Need help figuring out why App keeps stopping when I click "Settings" Button

Question

I receive the following error in Android Studio "Android Monitor"

There's a lot of mumbo-jumbo but it's essentially saying the cause of the error is the following:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual  method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a  null object reference
                                                                                 at com.example.robthoms.photopop.SettingsActivity.onCreate(SettingsActivity.java:28)

I'm trying to make Settings work on the Toolbar and I got the code from:

https://www.androidhive.info/2017/07/android-implementing-preferences-settings-screen/

If you click on this link you'll see the entire code for SettingsActivity.java that I'm trying to use but when I click on "settings" in toolbar, App closes.

What is wrong with SettingsActivity that the app closes?

My AndroidManifest.xml:

My styles.xml

Hides ActionBar in classes while styles.xml has Light.DarkActionBar

    ActionBar bar  = getSupportActionBar () ;
    if       (bar != null) bar.hide () ;

Answer 1

The problem is caused because your activity do not have any ActionBar. In android manifest, make sure your activity is using the theme which has an ActionBar. Make sure it doesn't have something like NoActionBar. If your activity is not using any theme, check your AppTheme in styles.xml.

One possible solution would be to use this in the manifest:

<activity
    android:name=".SettingsActivity"
    android:theme="@style/Theme.AppCompat.Light" />

Another way:

Add new style in styles.xml:

<style name="AppTheme.ActionBar" parent="AppTheme">
    <item name="windowActionBar">true</item>
    <item name="windowNoTitle">false</item>
</style>

And use new style in the manifest:

<activity
    android:name=".SettingsActivity"
    android:theme="@style/AppTheme.ActionBar" />

Answer 2

Your style theme is noactionbar 1. If you want an actionbar use actionbar containing theme OR 2. You can also make custom view similar to actionbar