首先：在 verify() 中打开对话框的 InputVerifier 的所有实现都是无效的。他们违反了他们的合同，API doc：
这种方法应该没有副作用。
“应该”的真正意思是“不得”。副作用的正确位置是 shouldYieldFocus。
第二：将副作用（显示消息对话框）正确移动到 shouldYieldFocus 中效果不佳......由于一个错误（他们称之为功能请求；-），这已经超过十年并且在前 10 名RFE
作为一个绕过漏洞的黑客，@dareurdrem 的 mouseListener 与任何可行的黑客一样好:-)
更新
在尝试了一些不同的选项来破解这个错误之后，这里是另一个 hack - 它和所有 hack 一样脆弱（并且不能在 LAF 切换中存活，如果需要动态切换，则必须重新安装）
为了破解鼠标行为，基本的方法是连接到 ui 安装的监听器：
- 找到原文
- 实现一个自定义侦听器，它将大多数事件直接委托给原始事件
- 对于按下的事件，首先请求焦点：如果将委托委托给原始，则不执行任何操作
最后一个项目符号稍微多一些，因为焦点事件可以是异步的，所以我们必须调用检查是否被聚焦。反过来，调用需要在没有人反对的情况下发送释放。
另一个怪癖是 rootPane 的按下操作（对于它的 defaultButton）：它通过无条件地调用 doClick 来完成而不尊重任何 inputVerifiers。这可以通过钩入动作来破解，遵循与钩入mouseListener相同的模式：
- 找到 rootPane 的按下操作
- 实现一个自定义操作，检查可能否决的 inputVerifier：如果不是，则委托给原始操作，否则什么也不做
沿这些行修改的示例：
public class VerifierTest implements Runnable {
private static final long serialVersionUID = 1L;
@Override
public void run() {
InteractiveTestCase.setLAF("Win");
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 200);
JTextField tf = new JTextField("TextField1");
tf.setInputVerifier(new PassVerifier());
frame.add(tf, BorderLayout.NORTH);
final JButton b = new JButton("Button");
frame.add(b);
b.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
System.out.println("Button clicked");
}
});
// hook into the mouse listener
replaceBasicButtonListener(b);
frame.add(new JTextField("not validating, something else to focus"),
BorderLayout.SOUTH);
frame.getRootPane().setDefaultButton(b);
// hook into the default button action
Action pressDefault = frame.getRootPane().getActionMap().get("press");
frame.getRootPane().getActionMap().put("press", new DefaultButtonAction(pressDefault));
frame.setVisible(true);
}
protected void replaceBasicButtonListener(AbstractButton b) {
final BasicButtonListener original = getButtonListener(b);
if (original == null) return;
Hacker l = new Hacker(original);
b.removeMouseListener(original);
b.addMouseListener(l);
}
public static class Hacker implements MouseListener {
private BasicButtonListener original;
/**
* @param original the listener to delegate to.
*/
public Hacker(BasicButtonListener original) {
this.original = original;
}
/**
* Hook into the mousePressed: first request focus and
* check its success before handling it.
*/
@Override
public void mousePressed(final MouseEvent e) {
if (SwingUtilities.isLeftMouseButton(e)) {
if(e.getComponent().contains(e.getX(), e.getY())) {
// check if we can get the focus
e.getComponent().requestFocus();
invokeHandleEvent(e);
return;
}
}
original.mousePressed(e);
}
/**
* Handle the pressed only if we are focusOwner.
*/
protected void handlePressed(final MouseEvent e) {
if (!e.getComponent().hasFocus()) {
// something vetoed the focus transfer
// do nothing
return;
} else {
original.mousePressed(e);
// need a fake released now: the one from the
// original cycle might never has reached us
MouseEvent released = new MouseEvent(e.getComponent(), MouseEvent.MOUSE_RELEASED,
e.getWhen(), e.getModifiers(),
e.getX(), e.getY(), e.getClickCount(), e.isPopupTrigger()
);
original.mouseReleased(released);
}
}
/**
* focus requests might be handled
* asynchronously. So wrap the check
* wrap the block into an invokeLater.
*/
protected void invokeHandleEvent(final MouseEvent e) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
handlePressed(e);
}
});
}
@Override
public void mouseClicked(MouseEvent e) {
original.mouseClicked(e);
}
@Override
public void mouseReleased(MouseEvent e) {
original.mouseReleased(e);
}
@Override
public void mouseEntered(MouseEvent e) {
original.mouseEntered(e);
}
@Override
public void mouseExited(MouseEvent e) {
original.mouseExited(e);
}
}
public static class DefaultButtonAction extends AbstractAction {
private Action original;
/**
* @param original
*/
public DefaultButtonAction(Action original) {
this.original = original;
}
@Override
public void actionPerformed(ActionEvent e) {
JRootPane root = (JRootPane) e.getSource();
JButton owner = root.getDefaultButton();
if (owner != null && owner.getVerifyInputWhenFocusTarget()) {
Component c = KeyboardFocusManager
.getCurrentKeyboardFocusManager()
.getFocusOwner();
if (c instanceof JComponent && ((JComponent) c).getInputVerifier() != null) {
if (!((JComponent) c).getInputVerifier().shouldYieldFocus((JComponent) c)) return;
}
}
original.actionPerformed(e);
}
}
/**
* Returns the ButtonListener for the passed in Button, or null if one
* could not be found.
*/
private BasicButtonListener getButtonListener(AbstractButton b) {
MouseMotionListener[] listeners = b.getMouseMotionListeners();
if (listeners != null) {
for (MouseMotionListener listener : listeners) {
if (listener instanceof BasicButtonListener) {
return (BasicButtonListener) listener;
}
}
}
return null;
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new VerifierTest());
}
public static class PassVerifier extends InputVerifier {
/**
* Decide whether or not the input is valid without
* side-effects.
*/
@Override
public boolean verify(JComponent input) {
final JTextField tf = (JTextField) input;
String pass = tf.getText();
if (pass.equals("Manish"))
return true;
return false;
}
/**
* Implemented to ask the user what to do if the input isn't valid.
* Note: not necessarily the best usability, it's mainly to
* demonstrate the different effects on not/agreeing with
* yielding focus transfer.
*/
@Override
public boolean shouldYieldFocus(final JComponent input) {
boolean valid = super.shouldYieldFocus(input);
if (!valid) {
String message = "illegal value: " + ((JTextField) input).getText();
int goAnyWay = JOptionPane.showConfirmDialog(input, "invalid value: " +
message + " - go ahead anyway?");
valid = goAnyWay == JOptionPane.OK_OPTION;
}
return valid;
}
}
}