Solve the Issue of Fetching JSON Responses in Flutter on Button Press

Learn how to properly handle fetching JSON responses in Flutter when a button is pressed. Discover the effective solution for managing state and ensuring accurate user input handling in your app.
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Handling JSON Response in Flutter on Button Press

When developing applications in Flutter, one common feature needed is fetching and displaying data from APIs, typically in JSON format. However, developers often encounter challenges, particularly when trying to ensure that the appropriate data is fetched after a user interacts with UI elements, such as pressing a button. One such issue was presented regarding the use of TextField for user input and how to fetch the corresponding JSON data correctly based on that input.

Understanding the Problem

In the given scenario, the developer encountered the issue where the JSON response function (fetchBalance()) was being executed prematurely—before the user had a chance to input their desired value into the TextField. This led to runtime exceptions, making it clear that the program was trying to fetch data based on an empty input.

The Solution

To address the problem, the solution involves a few key modifications to the existing code. Here’s a breakdown of how to effectively implement a fix:

1. Remove initState()

In the context of this problem, the initState() method, which initializes the Future for fetching balance, was causing the function to execute independently of the button press event. Removing or refactoring it to allow user input on demand can help.

2. Use setState() to Handle Button Press

Instead of initiating the fetch on the app’s start, you can invoke it within the button press event. By doing this, we ensure that the API function is called after the user has entered their data.

Here’s how the onPressed method should look:

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

3. Updating the UI with User Input

4. Complete Code Review

It's also critical to ensure other components of the code handle async responses correctly. By using a FutureBuilder, the framework takes care of managing the state while waiting for the fetch operation to complete, while also handling any potential errors effectively.

Here is how the complete structure would fit together:

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

Make sure your Balance model is correctly set up to process the data returned from your API.

Conclusion

Managing user input and fetching data from APIs in Flutter can often seem challenging, especially when coordinating user actions with asynchronous methods. By removing unnecessary initializations and carefully invoking state updates through UI interactions, you can streamline your app’s workflow and enhance user experience. Implement these changes to ensure that your app effectively receives and utilizes JSON responses only after user action.