Problema com Tela que não aparece

package Telas;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FormAttachment;
import org.eclipse.swt.layout.FormData;
import org.eclipse.swt.layout.FormLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Text;

import com.cloudgarden.resource.SWTResourceManager;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;


public class Observacoes extends Composite {
	private Label LabelNaoVenda;
	private Button bt_Salvar;
	private Text ed_Obs;
	private Button bt_Cancelar;

	{
		//Register as a resource user - SWTResourceManager will
		//handle the obtaining and disposing of resources
		SWTResourceManager.registerResourceUser(this);
	}

	public Observacoes(Composite parent, int style) {
		super(parent, style);
		initialize();
	}

	private void initialize() {
		FormLayout thisLayout = new FormLayout();
		this.setLayout(thisLayout);
		{
			ed_Obs = new Text(this, SWT.MULTI | SWT.WRAP);
			ed_Obs.setText("Observações");
			FormData ed_ObsLData = new FormData();
			ed_ObsLData.width = 202;
			ed_ObsLData.height = 191;
			ed_ObsLData.left =  new FormAttachment(0, 1000, 5);
			ed_ObsLData.top =  new FormAttachment(0, 1000, 33);
			ed_Obs.setLayoutData(ed_ObsLData);
		}
		{
			bt_Cancelar = new Button(this, SWT.PUSH | SWT.CENTER);
			bt_Cancelar.setText("Voltar");
			FormData bt_CancelarLData = new FormData();
             bt_Cancelar.addListener(SWT.MouseUp, new Listener(){

                public void handleEvent(Event arg0) {
                    Principal.trocarTela(Principal.CADASTROPEDIDOS);
                }

            });
			bt_CancelarLData.width = 84;
			bt_CancelarLData.height = 27;
			bt_CancelarLData.left =  new FormAttachment(0, 1000, 16);
			bt_CancelarLData.top =  new FormAttachment(0, 1000, 230);
			bt_Cancelar.setLayoutData(bt_CancelarLData);
			bt_Cancelar.setImage(SWTResourceManager.getImage("Telas/Imagens/Voltar.png"));
		}
		{
			bt_Salvar = new Button(this, SWT.PUSH | SWT.CENTER);
			bt_Salvar.setText("Salvar");
			FormData bt_SalvarLData = new FormData();
			bt_SalvarLData.width = 88;
			bt_SalvarLData.height = 27;
			bt_SalvarLData.left =  new FormAttachment(0, 1000, 106);
			bt_SalvarLData.top =  new FormAttachment(0, 1000, 230);
			bt_Salvar.setLayoutData(bt_SalvarLData);
			bt_Salvar.setImage(SWTResourceManager.getImage("Telas/Imagens/Salvar.png"));
		}
		{
			LabelNaoVenda = new Label(this, SWT.NONE);
			LabelNaoVenda.setText("Observações do Pedido");
			FormData LabelNaoVendaLData = new FormData();
			LabelNaoVendaLData.width = 208;
			LabelNaoVendaLData.height = 15;
			LabelNaoVendaLData.left =  new FormAttachment(0, 1000, 5);
			LabelNaoVendaLData.top =  new FormAttachment(0, 1000, 6);
			LabelNaoVenda.setLayoutData(LabelNaoVendaLData);
			LabelNaoVenda.setFont(SWTResourceManager.getFont("Segoe UI", 10, 1, false, false));
			LabelNaoVenda.setBackground(SWTResourceManager.getColor(64, 0, 128));
			LabelNaoVenda.setForeground(SWTResourceManager.getColor(255, 255, 255));
			LabelNaoVenda.setAlignment(SWT.CENTER);
		}
        pack();
		this.setSize(225, 277);
	}

}