Скачать или смотреть Resolving the Recycler must not be null Error in Kotlin for Android Apps

Learn how to fix the `recycler must not be null` error in Kotlin Android applications when dealing with empty lists using best practices and troubleshooting tips.
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This video is based on the question https://stackoverflow.com/q/66013249/ asked by the user 'mafortis' ( https://stackoverflow.com/u/8490993/ ) and on the answer https://stackoverflow.com/a/66013457/ provided by the user 'sasikumar' ( https://stackoverflow.com/u/3710865/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Recycler must not be null Error in Kotlin

If you're developing an Android application using Kotlin, chances are you'll implement a RecyclerView to display your lists. However, you might encounter the frustrating Recycler must not be null error, especially when your RecyclerView is empty, like when displaying previous orders for new users. This guide will dive into the causes of this error, typical scenarios leading to it, and how to fix it effectively.

What Causes the Error?

This error primarily arises when the RecyclerView has not been properly initialized or when you attempt to access it before it's available. Here are two common reasons you might run into this issue:

Incorrect Visibility Handling: If the visibility of your RecyclerView is set incorrectly, it might prompt the app to think the view is null when it's not explicitly made visible.

Improper RecyclerView ID Access: If the ID used to reference the RecyclerView does not match the ID specified in your XML layout, your code won't find the view, leading to potential null references.

Let's Fix This Step-by-Step

Step 1: Verify Your Fragment Layout

Let's start by checking your fragment's XML layout to ensure that your RecyclerView and IDs are properly set up. Here's a snippet of what your XML might look like:

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

Make sure the RecyclerView ID is ordersList, as seen above.

Step 2: Initialize the RecyclerView in Your Fragment

Next, revisit the fragment where you are using your RecyclerView. Before accessing it, ensure you are calling findViewById() and initializing it properly. Here’s how you can do this in your onCreateView method:

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

Step 3: Replace recycler with ordersList in Your Logic

In your API call response handler, replace the previous reference to recycler with ordersList. By doing so, you'll ensure that you're referencing the correctly initialized RecyclerView. Your updated code should look something like this:

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

Step 4: Ensure You Have the Required Plugins

Lastly, it’s important to verify you have the necessary plugins in your build.gradle file. Make sure to include the Kotlin Android extensions plugin as shown:

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

This step ensures that you can use synthetic properties for your views in Kotlin, reducing boilerplate code in your fragments.

Conclusion

By following these steps, you should successfully resolve the Recycler must not be null error and improve the handling of empty lists in your application. Always ensure that your views are correctly initialized and that you're using the right IDs to avoid common pitfalls in Android development. Happy coding!