AI-222.4459.24.2221.10121639, built on May 12, 2023)

In my case this was happening because for some reason I had TWO activity_main.xml objects under my layout folder. One was "Activity_main.xml" and the other was "(v31)activity_main.xml".

Of course, (v31)activity_main.xml didn't contain the button I was trying to use with findViewById and as a result it came back null.

I've no idea where "(v31)activity_main.xml" came from, but after I did a safe delete and removed it, the problem was gone.

Hope this helps someone in the future!

Upvotes: 0

user1506104

Reputation: 7106

I had the same .xml file in two seprate modules that had the same view id in it.

app/src/main/res/layout/header.xml
supportModule/src/main/res/layout/header.xml

Both layouts had TextViews with the same id @+id/tv_prompt.

My TextView tvPrompt = findViewById(R.id.tv_prompt); always returned null. I had to rename my other xml file to header_main.xml to fix the issue.

Upvotes: 1

Jennifer Kiesel

Reputation: 96

For me it was only null when using Evaluate Expression or the Debug Watch View of the IDE.

Upvotes: 0

Attila

Reputation: 308

For me it returned null because the given control was (programmatically) hidden. When I put a condition to call findViewByID(id) only when the control is visible, it started working again.

Upvotes: 0

AtomicBoolean

Reputation: 1230

The issue for me was that I had two layouts with the same file name activity_main.xml. (The layouts were in different libraries but in the same app) The issue was solved by renaming one of them to a unique name.

Upvotes: 0

Reejesh PK

Reputation: 4170

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.

Upvotes: 0

Rafael Costa

Reputation: 11

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);

Upvotes: 0

Jageloo Yadav

Reputation: 11

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);

Upvotes: 1

Lexo

Reputation: 437

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);

Upvotes: 0

Deividas Strioga

Reputation: 1467

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.

Upvotes: 2

Tabish

Reputation: 400

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 :)

Upvotes: -1

technocrat

Reputation: 3705

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)

Upvotes: 0

ferris

Reputation: 71

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.

Upvotes: 7

John D.

Reputation: 2599

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">

Upvotes: 3

Liangjun

Reputation: 601

My fix was to just clean the project.

Upvotes: -1

Suragch

Reputation: 512566

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...

Upvotes: 1

ARK

Reputation: 4084

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.

Upvotes: 1

CommonsWare

Reputation: 1007534

which returns null

Possibly because you are calling it too early. Wait until onFinishInflate(). Here is a sample project demonstrating a custom View accessing its contents.

Upvotes: 306

Shaw

Reputation: 1495

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

Upvotes: 2

repkap11

Reputation: 797

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);
}

Upvotes: 38

user2982286

Reputation: 21

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

Upvotes: 2

Matt

Reputation: 27

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);

Upvotes: 3

Neil Townsend

Reputation: 6084

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:

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.

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.

Upvotes: 20

JDJ

Reputation: 4328

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!

Upvotes: 3

Ajay Takur

Reputation: 6236

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

Upvotes: 2

Jonathan

Reputation: 7128

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

Upvotes: 12

kungfooman

Reputation: 4892

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...

Upvotes: 5

Tad

Reputation: 4784

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.

Upvotes: 0

Chris Klingler

Reputation: 5294

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?

Upvotes: 2

infografnet

Reputation: 4005

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.

Upvotes: 16

findViewByID returns null

Answers (30)

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