title: How to add cancel button in PopupPanel in Gwt
body: <p>I am new to programming.</p>
  
  <p>I have vertical panel.A button(lblAddFolderIcon) is added on the verticalPanel and also some widgets.</p>
  
  <p>on click of b1 there should be a popup panel with some more widgets and two button with add and cancel.</p>
  
  <p>My Code:</p>
  
  <pre><code>   lblAddFolderIcon.addClickHandler(new ClickHandler() {
          public void onClick(ClickEvent event) {
              String childFolder = item.getText();
              String[] mainRepository=getPath(item);
              String objectId=item.getTitle();
  
              final AddFolderPopup addFolderPopup = new AddFolderPopup(childFolder,mainRepository[0],objectId);
              addFolderPopup.setHeight("300px");
              addFolderPopup.setWidth("502px");
              addFolderPopup.setPopupPositionAndShow(new PopupPanel.PositionCallback() {
  
                  public void setPosition(int offsetWidth, int offsetHeight) {
                      // TODO Auto-generated method stub
                      int left = (Window.getClientWidth() - offsetWidth) / 3;
                      int top = (Window.getClientHeight() - offsetHeight) / 3;
                      addFolderPopup.setPopupPosition(left, top);
                  }
              });
              //addFolderPopup.show();
              addFolderPopup.addFolderGui();
          }
      });
  </code></pre>
  
  <hr>
  
  <pre><code>    public class AddFolderPopup extends PopupPanel {
  VerticalPanel vpPopupl = new VerticalPanel();
  private String childFolder;
  private String mainRepository;
  private String objectId;
  
  public AddFolderPopup(){
      super(true);
  }
  public AddFolderPopup(String childFolder, String mainRepository, String objectId) {
      this.childFolder = childFolder;
      this.mainRepository = mainRepository;
      this.objectId = objectId;   
  
  }
  public void addFolderGui() {
           // some widget to design Gui and
        Button btnCancel = new Button("Cancel");
      btnCancel.addClickHandler(new ClickHandler() {
          public void onClick(ClickEvent event) {
                                 /* i Dont Know what should i write here 
                                    so that this popupwindow is closed
                                  */
                  }
      });
        }
      }
  </code></pre>
  
  <p>Plz suggest some code to close this popup window and 
  also whether my approach is correct.</p>