小编eha*_*aat的帖子

我做了一个扫描图像的swing应用程序; 每个图像由一片叶子代表一棵树

我遇到的问题是它抛出了这个异常

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at com.sun.java.swing.plaf.windows.XPStyle$Skin.getWidth(XPStyle.java:513)
    at com.sun.java.swing.plaf.windows.XPStyle$Skin.getWidth(XPStyle.java:517)
    at com.sun.java.swing.plaf.windows.WindowsTreeUI$ExpandedIcon.getIconWidth(WindowsTreeUI.java:138)
    at javax.swing.plaf.basic.BasicTreeUI.drawCentered(BasicTreeUI.java:1580)
    at javax.swing.plaf.basic.BasicTreeUI.paintExpandControl(BasicTreeUI.java:1464)
    at javax.swing.plaf.basic.BasicTreeUI.paint(BasicTreeUI.java:1206)
    at javax.swing.plaf.ComponentUI.update(ComponentUI.java:143)
    at javax.swing.JComponent.paintComponent(JComponent.java:763)
    at javax.swing.JComponent.paint(JComponent.java:1027)
    at javax.swing.JComponent.paintToOffscreen(JComponent.java:5122)
    at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:285)
    at javax.swing.RepaintManager.paint(RepaintManager.java:1128)
    at javax.swing.JComponent._paintImmediately(JComponent.java:5070)
    at javax.swing.JComponent.paintImmediately(JComponent.java:4880)
    at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:723)
    at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:679)
    at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:659)
    at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:128)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

而且我不知道为什么会出现这种情况注意:我正在使用Windows外观

UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");

和windows 1.6下的java 1.6_22

我想p:selectOneMenu宽度是关于父细胞的自动关于它有的值.

<p:panelGrid>
    <p:row>
        <p:column><p:outputLabel value="Value01" for="idInput01"/></p:column>
        <p:column><p:inputText  value="#{bean.input01}" id="idInput01" /></p:column>
        <p:column><p:outputLabel value="Value02" for="idSelect" /></p:column>
        <p:column>
            <p:selectOneMenu value="#{bean.selectedObject}" id="idSelect" converter="objectConverter">
                <f:selectItems value="#{bean.objectsList}" var="varObject" itemLabel="#{varObject.label}" itemValue="#{varObject}" />
            </p:selectOneMenu>
        </p:column>
    </p:row>
</p:panelGrid>

我得到了什么:

我期待的是:

注意:我不想指定固定宽度.

p:selectOneMenu添加时选择存在问题f:selectItem.

视图:

<p:selectOneMenu value="#{selectionTest.selectedName}">
    <f:selectItem itemLabel="Select" noSelectionOption="true" />
    <f:selectItems value="#{selectionTest.allNames}" var="varName" itemLabel="#{varName}" itemValue="#{varName}" />
</p:selectOneMenu>

模型:

private List<String> allNames;
private String selectedName;

public MenuSelectionTestBean(){
    allNames = new ArrayList<String>();
    allNames.add("Ahmed");
    allNames.add("Mohamed");
    allNames.add("Ibrahim");
    allNames.add("Walid");

    selectedName ="Walid";
}

结果:

应选择"Walid"项,但选择"Ibrahim".我认为PrimeFaces根据列表中的索引选择项目,而不是项目的值.

这是怎么造成的,我该如何解决？

使用nQueens问题 如何将此算法转换为java代码

 function MIN-CONFLICTS(csp,max_steps) returns a solution or failure
   inputs: csp, a constraint satisfaction problem
           max_steps,the number of steps allowed before giving up
   current<-- an initial assignment for csp
   for i=1 to max_steps do
       if current is a solution of csp then return current
       var<-- a randomly chosen, conflicted variable from VARIABLES[csp]
       value<-- the value v for var that minimizes CONFLICTS(var,v,current,csp)
       set var = value in current
 return failure