private void initAssetManager() {
        URL assetCfgUrl = null;

        if (settings != null) {
            String assetCfg = settings.getString("AssetConfigURL");
            if (assetCfg != null) {
                try {
                    assetCfgUrl = new URL(assetCfg);
                } catch (MalformedURLException ex) {
                    //do nothing, we check assetCfgUrl
                }
                if (assetCfgUrl == null) {
                    assetCfgUrl = Resources.getResource(assetCfg);
                    if (assetCfgUrl == null) {
                        logger.log(
                            Level.SEVERE,
                            "Unable to access AssetConfigURL in asset config:{0}",
                            assetCfg
                        );
                        return;
                    }
                }
            }
        }
        if (assetCfgUrl == null) {
            assetCfgUrl = JmeSystem.getPlatformAssetConfigURL();
        }
        if (assetManager == null) {
            assetManager = JmeSystem.newAssetManager(assetCfgUrl);
        }
    }
Enable or disable pause on lost focus.
<p>
By default, pause on lost focus is enabled.
If enabled, the application will stop updating
when it loses focus or becomes inactive (e.g. alt-tab).
For online or real-time applications, this might be undesirable,
so this feature should be disabled. For other applications,
it is best to keep it enabled so the CPU is not used unnecessarily.

@param pauseOnLostFocus True to enable pause on lost focus, false
otherwise.

@see #setLostFocusBehavior(com.jme3.app.LostFocusBehavior)
jme3-core/src/main/java/com/jme3/app/LegacyApplication.java