從數據庫加載頂點和邊時，Vertex Painter遇到錯誤

Question

我正在構建簡單的家譜應用程序，並使用Jung繪制圖表。 到目前為止，我已經能夠使用zentus的sqlitejdbc繪制圖表並將其保存到嵌入式數據庫中。 我仍然創建了清除畫布的功能，因此我必須重新啟動應用程序以測試打開數據庫。 但是，當我想將它們重新加載時，應用程序凍結了，我遇到了此錯誤。

  path:C:\\Users\\PaLi\\Desktop\\psm things\\chart4.db Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at FamTree.vertexPainter.transform(vertexPainter.java:20) at FamTree.vertexPainter.transform(vertexPainter.java:1) at edu.uci.ics.jung.visualization.renderers.BasicVertexRenderer.paintShapeForVertex(BasicVertexRenderer.java:98) at edu.uci.ics.jung.visualization.renderers.BasicVertexRenderer.paintIconForVertex(BasicVertexRenderer.java:74) at edu.uci.ics.jung.visualization.renderers.BasicVertexRenderer.paintVertex(BasicVertexRenderer.java:37) at edu.uci.ics.jung.visualization.renderers.BasicRenderer.renderVertex(BasicRenderer.java:70) at edu.uci.ics.jung.visualization.renderers.BasicRenderer.render(BasicRenderer.java:55) at edu.uci.ics.jung.visualization.BasicVisualizationServer.renderGraph(BasicVisualizationServer.java:367) at edu.uci.ics.jung.visualization.BasicVisualizationServer.paintComponent(BasicVisualizationServer.java:321) at javax.swing.JComponent.paint(JComponent.java:1054) at javax.swing.JComponent.paintToOffscreen(JComponent.java:5221) at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1482) at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1413) at javax.swing.RepaintManager.paint(RepaintManager.java:1206) at javax.swing.JComponent._paintImmediately(JComponent.java:5169) at javax.swing.JComponent.paintImmediately(JComponent.java:4980) at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:770) at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:728) at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:677) at javax.swing.RepaintManager.access$700(RepaintManager.java:59) at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1621) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:705) at java.awt.EventQueue.access$000(EventQueue.java:101) at java.awt.EventQueue$3.run(EventQueue.java:666) at java.awt.EventQueue$3.run(EventQueue.java:664) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76) at java.awt.EventQueue.dispatchEvent(EventQueue.java:675) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105) at java.awt.EventDispatchThread.run(EventDispatchThread.java:90) 

這是頂點繪制器轉換器的代碼。 如果它不加載數據庫部分，則工作得很好。

package FamTree;

import org.apache.commons.collections15.Transformer;

import java.awt.*;
import java.util.Map;

class vertexPainter implements Transformer<Integer, Paint>
{
private Map<Integer,Person> tempV;

public vertexPainter(Map<Integer,Person> passV)
{
    tempV = passV;
}
public Paint transform(Integer v) 
{

    if (tempV.get(v).getpSex().equalsIgnoreCase("male")) 
        return (Color.blue); 
    else
    return (Color.red);

}
}

這是圖形的初始化並設置vv。

     public TCanvas(){

     graph = new SparseMultigraph<Integer,Number>();

     layout2 = new StaticLayout<Integer,Number>(graph,new Dimension(2000,2000));

     vv =  new VisualizationViewer<Integer,Number>(layout2);
     vv.setBackground(Color.white);
     vv.setVertexToolTipTransformer(new ToStringLabeller<Integer>());
     vv.getRenderContext().setVertexFillPaintTransformer(new vertexPainter(vertex));
vv.getRenderer().getVertexLabelRenderer().setPosition(Renderer.VertexLabel.Position.S);
     vv.getRenderContext().setVertexLabelTransformer(new vertexLabel(vertex));
     vv.getRenderContext().setEdgeDrawPaintTransformer(new edgePainter());

     Transformer<Number,String> stringer = new Transformer<Number,String>(){
         public String transform(Number e) {
             return "Edge:"+e+ "-"+graph.getEndpoints(e).toString();
         }
     };

     vv.getRenderContext().setEdgeLabelTransformer(stringer);

     EdgeLabelRenderer edgeLabelRenderer= vv.getRenderContext().getEdgeLabelRenderer();
     edgeLabelRenderer.setRotateEdgeLabels(false);



     gm = new DefaultModalGraphMouse<Integer, Number>();
     vv.setGraphMouse(gm);
     gm.add(new PopupGraphMousePlugin());

     GraphZoomScrollPane scrollPane2 = new GraphZoomScrollPane(vv);

     JPanel vvPanel = new JPanel();
     vvPanel.setLayout(new BorderLayout());
     vvPanel.add(scrollPane2);

     addBottomControls(vvPanel);

     Container content = getContentPane();
     content.add(vvPanel);  
     }//TCanvas()

這是加載數據庫的部分。

     menu.add(new AbstractAction("Open") {
        public void actionPerformed(ActionEvent e) {

            JFileChooser open  = new JFileChooser();
            final File file ;

            int vat = open.showOpenDialog(rootPane);

            if(vat==JFileChooser.APPROVE_OPTION){

                file = open.getSelectedFile();

                String fPath = file.getAbsolutePath();

                System.out.println("path:"+fPath);
                try{

                    Class.forName("org.sqlite.JDBC");
                    Connection conn = DriverManager.getConnection("jdbc:sqlite:"+fPath);

                     Statement stat = conn.createStatement();

                     ResultSet rs = stat.executeQuery("select * from Person;");
                     while (rs.next()) {


                        Integer pid = rs.getInt("pID");
                        String pname = rs.getString("pName");
                        String psex = rs.getString("pSex");
                        Integer fatherid = (Integer)rs.getInt("fatherID");
                        Integer motherid = (Integer)rs.getInt("motherID");
                        Integer spouseid = (Integer)rs.getInt("spouseID");

                        Person personInfo = new Person();

                        personInfo.setpID(pid);
                        personInfo.setpName(pname);
                        personInfo.setpSex(psex);
                        personInfo.setFatherID(fatherid);
                        personInfo.setMotherID(motherid);
                        personInfo.setSpouseID(spouseid);

                        vertex.put(pid,personInfo);
                        graph.addVertex(pid);
                        vv.repaint();

                        ResultSet rs2 = stat.executeQuery("select * from Location;");
                         while (rs2.next()) {

                             if(rs2.getInt("pID")==pid){

                                 Point2D.Double loc = new Point2D.Double();

                                 Double x = rs2.getDouble("pointX");
                                 Double y = rs2.getDouble("pointY");
                                 loc.setLocation(x, y);

                                 layout2.setLocation(pid, vv.getRenderContext().getMultiLayerTransformer().inverseTransform(loc));
                                 vv.repaint();
                             }
                         }
                         rs2.close();


                     }
                     rs.close();

                    ResultSet rs3 = stat.executeQuery("select * from Relation;");

                    while (rs3.next()) {

                         Point2D.Double loc2 = new Point2D.Double();

                         Number edgeid = (Number)rs3.getInt("edgeID");
                         Integer v1 = rs3.getInt("vertex1");
                         Integer v2 = rs3.getInt("vertex2");
                         String type = rs3.getString("RelationType");

                         Relation relation = new Relation(edgeid, v1, v2, type);
                         edge.put(edgeid, relation);
                         if(type.equalsIgnoreCase("DIRECTED")){
                             graph.addEdge(edgeid, v1, v2, EdgeType.DIRECTED);
                         }
                         if(type.equalsIgnoreCase("UNDIRECTED")){
                             graph.addEdge(edgeid, v1, v2, EdgeType.UNDIRECTED);
                         }
                        vv.repaint();


                    }
                    rs3.close();

                    conn.close();
                    vv.repaint();

                }
                catch (Exception ex) {
                    // TODO: handle exception
                    ex.printStackTrace();
                }

            }

        }});

我真的不知道這里發生了什么，因為我很確定打開和檢索數據庫部分沒有問題。

Answer 1

在vertexPainter#transform ，映射為null或它不具有整數鍵（“ v ”）的值，或者一個記錄的pSex屬性值為null（可能未在數據庫表上設置）。

調試器可以告訴您確切的實際問題是什么。

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在TCanvas構造函數中，我看到以下代碼行：

vv.getRenderContext().setVertexFillPaintTransformer(new vertexPainter(vertex));

那是您使用地圖創建畫家的地方，但是我看不到該地圖的聲明和初始化。 因此，您很有可能將一個空的地圖傳遞給繪畫者，因此繪畫者無法找到鍵的值（因為該地圖是空的）。 這肯定會導致NPE。

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這與研究錯誤日志無關。 在日食中：

1. 切換到調試透視圖
2. 找到“斷點”視圖（通常是右上角的標簽）
3. 在該視圖上，有一個帶有“ J”和感嘆號的按鈕，工具提示顯示“添加Java異常斷點”
4. 單擊該按鈕並鍵入NPE，然后選擇NullPointerException
5. 現在您有了一個斷點，該斷點將在每個空指針異常時停止
6. 調試您的應用程序（例如“運行”）
7. 最終，應用程序將停止運行，並且您將在“調試”視圖中看到一個堆棧跟蹤。 將您的vertexPainter框架一幀，選擇該行，它將帶您到引發NPE的代碼行。 現在，您必須查看變​​量值並使用檢查功能。