GEF了解系列五（2）

二、建立連接配接模型

建立連接配接模型，過程大同小異。此時需要在結點模型上安裝Policy，Policy的類型為：GraphicalNodeEditPolicy。

在HelloWorldEditPart的createEditPolicies()方法裡追加：

installEditPolicy(EditPolicy.GRAPHICAL_NODE_ROLE, new HelloWorldGraphicalNodeEditPolicy());

其中HelloWorldGraphicalNodeEditPolicy是我們的Policy實作類。還是一樣，先完成Command，再回過頭來完成Policy。

要成功的實作一個連接配接，首先我們知道至少需要有三個對象：連接配接線、源結點和目标結點。是以我們的command的可以如下實作： 這時顯示出來的效果和上一節一樣：能建立，不顯示。還是因為沒重新整理的問題。增加一個重新整理事監聽即可。如下：

public class AddConnectionCommand extends Command {

      private AbstractConnectionModel connection;

      public AddConnectionCommand(AbstractConnectionModel connection) {

            super();

            this.connection = connection;

      }

      public void setSrc(HelloWorldModel src) {

            connection.setSrc(src);

      }

      public void setTarget(HelloWorldModel target) {

            connection.setTarget(target);

      }

      public void setConnection(AbstractConnectionModel connection) {

            this.connection = connection;

      }

      @Override

      public void execute() {

            connection.attachSource();

            connection.attachTarget();

      }

      @Override

      public void undo() {

            connection.deattachTarget();

            connection.deattachSource();

      }

}

然後我們實作我們的Policy。這裡要分兩步進行，首先是完成源結點的連接配接，然後就完成目标結點的連接配接，代碼如下：

      @Override

      protected Command getConnectionCompleteCommand(

                  CreateConnectionRequest request) {

            AddConnectionCommand command = (AddConnectionCommand) request

                        .getStartCommand();

            command.setTarget((HelloWorldModel) getHost().getModel());

            return command;

      }

      @Override

      protected Command getConnectionCreateCommand(CreateConnectionRequest request) {

            AddConnectionCommand command = new AddConnectionCommand(

                        (AbstractConnectionModel) request.getNewObject());

            command.setSrc((HelloWorldModel) getHost().getModel());

            request.setStartCommand(command);

            return command;

      }

修改HelloWorldModel裡與連接配接相關的四個方法如下：

      public static final String P_SOURCE = "p_source";

      public static final String P_TARGET = "p_target";

      public void addInput(AbstractConnectionModel model) {

            if (!inputs.contains(model)) {

                  inputs.add(model);

                  firePropertyChange(P_TARGET, null, model);

            }

      }

      public void addOut(AbstractConnectionModel model) {

            if (!outputs.contains(model)) {

                  outputs.add(model);

                  firePropertyChange(P_SOURCE, null, model);

            }

      }

      public void removeInput(AbstractConnectionModel model) {

            if (inputs.contains(model)) {

                  inputs.remove(model);

                  firePropertyChange(P_TARGET, model, null);

            }

      }

      public void removeOut(AbstractConnectionModel model) {

            if (outputs.contains(model)) {

                  outputs.remove(model);

                  firePropertyChange(P_SOURCE, model, null);

            }

      }

然後再修改對應的EditPart的propertyChange()方法如下：

      public void propertyChange(PropertyChangeEvent evt) {

            if(evt.getPropertyName().equals(HelloWorldModel.P_CONSTRAINT)){

                  refreshVisuals();

            }else if(evt.getPropertyName().equals(HelloWorldModel.P_SOURCE)){

                  refreshSourceConnections();

            }else if(evt.getPropertyName().equals(HelloWorldModel.P_TARGET)){

                  refreshTargetConnections();

            }

      }

最後試一下效果：

圖三

 小提示：EditPolicy的getHost()方法傳回的是安裝這個Policy的那個對象。也就是安裝這個Policy的那個EditPart。