java swing jeditorpane中段落内的可折叠句子

Question

I want to create collapsable (or foldable ) sentences. Importantly, they should be embedded into paragraphs and flow with the rest of the text. I'm working with Java / Swing, in a JEditorpane and an extension of the DefaultStyledDocument . For instance:

[-] This is sentence
one. [-] This is
sentence two. [-] This is
sentence three.

When sentence two is collapsed, it becomes:

[-] This is sentence
one. [+] [-] This is
sentence three.

The webpage has an example of how to collapse a region of the document, but this region is not embedded into the paragraph. My problem is trying to decide which View to base this on.

• Create SentenceView as extension of LabelView : problem is that LabelView does not support sections with different style attributes. Maybe I can add this, but most Views with multiple children are based on CompositeView.
• Create SentenceView as extension of BoxView : maybe, but I cannot figure out how to get this embedded into a ParagraphView in a way that it flows properly with the text.
• Extend ParagraphView : I could create some sort of super-aware ParagraphView that understands where sentences start and end and handles all the collapsing. I could probably get this to work, but this is almost surely the wrong-way-to-do-it.

If anybody could give me a pointer (or gut feeling) what I could best base SentenceView on (or some other tip to help me a long) I would highly appreciate that.

Answer 1

I'll try to answer my own question. After some code review of the standard Java Swing classes I decided that much of the functionality that I needed is implemented in FlowView and ParagraphView . Notably, there is the layoutRow method of FlowStrategy that is responsible for finding breakpoints and delivering rows of text. In my SentenceView I have to do more or less exactly the same. The only difference is that I don't want to layout rows myself. Instead, my SentenceView needs to implement breakView , so that the paragraph that contains the sentence can cut up the sentence in pieces and lay them out. Unfortunately, I cannot find a way in which I can re-use the function layoutRow and I ended up copy/pasting a fair bit of that code.

During the implementation of my (collapsable) SentenceView I bumped into a number of Java 7 bugs. For instance, see the Java 7 line wrapping bug . Also, it seems to be ambiguous in Java whether the minimumSize is based on breakpoints at spaces (which are excellent break weights) or at characters (which are good break weights). GlyphView and LabelView give their minimumSize on the basis of excellent break weights, but ParagraphView mixes this with any breakpoints better than BadBreakWeight (see the code for calculateMinorAxisRequirements ). Which is rather confusing.

Anyway, let me highlight the most important parts of my implementation of SentenceView . I'm leaving out the actual foldable part as it is a bit fiddly and not the part I was struggling with. I'll focus on the breakView functionality.

public class SentenceView extends BoxView {
    boolean containsStart;
    boolean containsEnd;
    public SentenceView(Element elem) {
        super(elem, View.X_AXIS);
        containsStart = true;
        containsEnd = true;
    }
    ...

I also have a getter isStart for containsStart and isEnd for containsEnd . The breakView method is mostly copied, as I said:

public View breakView(int axis, int p0, float pos, float len) {
    if (axis == View.Y_AXIS) return this;
    if (p0 == getStartOffset() && len >= getPreferredSpan(axis)) return this;
    float spanLeft = len;

    int p = p0;
    float x = pos;
    int end = getEndOffset();
    Row row = new Row(getElement());
    TabExpander te = (this instanceof TabExpander) ? (TabExpander)this : null;
    int breakWeight = BadBreakWeight;
    float breakX = 0f;
    float breakSpan = 0f;
    int breakIndex = -1;
    int n = 0;

    if (p0 == getStartOffset() && isStart()) row.setContainsStart(true);

    Vector<View> viewBuffer = new Vector<View>(10, 10);
    while (p < end && spanLeft >= 0) {
        View v = createView(p);
        if (v == null) break;

        int bw = v.getBreakWeight(axis, x, spanLeft);
        if (bw >= ForcedBreakWeight) {
            View w = v.breakView(axis, p, x, spanLeft);
            if (w != null) {
                viewBuffer.add(w);
            } else if (n == 0) {
                viewBuffer.add(v);
            }
            break;
        } else if (bw >= breakWeight && bw > BadBreakWeight) {
            breakWeight = bw;
            breakX = x;
            breakSpan = spanLeft;
            breakIndex = n;
        }

        float chunkSpan;
        if (v instanceof TabableView) {
                chunkSpan = ((TabableView)v).getTabbedSpan(x, te);
            } else {
                chunkSpan = v.getPreferredSpan(axis);
            }
        if (isEnd() && v.getEndOffset() == end) {
            if ((chunkSpan <= spanLeft) && (chunkSpan > spanLeft)) {
                spanLeft = chunkSpan - 1;
            }
        }
        if (chunkSpan > spanLeft && breakIndex >= 0) {

                if (breakIndex < n) {
                    v = viewBuffer.get(breakIndex);
                }
                for (int i = n - 1; i >= breakIndex; i--) {
                    viewBuffer.remove(i);
                }

                v = v.breakView(axis, v.getStartOffset(), breakX, breakSpan);
        }

        spanLeft -= chunkSpan;
        x += chunkSpan;
        viewBuffer.add(v);
        p = v.getEndOffset();
        n++;
    }
    // cloning:
    Vector<View> viewBuffer2 = new Vector<>();
    for (int j = 0; j < viewBuffer.size(); j++) {

        View v = viewBuffer.get(j);
        if (v instanceof MyLabelView) {
            v = (View) ((MyLabelView)v).createClone();
        }  else {
            throw new RuntimeException("SentenceView can only contain MyLabelView");
        }
        viewBuffer2.add(v);
    }
    View[] views = new View[viewBuffer2.size()];
        viewBuffer2.toArray(views);
        row.replace(0, row.getViewCount(), views);
        return row;
    }       

There are a few things to note here. First, breakView will return itself or a SentenceView.Row . Secondly, I'm using a MyLabelView instead of LabelView , mostly because of the earlier mentioned line wrapping bug. I'm still new to Java and Java Swing and I was struggling a bit with the Cloneable interface and clone is protected and final. So, I just implemented createClone to call clone . Not very elegant, but not my main worry either. The cloning I needed because the subviews get reparented when they are added to a Row . But, if at a later stage the original SentenceView gets displayed again (because breaking is no longer necessary), this leads to problems. I think a better way may be to reparent all the subviews back to this but I could not figure out where to best do this. I would welcome comments on this, though. Also, in order to actually implement foldability, the SentenceView will have to share its foldable status with the created Rows . I did that by wrapping a boolean in an object and then sharing the object.

I'll give the following methods without code, as they are not too difficult or can be copied/amended from ParagraphView .

protected SizeRequirements calculateMajorAxisRequirements(int axis,
                                                 SizeRequirements r)
protected SizeRequirements calculateMinorAxisRequirements(int axis, SizeRequirements r)
public View createFragment(int p0, int p1)
protected View createView(int startOffset)

protected void layoutMinorAxis(int targetSpan, int axis, int[] offsets, int[] spans) {
    baselineLayout(targetSpan, axis, offsets, spans);
}

And then, finally, there is the Row inner class:

class Row extends SentenceView {
    Row(Element elem) {
        super(elem);
        containsStart = false;
        containsEnd = false;
    }
    public float getAlignment(int axis) {
        if (axis == View.X_AXIS) return 0;
        return super.getAlignment(axis);
    }

    public AttributeSet getAttributes() {
        View p = getParent();
        return (p != null) ? p.getAttributes() : null;
    }
    protected int getViewIndexAtPosition(int pos) {
        if(pos < getStartOffset() || pos >= getEndOffset())
            return -1;
        for(int counter = getViewCount() - 1; counter >= 0; counter--) {
            View v = getView(counter);
            if(pos >= v.getStartOffset() &&
               pos < v.getEndOffset()) {
                return counter;
            }
        }
        return -1;
    }
    protected void loadChildren(ViewFactory f) {
    }
}

That works. It is a bit unfortunate that I ended up replicating quite a bit of existing code, but it isn't obvious to me how to implement breakView on the X axis in paragraphView or how to find another way to do this. Also, in order to implement foldability, a bit more work needs to be done. The paint method needs to be altered to draw [-] in front (if containsStart is true). The minimumSize and preferredSize need to take into account this extra bit of space (I'm using insets for that). The SentenceView and the Rows it creates need to share the folded-status. If the view is folded, the minimumSize and preferredSize will be equal to the size of the [+] marker. There is some fiddling around with viewToModel , modelToView , getNextEastWestVisualPositionFrom . This is all similar to Folding (collapsible) area in the JEditorPane/JTextPane . The only thing that I like a bit better in my code is the part in the mouse listener that checks whether the event took place inside a SentenceView as I'm avoiding the use of viewToModel . So, let me give that as well:

MouseListener sentenceCollapse = new MouseAdapter() {
    public void mouseClicked(MouseEvent e) {
        JEditorPane src = (JEditorPane)e.getSource();
        View v = src.getUI().getRootView(src);
        Insets ins = src.getInsets();
        int x = ins.left;
        int y = ins.top;
        Point p = e.getPoint();
        p.translate(-x, -y);
        Rectangle alloc = new Rectangle(0,0,Short.MAX_VALUE,Short.MAX_VALUE);

        while (v != null && !(v instanceof SentenceView)) {
            View vChild = null;
            int n = v.getViewCount();
            for (int i = 0; i < n; i++) {
                Rectangle r = v.getChildAllocation(i, alloc).getBounds();

                if (r.contains(p)) {
                    vChild = v.getView(i); 
                    alloc = (Rectangle) r.clone();
                }
            }
            v = vChild;
        }
        if (v != null && v instanceof SentenceView) {
        <<< unfold or fold the Sentence View >>>
        src.repaint();
    }
};

Hope this is useful.