限制JavaFX TextField的字符数会导致撤消时出现IndexOutOfBounds [英] Limiting character count of JavaFX TextField causes IndexOutOfBounds on Undo

问题描述

我要求限制用户可以输入的字符数到 TextField JavaFX控件。我已扩展 TextField ，因此

I have the requirement to limit the number of characters a user can input into a TextField JavaFX control. I have extended TextField like so

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），我收到以下异常，文本保持不变。

This does work as intended. However, lets say that for a particular LengthLimitedTextField the maxCharacters is set to 3. If the user enters 4 or more characters, and attempts to Undo (either via CTRL+Z or mouse context menu), I receive the following Exception and the text is left unchanged.

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)

我不知道我是怎么做的可以解决这个问题一个可能的（但不是理想的）解决方案是完全禁用撤消/重做，但如果没有完全覆盖上下文菜单（根据此 SO answer ，并不容易）和默认的键盘快捷键。

I'm not sure how I can resolve this. A possible (but not ideal) solution was to disable Undo/Redo completely, but that doesn't appear possible without completely override the context menu (which according to this SO answer, isn't easy) and the default keyboard shortcuts.

所以最终，我的问题是双重的：

So ultimately, my question is twofold:

是否有其他方法可以限制字符数一个 TextField 而没有在撤消上抛出异常？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？

Is there possibly another way I can limit the number of characters of a TextField without throwing an exception on Undo? Or is there a clean way to completely disable Undo in the application?

编辑：我做了一些研究并根据 https://javafx-jira.kenai.com/browse/RT-30881 这似乎是是个bug。参见此评论。那么也许这是不可能实现的呢？我将打开这个问题，希望有人确实有可能的解决方法。

Edit: I did some more research and according to https://javafx-jira.kenai.com/browse/RT-30881 this appears to be a bug. See this comment. So perhaps this isn't possible to achieve then? I'm going to leave the question open in hopes someone does have a possible workaround.

推荐答案

我在这里怎么做：
我会使用普通的文本字段，并会添加一个事件过滤器。

Here how I would do it: I would use a normal textfield, and would add an event filter.

设置：

The set up:

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

事件处理程序：

The event handler:

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();
                }

            }

        };

    }

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