禁止在JTabbedPane中更改选项卡

问题描述：

我正在尝试阻止用户在当前标签无效时更改标签。
所以当他点击一个标签时，我想检查当前标签是否有效，如果不是，请保持当前标签。
我试图使用不起作用的VetoableChangeListener，代码永远不会进入vetoableChange方法：

I'm trying to prevent the user from changing a tab when the current tab is not valid. So when he clicks on a tab, I want to check if the current one is "valid", and if not, stay on the current tab. I tried to use a VetoableChangeListener which didn't work, the code never goes inside the vetoableChange method:

jTabbedPane.addVetoableChangeListener(new VetoableChangeListener() {

  @Override
  public void vetoableChange(PropertyChangeEvent evt) throws PropertyVetoException {
    if (!isCurrentTabValid()) {
      throw new PropertyVetoException("test", evt);
    }
  }
});

我该如何正确地做到这一点？

How can I do this properly?

谢谢！

答

VetoableChangeListener仅在其注册的类触发可否决的propertyChange时才有用。 JComponents和子类中的大多数（所有？从未遇到过）属性都不可撤销。此外，选择由SingleSelectionModel处理，而不是组件本身。

A VetoableChangeListener is useful only if the class it is registered with fires a vetoable propertyChange. Most (all? never came across one) properties on JComponents and subclasses are not vetoable. Plus the selection is handled by a SingleSelectionModel, not the component itself.

该模型是支持可否决更改的钩子

That model is the hook to support vetoable changes

实现一个自定义模型，在选择更改时触发vetoablePropertyChange

如果没有任何侦听器反对，请继续进行更改，否则什么都不做

将自定义模型设置为tabbedPane

实现包含验证逻辑的VetoablePropertyChangeListener

将vetoableListener注册到代码中的模型

implement a custom model that fires a vetoablePropertyChange on selection change
if none of its listeners object, go ahead with the change, otherwise do nothing
set the custom model to the tabbedPane
implement a VetoablePropertyChangeListener which contains the validation logic
register the vetoableListener to the model

，类似于

public static class VetoableSingleSelectionModel extends
        DefaultSingleSelectionModel {

    private VetoableChangeSupport vetoableChangeSupport;

    @Override
    public void setSelectedIndex(int index) {
        if (getSelectedIndex() == index)
            return;
        try {
            fireVetoableChange(getSelectedIndex(), index);
        } catch (PropertyVetoException e) {
            return;
        }
        super.setSelectedIndex(index);
    }

    private void fireVetoableChange(int oldSelectionIndex,
            int newSelectionIndex) throws PropertyVetoException {
        if (!isVetoable())
            return;
        vetoableChangeSupport.fireVetoableChange("selectedIndex",
                oldSelectionIndex, newSelectionIndex);

    }

    private boolean isVetoable() {
        if (vetoableChangeSupport == null)
            return false;
        return vetoableChangeSupport.hasListeners(null);
    }

    public void addVetoableChangeListener(VetoableChangeListener l) {
        if (vetoableChangeSupport == null) {
            vetoableChangeSupport = new VetoableChangeSupport(this);
        }
        vetoableChangeSupport.addVetoableChangeListener(l);
    }

    public void removeVetoableChangeListener(VetoableChangeListener l) {
        if (vetoableChangeSupport == null)
            return;
        vetoableChangeSupport.removeVetoableChangeListener(l);
    }

}

// usage
JTabbedPane pane = new JTabbedPane();
VetoableSingleSelectionModel model = new VetoableSingleSelectionModel();
VetoableChangeListener validator = new VetoableChangeListener() {

    @Override
    public void vetoableChange(PropertyChangeEvent evt)
            throws PropertyVetoException {
        int oldSelection = (int) evt.getOldValue();
        if ((oldSelection == -1) || isValidTab(oldSelection)) return;

        throw new PropertyVetoException("change not valid", evt);

    }

    private boolean isValidTab(int oldSelection) {
        // implement your validation logic here
        return false;
    }
};
model.addVetoableChangeListener(validator);
pane.setModel(model);
pane.addTab("one", new JLabel("here we are and stay"));
pane.addTab("other", new JLabel("poor me, never shown"));

禁止在JTabbedPane中更改选项卡

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