Put the layer you want to reveal on the layer below the animation. Use Keylight to pull the chroma key.
Dave, thanks very much for your response; I've done what you recommended, but this reveals all of the layer below, but I want to have the green area act as a mask rather than simply transparent. Perhaps this will help clarify:
There are 3 layers, video layer 1, video layer 2, and 1 SWF animation layer. In the SWF Animation layer, there is a green shape on a transparent background. I want the green shape to be replaced with video layer 2, and I want the transparent background (of that same SWF animation layer) to reveal video layer 1.
Currently, when I pull the chroma key (with key light, by selecting the color of the green shape), this makes the green shape transparent, along with the background, so all I see is video layer 2. I want the green shape to be replaced with video layer 2, and the transparent background of that same layer to display video layer 1. In other words, i want to make an animated mask, but rather than animating a mask path, I want to import the animated mask shape as an SWF from adobe animate. I appreciate your help!
That's simply not how it works. AE cannot generate masks from SWFs nor will it automatically inherit any transform animation from such a file. Your workflow simply makes no sense. You can't avoid having to re-create the rectangle in AE in some form, be that native layer animation or using hacky workarounds like tracking it in AE. If the transform is not relevant, the rectangle could serve as a matte as well, but that may require a separately exported duplicate of the animation with only the rectangle.
Use color correction (levels) to turn your green layer (swf) black.
Put a white solid behind/below it and then pre-compose the two layers to serve as a matte.
Put the pre-comp layer directly above video layer 2 & set VL2s track matte to "Luma Inverted".
Put video layer 1 at the bottom of the stack and you should have what you want.
Assuming i understand you correctly
Also AE can automatically create animated masks (or do it's best to , anyway) from alpha channels using the auto trace feature under Layer Menu.
But a mask is not what you want. You want a matte.
Of course you could just create your animation in black and white to begin with.
Your mistake was thinking you need "green screen". Nope, matte.
Gutter Fish, thank you so much! Your advice resolved my issue. I really appreciate your help!
No problem. As it turns out I made it more complicated than necessary. Since you already had the transparency the pre-comp wasn't necessary. You could have just changed the green to black (or white) and the set the appropriate track matte.