Fixing the Null Object Reference Error When Hiding the Action Bar in Your Android App

Solve the `NullPointerException` in your Android app by understanding how themes affect the Action Bar visibility in your application.
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This video is based on the question https://stackoverflow.com/q/65840814/ asked by the user 'Nilargha Roy' ( https://stackoverflow.com/u/11155945/ ) and on the answer https://stackoverflow.com/a/65843513/ provided by the user 'Kidus' ( https://stackoverflow.com/u/10644546/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing the Null Object Reference Error When Hiding the Action Bar in Your Android App

When developing Android applications, you may encounter various errors that can stump even the most seasoned developers. One such common issue is encountering a NullPointerException when trying to manipulate UI elements, such as the Action Bar. In this guide, we’ll dive into a specific error message you might have come across:

[[See Video to Reveal this Text or Code Snippet]]

This error often indicates a misunderstanding of how Android themes and UI components interrelate. Let’s uncover what causes this error, and how you can effectively fix it in your application.

Understanding the Problem

The Error Message

The error message you see:

[[See Video to Reveal this Text or Code Snippet]]

is telling you that your code is attempting to call the hide method on an Action Bar object that is currently null.

The Root Cause

In the provided MainActivity.java, you have the following line in the onCreate method:

[[See Video to Reveal this Text or Code Snippet]]

However, this line is fetching the Action Bar using getActionBar(). The issue is that your app is utilizing a theme that doesn't include an Action Bar:

[[See Video to Reveal this Text or Code Snippet]]

Here, the parent theme Theme.MaterialComponents.DayNight.NoActionBar specifically indicates that there is no Action Bar available, which leads to a null reference when you try to access it in your code.

The Solution

Remove the Action Bar Hiding Code

To resolve this problem, you simply need to remove the line that attempts to hide the Action Bar, as there is none to hide in your current theme.

Here’s how your onCreate() method should look after the fix:

[[See Video to Reveal this Text or Code Snippet]]

Testing the Application

After implementing this change, make sure to test the application in both Light and Dark modes to verify that it is functioning correctly without crashing. If everything is correctly set up, you should no longer face the Null Object Reference error.

Conclusion

Encountering errors like NullPointerException during Android development can be frustrating. However, understanding the relationship between themes and UI elements, such as Action Bars, is critical in resolving such issues. Remember to always check your theme settings and the availability of UI elements before manipulating them in your code.

By following the simple fix of removing the offending line, your application should run smoothly in all modes without the unexpected crashing you experienced.

Happy coding!