Error for checkbox android.widget.CheckBox.setVisibility(int)' on a null object reference

Question

   checkBox=(CheckBox) findViewById(checkbox);
   checkBox.setVisibility(View.GONE);

    db = new Db(Listdata.this,"register2",null,2);
    list2 = db.listdata();
    Log.d("list", String.valueOf(list2));
    listAdapter adapter = new listAdapter(Listdata.this,list2);
    listView.setAdapter(adapter);
    a= list2.size();
    Log.d("teb", String.valueOf(a));

    listView.setLongClickable(true);
    listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
        public boolean onItemLongClick(AdapterView<?> arg0, View arg1, int pos, long id) {
            for(int i = 0; i!=a; i++) {
                checkBox = (CheckBox) listView.getChildAt(i).findViewById(R.id.checkbox);
                checkBox.setVisibility(View.VISIBLE);
            }
            return true;
        }
    });

FATAL EXCEPTION: main Process: com.example.developer.register, PID: 21571

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
                                                                                at com.example.developer.register.Listdata$1.onItemLongClick(Listdata.java:52)
                                                                                at android.widget.AbsListView.performLongPress(AbsListView.java:3112)
                                                                                at android.widget.AbsListView$CheckForLongPress.run(AbsListView.java:3061)
                                                                                at android.os.Handler.handleCallback(Handler.java:739)
                                                                                at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                at android.os.Looper.loop(Looper.java:135)
                                                                                at android.app.ActivityThread.main(ActivityThread.java:5221)
                                                                                at java.lang.reflect.Method.invoke(Native Method)
                                                                                at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
                                                                                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

did you checked the checkbox id ? I think you are giving the wrong Id to your check box. — Umair, Dec 15 '17 at 08:00
you are trying to set visibility on null ref `checkBox.setVisibility()` — akhilesh0707, Dec 15 '17 at 08:00
When i run it it shows error in the line checkbox.setVisibility(View.VISIBLE); — Gmadhana Kumar, Dec 15 '17 at 08:00
what is the value of `checkbox` inside `findViewById(checkbox);` — akhilesh0707, Dec 15 '17 at 08:02
i have a listview in that when i press long on the particular list the check box should be visible for all the list — Gmadhana Kumar, Dec 15 '17 at 08:11

score 1 · Answer 1 · edited Dec 15 '17 at 08:09

1

If you are trying to get value from ListView checkbox try this

View view = ((ViewGroup)arg1).getChildAt(i);
checkBox = (CheckBox) view.findViewById(R.id.checkboxId);
checkBox.setVisibility(View.VISIBLE);

edited Dec 15 '17 at 08:09

akhilesh0707

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answered Dec 15 '17 at 08:03

Dharmishtha

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Error for checkbox android.widget.CheckBox.setVisibility(int)' on a null object reference

1 Answers1