Getting "on a null object reference"

Question

So i'm getting " on a null object reference" on my l1 and have no idea how to fix it after googling. I've tried multiple coding discords but they say it's because of the depreciated code but when I googled it shows that the depreciated code still works and the youtube tutorial I was following for it worked fine .

MainActivity -

package com.getcontacts;

import android.database.Cursor;
import android.provider.ContactsContract;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;






public class MainActivity extends AppCompatActivity {

    ListView l1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        l1 = findViewById(R.id.listView);
    }

    public void get(View v) {
        Cursor cursor = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI,null,null,null,null);
        startManagingCursor(cursor);


        String[] from = {ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME, ContactsContract.CommonDataKinds.Phone.NUMBER,
                ContactsContract.CommonDataKinds.Phone._ID};

        int[] to = {android.R.id.text1,android.R.id.text2};



        SimpleCursorAdapter simpleCursorAdapter = new SimpleCursorAdapter(this,android.R.layout.simple_list_item_2,cursor,from,to,1);
        l1.setAdapter(simpleCursorAdapter);
        l1.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);


    }
}

and this is the error -

D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.getcontacts, PID: 599
    java.lang.IllegalStateException: Could not execute method for android:onClick
        at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:390)
        at android.view.View.performClick(View.java:5205)
        at android.view.View$PerformClick.run(View.java:21164)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:148)
        at android.app.ActivityThread.main(ActivityThread.java:5417)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)
     Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
        at android.view.View.performClick(View.java:5205) 
        at android.view.View$PerformClick.run(View.java:21164) 
        at android.os.Handler.handleCallback(Handler.java:739) 
        at android.os.Handler.dispatchMessage(Handler.java:95) 
        at android.os.Looper.loop(Looper.java:148) 
        at android.app.ActivityThread.main(ActivityThread.java:5417) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620) 
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
        at com.getcontacts.MainActivity.get(MainActivity.java:42)
        at java.lang.reflect.Method.invoke(Native Method) 
        at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385) 
        at android.view.View.performClick(View.java:5205) 
        at android.view.View$PerformClick.run(View.java:21164) 
        at android.os.Handler.handleCallback(Handler.java:739) 
        at android.os.Handler.dispatchMessage(Handler.java:95) 
        at android.os.Looper.loop(Looper.java:148) 
        at android.app.ActivityThread.main(ActivityThread.java:5417) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)

score -1 · Answer 1 · answered Apr 01 '19 at 20:03

-1

apparently this : findViewById(R.id.listView); returns null please double check your tags and wether this element actually exists at the time of the call

answered Apr 01 '19 at 20:03

jonathan Heindl

844
7
16

score -1 · Answer 2 · answered Apr 01 '19 at 20:05

-1

Check the l1 you are trying to reference in your layout file to ensure you provided the id and spelled it exactly as you are calling it in the Java.

answered Apr 01 '19 at 20:05

KReth

11
6

THANK YOU! I hadn't actually actually added android:id="@+id/listView" to the ListView thank you so much – lynchbox Apr 01 '19 at 20:11
No problem. I have run into this periodically myself so I understand the frustration it can cause. – KReth Apr 01 '19 at 20:37

Getting "on a null object reference"

2 Answers2