ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference

Question

import android.content.Context;
import android.graphics.Color;
import android.icu.text.SimpleDateFormat;
import android.os.Bundle;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.widget.Toast;

import com.github.sundeepk.compactcalendarview.CompactCalendarView;
import com.github.sundeepk.compactcalendarview.domain.Event;

import java.util.Date;
import java.util.Locale;

public class Calendarpage extends AppCompatActivity {

    //modify here
    ActionBar actionBar = null;

    CompactCalendarView compactCalendar;
    private SimpleDateFormat dateFormatMonth = new SimpleDateFormat ("MMM- yyyy", Locale.getDefault());

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_calendar);

        // modify here
        ActionBar myActionBar = getSupportActionBar();
        if (myActionBar != null) {
            myActionBar.setDisplayHomeAsUpEnabled(true);
            actionBar.setTitle(null);
        }

        compactCalendar = (CompactCalendarView) findViewById(R.id.compactcalendar_view);
        compactCalendar.setUseThreeLetterAbbreviation(true);

        Event ev1 = new Event(Color.RED, 1514160000L, "Chirstmas Day");
        compactCalendar.addEvent(ev1);

        compactCalendar.setListener(new CompactCalendarView.CompactCalendarViewListener() {
            @Override
            public void onDayClick(Date dateClicked) {
                Context context = getApplicationContext();

                if (dateClicked.toString().compareTo("Mon Dec 25 00:00:00 AST 2017") == 0) {
                    Toast.makeText(context, "Christmas Day", Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(context, "No Events Planned That Day", Toast.LENGTH_SHORT).show();
                }
            }

            @Override
            public void onMonthScroll(Date firstDayOfNewMonth) {
                getSupportActionBar.setTitle(String.valueOf(dateFormatMonth.format(firstDayOfNewMonth)));
            }
        });
    }
}

now added the changes you made but the getSupportActionBar. is in red? its just asking me to create local variables when right clicking. very stressed with this as I can't move on until this page works.. as I still need to be able to add events to dates

Possible duplicate of [What is a NullPointerException, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Luiz Fernando Salvaterra, Apr 28 '17 at 13:03

VelocityPulse · Accepted Answer · 2017-04-28T17:37:41.197

0

Try to make this change

In your OnCreate :

    ActionBar myActionBar = getSupportActionBar();
    if (myActionBar != null) {
        myActionBar.setDisplayHomeAsUpEnabled(true);
        actionBar.setTitle(null);
    }

In your setListener

        @Override
        public void onMonthScroll(Date firstDayOfNewMonth) {
             getSupportActionBar().setTitle(String.valueOf(
             dateFormatMonth.format(firstDayOfNewMonth)));
        }

Good luck

EDIT try this

        compactCalendar.setListener(new CompactCalendarView.CompactCalendarViewListener() {    
            @Override
            public void onMonthScroll(Date firstDayOfNewMonth) {
                setNewTitleBar(dateFormatMonth.format(firstDayOfNewMonth));
            }
        });
    }

    private void setNewTitleBar(String newTitle) {
        getSupportActionBar().setTitle(newTitle);
    }
}

edited Apr 28 '17 at 17:37

answered Apr 28 '17 at 13:12

VelocityPulse

613
7
13

I am now getting this when I swipe to next month? – Callum Ronney Apr 28 '17 at 13:18
Your new error is made because actionBar.setTitle need a String object and your put a charSequence with dateFormatMonth.format(firstDayOfNewMonth) – VelocityPulse Apr 28 '17 at 13:27
I'm still getting the same error once I do the change? @ClémentChameyrat – Callum Ronney Apr 28 '17 at 13:38
also added my xml file now too – Callum Ronney Apr 28 '17 at 13:39
So I need to edit where it says modify here, because when running that and sliding to another month it crashes with the same error.. – Callum Ronney Apr 28 '17 at 14:01
is it because I don't actuallyy have a title bar in the xml file? if so how would I add one – Callum Ronney Apr 28 '17 at 14:01
You can't mention the title bar in the xml file. Have you try my EDIT modification ? If yes can you tell me the result ? – VelocityPulse Apr 28 '17 at 14:05
I got the same error when sliding to a different month on the onMonthScroll line 58 – Callum Ronney Apr 28 '17 at 14:14
No idea how to fix this.. @ClémentChameyrat – Callum Ronney Apr 28 '17 at 14:30
Try my modifications ;) – VelocityPulse Apr 28 '17 at 14:39
code is now changed... but doesn't work :( @ClémentChameyrat – Callum Ronney Apr 28 '17 at 15:07
My bad ! add "()" to getSupportActionBar ! – VelocityPulse Apr 28 '17 at 15:18
FATAL EXCEPTION: main Process: a2day.a2day, PID: 18642 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference at a2day.a2day.Calendarpage$1.onMonthScroll(Calendarpage.java:57) – Callum Ronney Apr 28 '17 at 16:30
@Override public void onMonthScroll(Date firstDayOfNewMonth) { getSupportActionBar().setTitle(String.valueOf(dateFormatMonth.format(firstDayOfNewMonth))); } }); } – Callum Ronney Apr 28 '17 at 16:30

ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference

1 Answers1