CODEWITHSUNDEEP
android
Lara
Lara

Reputation: 172

setOnClickListener causes crash

Button start_game;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);          
    start_game = (Button) findViewById(R.id.start_game);
    start_game.setOnClickListener(this);
    setContentView(R.layout.welcome);
 }

I don't know why, but if I remove the line setOnClickListener my app starts (of course my button doesn't do anything then). Logcat gives me this:

java.lang.RuntimeException: Unable to start activity ComponentInfo{de.test.testabc/de.test.testabc.Welcome}: java.lang.NullPointerException

Upvotes: 0

Views: 370

Answers (1)

Alexis C.
Alexis C.

Reputation: 93842

You have to inflate your layout before getting the UI elements, otherwise findViewById returns null and hence you got the NullPointerException at the line start_game.setOnClickListener(this);.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);    

    setContentView(R.layout.welcome); //layout inflated now it's ok to get your button

    start_game = (Button) findViewById(R.id.start_game);
    start_game.setOnClickListener(this);
}

Upvotes: 8

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