Android Error : Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.hide()' on a null object reference

Question

So I'm writing code for turning a website into it's web view app, it's working fine when Dark Mode is switched on & is crashing when it's off, however, I haven't written any piece of code keeping those modes in my mind.

I'm getting the following error:

2021-01-22 11:51:40.868 7271-7271/com.shopitapp.shopit E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.shopitapp.shopit, PID: 7271
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.shopitapp.shopit/com.shopitapp.shopit.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.hide()' 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.appcompat.app.ActionBar.hide()' on a null object reference
        at com.shopitapp.shopit.MainActivity.onCreate(MainActivity.java:23)
        at android.app.Activity.performCreate(Activity.java:8000)
        at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
        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) 
2021-01-22 11:51:40.926 7271-7271/com.shopitapp.shopit I/Process: Sending signal. PID: 7271 SIG: 9

MainActivity.java

package com.shopitapp.shopit;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.KeyEvent;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class MainActivity extends AppCompatActivity {

    WebView web;


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



        getActionBar().hide();
        web = findViewById(R.id.webView);
        WebSettings webSettings = web.getSettings();
        webSettings.setJavaScriptEnabled(true);

        web.setWebViewClient(new Callback());
        web.loadUrl("https://shopit.app/");
    }

    private class Callback extends WebViewClient {
        @Override
        public boolean shouldOverrideKeyEvent(WebView view, KeyEvent event) {
            return false;
        }
    }

    /*@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(event.getAction()==KeyEvent.ACTION_DOWN)
        {
            switch(keyCode) {
                case KeyEvent.KEYCODE_BACK:
                if(web.canGoBack())
                    web.goBack();
                else
                    finish();
            }
        }
        return super.onKeyDown(keyCode, event);
    }*/

    @Override
    public void onBackPressed() {
        if(web.canGoBack())
            web.goBack();
        else
        super.onBackPressed();
    }
}

SplashScreen.java

package com.shopitapp.shopit;

import android.content.Intent;
import android.os.Bundle;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

public class SplashScreen extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        /*Bitmap bitmapImage = BitmapFactory.decodeFile("src\main\res\drawable\logo.png");
        int nh = (int) ( bitmapImage.getHeight() * (512.0 / bitmapImage.getWidth()) );
        Bitmap scaled = Bitmap.createScaledBitmap(bitmapImage, 512, nh, true);
        ImageView your_imageview = null;
        your_imageview.setImageBitmap(scaled);*/

        startActivity(new Intent(this,MainActivity.class));
        finish();
    }

}

Android Manifest:


<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.shopitapp.shopit">

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:networkSecurityConfig="@xml/network_security_config"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.Shopit">
        <activity android:name="com.shopitapp.shopit.SplashScreen"
            android:theme="@style/SplashScreen">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity android:name="com.shopitapp.shopit.MainActivity"
            android:theme="@style/Theme.Shopit"></activity>
    </application>

</manifest>

themes.xml

<resources xmlns:tools="http://schemas.android.com/tools">
    <!-- Base application theme. -->
    <style name="Theme.Shopit" parent="Theme.MaterialComponents.DayNight.NoActionBar">
        <!-- Primary brand color. -->
        <item name="colorPrimary">@color/purple_500</item>
        <item name="colorPrimaryVariant">@color/purple_700</item>
        <item name="colorOnPrimary">@color/white</item>
        <!-- Secondary brand color. -->
        <item name="colorSecondary">@color/teal_200</item>
        <item name="colorSecondaryVariant">@color/teal_700</item>
        <item name="colorOnSecondary">@color/black</item>
        <!-- Status bar color. -->
        <item name="android:statusBarColor" tools:targetApi="l">?attr/colorPrimaryVariant</item>
        <!-- Customize your theme here. -->
    </style>
    
    <style name="SplashScreen" parent="Theme.AppCompat.Light.NoActionBar">
        <item name="android:windowBackground">@drawable/background_splashscreen</item>
    </style>
</resources>

themes.xml(night)


<resources xmlns:tools="http://schemas.android.com/tools">
    <!-- Base application theme. -->
    <style name="Theme.Shopit" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
        <!-- Primary brand color. -->
        <item name="colorPrimary">@color/purple_200</item>
        <item name="colorPrimaryVariant">@color/purple_700</item>
        <item name="colorOnPrimary">@color/black</item>
        <!-- Secondary brand color. -->
        <item name="colorSecondary">@color/teal_200</item>
        <item name="colorSecondaryVariant">@color/teal_200</item>
        <item name="colorOnSecondary">@color/black</item>
        <!-- Status bar color. -->
        <item name="android:statusBarColor" tools:targetApi="l">?attr/colorPrimaryVariant</item>
        <!-- Customize your theme here. -->
    </style>
</resources>

please include all relevant code here, not on an off-site resource — a_local_nobody, Jan 22 '21 at 07:33
also, android studio is just an IDE, it just helps you to code, so unless you're asking about a feature of the IDE specifically, there's no need to include the tag — a_local_nobody, Jan 22 '21 at 07:34
@a_local_nobody Can you please check now? I've done as you said. — Nilargha Roy, Jan 22 '21 at 07:40
`getActionBar().hide();` this is the code which is causing your crash. you have to check if `getActionBar` isn't null before using it. why it's null probably has to do with your themes, you're using `NoActionBar` and `DarkActionBar` — a_local_nobody, Jan 22 '21 at 07:42

score 1 · Accepted Answer · answered Jan 22 '21 at 10:35

On your MainActivity you are trying to hide the Action Bar by using the code getActionBar().hide,

But the problem is your MainActivity doesn't have an Action Bar because your Main Activity is using the Theme called Theme.Shopit which removes the Action Bar by default because its parent is Theme.MaterialComponents.DayNight.NoActionBar.

So to fix this issue you can simply remove the code getActionBar().hide from your MainActivity.

Android Error : Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.hide()' on a null object reference

1 Answers1