NullPointerException in onCreate() when using findViewById - setContentView is used before?

Question

Hello I'm writing a little Android app (Version 2.3.3). Now i get this strange NullPointer Exception in this very basic code:

public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.mainmenu); newDeck = (Button) findViewById(R.id.newDeckB); loadDeck = (Button) findViewById(R.id.loadDeckB); viewEdition = (Button) findViewById(R.id.viewEditionB); newDeck.setOnClickListener(this); loadDeck.setOnClickListener(this); viewEdition.setOnClickListener(this); }

Im using this simple layout at the moment in main menu.xml:

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <Button android:id="@+id/newDeckB" android:text="New Deck" android:layout_width="fill_parent" android:layout_height="wrap_content"/> <Button android:id="@+id/loadDeckB" android:text="Load Deck" android:layout_width="fill_parent" android:layout_height="wrap_content"/> <Button android:id="@+id/viewEditionB" android:text="View Edition" android:layout_width="fill_parent" android:layout_height="wrap_content"/> <TextView android:id="@+id/currentDeckTextView" android:text="Default Deck" android:layout_width="wrap_content" android:layout_height="wrap_content"/> </LinearLayout>

Now my problem is a nullpointexception in line 25, which is the line where i set the first clickListener

newDeck.setOnClickListener(this);

Using the debugger i figured out that the button newDeck is null. I searched a lot in the web but the only answer to such kind of problem was to check that the setContentView is set before the findViewById. This is obviously the case here.

I would be very glad for any kind of advice.

Thx in Before!

I was having the exact same problem (frustrating!), and it was the comment below (@manelizzard) that solved it for me: 'Sometimes you need to "clean" and rebuild the project to get the correct resurces compiled, it's something from Eclipse'. (i.e. you don't need to use onPostCreate() !) — coco
– coco, Commented Aug 1, 2012 at 14:55

manelizzard · Accepted Answer · 2011-08-21 10:28:31Z

10

Get your views and set the listeners in onPostCreate() method.

answered Aug 21, 2011 at 10:28

manelizzard

1,0689 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

Neuhier Over a year ago

Thx a lot for your posts. I don't really understand why but now it works. I just changed the id-Names in both the java code and the xml (from newDeckB to newDeckButton) and now it works. I really don't get it because i tried that already yesterday and it did not solve the problem.

manelizzard Over a year ago

Sometimes you need to "clean" and rebuild the project to get the correct resurces compiled, it's something from Eclipse. The onPostCreate() method is executed when the content is fully loaded. Accept the answer, plz =)

Neuhier Over a year ago

Soory i searched the faq but still don't see a button to accept an answer. Or to set this topic to solved... Sorry i am zoo nooby.

Dave Over a year ago

Just to be pedantic, onPostCreate is really meant for framework use, and typically is not expected to be used in applications. Any logic should be contained at the end of onCreate instead.

Muhammad Babar Over a year ago

@manelizzard but im changing the content view after onCreate()!. Getting null with findViewById().

|

Jonathan · Accepted Answer · 2015-02-10 21:18:30Z

There are two events that the App expects, onCreate(), and onStart()

Which one you put this function in, matters.

I had to move "findViewByID" from onCreate() to onStart()

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

There are two events that the App expects, onCreate(), and onStart() Which one you put this function in, matters.

Collectives™ on Stack Overflow

NullPointerException in onCreate() when using findViewById - setContentView is used before?

2 Answers 2

7 Comments

2 Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

7 Comments

2 Comments

Related