Transitioning to SceneGraph

The following summarizes how to transition from the older Roku API to SceneGraph applications. In general, SceneGraph handles events without requiring you to write custom event loops, and allows you easily add custom event handlers by observing virtually any of the fields used in your SceneGraph application. Also, SceneGraph supplies built-in node classes that are very similar to some BrightScript UI screen components, but also gives you much greater flexibility to build your own custom screens. Because SceneGraph is more dynamic, flexible, and object-oriented than the older Roku API for building UI elements, you cannot write an equivalent SceneGraph application by simply substituting different function names and argument lists for UI elements.

However, much of your existing BrightScript code that handles other aspects of your application can probably be used in the new context of a SceneGraph application. For example, calls to your existing BrightScript functions can be added to any SceneGraph XML component file, by specifying the location of the BrightScript file in the package components directory in the <script> element. For example, if you had a set of functions to manipulate URLs, you could add the following <script> element to allow a SceneGraph component to call the functions:

<script type = "text/brightscript" uri = "pkg:/components/uriutils.brs"/>

If these calls relied on application global data, you would have to set up a global node as described in Data scoping for this data.

There is a simplifying assumption you can make when transitioning an older Roku API application to SceneGraph. In many cases, SceneGraph replaces a series of BrightScript component interface function calls with setting and reading of node class fields of the equivalent parameters. For example, the SetNumPinEntryFields() interface function call for the roPinEntryDialog component is replaced by setting the pinLength field of the internal PinPad node object of a PinDialog node. But note that for many of the older Roku API screen components, you must develop your own custom screen component equivalent from more fundamental SceneGraph node classes. For example, you must develop an equivalent of the roSearchScreen component using the MiniKeyboard node class as the user input basis of a custom SceneGraph search screen component. You must then write additional BrightScript code to replicate the function of the roSearchScreen component.