Скачать или смотреть Resolving the FormatException Error in Flutter: A Step-By-Step Guide

Learn how to troubleshoot and fix the `FormatException` error in Flutter when performing HTTP delete operations. Follow our guide for effective solutions and tips.
---
This video is based on the question https://stackoverflow.com/q/74978503/ asked by the user 'Ali Mustadji' ( https://stackoverflow.com/u/20891998/ ) and on the answer https://stackoverflow.com/a/74979837/ provided by the user 'GrahamD' ( https://stackoverflow.com/u/10376604/ ) 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: Exception has occurred. FormatException (FormatException: Unexpected character (at character 1) !DOCTYPE html ^ )

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.
---
Resolving the FormatException Error in Flutter

When developing applications with Flutter, developers often encounter various exceptions, one of which is the FormatException. This particular error can be frustrating as it interrupts the normal flow of your application. If you've ever seen the error message:

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

then you're in the right place.

In this guide, we'll discuss the causes of this error and provide a step-by-step solution to fix it in your Flutter application.

Understanding the Problem

The FormatException typically occurs when you're trying to decode a response that is not in the expected format. Specifically, when using the json.decode() function, it expects a JSON string, but if the response is HTML (like an error page), you'll encounter the FormatException.

Common Causes of FormatException

Incorrect URL Format: If your endpoint URL is wrongly formatted (missing slashes or equal signs), it may lead to incorrect responses.

HTTP Status Codes: Not checking the HTTP status code before processing the response can also lead to errors.

Network Issues: Sometimes, network issues can cause unexpected responses that lead to format exceptions.

Step-by-Step Solution

Here’s how to troubleshoot and fix the issue in your code.

Step 1: Check the URL

Ensure that your URL is correctly formatted. In your case, make sure that the productId is appended correctly. The URL should have a structure like this:

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

Notice the added closing slash after products. This is crucial for concatenating the productId properly.

Step 2: Check HTTP Response Status

Before decoding the response, always check the HTTP status code. This will help you determine if the request was successful (HTTP 200) or if there was an error.

Here’s how you can implement the check:

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

Step 3: Handle Unexpected Responses

Ensure that you have appropriate error handling in place. If the server responds with an unexpected format (e.g., HTML for an error page), you can log this or show a friendly error message to the user.

Summary

When facing the FormatException, remember to check the URL formatting, validate the HTTP response status, and implement robust error handling. These steps will help you maintain the integrity of your application and enhance user experience.

By following the above guide, you should be able to resolve the FormatException in your Flutter application successfully.

If you have any further questions or need additional assistance, feel free to reach out!