Missing Something Easy (Button OnClick Causing Null Pointer)

Question

Suddenly my buttons cause null pointer exceptions. I have not changed any code in this activity class. I have been up most of the weekend trying to pin this down. I get null pointer exceptions in both the emulator and on device.

This is a simple screen with buttons. I could easily scrap this and write new code, but would like to know what has caused this issue. If not, I will just write new code.

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;


Button b1 = (Button) findViewById(R.id.MainActBtn);

b1.setOnClickListener(new View.OnClickListener() { //Error is here

        public void onClick(View v) {
            Intent intent = new Intent(StartScreen.this, MainActivity.class);
            startActivity(intent);

        }
    });

Any help?

Add your layout xml or make sure you put the right id and done this process after setContentView() — Adil Soomro
– Adil Soomro, Commented Oct 17, 2011 at 9:21
Yes. The error is actually pointing to the onclicklistener line — Phobos
– Phobos, Commented Oct 17, 2011 at 9:22

HefferWolf · Accepted Answer · 2011-10-17 09:28:06Z

2

Try a fresh clean and build of your project. I got this error too in the past, caused by a changed R.class Resource class, but the static references in the using classes weren't properly replaced by the incremental java compiler, so the resources are no longer found.

answered Oct 17, 2011 at 9:28

HefferWolf

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1 Comment

Phobos Over a year ago

I knew it would be something extremely easy. After a complete clean and rebuild the R resources were recompiled. Eclipse sometimes does things that I am not aware of.

MKJParekh · Accepted Answer · 2011-10-17 09:27:42Z

1

I think You are not getting Null Pointer Exception because of the Button click just because of the declaration of the button..

You can check before writting the onClickListener..

if(b1==null)
 Log.i("Null","Null");

The Problem is may be in setting the XML view or also check the button you are using is defined in the same xml you are using in setContentView.

After this all, also Clean and Build your project.

answered Oct 17, 2011 at 9:27

MKJParekh

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2 Comments

Phobos Over a year ago

I have all ready added the line in order to check before I posted the question.

Phobos Over a year ago

Frank, I had to uncheck Build Automatically, and the clean the project, and then recheck Build Automatically.

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