Скачать или смотреть Solving the Illegal State Exception in Your Kotlin Application

Learn how to fix the `Illegal State Exception` in your Kotlin app when handling button clicks and random word generation. This guide will help you understand array indexing and improve code robustness.
---
This video is based on the question https://stackoverflow.com/q/65829845/ asked by the user 'salih suat kükrer' ( https://stackoverflow.com/u/14221638/ ) and on the answer https://stackoverflow.com/a/65829978/ provided by the user 'a_local_nobody' ( https://stackoverflow.com/u/4729721/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Illegal state exception OnClick Method

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding the Illegal State Exception in Kotlin Applications

As a newcomer to Kotlin, you may encounter several common errors while developing your applications. One such error is the Illegal State Exception, particularly when handling button clicks for generating random words. If you're designing a game similar to Taboo with text views representing main and forbidden words, you might face unexpected crashes.

In this guide, we will discuss the typical error you might encounter, explain why it happens, and guide you through the correct approach to avoid such issues.

The Problem: Illegal State Exception

After successfully coding your application to display random words upon button clicks, you might start receiving an Illegal State Exception. The error could manifest as follows:

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

This error indicates that your code tried to access an index in a list that's out of bounds, leading to a crash.

Understanding the Code

Your Current Setup

Let's review the vital parts of your code:

Variable Definitions:

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

Initializing Views:

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

Random Word Generation Logic:

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

Identifying the Issue

The critical flaw lies in the random word generation line:

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

Here, tabooList.size returns the total count of items in the list. Since arrays and lists are zero-indexed, the last valid index is actually size - 1. If your list has three items, valid indices are 0, 1, and 2. However, calling (0..tabooList.size) creates a range that includes one extra number (the size itself), potentially causing an IndexOutOfBoundsException.

The Solution: Adjusting the Random Selection

To resolve this error, you need to change your random selection logic. Here’s how to do it:

Updated Code

Modify your randomWord method to properly account for zero-based indexing:

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

Explanation of Changes

Using until: The until function creates a range from 0 to size - 1, ensuring that your random number will always fall within the valid index range for the array.

Robustness Checking: Consider adding checks to ensure tabooList is not empty before attempting to access its elements, preventing potential runtime errors in edge cases.

Conclusion

Handling exceptions can be tricky, especially when managing collections in Kotlin. By correctly understanding how to index arrays and lists, you can easily avoid common pitfalls that lead to Illegal State Exceptions. Always remember the importance of robust condition checking to make your code resilient.

With the provided solution, your Kotlin application should function smoothly without unexpectedly crashing during button clicks. Happy coding!