# addRetained method

EngineLayer addRetained (EngineLayer retainedLayer)

Add a retained engine layer subtree from previous frames.

All the engine layers that are in the subtree of the retained layer will be automatically appended to the current engine layer tree.

Therefore, when implementing a subclass of the `Layer` concept defined in the rendering layer of Flutter's framework, once this is called, there's no need to call `addToScene` for its children layers.

## Implementation

    EngineLayer addRetained(EngineLayer retainedLayer) native 'SceneBuilder_addRetained';