我跟着这个oracle tutorial,它给出了一个JButton的例子,我尝试了它并且工作正常,但是当我用JComboBox尝试它时它不起作用！
我试图删除SPACE键,这是为了防止JComponent响应SPACE按键
firstButton.getInputMap().put(KeyStroke.getKeyStroke("SPACE"),"none");
JComboBox也是如此
sizesComboBox.getInputMap().put(KeyStroke.getKeyStroke("SPACE"),"none");
但是不起作用,它(JComboBox)仍然响应SPACE键
对于我删除了SPACE印刷机效果的firstButton;我添加了键F,所以现在当你按下键盘上的F键时按下了firstButton,ant没有响应SPACE(意图).请注意,即使firstButton没有焦点,也会发生F的按下(JComponent.WHEN_IN_FOCUSED_WINDOW)
这是一个显示我的例子的SSCCE代码：
注意：我故意没有将上面的代码行添加到第二个按钮“secondButton”,因此它默认仍然响应SPACE.
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.*;
public class KeyStrokeTest extends JPanel
{
JPanel widgetPanel;
JPanel textAreaPanel;
JButton firstButton;
JButton secondButton;
JTextArea textArea;
JComboBox<Integer> sizesComboBox;
public KeyStrokeTest()
{
firstButton = new JButton("First");
firstButton.addActionListener(eventWatcher);
firstButton.getInputMap().put(KeyStroke.getKeyStroke("SPACE"),"none");
firstButton.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke("F"),"F Key");
firstButton.getActionMap().put("F Key",eventWatcher);
secondButton = new JButton("Second");
secondButton.addActionListener(eventWatcher);
sizesComboBox = new JComboBox<>();
sizesComboBox.addItemListener(new itemListenerClass());
for (int i = 1; i <= 8; i++)
{
sizesComboBox.addItem(i);
}
sizesComboBox.setSelectedIndex(0);
sizesComboBox.getInputMap().put(KeyStroke.getKeyStroke("SPACE"),"none");
textArea = new JTextArea(0,0);
JScrollPane scrollTextArea = new JScrollPane(textArea);
scrollTextArea.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
textArea.setEditable(false);
widgetPanel = new JPanel();
textAreaPanel = new JPanel(new BorderLayout());
widgetPanel.add(firstButton);
widgetPanel.add(secondButton);
widgetPanel.add(sizesComboBox);
textAreaPanel.add(scrollTextArea,BorderLayout.CENTER);
JSplitPane splitPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,textAreaPanel,widgetPanel);
splitPane.setDividerLocation(280);
splitPane.setResizeWeight(.5d);
this.setLayout(new BorderLayout());
this.add(splitPane);
}
AbstractAction eventWatcher = new AbstractAction()
{
@Override
public void actionPerformed(ActionEvent ae)
{
Object source = ae.getSource();
if (source == firstButton)
{
textArea.append("First button clicked\n");
}
if (source == secondButton)
{
textArea.append("Second button clicked\n");
}
}
};
private class itemListenerClass implements ItemListener
{
@Override
public void itemStateChanged(ItemEvent e)
{
if (e.getSource() == sizesComboBox)
{
if (textArea != null)
{
textArea.append("Item " + sizesComboBox.getSelectedItem() + "\n");
}
}
}
}
private static void createAndShowGUI()
{
JFrame frame = new JFrame("KeyStroke Test");
frame.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500,300);
frame.add(new KeyStrokeTest(),BorderLayout.CENTER);
frame.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
UIManager.put("swing.boldMetal",Boolean.FALSE);
createAndShowGUI();
}
});
}
}
我想要控制JComponent的默认击键的原因是因为我想在所有JComponent上删除SPACE的默认效果,除了一个按钮,它将响应SPACE按下,无论焦点在哪里,使用JComponent.WHEN_IN_FOCUSED_WINDOW,因此,单击另一个组件(并将焦点从例外按钮移开)将不会阻止SPACE对该按钮的影响.
另一点：如果您测试了上面的代码,您会注意到从JComboBox中选择一个项目会产生两行,如果您选择项目“4”,则JTextArea中的输出为
06003
为什么两个？
谢谢.
解决方法
But doesn’t work,that it is (JComboBox) still respond to the SPACE
key
您应该像这样使用JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT InputMap(您可能会注意到我使用了KeyEvent和KeyStroke.getKeyStroke(int key,int modifier,boolean onRelease),因为它更易读,更不容易出错,即键入错误的字符串参数等.)：
sizesComboBox.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT) .put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE,false),"none");
据我所知,其原因很好地解释了here：
The component contains (or is) the component that has the focus. This
input map is commonly used for a composite component — a component
whose implementation depends on child components. For example,JTables
make all their bindings usingWHEN_ANCESTOR_OF_FOCUSED_COMPONENTso
that if the user is editing,the up-arrow key (for example) still
changes the selected cell.
所以我推断JComboBox是一个复合组件,因此我们需要正确的InputMap – WHEN_ANCESTOR_OF_FOCUSED_COMPONENT,以删除其特定键的所有内部组件KeyBinding功能,即SPACE.
Another point: If you tested the code above,you will notice that
selecting an item from theJComboBoxpoduces two lines of,if you
select item “4” the output in theJTextAreais06001
Why two??
正如@mKorbel所述(他的评论中有1条)可能会发生两件事：
>取消选择一个项目
>选择了一个项目
这些事件成对出现,就像我们选择新值时取消选择旧值一样.因此,我们必须检查并采取适当行动：
@Override
public void itemStateChanged(ItemEvent e)
{
if(e.getStateChange()==ItemEvent.SELECTED) {
//am item was selected do something
}
}
其他建议：
>不要在JFrame上调用setSize.>使用适当的LayoutManager和/或覆盖getPreferredSize以返回适合内容的Dimensions,并在设置可见之前和添加组件之后调用JFrame上的pack().
