HMCL-dev/HMCL · error · IOException

Installed theme pack does not contain theme:

Error message

Installed theme pack does not contain theme: 

What it means

The two-argument apply(ThemePack, Theme) convenience re-installs the pack file and then looks up the requested theme id in the freshly installed manifest. If findTheme(theme.id()) returns null, the installed pack does not contain that theme and this IOException is thrown with the theme id.

Solutions

1. Obtain the Theme object from installedThemePack.manifest().findTheme(id) of the same pack you are applying, rather than reusing a stale Theme instance.
2. Check themePack.manifest().findTheme(theme.id()) != null before calling apply.
3. Update stored theme references after the pack file changes, since ids may be renamed between versions.

Example fix

// before
ThemePackManager.apply(packFile, staleTheme);
// after
InstalledThemePack installed = ThemePackManager.install(packFile);
Theme theme = installed.manifest().findTheme("my-theme");
if (theme != null) ThemePackManager.apply(installed, theme);

InstalledThemePack installed = ThemePackManager.install(pack.file());
Theme theme = installed.manifest().findTheme(themeId);
if (theme == null) throw new IllegalArgumentException("theme " + themeId + " not in pack");
ThemePackManager.apply(installed, theme);

try {
    ThemePackManager.apply(packFile, theme);
} catch (IOException e) {
    if (e.getMessage().startsWith("Installed theme pack does not contain theme")) {
    // refresh the Theme reference from the pack's current manifest
    }
}

When it happens

Trigger: Calling apply(themePack, theme) with a Theme whose id does not exist in themePack's manifest — typically because the Theme object came from a different pack or an older/cached manifest than the file being installed.

Common situations: Applying a theme that was removed or renamed in an updated version of the pack; mixing Theme instances across packs; caching Theme references across an uninstall/reinstall of a different pack version.

Understand the failure class

Background: "Not found" and "does not exist" errors: why "Task not found", "No such folder", and "Can't find" fire when a lookup comes back empty — this error's family across 14 libraries.

Related errors

• Theme-pack asset entry is empty
• Theme-pack asset entry must be relative:
• Theme-pack asset entry must be under assets/:
• Theme-pack asset entry must be a file:
• Theme-pack asset entry contains an unsafe segment:

AI-assisted analysis of HMCL-dev/HMCL@24702dc5a0 (2026-09-10). Data as JSON: /api/errors/94aedba53c68e6b5. Report an issue: GitHub.

Appendix: source

Thrown at HMCL/src/main/java/org/jackhuang/hmcl/theme/ThemePackManager.java:582

            if (replacementTheme == null) {
                settings().selectedThemeProperty().set(BUILTIN_DEFAULT_THEME_REFERENCE);
            }
        }
    }

    /// Applies one theme from a loaded theme pack to current launcher settings.
    ///
    /// @param themePack the loaded theme pack
    /// @param theme     the theme to apply
    /// @throws IOException if the pack cannot be installed, referenced assets cannot be read, or settings cannot be applied
    public static void apply(LoadedThemePack themePack, Theme theme) throws IOException {
        Objects.requireNonNull(themePack);
        Objects.requireNonNull(theme);

        InstalledThemePack installedThemePack = install(themePack.file());
        @Nullable Theme installedTheme = installedThemePack.manifest().findTheme(theme.id());
        if (installedTheme == null) {
            throw new IOException("Installed theme pack does not contain theme: " + theme.id());
        }
        apply(installedThemePack, installedTheme);
    }

    /// Applies one theme from an installed theme pack to current launcher settings.
    ///
    /// @param themePack the installed theme pack
    /// @param theme     the theme to apply
    /// @throws IOException if referenced assets cannot be read or settings cannot be applied
    public static void apply(InstalledThemePack themePack, Theme theme) throws IOException {
        Objects.requireNonNull(themePack);
        Objects.requireNonNull(theme);

        apply(themePack.manifest(), theme);
    }

    /// Applies one theme to current launcher settings.
    ///

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