Android: ImageButton causes crash upon assigning it a listener

Question

So, basically, I have an ImageButton called boutonPortail , and another called logo . Initializing boutonPortail works fine, but when I assign it its listener with boutonPortail.setOnClickListener(boutonPortailListener); the app crashes, and I don't know why at all. It's not a problem with the listener since when I assign it to logo it works just fine. I doubt it is a problem with the XML since I copy/pasted the code of logo .

My app prompts for a password, and if the password is correct it switches to another view with the logo and the boutonPortail . Note that the password prompt view also has the logo .

Is the problem that boutonPortail is not on the main view? I tried assigning the listener after switching views, but it still crashes.

EDIT: After putting the button in the main view, the problem is definitely that the button is not in the main view, when I put it in the main view it works fine. Why does it crashes though?

Also, for some reason I can't manage to change the image of the button with boutonPortail.setImageResource(R.drawable.boutonfermer); . (this doesn't happen when it is in the main view)

onCreate method:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    logo = (ImageButton)findViewById(R.id.logo);
    boutonPortail = (ImageButton)findViewById(R.id.boutonPortail);
    codeEntered = (EditText)findViewById(R.id.codeEntered);
    codeSurNotice = (TextView)findViewById(R.id.codeSurNotice);

    //attribute all listeners
    logo.setOnClickListener(boutonPortailListener);
    codeEntered.addTextChangedListener(textWatcher);
    codeEntered.setOnKeyListener(codeEnteredListener);

Method to change view:

void codeCorrect() {
    setContentView(R.layout.activity_readytopress);
    boutonPortail.setOnClickListener(boutonPortailListener); //this line crashes the app, even if put in the onCreate
}

Listener:

private OnClickListener boutonPortailListener = new OnClickListener() {
    @Override
    public void onClick(View v) {
        boutonState++;
        if(boutonState>=4)
            boutonState=0;
        boutonPortail.setImageResource(R.drawable.boutonfermer);

    }
};

XML:

<ImageButton
    android:id="@+id/boutonPortail"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:padding="40dip"
    android:src="@drawable/boutonouvrir"
    android:background="#00000000"
    style="#00000000"
    android:layout_gravity="center"
    />

Here's my full code if you want to test it (note that you'll have to call the codeCorrect() method manually since you don't have access to the bluetooth device I use):

MainActivity.java http://pastebin.com/ZXDahPZ6 activity_main.xml http://pastebin.com/f14cVBKj activity_readytopress.xml http://pastebin.com/0iZm91eq boutonouvrir.png http://puu.sh/mLGeU.png ouvertureencours.png http://puu.sh/mLGfI.png boutonfermer.png http://puu.sh/mLGe5.png fermetureencours.png http://puu.sh/mLGgW.png

Thanks :)

Answer 1

You do not have a button with the id boutonPortail in activity_main.xml

It is crashing with a Null Pointer Exception. You cannot add a listener to a null object.

Here is your relevant code:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // On récupère toutes les vues dont on a besoin
    logo = (ImageButton)findViewById(R.id.logo);
    boutonPortail = (ImageButton)findViewById(R.id.boutonPortail);

So you call setContentView(R.layout.activity_main) and then you call findViewById(R.id.boutonPortail)

The findContentView() will return null, because acitivty_main.xml does not have a view ID of that value. So now boutonPortail is null.

Then you call boutonPortail.setOnClickListener(boutonPortailListener) which will crash with a Null Pointer Exception because boutonPortail is null