layout - 将 TextArea 高度绑定到其内容

Question

JavaFX：是否可以将TextArea高度（行数）绑定到其内容的高度？
我想TextArea在编写文本时动态更改高度。

Answer 1

看看JavaFX 实用程序类。虽然这不是使用绑定的解决方案，但computeTextHeight(Font font, String text, double wrappingWidth)方法可以帮助您。

Answer 2

这是一个准确、简单且有效的解决方案：

SimpleIntegerProperty count = new SimpleIntegerProperty(20);
int rowHeight = 10;

txtArea.prefHeightProperty().bindBidirectional(count);
txtArea.minHeightProperty().bindBidirectional(count);
txtArea.scrollTopProperty().addListener(new ChangeListener<Number>(){
    @Override
    public void changed(ObservableValue<? extends Number> ov, Number oldVal, Number newVal) {
        if(newVal.intValue() > rowHeight){
            count.setValue(count.get() + newVal.intValue());
        }
    }
});

或者，您可以使用 lambdas 来进一步简化语法：

SimpleIntegerProperty count=new SimpleIntegerProperty(20);
int rowHeight = 10;

textArea.prefHeightProperty().bindBidirectional(count);
textArea.minHeightProperty().bindBidirectional(count);
textArea.scrollTopProperty().addListener((ov, oldVal, newVal) -> {
    if(newVal.intValue() > rowHeight){
        count.setValue(count.get() + newVal.intValue());
    }
});

Answer 3

在 javafx8 中运行良好的解决方案（隐藏工具栏的灵感来自JavaFX TextArea Hiding Scroll Bars）：

class MyTextArea extends TextArea {

    @Override
    protected void layoutChildren() {
        super.layoutChildren();
        ScrollBar scrollBarv = (ScrollBar) this.lookup(".scroll-bar:vertical");
        if (scrollBarv != null) {
            System.out.println("hiding vbar");
            ((ScrollPane) scrollBarv.getParent()).setVbarPolicy(ScrollPane.ScrollBarPolicy.NEVER);
        }
        ScrollBar scrollBarh = (ScrollBar) this.lookup(".scroll-bar:horizontal");
        if (scrollBarh != null) {
            System.out.println("hiding hbar");
            ((ScrollPane) scrollBarh.getParent()).setHbarPolicy(ScrollPane.ScrollBarPolicy.NEVER);
        }
    }

    @Override
    protected double computePrefWidth(double width) {
        Bounds bounds = getTextBounds();
        Insets insets = getInsets();
        double w = Math.ceil(bounds.getWidth() + insets.getLeft() + insets.getRight());
        return w;
    }

    @Override
    protected double computePrefHeight(double height) {
        Bounds bounds = getTextBounds();
        Insets insets = getInsets();
        double h = Math.ceil(bounds.getHeight() + insets.getLeft() + insets.getRight());
        return h;
    }

    //from https://stackoverflow.com/questions/15593287/binding-textarea-height-to-its-content/19717901#19717901
    public Bounds getTextBounds() {
        //String text = (textArea.getText().equals("")) ? textArea.getPromptText() : textArea.getText();
        String text = "";
        text = this.getParagraphs().stream().map((p) -> p + "W\n").reduce(text, String::concat);
        text += "W";
        helper.setText(text);
        helper.setFont(this.getFont());
        // Note that the wrapping width needs to be set to zero before
        // getting the text's real preferred width.
        helper.setWrappingWidth(0);
        return helper.getLayoutBounds();
    }
}