java - 段落 View 首选项更改

Question

我的 Swing 应用程序中有一个 JTextPane，其上方有一个 JSlider。当我拖动 slider 时，我希望当前具有插入符号的 JTextPane 段落减少/增加其宽度(并相应地调整高度)。我已经实现了以下代码，但似乎没有任何效果。我之前已经实现了一些与此类似的功能，但我想我现在缺少一些东西。谁能指出错误。

public class ExtendedParagraphView extends ParagraphView {
    /** Maximum width of a single char (assuming monospaced font) {#{@value}}*/
    public  static  final   float   CHARACTER_WIDTH = (float) 8.0;
    /* DELTA is used to adjust the width of the paragraph view */
    private float   DELTA = (float) 0.0;
    public ExtendedParagraphView(Element arg0) {
        super(arg0);
    }

    /**
     * Shift the paragraph to the left/right by an amount given by the 
     * difference between the end and the start position
     * @param start
     * @param end
     */
    public void shiftParagraphView (int start, int end) {
        /* The difference in pixel position is always calculated in terms of the
         * difference between the end and start position */
        DELTA = (float)(end - start) * ExtendedParagraphView.CHARACTER_WIDTH;
    }

    @Override
    public float getPreferredSpan (int axis) {
        if (axis == View.Y_AXIS) {
            return  super.getPreferredSpan(axis);
        }
        return  super.getPreferredSpan(axis) - this.DELTA;
    }
}

以下是调用 ExtendedParagraphView 内的 shiftParagraphView 方法的代码。

protected void shiftTextPaneElement (int start, int end) {
    if (start == end) {
        return;
    }

    int dot = this.textpane.getCaret().getDot();
    int mark = this.textpane.getCaret().getMark();
    int pos = mark <= dot ? mark : dot;

    View view = textpane.getUI().getRootView(textpane);
    int n = view.getViewCount();
    for (int i = 0; i < n; i++) {
        View v = view.getView(i);
        if (v instanceof BoxView) {
            int m = v.getViewCount();
            for (int k = 0; k < m; k++) {
                View vv = v.getView(k);
                if (vv instanceof ExtendedParagraphView) {
                    ((ExtendedParagraphView) vv).
                        shiftParagraphView(start, end);
                    return; //only a single paragraph is currently shifted
                }
            }
        }
    }
}

注意:经过一番尝试和错误后，以下内容似乎有效，

public void shiftParagraphView (int start, int end) {
    DELTA = (float)(end - start) * ExtendedParagraphView.CHARACTER_WIDTH;
    this.setInsets(getTopInset(), (short) (getLeftInset() + DELTA), 
        getBottomInset(), getRightInset());
    this.getParent().preferenceChanged(this, true, false);
    this.getContainer().repaint();
}

Answer 1

使用 yourStyledDocument.setParagraphAttributes() 而不是指定所需的左右缩进。