我需要限制用户可以输入到 TextField JavaFX 控件中的字符数。我像这样扩展了 TextField

public class LengthLimitedTextField extends TextField {
    /**
     * @param maxCharacters The max allowed characters that can be entered into this {@link TextField}.
     */
    public LengthLimitedTextField(final int maxCharacters) {
        final TextField thisField = this;
        this.textProperty().addListener(new ChangeListener<String>() {
            @Override
            public void changed(ObservableValue<? extends String> observable,
                                String oldValue, String newValue) {
                // Force correct length by deleting the last entered character if text is longer than maxCharacters
                if (newValue.length() > maxCharacters) {
                    thisField.deleteNextChar();
                }
            }
        });
    }
}

这确实按预期工作。但是，假设对于特定的 LengthLimitedTextField，maxCharacters 设置为 3。如果用户输入 4 个或更多字符，并尝试撤消(通过 CTRL+Z 或鼠标上下文菜单)，我收到以下 Exception 并且文本保持不变。

java.lang.IndexOutOfBoundsException
    at javafx.scene.control.TextInputControl.replaceText(TextInputControl.java:368)
    at com.sun.javafx.scene.control.skin.TextFieldSkin.replaceText(TextFieldSkin.java:572)
    at com.sun.javafx.scene.control.behavior.TextFieldBehavior.replaceText(TextFieldBehavior.java:159)
    at com.sun.javafx.scene.control.behavior.TextInputControlBehavior$UndoManager.undo(TextInputControlBehavior.java:442)
    at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.callAction(TextInputControlBehavior.java:137)
    at com.sun.javafx.scene.control.skin.TextInputControlSkin$ContextMenuItem$1.handle(TextInputControlSkin.java:595)
    at com.sun.javafx.scene.control.skin.TextInputControlSkin$ContextMenuItem$1.handle(TextInputControlSkin.java:593)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:28)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.control.MenuItem.fire(MenuItem.java:456)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1197)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer$6.handle(ContextMenuContent.java:1148)
    at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer$6.handle(ContextMenuContent.java:1146)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3328)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3168)
    at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3123)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1563)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2265)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:250)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:173)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:292)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:528)
    at com.sun.glass.ui.View.notifyMouse(View.java:922)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
    at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:73)
    at java.lang.Thread.run(Thread.java:724)

我不确定如何解决这个问题。一个可能(但不理想)的解决方案是完全禁用撤消/重做，但如果不完全覆盖上下文菜单(根据 SO answer ，这并不容易)和默认键盘快捷键，这似乎是不可能的。

所以最终，我的问题是双重的:

是否有其他方法可以限制 TextField 的字符数而不在撤消时抛出异常？或者是否有一种干净的方法可以在应用程序中完全禁用撤消？

编辑:我做了更多研究，根据 https://javafx-jira.kenai.com/browse/RT-30881 的说法，这似乎是一个错误。见 this comment 。那么也许这不可能实现？我打算留下这个问题，希望有人确实有可能的解决方法。

最佳答案

这里我会怎么做: 我会使用普通的文本字段，并添加一个事件过滤器。

设置:

TextField tx = new TextField();
        tx.addEventFilter(KeyEvent.KEY_TYPED, maxLength(3));

事件处理程序:

public EventHandler<KeyEvent> maxLength(final Integer i) {
        return new EventHandler<KeyEvent>() {

            @Override
            public void handle(KeyEvent arg0) {

                TextField tx = (TextField) arg0.getSource();
                if (tx.getText().length() >= i) {
                    arg0.consume();
                }

            }

        };

    }

关于java - 限制 JavaFX TextField 的字符数导致撤消时出现 IndexOutOfBounds，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19184305/