findViewById() returns null on included layout?

Question

I have an included layout in my activity's XML layout like so:

<include
    layout="@layout/info_button"
    android:id="@+id/config_from_template_info_btn"/>

I'm trying to set an OnClickListener for the button inside of that included layout by doing this:

findViewById(R.id.config_from_template_info_btn)
        .findViewById(R.id.info_btn)
        .setOnClickListener(new View.OnClickListener()
{
    @Override
    public void onClick(View v)
    {
        //Do things
    }
});

However, this crashes on runtime with:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference

The info_btn.xml layout simply contains Button widget like so:

<merge xmlns:android="http://schemas.android.com/apk/res/android">
    <Button
        android:id="@+id/info_btn"
        ...
        />
</merge>

What am I doing wrong here?

@Mett if you meant `setContentView()`, then nope, this code is directly after that call. — You'reAGitForNotUsingGit, May 09 '18 at 16:18
It'd be helpful to know which `findViewById()` is throwing the exception. — Jeffrey Blattman, May 09 '18 at 16:18
You could use the Layoutinspector (Tools -> Layoutinspector) to find out if thats the case. (Remove the findViewById part for now) — Gerrit Sedlaczek, May 09 '18 at 16:22
@JeffreyBlattman ok, I replaced the `` with a `` in `info_btn.xml` and it works! If you go ahead and write an answer, I'll accept it :) — You'reAGitForNotUsingGit, May 09 '18 at 16:33

Jeffrey Blattman · Accepted Answer · 2018-05-10T19:53:24.267

The <merge.../> tag is removing the outer layout, which is the one with that ID. That's the purpose of merge: to collapse unnecessary layouts for better performance. Yours is one common case. You need a top-level XML container to hold the included views, but you don't actually need view layout functionality.

Either just use one find on info_btn, or don't use merge. The only reason you'd need to do the double find is if you were including multiple layouts that each had views with an ID of info_btn.

score 0 · Answer 2 · answered May 09 '18 at 16:21

0

If you have an included layout in your activity, you can access to the Button like if the button was inside the activity.

You only need to do:

findViewById(R.id.info_btn)
    .setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //Do things
        }
});

answered May 09 '18 at 16:21

Fran Dioniz

1,134
9
12

The problem with that approach is that I include the layout in multiple places, so I need to be able to set a different listener for each one individually – You'reAGitForNotUsingGit May 09 '18 at 16:22

score 0 · Answer 3 · answered May 09 '18 at 16:22

0

You just need to do this:

findViewById(R.id.info_btn)
    .setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v)
{
    //Do things
}
});

answered May 09 '18 at 16:22

Daniel RL

353
1
12

The problem with that approach is that I include the layout in multiple places, so I need to be able to set a different listener for each one individually – You'reAGitForNotUsingGit May 09 '18 at 16:23
Then you need to set differents ids for each, it's not valid if you use the same component in one layout. – Daniel RL May 09 '18 at 16:25

score 0 · Answer 4 · answered May 09 '18 at 16:24

0

Included layouts are added to your view already. You can do this way also.

findViewById(R.id.info_btn)
    .setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

        }
});

answered May 09 '18 at 16:24

Khemraj Sharma

57,232
27
203
212

If you included same layout in one layout multiple times then you need to define id for each. – Khemraj Sharma May 09 '18 at 16:25

findViewById() returns null on included layout?

4 Answers4