def _set_screen_brightness(self, br: float) -> None:
        """br is the desired screen brightness, a value in the [0, 1] interval.
        A negative value, e.g. -1.0, means a "reset" back to the system preferred value.
        """
        if not self.isAndroid():
            return
        from android.runnable import run_on_ui_thread

        @run_on_ui_thread
        def set_br():
            window = jpythonActivity.getWindow()
            attrs = window.getAttributes()
            attrs.screenBrightness = br
            window.setAttributes(attrs)
        set_br()
br is the desired screen brightness, a value in the [0, 1] interval.
        A negative value, e.g. -1.0, means a "reset" back to the system preferred value.
        
electrum/gui/qml/qeapp.py