Question

场合

我使用JGraph进行了可视化。该图由不同的线程更新为实例化Visualization的线程。

预期行为

图表应该由各种工作线程更新。线程调用以更新图形的函数是syncronized，因此工作线程不会导致它们之间的并发问题。

实际行为

绘制时，AWT-EventQueue线程中抛出异常（ ocassionally ）。有时它是一个空指针，有时它是一个超出范围的索引。这是一个堆栈跟踪：

线程“AWT-EventQueue-0”中的异常java.lang.NullPointerException 在com.mxgraph.shape.mxConnectorShape.translatePoint（未知来源）在com.mxgraph.shape.mxConnectorShape.paintShape（未知来源）在com.mxgraph.canvas.mxGraphics2DCanvas.drawCell（未知来源） at com.mxgraph.view.mxGraph.drawState（Unknown Source） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.drawCell（Unknown Source） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.drawChildren（Unknown Source） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.drawCell（Unknown Source） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.drawChildren（Unknown Source） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.drawCell（Unknown Source） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.drawChildren（Unknown Source） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.drawCell（Unknown Source） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.drawFromRootCell（Unknown Source） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.drawGraph（Unknown Source） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.paintComponent（Unknown Source）在javax.swing.JComponent.paint（JComponent.java:1029） at com.mxgraph.swing.mxGraphComponent $ mxGraphControl.paint（Unknown Source）在javax.swing.JComponent.paintChildren（JComponent.java:866）在javax.swing.JComponent.paint（JComponent.java:1038）在javax.swing.JViewport.paint（JViewport.java:764）在javax.swing.JComponent.paintToOffscreen（JComponent.java:5138）在javax.swing.BufferStrategyPaintManager.paint（BufferStrategyPaintManager.java:302）在javax.swing.RepaintManager.paint（RepaintManager.java:1188）在javax.swing.JComponent._paintImmediately（JComponent.java:5086）在javax.swing.JComponent.paintImmediately（JComponent.java:4896）在javax.swing.RepaintManager.paintDirtyRegions（RepaintManager.java:783）在javax.swing.RepaintManager.paintDirtyRegions（RepaintManager.java：735）在javax.swing.RepaintManager.prePaintDirtyRegions（RepaintManager.java:677）在javax.swing.RepaintManager.access $ 700（RepaintManager.java:58）在javax.swing.RepaintManager $ ProcessingRunnable.run（RepaintManager.java:1593） at java.awt.event.InvocationEvent.dispatch（InvocationEvent.java:226） at java.awt.EventQueue.dispatchEventImpl（EventQueue.java:647） at java.awt.EventQueue.access $ 000（EventQueue.java:96） at java.awt.EventQueue $ 1.run（EventQueue.java:608） at java.awt.EventQueue $ 1.run（EventQueue.java:606） at java.security.AccessController.doPrivileged（Native Method） at java.security.AccessControlContext $ 1.doIntersectionPrivilege（AccessControlContext.java:105） at java.awt.EventQueue.dispatchEvent（EventQueue.java:617） at java.awt.EventDispatchThread.pumpOneEventForFilters（EventDispatchThread.java:275） at java.awt.EventDispatchThread.pumpEventsForFilter（EventDispatchThread.java:200） at java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:190） at java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:185） at java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:177）在java.awt.EventDispatchThread.run（EventDispatchThread.java:138）

它似乎不会对应用程序的运行产生负面影响。一个新的AWT-EventQueue产生，在某个阶段将不可避免地遇到同样的问题。

原因

我认为它必须通过在单独的线程中将图形更新为JFrame实例化的图形来引起。在paint方法试图绘制它们时，需要绘制的东西正在被更改。

问题

如何解决此问题？我能以某种方式将paint方法与更新图形的方法同步吗？

可视化代码

package ui;

import javax.swing.JFrame;

import com.mxgraph.layout.mxOrganicLayout;
import com.mxgraph.layout.mxStackLayout;
import com.mxgraph.model.mxCell;
import com.mxgraph.model.mxGraphModel;
import com.mxgraph.swing.mxGraphComponent;
import com.mxgraph.view.mxGraph;

import core.Container;
import core.Node;
import core.WarehouseGraph;

public class Visualisation extends JFrame{
    private static final long serialVersionUID = 8356615097419123193L;
    private mxGraph graph = new mxGraph();
    Object parent = graph.getDefaultParent();
    mxOrganicLayout graphlayout = new mxOrganicLayout(graph);
    mxStackLayout containerLayout = new mxStackLayout(graph, true, 10);

    public Visualisation(WarehouseGraph model){
        super("Warehouse Simulator");

        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(800, 600);

        graph.getModel().beginUpdate();
        try{
            for(Node node : model.getNodes().values()){
                mxCell cell = (mxCell)graph.insertVertex(parent, node.getId(), node.getId(), 0, 0, 60, 30);

                Object prev = null;
                for(Container container : node.getContainers()){
                    Object newCont = graph.insertVertex(cell, container.getId(), container.getId(), 0, 0, 60, 20);
                    if(prev != null) graph.insertEdge(cell, null, null, prev, newCont);
                    prev = newCont;
                }
            }

            for(Node node : model.getNodes().values()){
                for(Node toNode : node.getDownstreamNodes()){
                    Object fromCell = ((mxGraphModel)graph.getModel()).getCell(node.getId());
                    Object toCell = ((mxGraphModel)graph.getModel()).getCell(toNode.getId());
                    graph.insertEdge(parent, null, null, fromCell, toCell);
                }
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            graph.getModel().endUpdate();
        }

        graphlayout.execute(parent);

        Object[] nodes = mxGraphModel.getChildVertices(graph.getModel(), parent);
        for(Object cell : nodes){
            containerLayout.execute(cell);
            graph.updateCellSize(cell);
        }


        mxGraphComponent graphComponent = new mxGraphComponent(graph);
        getContentPane().add(graphComponent);

        this.setVisible(true);
    }

    //CALLED FROM SYNCHRONIZED FUNCTION
    public void moveContainer(Container container, Node to){
        graph.getModel().beginUpdate();
        mxCell toCell = (mxCell)((mxGraphModel)graph.getModel()).getCell(to.getId());
        mxCell containerCell = (mxCell)((mxGraphModel)graph.getModel()).getCell(container.getId());
        mxCell fromCell = (mxCell)containerCell.getParent();

        try{
            Object[] edges = mxGraphModel.getEdges(graph.getModel(), containerCell);
            graph.removeCells(edges);

            containerCell.removeFromParent();

            graph.addCell(containerCell, toCell);

            Object[] containers = mxGraphModel.getChildVertices(graph.getModel(), toCell);
            if(containers.length >= 2)
                graph.insertEdge(toCell, null, null, containerCell, containers[containers.length-2]);
            containerLayout.execute(toCell);
            containerLayout.execute(fromCell);
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            graph.getModel().endUpdate();
        }
    }
}

控制器代码

package core;
import serialisation.JsonUtil;
import ui.Visualisation;

public class Controller{
    private WarehouseGraph graph;
    Visualisation viz;

    public static void main(String[] args){
        Controller.getInstance();
    }

    private Controller(){
        graph = JsonUtil.initFromJson(); //graph has many worker threads running which can call containerMoved
        viz = new Visualisation(graph);
    }

    private static class SingletonHolder{
        private static final Controller INSTANCE = new Controller();
    }

    public static Controller getInstance(){
        return SingletonHolder.INSTANCE;
    }

    public synchronized void containerMoved(Container container, Node from, Node to){
        viz.moveContainer(container, to);
    }
}

Answer 1

不回答你的问题，只是注意你的概念。

您能告诉我们您的public static void main(String[] args) {...}方法吗？我希望有一些看起来像：

public static void main（String [] args）{ SwingUtilities.invokeLater（new Runnable（）{
```
        public void run() {
            Visualisation vis = new Visualisation();
        }
    });
}
```
this.setSize(800, 600);应为this.setpreferredSize(new Dimension(800, 600));
然后在最后一行（this.pack();）之前添加this.setVisible(true);

编辑：

哪种类型的组件返回mxGraphComponent graphComponent = new mxGraphComponent(graph);，因为如果是基于JPanel的自定义组件，那么

getContentPane().add(graphComponent);应为add(graphComponent);

来自backGround线程/任务的所有输入都必须包含在invokeLater()中。如果它是闪烁或冻结，那么你必须寻找invokeAndWait()。我个人认为那里存在invokeAndWait()，但对于这种方法，我无法给你一些正确的建议。或者：
如果您要在某些期刊基础上运行任务，那么您必须查找Runnable（输出必须包装到invokeLater中）或SwingWorker。

涂料上的JGraph AWT EventQueue异常（带多线程）

场合

预期行为

实际行为

原因

问题

可视化代码

控制器代码

1 个答案: