Android : Jitsi_Android can't receive FileTransfer event

I want to implement filetransfer in jitsi_android,I use OperationSetFileTransfer.class to implement it. This my code:

OperationSetFileTransfer ftOpSet = protoContact
                    .getProtocolProvider().getOperationSet(
                            OperationSetFileTransfer.class);

            if (ftOpSet != null) {
                ftOpSet.addFileTransferListener(new FileTransferListener() {

                    @Override
                    public void fileTransferRequestRejected(FileTransferRequestEvent event) {
                        Log.e(TAG, "file rejected");
                    }

                    @Override
                    public void fileTransferRequestReceived(FileTransferRequestEvent event) {
                        Log.e(TAG, "file received");
                    }

                    @Override
                    public void fileTransferRequestCanceled(FileTransferRequestEvent event) {
                        Log.e(TAG, "file canceled");
                    }

                    @Override
                    public void fileTransferCreated(FileTransferCreatedEvent event) {
                        Log.e(TAG, "file create");
                    }
                });
            }else{
                Log.d(TAG, "ftOpSet is null");
            }

As a result i can't receive any event but FileTransferCreatedEvent event.Is there something wrong?