我尝试将一个mxGraph居中，这个mxGraph有hierarchicalLayout，以便在JFrame中动态排列单元格。每次渲染jFrame时，mxGraph都被绘制在框架的左上角，我找不到修改图形位置的方法。如何实现这一点？

public class Test {

    public Test() {
        Object v1;
        Object v2;
        Object v3;
        JFrame f = new JFrame();
        f.setSize(500, 500);
        f.setLocation(300, 200);

        mxGraph graph = new mxGraph();
        mxGraphComponent graphComponent = new mxGraphComponent(graph);
        f.getContentPane().add(BorderLayout.CENTER, graphComponent);
        f.setVisible(true);

        Object parent = graph.getDefaultParent();
        graph.getModel().beginUpdate();
        try {
             v1 = graph.insertVertex(parent, null, "node1", 100, 100, 80, 30);
            v2 = graph.insertVertex(parent, null, "node2", 100, 100, 80, 30);
             v3 = graph.insertVertex(parent, null, "node3", 100, 100, 80, 30);

            graph.insertEdge(parent, null, "Edge", v1, v2);
            graph.insertEdge(parent, null, "Edge", v2, v3);

        } finally {
            graph.getModel().endUpdate();
        }

        // define layout
        mxIGraphLayout layout = new mxHierarchicalLayout(graph);

        // layout using morphing
        graph.getModel().beginUpdate();
        try {
            layout.execute(graph.getDefaultParent());
        } finally {
                    graph.getModel().endUpdate();
                    // fitViewport();
        }

    }

    public static void main(String[] args) {
        Test t = new Test();

    }
}