English 中文

Qt for HarmonyOS Theme Setting API Documentation

Qt provides a set of APIs on the HarmonyOS (OHOS) platform to control and detect the application's theme mode (Light / Dark / Follow System).

1. API Documentation

1.1 Query Current Theme Status

bool QOhosAppContext::darkThemeActive() const

Used to determine whether the Qt application is currently in dark theme mode.

Return Value	Description
true	Dark theme is currently active
false	Light theme is currently active

1.2 Theme Switch Notification

void QOhosAppContext::darkThemeActiveChanged(bool darkThemeActive)

A signal emitted when the theme of the Qt application is switched.

Parameter	Description
darkThemeActive	true indicates switching to dark theme, false indicates switching to light theme

Applications can connect to this signal to update the UI style when the theme switches.

1.3 Set Application Theme Mode

void QOhosAppContext::setColorThemeMode(ColorThemeMode mode)

Used to set the theme mode of the Qt application.

ColorThemeMode Enumeration Values

Enumeration Value	Description
LightTheme	Light theme (default theme for Qt applications)
DarkTheme	Dark theme
FollowSystemSetting	Follow the system theme settings; the Qt application switches synchronously when the system theme changes

2. Usage Example

The following example demonstrates how to set the theme mode to "Follow System" in a Qt application and receive notifications when the theme changes:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QWidget window;

    auto *appContext = QtOhosExtras::QOhosAppContext::instance();
    appContext->setColorThemeMode(
        QtOhosExtras::QOhosAppContext::ColorThemeMode::FollowSystemSetting);

    QLabel *label = new QLabel(&window);

    QObject::connect(
        appContext,
        &QtOhosExtras::QOhosAppContext::darkThemeActiveChanged,
        label,
        [label](bool darkThemeActive) {
            // Theme change callback
            // Update UI according to darkThemeActive
        }
    );

    window.show();
    return app.exec();
}

3. Notes

If set to
```
FollowSystemSetting
```
, the application theme will automatically align with the system theme.
The current theme status can be queried at any time via
```
darkThemeActive()
```
.
It is recommended to uniformly update the color configuration of palettes, style sheets, or custom-painted widgets in the theme switch callback.