Скачать или смотреть Resolving NullPointerException and IllegalStateException Issues in Android's Directions API

Learn how to effectively handle exceptions in your Android app when using Google Directions API, ensuring a smooth user experience and robust functionality.
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This video is based on the question https://stackoverflow.com/q/66891838/ asked by the user 'p0var' ( https://stackoverflow.com/u/15523899/ ) and on the answer https://stackoverflow.com/a/66892371/ provided by the user 'Tiago Oliveira' ( https://stackoverflow.com/u/5467727/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving NullPointerException and IllegalStateException Issues in Android's Directions API

When developing Android applications that utilize the Google Directions API, developers may encounter unexpected exceptions like NullPointerException or IllegalStateException. A user recently faced such issues while attempting to create and overlay routes between two geographical points, and found that the errors appeared only under normal operating conditions, but not in debug mode. In this guide, we'll break down the problem and explore a robust solution to ensure your application functions correctly in all scenarios.

Understanding the Problem

The user’s code triggers exceptions when executing the TravelCost method, which requests directions. The exceptions reported in the logs suggest issues with the click logic in the XML layout and the handling of asynchronous network calls.

Key Exceptions Identified:

NullPointerException: Occurs when the app attempts to access or modify an object that hasn't been initialized.

IllegalStateException: Can arise when the program's state does not meet certain conditions squarely; in this case, it can indicate a missing point in the route.

In particular, the trace related to LatLngBounds.Builder.build() highlights the necessity of ensuring that valid points are included before trying to build the bounds.

Step-by-Step Solution

1. Replace android:onClick with Click Listeners

The use of android:onClick in XML can lead to issues if the method name is changed during compilation (which can happen when proguard is enabled). A preferred approach is to implement click listeners programmatically. You can replace the XML onClick attribute in your layout like this:

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Then, in your activity's onCreate method, set the listener:

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Note: Here, we can simplify the onMapSearch method by removing the View parameter since it is not utilized.

2. Handling Network Calls Outside the Main Thread

Android requires that network requests operate outside the main UI thread to maintain responsiveness. To fix potential android.os.NetworkOnMainThreadException, we recommend delegating network calls to a dedicated Executor. Here’s a simple setup:

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You can then perform the network operation in your TravelCost method like this:

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

3. Ensuring Valid Route Check

When building your route with LatLngBounds.Builder, ensure you handle situations in which routes could be empty. Always check the available routes after the API callback returns:

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

Conclusion

Handling exceptions effectively while using the Google Directions API improves both the stability and user experience of your Android applications. By switching to click listeners, ensuring asynchronous execution of network requests, and robustly checking for available routes, you can mitigate the risks of NullPointerException and IllegalStateException. Following these guidelines will help you create a more resilient application capable of navigating the complexities of location-based services.

If you found this article helpful or have additional questions, feel free to leave a comment below!