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A comprehensive guide to using WillPopScope in Flutter apps with go_router to exit your app when the back button is pressed from a subroute.
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This video is based on the question https://stackoverflow.com/q/76763028/ asked by the user 'Safiul islam' ( https://stackoverflow.com/u/10016592/ ) and on the answer https://stackoverflow.com/a/76768160/ provided by the user 'Vivek Chib' ( https://stackoverflow.com/u/21590733/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Exit Your Flutter App on Back Button Press from a Subroute

Navigating through various screens is a common necessity in app development. Often, you may want to give users the ability to exit your app when they are deep within a navigation flow – for example, when they press the back button from a subroute. In this guide, we’ll explore how to achieve this in a Flutter application using the go_router package.

The Problem

Imagine you have an app with multiple routes, such as /, /a, /b, and specific subroutes like /a/1. When a user is on the /a/1 route, you'd like them to exit the app completely when they press the back button, instead of just moving back to /a. This can improve user experience by preventing them from navigating through unnecessary routes before exiting. So, how do you implement this behavior?

The Solution

To exit your Flutter app on back button press from a specific subroute, you can leverage the WillPopScope widget. This widget allows you to intercept the back button action and execute custom logic. Here’s how to do it step by step:

Step 1: Wrap Your Page with WillPopScope

The first step is to wrap your Scaffold with the WillPopScope widget. This widget provides an onWillPop callback which you can use to define what should happen when the back button is pressed.

Example Code

Here is an example of how to implement WillPopScope in your page:

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

Step 2: Handling the onWillPop Callback

In the onWillPop callback, you will invoke the SystemNavigator.pop method from the SystemChannels. This method effectively tells the operating system to close the app. Here’s how the callback works:

await SystemChannels.platform.invokeMethod('SystemNavigator.pop');: This line makes the call to close the app.

return false;: Returning false indicates that you don’t want to pop the current route. Instead, the app will exit.

Why Use WillPopScope?

Using WillPopScope not only enhances your app but also provides a clean way to manage the back navigation. Following are a few advantages of using this widget:

Control Over Navigation: It gives you fine control over the navigation flow.

Consistency Across Platforms: It ensures uniform behavior for back navigation across both Android and iOS platforms.

Custom Logic: You can easily implement additional logic before exiting, such as showing confirmation dialogs or logging events.

Conclusion

By utilizing the WillPopScope widget in your Flutter application, you can easily manage the back button press behavior to ensure your app exits when required. This not only enhances user experience but also simplifies navigation flow. Next time you find yourself needing to exit to the home screen from a subroute, remember this simple technique! Happy coding!