Setting OnClickListener throws an exception?

Question

I want to know why my application is throwing a runtime exception when I run it? I used to the code in the following link for my application, dynamically add and remove view to viewpager.

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

    ActionBar ab=getActionBar();

    pagerAdapter = new MainPagerAdapter();
    pager = (ViewPager) findViewById (R.id.pager);

    pager.setAdapter (pagerAdapter);


    inflater = (LayoutInflater)getSystemService
              (Context.LAYOUT_INFLATER_SERVICE);
    v0 = (FrameLayout) inflater.inflate (R.layout.listlayout, null);
    Button button=(Button)findViewById(R.id.button1);
    button.setOnClickListener(this);

    pagerAdapter.addView (v0, 0);

    pagerAdapter.notifyDataSetChanged();

}
@Override
public void onClick(View v) {
    if(v.getId()==R.id.button1)
    {
        pagerAdapter.addView (v0);

        pagerAdapter.notifyDataSetChanged();
    }

}

LogCat:

  FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.todolistworkable/com.example.todolistworkable.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1970)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1995)
at android.app.ActivityThread.access$600(ActivityThread.java:128)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1161)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4514)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
at dalvik.system.NativeStart.main(Native Method)Caused by: java.lang.NullPointerException
at com.example.todolistworkable.MainActivity.onCreate(MainActivity.java:43)
at android.app.Activity.performCreate(Activity.java:4465)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1053)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1934)

Can you post more of your code? I can't see the onClick method... — Phantômaxx, Mar 11 '14 at 15:34
Dunno which line #43 is, but getActionBar() can return null if the Activity has no Action Bar. — Turnsole, Mar 11 '14 at 15:34
I doubt this is related to adding onClickListener. Check your code to make sure your views and your adapter are not null. I'd even check that LayoutInflater. — Rarw, Mar 11 '14 at 15:38
How can i check whether views or adapter are null? If i remove the setonclicklistener line it works fine? — afnan1992, Mar 11 '14 at 16:11
@afnan1992 comment the 2 lines inside onClick and run it should be alright. see if exception is thrown — Raghunandan, Mar 11 '14 at 16:19

score 0 · Accepted Answer · edited May 23 '17 at 10:33

0

the object on line 43 of your code within your onCreate method is null. Most likely the target of one of your findViewById calls is not returning what you expect it to.

See this for more info. How to interpret Logcat

edited May 23 '17 at 10:33

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answered Mar 11 '14 at 15:35

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If I remove the button.SetOnClickListener() line it works fine. Why is that the case? – afnan1992 Mar 11 '14 at 15:47
1

Because activity_main.xml most likely doesn't contain a Button named button1 – DigCamara Mar 11 '14 at 16:14

Setting OnClickListener throws an exception?

1 Answers1