Android show camera capture on screen before getting a peer connection

Question

I am using appRTC to make video calls, but there is a time when the screen is black before connecting to the server, instead I would like to show the camera capture on the screen while waiting :

VideoCapturer videoCapturer = createVideoCapturer();
//what to do here before creating a peer connection
peerConnectionClient.createPeerConnection(rootEglBase.getEglBaseContext(), localProxyRenderer, remoteRenderers, videoCapturer, signalingParameters);

thank you