vertex - JGraphXで頂点を前面に出す方法

Question

私は JGraphX を使用しており、3 つのポートを持つ頂点がありますが、頂点を前面に配置したいのですが、何らかの理由で頂点が前面に表示されません。何が欠けているのでしょうか?

    final int PORT_DIAMETER = 20;
    final int PORT_RADIUS = PORT_DIAMETER / 2;
        mxGeometry geo1 = new mxGeometry(0, 0.5, PORT_DIAMETER,
                    PORT_DIAMETER);
        // Because the origin is at upper left corner, need to translate to
        // position the center of port correctly
        geo1.setOffset(new mxPoint(-PORT_RADIUS, -PORT_RADIUS));
        geo1.setRelative(true);
        geo1.setWidth(10);

    mxCell port1 = new mxCell(null, geo1,
                    "port;image=/Images/blue-right-arrow.png");
    port1.setVertex(true);

    mxGeometry geo2 = new mxGeometry(1.0, 0.5, PORT_DIAMETER,
                PORT_DIAMETER);
    geo2.setOffset(new mxPoint(-PORT_RADIUS, -PORT_RADIUS));
    geo2.setRelative(true);

    mxCell port2 = new mxCell(null, geo2,
                    "port;image=/Images/blue-right-arrow.png");
    port2.setVertex(true);

    mxGeometry geo3 = new mxGeometry(0.5, 1, PORT_DIAMETER,
                PORT_DIAMETER);
    geo3.setOffset(new mxPoint(-PORT_RADIUS, -PORT_RADIUS));
    geo3.setRelative(true);

    mxCell port3 = new mxCell(null, geo3,
                    "port;image=/Images/blue-up-arrow.png");
    port3.setVertex(true);

    graph.addCell(port1, this);        
    graph.addCell(port2, this);
    graph.addCell(port3, this);
    graph.cellsOrdered(new Object[]{port1,port2,port3}, true);
    graph.cellsOrdered(new Object[]{this}, false);