선택 취소 jList

Question

jtree는 jlist를 가지고 있고, jlist는 jtree 노드가 선택되어 있는지에 따라 다릅니다. 노드 색상을 선택하면 jlist가 두 항목을 추가합니다. 그런 다음 jlist에서 선택된 값을 넣는 jTextfield가 있습니다.

제 문제는 jlist의 값을 갖는 jTree에서 다른 노드를 선택하려고 할 때입니다.

이

내가 jTreeValueChanged의 행동이 무엇을

private void jTree1ValueChanged(javax.swing.event.TreeSelectionEvent evt) {          

    jTextField1.setText(""); 
    jList1.clearSelection(); 


    jList1.repaint(); 
    //DefaultMutableTreeNode seleccion; 
    seleccion=(DefaultMutableTreeNode) jTree1.getLastSelectedPathComponent(); 

    if(seleccion.toString()=="colors"){ 

     jList1.setModel(model ); 
     model.addElement("rojo"); 
     model.addElement("azul"); 
    } 
    else if(seleccion.toString()=="sports"){ 
     jList1.setModel(model); 
     model.addElement("futbol"); 
     model.addElement("beisbol"); 

    } 

} 

지금 이것은 jListValueChanged에 Thew 보낸 코드 :

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException 
at navegacion.arbolconlist.jList1ValueChanged(arbolconlist.java:124) 
at navegacion.arbolconlist.access$100(arbolconlist.java:17) 
at navegacion.arbolconlist$2.valueChanged(arbolconlist.java:60) 
at javax.swing.JList.fireSelectionValueChanged(JList.java:1796) 
at javax.swing.JList$ListSelectionHandler.valueChanged(JList.java:1810) 
at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:184) 
at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:164) 
at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:211) 
at javax.swing.DefaultListSelectionModel.changeSelection(DefaultListSelectionModel.java:405) 
at javax.swing.DefaultListSelectionModel.changeSelection(DefaultListSelectionModel.java:415) 
at javax.swing.DefaultListSelectionModel.removeSelectionIntervalImpl(DefaultListSelectionModel.java:576) 
at javax.swing.DefaultListSelectionModel.clearSelection(DefaultListSelectionModel.java:420) 
at javax.swing.JList.clearSelection(JList.java:2043) 
at navegacion.arbolconlist.jTree1ValueChanged(arbolconlist.java:101) 
at navegacion.arbolconlist.access$000(arbolconlist.java:17) 
at navegacion.arbolconlist$1.valueChanged(arbolconlist.java:53) 
at javax.swing.JTree.fireValueChanged(JTree.java:2921) 
at javax.swing.JTree$TreeSelectionRedirector.valueChanged(JTree.java:3382) 
at javax.swing.tree.DefaultTreeSelectionModel.fireValueChanged(DefaultTreeSelectionModel.java:635) 
at javax.swing.tree.DefaultTreeSelectionModel.notifyPathChange(DefaultTreeSelectionModel.java:1093) 
at javax.swing.tree.DefaultTreeSelectionModel.setSelectionPaths(DefaultTreeSelectionModel.java:294) 
at javax.swing.tree.DefaultTreeSelectionModel.setSelectionPath(DefaultTreeSelectionModel.java:188) 
at javax.swing.JTree.setSelectionPath(JTree.java:1633) 
at javax.swing.plaf.basic.BasicTreeUI.selectPathForEvent(BasicTreeUI.java:2393) 
at javax.swing.plaf.basic.BasicTreeUI$Handler.handleSelection(BasicTreeUI.java:3609) 
at javax.swing.plaf.basic.BasicTreeUI$Handler.mousePressed(BasicTreeUI.java:3548) 
at java.awt.Component.processMouseEvent(Component.java:6524) 
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321) 
at java.awt.Component.processEvent(Component.java:6292) 
at java.awt.Container.processEvent(Container.java:2234) 
at java.awt.Component.dispatchEventImpl(Component.java:4883) 
at java.awt.Container.dispatchEventImpl(Container.java:2292) 
at java.awt.Component.dispatchEvent(Component.java:4705) 
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898) 
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4530) 
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462) 
at java.awt.Container.dispatchEventImpl(Container.java:2278) 
at java.awt.Window.dispatchEventImpl(Window.java:2739) 
at java.awt.Component.dispatchEvent(Component.java:4705) 
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746) 
at java.awt.EventQueue.access$400(EventQueue.java:97) 
at java.awt.EventQueue$3.run(EventQueue.java:697) 
at java.awt.EventQueue$3.run(EventQueue.java:691) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75) 
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86) 
at java.awt.EventQueue$4.run(EventQueue.java:719) 
at java.awt.EventQueue$4.run(EventQueue.java:717) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75) 
at java.awt.EventQueue.dispatchEvent(EventQueue.java:716) 
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201) 
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) 
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) 
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) 
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82) 

:

private void jList1ValueChanged(javax.swing.event.ListSelectionEvent evt) { 

    String seleccion =jList1.getSelectedValue().toString(); 
    jTextField1.setText(seleccion); 


} 

내가 다른 노드를 선택하면 예외가가

Answer 1

먼저에서 값을 가져 오기 전에 선택을 확인하십시오. 0. 선택이 없으면 null을 반환하는 JList#getSelectedValue() 대신 선택 사항이없는 경우 JList#getSelectedIndex()을 반환하여 -1을 반환하는 것으로 시도하십시오.

다음 행 아래 어떤 선택이 How to Use Lists 대해 자세히 알아뿐만 아니라 샘플 코드를 찾을 수 NullPointerException

String seleccion =jList1.getSelectedValue().toString(); 

발생하지 않습니다이 있다면.