One-click theme packs come to Android with Google’s new Theme Manager

Pixel phones haven’t traditionally been known for offering extensive customization options, but that perception is changing as Google adds new home and lock screen customization features in the latest version of Android. The introduction of Material 3 Expressive in the first quarterly release of Android 16 significantly overhauled the look and feel of Android on Pixel phones, bringing a new and more dynamic experience across the board.

Still, Pixel phones lag behind some of their competitors in terms of ease of customization. While many competing devices let you completely change the look of the UI with custom themes with just one click, Pixel phones lack this convenience, requiring you to manually configure the home and lock screens to achieve the look you want.

Fortunately, this could change in the near future. Back in May, we revealed that Google was working on theme packs to help you personalize your Pixel phone. We discovered a new “Themes” entry in the “Wallpaper & Style” app on Pixel phones, and while it wasn’t functional, its description provided crucial information. Our discovery confirmed that Google is working on “Pixel Themes” consisting of multiple customization options grouped into packs, but details were scarce at the time.

In recent weeks, however, we’ve learned more about how the Pixel Themes feature works. Specifically, we found evidence in the Android 16 QPR2 betas that Google is developing a new system feature called Theme Manager. This forms the basis of Pixel Themes by improving the way system themes are handled in Android. Here’s how.

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How Google is evolving theme support on Android

Before this year, the last time Google overhauled Android’s UI was in 2021 with the release of Android 12, which introduced the original Material Design 3, also known as Material You. The centerpiece of Material You was “Dynamic Color,” a theme engine that automatically extracts colors from your wallpaper and applies them across the entire user interface, from the quick settings and volume panel to compatible third-party apps.

The process Material You follows to generate a theme can be broken down into three parts:

1. Color extraction. When you apply a wallpaper, Android analyzes it to determine the dominant color. This color is used as a “seed” from which five unique tonal palettes (three accents and two neutrals) are generated. Each of these palettes contains 13 colors of different luminance values.
2. Application of colors. Android then replaces the system color values ​​read by apps with these 65 new colors. It does this by generating runtime resource overlays (RROs), which allow Android to replace resource values ​​on the fly without restarting the device.
3. Storage of preferences. Finally, Android stores the user’s theme preferences. This includes the source of the starting color (the lock screen wallpaper, home screen wallpaper, or a preset), the theme style (what variation of the dynamic color algorithm was used), and the time the theme was applied.

While this process works on the surface, Google seems to believe that the way Android currently stores user theme preferences is outdated. Currently, the user’s entire theme configuration is stored as a raw block of JSON in the file THEME_CUSTOMIZATION_OVERLAY_PACKAGES secure environment. Every time the system needs to change themes (for example, when the user changes their wallpaper), it must read the entire block of text, change only the relevant parts, and then rewrite it.

The problem with this approach is that it is fragile. If a change corrupts the text block, it could cause the theme to break or, even worse, SystemUI to crash. Additionally, the lack of a central authority managing theme changes can lead to conflicts when multiple applications attempt to make changes simultaneously. Although only privileged applications can access and modify the configuration, the WRITE_SECURE_SETTINGS the permission they need is too broad, giving access to more than just setting up the theme. As Google expands Android’s theme options and introduces more apps capable of changing the system’s theme, it has become necessary to modernize the theme architecture.

This is likely why Google created the new Theme Manager API, a complete architectural overhaul of Android’s theme system. It addresses many of the aforementioned issues by moving toward a formalized, service-oriented architecture. Instead of manipulating the raw theme configuration text, applications now pass a structured object to the Theme Manager, which acts as a central gatekeeper, validating, storing, and applying the theme.

Under this new system, only applications with the UPDATE_THEME_SETTINGS permission can change the system theme. This permission is limited to applications signed with the platform certificate, making it both less accessible and less broad than the previous permission.

So what does Theme Manager mean for Pixel themes? It comes down to how the new API makes it easier to manage pre-built themes. While the old system focused on dynamically extracting colors from user-provided wallpapers, the new system expands on this by making it easier for apps to provide predefined theme settings, i.e. theme packs. Google’s new personalization app, for example, can use the new ThemeSettingsPreset class to send explicit system and accent colors defined by a theme pack.

While Pixel theme packs will likely encompass more than preset wallpapers and colors, the new Theme Manager API is a crucial part of Google’s efforts to expand theme support on Android. We can’t wait to see what Google designers create for Pixel users, and hopefully we won’t have to wait too long to try them out. Since the Theme Manager API is not public, there is nothing stopping Google from offering Pixel themes in Android 16 QPR2, which will be released months before next year’s Android 17 update.

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