CODEWITHSUNDEEP
androidandroid-studionullpointerexception
Reqedd
Reqedd

Reputation: 123

Getting error NullPointerException when using DrawerLayout in Android Studio

Getting a NullPointerException Error when trying to run my app, I will link code and Logcat error below, help would be greatly appreciated.

In my XML class with the DrawerLayout I have the ID for the drawer set to drawer_layout (renamed using android:id).

Logcat Error

2022-11-23 01:35:49.526 4976-4976/com.example.appdev2finalproject E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.appdev2finalproject, PID: 4976
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.appdev2finalproject/com.example.appdev2finalproject.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.drawerlayout.widget.DrawerLayout.addDrawerListener(androidx.drawerlayout.widget.DrawerLayout$DrawerListener)' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:223)
    at android.app.ActivityThread.main(ActivityThread.java:7656)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.drawerlayout.widget.DrawerLayout.addDrawerListener(androidx.drawerlayout.widget.DrawerLayout$DrawerListener)' on a null object reference
    at com.example.appdev2finalproject.MainActivity.onCreate(MainActivity.java:21)
    at android.app.Activity.performCreate(Activity.java:7994)
    at android.app.Activity.performCreate(Activity.java:7978)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)

Code From Main

package com.example.appdev2finalproject;

import androidx.appcompat.app.ActionBarDrawerToggle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.drawerlayout.widget.DrawerLayout;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {
    DrawerLayout drawerLayout;
    ActionBarDrawerToggle actionBarDrawerToggle;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        drawerLayout = findViewById(R.id.drawer_layout);
        actionBarDrawerToggle = new ActionBarDrawerToggle(this, drawerLayout, R.string.nav_open,
                R.string.nav_close);

        drawerLayout.addDrawerListener(actionBarDrawerToggle);
        actionBarDrawerToggle.syncState();

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    }
}

Edit: Adding Activity Main Code

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:id="@+id/drawer_layout"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.google.android.material.navigation.NavigationView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:menu="@menu/navigation_menu"/>

</androidx.drawerlayout.widget.DrawerLayout>

Upvotes: 0

Views: 214

Answers (2)

Reqedd
Reqedd

Reputation: 123

Error found; I had forgotten to change the layout.activity_main toactivity_dashboard after creating new file to hold the Drawer Layout

Upvotes: 1

Bhavnik
Bhavnik

Reputation: 2048

I can't see any import statment of the resource file (i.e R.layout.file_name). It seems like you are importing your layout file from the wrong directory. It should be from com.example.appdev2finalproject.R. Put this import statement and your code should work fine then.

Upvotes: 1

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