ClassCastException: android.widget.Button

Question

I have a really really really strange issue here.

I have this line of code:

SeekBar mProgressBar =  (SeekBar) findViewById(R.id.SeekBar);

And it throws a ClassCastException: android.widget.Button as the title indicates. The XML file looks like this:

...
<SeekBar
android:id="@+id/SeekBar"
android:layout_height="wrap_content"
android:layout_width="fill_parent"
/>
...

If I change the code to

Button mProgressBar =  (Button) findViewById(R.id.SeekBar);

It "works" (e.i that single line works. The programs then fails for other reasons because it's now a button). I have the exact same line in another file without problems. Any idea what could be wrong?

Do you have the correct R imported?

Haphazard
– Haphazard

2011-05-20 18:59:15 +00:00
Commented May 20, 2011 at 18:59 — Haphazard
– Haphazard, Commented May 20, 2011 at 18:59

compostus · Accepted Answer · 2011-05-20 19:00:30Z

19

Must be an outdated auto-generated R class. Sometimes it gets messed up, i had it just moments ago. Try to clean the project and rebuild again. Or change something in the layout XML and save, Eclipse should refresh the R class (that is, if you're using eclipse).

answered May 20, 2011 at 19:00

compostus

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2 Comments

compostus Over a year ago

One guy reported that even rebuilding did not help and needed to re-add the project to eclipse. See here. I'm sure there is a way to force complete rebuild of R.java also from command line, but i never looked for that.

Steve Bergamini Over a year ago

This had happened to me a few times. Changing a simple thing in an xml layout and saving solved the issue. Thanks.

IgorGanapolsky · Accepted Answer · 2011-12-03 16:52:10Z

1

If it's an outdated R class and your Eclipse is not updating it, then just create a new XML layout file with the same contents as the previous one. Then delete the previous layout file. Your R class should then be updated. I have this problem frequently on Linux, and this is the solution that works for me.

Choosing Project -> Clean does NOT solve my problem on Linux because the R class doesn't get recreated...

answered Dec 3, 2011 at 16:52

IgorGanapolsky

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Comments

James Campbell · Accepted Answer · 2012-10-31 11:56:18Z

0

Have you checked you got the right Button class from the right library imported. Sometimes other libraries can provide their own implementation and Eclipse will choose them over android.widget.Button. Obviously this will cause a crash as your layout will be referring to the button in the android library.

answered Oct 31, 2012 at 11:56

James Campbell

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