Скачать или смотреть Fixing Unable to Resolve Host Error on Android with Retrofit by Adjusting Battery Settings

Learn how to solve the 'Unable to resolve host' error in Android Retrofit apps, especially on newer devices, by managing battery optimization and power saving modes.
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This video is based on the question https://stackoverflow.com/q/79282505/ asked by the user 'KHY' ( https://stackoverflow.com/u/11493090/ ) and on the answer https://stackoverflow.com/a/79347609/ provided by the user 'KHY' ( https://stackoverflow.com/u/11493090/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

When building Android apps with Retrofit to call APIs, you might encounter the error:

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

This error often arises even if your network connection seems fine, and can be especially puzzling when it occurs on only some devices.



The Problem

A developer noticed this issue on their Samsung S24 Ultra running Android 14, while the same app worked perfectly on emulators and an older Samsung S22 Ultra with the same OS version.

Key observations:

The error occurred after switching from WiFi to mobile data and then even after reconnecting to WiFi.

Changing DNS servers (to 1.1.1.1 or 8.8.8.8), restarting the phone, and reinstalling the app had no effect.



Root Cause: Power Saving Mode Interference

Newer Android devices aggressively optimize battery usage by restricting network access for apps when in power saving mode. This can cause network requests to fail silently, resulting in DNS resolution errors.

The key insight is that power saving mode can block Retrofit from resolving hostnames, leading to "Unable to resolve host" errors.



Solution: Adjust Battery Optimization Settings

To fix this:

Turn off Power Saving Mode:

Go to Settings Battery Power Saving Mode and disable it.

Allow Unrestricted Battery Usage for Your App:

Go to Settings Apps [Your App] Battery

Set Battery optimization to Unrestricted or disable optimization for the app.

This allows your app to maintain network activity without restrictions, resolving the hostname correctly.



Best Practices

Check battery optimization settings when network issues occur only on certain devices.

Test your app with power saving modes enabled and disabled to identify any connectivity issues.

Consider notifying users if network requests might be blocked due to battery optimization.



Summary

If your Android Retrofit API calls fail with "Unable to resolve host" on specific devices, especially newer ones,

Don’t just check network and DNS settings;

Investigate power saving and battery optimization settings;

Grant your app unrestricted battery use to ensure uninterrupted network access.

This straightforward step often resolves the frustrating DNS resolution failures.