清除選擇的jList

我有一個jtree一個jlist，jlist取決於什麼jtree節點被選中，當我選擇de節點顏色時，jlist添加兩個項目。然後我有一個jTextfield，我把選中的值放入jlist。清除選擇的jList

我的問題是，當我想選擇另一個jTree中選擇的jlist上的值的節點。

這是我在jTreeValueChanged行動

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"); 

    } 

}

現在，這是在jListValueChanged thew代碼：

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

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


}

有例外，當我選擇其他節點：

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)

來源

2014-06-06 Jesz Suarez

'seleccion.toString（）==「colors」'看起來不太好。看看[怎麼做我比較字符串在Java]（http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java） – Pshemo

謝謝你評論，我解決，但我仍然有同樣的問題，當我選擇其他節點。你知道我能做什麼嗎？ –

從獲取值之前首先檢查選擇0。如果沒有選擇，則使用JList#getSelectedIndex()嘗試返回-1，而不是JList#getSelectedValue()，如果沒有選擇，則返回null。

如果沒有選擇，那麼下面一行將導致NullPointerException

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

瞭解更多關於How to Use Lists，發現樣本代碼。

來源

2014-06-06 19:31:26 Braj

感謝您的回答！我會試試看。 –

卓越，非常感謝。它解決了我的問題！ –

聽起來不錯。不用客氣。 – Braj

清除選擇的jList

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