用繪製圖形方法繪製一個形狀？

Question

我試圖繪製一個基於形狀的圖形，獲得一個點的幾何形狀，並且一旦選擇了這個幾何體的行「bornes」，就會改變它的顏色問題是我每次選擇一行時都會出現這個錯誤日誌文件： 由於事先

 Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException 
at com.vividsolutions.jump.workbench.ui.renderer.java2D.Java2DConverter.toShape(Java2DConverter.java:313) 
at com.vividsolutions.jump.workbench.ui.plugin.specific.SearchPropertiesPlugin$2.valueChanged(SearchPropertiesPlugin.java:144) 
at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:167) 
at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:147) 
at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:194) 
at javax.swing.DefaultListSelectionModel.changeSelection(DefaultListSelectionModel.java:388) 
at javax.swing.DefaultListSelectionModel.changeSelection(DefaultListSelectionModel.java:398) 
at javax.swing.DefaultListSelectionModel.setSelectionInterval(DefaultListSelectionModel.java:442) 
at javax.swing.JTable.changeSelectionModel(JTable.java:2352) 
at javax.swing.JTable.changeSelection(JTable.java:2421) 
at javax.swing.plaf.basic.BasicTableUI$Handler.adjustSelection(BasicTableUI.java:1085) 
at javax.swing.plaf.basic.BasicTableUI$Handler.mousePressed(BasicTableUI.java:1008) 
at java.awt.AWTEventMulticaster.mousePressed(AWTEventMulticaster.java:263) 
at java.awt.Component.processMouseEvent(Component.java:6294) 
at javax.swing.JComponent.processMouseEvent(JComponent.java:3275) 
at java.awt.Component.processEvent(Component.java:6062) 
at java.awt.Container.processEvent(Container.java:2039) 
at java.awt.Component.dispatchEventImpl(Component.java:4660) 
at java.awt.Container.dispatchEventImpl(Container.java:2097) 
at java.awt.Component.dispatchEvent(Component.java:4488) 
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4575) 
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4233) 
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4166) 
at java.awt.Container.dispatchEventImpl(Container.java:2083) 
at java.awt.Window.dispatchEventImpl(Window.java:2489) 
at java.awt.Component.dispatchEvent(Component.java:4488) 
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:668) 
at java.awt.EventQueue.access$400(EventQueue.java:81) 
at java.awt.EventQueue$2.run(EventQueue.java:627) 
at java.awt.EventQueue$2.run(EventQueue.java:625) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87) 
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98) 
at java.awt.EventQueue$3.run(EventQueue.java:641) 
at java.awt.EventQueue$3.run(EventQueue.java:639) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87) 
at java.awt.EventQueue.dispatchEvent(EventQueue.java:638) 
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) 
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) 
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) 
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122) 

這裏是這個錯誤有關的代碼行，它發生在bornesTable的包含爾納（姓名，X，Y）

 searchProperties.getBornesTable().getSelectionModel().addListSelectionListener(new ListSelectionListener(){ 

    @Override 
    public void valueChanged(ListSelectionEvent e) { 

     try { 

      if (search()!= null){ 
     // here's the line 144 in toShape() method  
      final Shape shape = context.getLayerViewPanel().getViewport().getJava2DConverter().toShape(selectedBornes()); 
      Color color = Color.yellow; 
      Stroke stroke =new BasicStroke(5, BasicStroke.CAP_ROUND,BasicStroke.JOIN_ROUND); 
      final Graphics2D graphics = (Graphics2D) context.getLayerViewPanel().getGraphics(); 
      graphics.setColor(color); 
      //graphics.setXORMode(Color.white); 
      graphics.setStroke(stroke); 
      graphics.fill(shape); 

      } 
      else 
        JOptionPane.showMessageDialog(null, "vous n'avez pas selectionner une bornes "); 

     } catch (NoninvertibleTransformException e1) { 
      // TODO Auto-generated catch block 
      e1.printStackTrace(); 
     } 




    } 

    }); 

這裏的監聽器方法：selectedBornes（）

public Geometry selectedBornes() { 

    if (getSelectedRowIndex()> 0) 
    { 
    Geometry geometry; 
    geometry = searchBorne().get(getSelectedRowIndex()).getGeometry(); 
    return geometry; 
    } 
    return null; 

} 

和方法serchBornes（）有這個沒有問題，但我會後

private List<BasicFeature> searchBorne() { 

    final List<BasicFeature> basicFeatureBornes = new ArrayList<BasicFeature>(); 

    for(BasicFeature basicFeature : BornesList) { 

       if (searchProperties.getNumTextField().getText().equals(basicFeature.getString("num")) && 
         searchProperties.getComplementComboBox().getSelectedItem().equals(basicFeature.getString("complement"))) 
        basicFeatureBornes.add(basicFeature); 


        } 
    return basicFeatureBornes; 

} 

有方法getSelectedRowIndex（）也與這個沒有問題，但我會後

public int getSelectedRowIndex() { 

    int row = 0; 
    for(int i = 0; i < searchBorne().size() ; i++) { 

      row = searchProperties.getBornesTable().getSelectedRow(); 

    } 

    return row; 

} 

Answer 1

public Geometry selectedBornes() { 
    if (getSelectedRowIndex()> 0) 
    { 
    Geometry geometry; 
    geometry = searchBorne().get(getSelectedRowIndex()).getGeometry(); 
    return geometry; 
    } 

如果所選索引是0（對於第一個元素）會發生什麼？它返回null並且方法崩潰。如果未選擇任何內容，請添加支票以處理個案。

Answer 2

final Shape shape = context.getLayerViewPanel().getViewport().getJava2DConverter().toShape(selectedBornes()); 

這裏您在selectedBornes()值直接傳遞給toShape方法，但你沒有檢查selectedBornes()值是否爲空或不作爲的結果你得到NullPointerException沒有被選擇的rowIndex因此改變你的代碼

Goemetry newGometry=selectedBornes(); 
if (newGometry !=null){ 
final Shape shape = context.getLayerViewPanel().getViewport().getJava2DConverter().toShape(newGometry); 
}