Java Swing - 如何在 Canvas 中绘制新线并将其添加到现有线中？

Question

我已经在 J​​ava Swing 中制作了哥本哈根 map ，但我希望能够在 map 上绘制新线，然后将它们添加到我从缓冲阅读器中获取的现有线中。我尝试将新绘制的线条添加到临时线条的数组列表中，但这似乎不起作用 - 我根本无法再在 Canvas 上绘制。有人可以帮忙吗？

public class Model extends Observable implements Iterable<Line2D>, Serializable {
    private List<Line2D> lines;
    private List<Line2D> tmpLines;

    public Model() {
        lines = new ArrayList<>();
        tmpLines = new ArrayList<>();
    }

    public Model(String filename) {
        readFromFile(filename);
    }

    public void add(Line2D line) {
        lines.add(line);
        dirty();
    }

    public void dirty() {
        setChanged();
        notifyObservers();
    }

    public void readFromFile(String filename) {
        lines = new ArrayList<>();
        tmpLines = new ArrayList<>();
        try {
            BufferedReader b = new BufferedReader(new FileReader(filename));
            for (String line = b.readLine(); line != null; line = b.readLine() ) {
                String[] tokens = line.split(" ");
                if (tokens[0].equals("LINE")) {
                    double x1 = Double.parseDouble(tokens[1]);
                    double y1 = Double.parseDouble(tokens[2]);
                    double x2 = Double.parseDouble(tokens[3]);
                    double y2 = Double.parseDouble(tokens[4]);
                    lines.add(new Line2D.Double(x1, y1, x2, y2));
                }

            }

        } 
        catch (FileNotFoundException e) {
            e.printStackTrace();
        } 
        catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * Returns an iterator over elements of type {@code T}.
     *
     * @return an Iterator.
     */
    @Override
    public Iterator<Line2D> iterator() {
        return lines.iterator();
    }

    public Line2D removeLastFromTmpLines() {
        Line2D line = tmpLines.remove(tmpLines.size() - 1);
        dirty();
        return line;
    }

    public Line2D removeLastFromLines() {
        Line2D line = lines.remove(lines.size() - 1);
        dirty();
        return line;
    }

    public void addTmpLinesToLines() {
        lines.addAll(tmpLines);
        dirty();
    }

    public void addToTmpLines(Line2D line2D) {
        tmpLines.add(line2D);
        dirty();
    }

    public List<Line2D> getTmpLines() {
        return tmpLines;
    }
}
public class MouseController extends MouseAdapter {
    private Model model;
    private CanvasView canvas;
    private Point2D lastMousePosition;

    public MouseController(CanvasView c, Model m) {
        canvas = c;
        model = m;

        canvas.addMouseListener(this);
        canvas.addMouseWheelListener(this);
        canvas.addMouseMotionListener(this);
    }

    @Override
    public void mouseDragged(MouseEvent e) {
        Point2D currentMousePosition = e.getPoint();
        if (canvas.inDrawingMode()) {
            Point2D origin = model.removeLastFromTmpLines().getP1();
            model.addToTmpLines(new Line2D.Double(origin, canvas.toModelCoords(currentMousePosition)));
        }
        else {
            double dx = currentMousePosition.getX() - lastMousePosition.getX();
            double dy = currentMousePosition.getY() - lastMousePosition.getY();
            canvas.pan(dx, dy);
        }
        lastMousePosition = currentMousePosition;
    }

    @Override
    public void mousePressed(MouseEvent e) {
       lastMousePosition = e.getPoint();
       if (canvas.inDrawingMode()) {
           model.addToTmpLines(new Line2D.Double(
               canvas.toModelCoords(lastMousePosition),
               canvas.toModelCoords(lastMousePosition)));
       }
    }

    public void mouseMoved(MouseEvent e) {
        Point2D modelCoords = canvas.toModelCoords(e.getPoint());
        //System.out.println("Screen: [" + e.getX() + ", " + e.getY() + "], "+"Model: [" + modelCoords.getX() + ", " + modelCoords.getY() + "]");
    }


    @Override
    public void mouseWheelMoved(MouseWheelEvent e) {
        double factor = pow(1.1, e.getWheelRotation());
        canvas.zoom(factor, -e.getX(), -e.getY());
    }
}

Answer 1

说实话，我不太理解代码，因为我没有看到paint方法，所以我不明白你对数组做了什么。我假设您在列表中添加行并使用迭代器方法将它们返回到绘制方法。

我假设您在此处按下鼠标按钮时添加一个点，而不是一条线:

model.addToTmpLines(new Line2D.Double(
               canvas.toModelCoords(lastMousePosition),
               canvas.toModelCoords(lastMousePosition)));

一个点，因为坐标相同。然后，当拖动鼠标时，您将删除最后一条线(点)并从点的起始坐标到实际鼠标位置添加一条新线。这样对吗？但是，什么时候将行从 tmp 列表传递到实际列表呢？您是否不需要 mouseReleased 方法将行从 tmp 列表传递到实际列表？并且迭代器方法仅返回列表行，因此我假设最后一行(被拖动的行)未绘制，因为实际的新行位于 tmpLines 列表中并且未返回。

但我认为我没有看到全貌，所以我的评论可能没有用......