Java-拉线动画滞后且不可见

Question

我的程序中的自定义绘图部分出现问题。我希望用户单击界面，然后拖动，同时程序绘制一条跟随光标的线。但问题是，我几乎看不到它。此外，在释放光标按钮后，该线不会停留。

自定义绘制线代码:

public void drawTemporaryLine(int x1,int y1,int x2,int y2,ArrayList<Line> lines){
    repaint();
    g2d = (Graphics2D) getGraphics();
    g2d.setStroke(new BasicStroke(3));
    g2d.setColor(Color.black);
    for(Line l:lines){
        g2d.drawLine(l.getX1(),l.getY1(),l.getX2(),l.getY2());
    }
    g2d.drawLine(x1, y1, x2, y2);
}

鼠标监听器代码:

@Override
    public void mousePressed(MouseEvent e){
        if(draw_on){
            x = e.getX();
            y = e.getY();
        }
    }

    @Override
    public void mouseDragged(MouseEvent e){
        if(draw_on){
            drawPanel.drawTemporaryLine(x, y, e.getX(), e.getY(),lines);
        }
    }

    @Override
    public void mouseReleased(MouseEvent e){
        if(draw_on){
            lines.add(new Line(x,y,e.getX(),e.getY()));
            optionButtons[0].setSelected(false);
            draw_on = false;
        }
    }

有什么办法可以解决吗？谢谢。

Answer 1

尝试覆盖paintComponent。

我尝试自己重现它:

试试这个:)

DrawPanel(扩展 JPanel)

private ArrayList<Line> lines = new ArrayList<Line>();
private Line tmpLine = null;

public DrawPanel() {
    initComponents();
}

public void drawTemporaryLine(int x1, int y1, int x2, int y2) {
    tmpLine = new Line(x1, y1, x2, y2);
}

public void setTemporaryLine(int x1, int y1, int x2, int y2) {
    lines.add(new Line(x1, y1, x2, y2));
}

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D) g;
    g2d.setStroke(new BasicStroke(3));
    g2d.setColor(Color.black);
    for (Line l : lines) {
        g2d.drawLine(l.getX1(), l.getY1(), l.getX2(), l.getY2());
    }
    if (tmpLine != null) {
        g2d.drawLine(tmpLine.getX1(), tmpLine.getY1(), tmpLine.getX2(), tmpLine.getY2());
    }
}

NewJFrame(扩展 JFrame):

private DrawPanel draw = new DrawPanel();
private int x = 0;
private int y = 0;
public NewJFrame() {
    initComponents();
    setSize(800,600);

    add(draw);
    draw.addMouseListener(new java.awt.event.MouseAdapter() {
        public void mouseReleased(java.awt.event.MouseEvent evt) {
            draw.setTemporaryLine(x, y, evt.getX(), evt.getY());
            draw.repaint();
        }
        public void mousePressed(java.awt.event.MouseEvent evt) {
            x = evt.getX();
            y = evt.getY();
        }
    });
    draw.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() {
        public void mouseDragged(java.awt.event.MouseEvent evt) {
            draw.drawTemporaryLine(x, y, evt.getX(), evt.getY());
            draw.repaint();
        }
    });
}