How to Handle NumberFormatException in Kotlin EditText for Integer Input

Learn how to prevent `NumberFormatException` when using EditText in Kotlin for integer inputs in your Android app. This guide provides a clear explanation and solution for handling user input effectively.
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This video is based on the question https://stackoverflow.com/q/70486784/ asked by the user 'Teebow' ( https://stackoverflow.com/u/17732594/ ) and on the answer https://stackoverflow.com/a/70486855/ provided by the user 'Jakir Hossain' ( https://stackoverflow.com/u/4854891/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding NumberFormatException in Kotlin EditText

Creating an Android app where users guess numbers can be fun, but it can also lead to unexpected crashes if not handled properly. One common issue developers face is the java.lang.NumberFormatException, often triggered when trying to convert an invalid string input to an integer. This error usually occurs when the input fields are empty. In this guide, we'll address this issue and provide a solution to ensure your app runs smoothly.

The Problem

In your app, you want users to guess two numbers that add up to a random number. However, an error arises on the line where you try to convert the input from EditText to an integer:

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If the EditText fields are empty when this line is executed, the conversion fails and the app crashes, displaying a NumberFormatException. This occurs because there cannot be a conversion from an empty string to an integer.

The Solution

To resolve this issue and prevent the application from crashing, it's important to first check whether the input fields are empty before trying to convert their values. Below is a step-by-step solution that provides a safer approach to handle user input.

Step 1: Get Input as String

Instead of immediately converting the input to an integer, first retrieve the input as a string:

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Step 2: Validate Input

Before proceeding with any calculations, check if the input strings are not empty. You can do this using an if statement within the setOnClickListener for your button:

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Explanation:

isNotEmpty(): This function checks if the string is not empty.

Toast Message: If either field is empty, a message prompts the user to fill in both fields.

Step 3: Complete the Logic

Make sure that your checkNumbers function operates correctly with the integers that will be passed after the validation. You can keep the rest of your logic the same, ensuring that you are now safely working with validated integers.

Full Example Code

Here’s how your main activity might look after implementing the changes:

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Conclusion

By validating the input from EditText fields before converting to integers, you can avoid the dreaded NumberFormatException and create a much smoother user experience in your app. Remember, always ensure your app can handle unexpected inputs gracefully. With these changes, you're on your way to creating a more robust Android application!

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