JPanel缩小

Question

以下代码非常适合放大和缩小，但有限制缩小。如何改进此代码以允许无限制地缩小。在这个例子中 您可以随意放大，但缩小可以将放大的面板恢复到原始状态。

public class FPanel extends javax.swing.JPanel {

private Dimension preferredSize = new Dimension(400, 400);    
private Rectangle2D[] rects = new Rectangle2D[50];

public static void main(String[] args) {        
    JFrame jf = new JFrame("test");
    jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    jf.setSize(400, 400);
    jf.add(new JScrollPane(new FPanel()));
    jf.setVisible(true);
}    

public FPanel() {
    // generate rectangles with pseudo-random coords
    for (int i=0; i<rects.length; i++) {
        rects[i] = new Rectangle2D.Double(
                Math.random()*.8, Math.random()*.8, 
                Math.random()*.2, Math.random()*.2);
    }
    // mouse listener to detect scrollwheel events
    addMouseWheelListener(new MouseWheelListener() {
        public void mouseWheelMoved(MouseWheelEvent e) {
            updatePreferredSize(e.getWheelRotation(), e.getPoint());
        }
    });
}

private void updatePreferredSize(int n, Point p) {
    double d = (double) n * 1.08;
    d = (n > 0) ? 1/d : -d;

    int w = (int) (getWidth() * d);
    int h = (int) (getHeight() * d);
    preferredSize.setSize(w, h);

    int offX = (int)(p.x * d) - p.x;
    int offY = (int)(p.y * d) - p.y;
    setLocation(getLocation().x-offX,getLocation().y-offY);

    getParent().doLayout();
}

public Dimension getPreferredSize() {
    return preferredSize;
}

private Rectangle2D r = new Rectangle2D.Float();
public void paint(Graphics g) {
    super.paint(g);
    g.setColor(Color.red);
    int w = getWidth();
    int h = getHeight();
    for (Rectangle2D rect : rects) {
        r.setRect(rect.getX() * w, rect.getY() * h, 
                rect.getWidth() * w, rect.getHeight() * h);
        ((Graphics2D)g).draw(r);
    }       
  }
}

Answer 1

如果我是正确的，您希望将面板缩小至小于100％（原始尺寸或JFrame的尺寸）。 检查此代码。

public class FPanel extends javax.swing.JPanel {

private static int prevN = 0;
private Dimension preferredSize = new Dimension(400,400);    
private Rectangle2D[] rects = new Rectangle2D[50];

public static void main(String[] args) {        
    JFrame jf = new JFrame("test");
    jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    jf.setSize(400, 400);

    JPanel containerPanel = new JPanel();     // extra JPanel 
    containerPanel.setLayout(new GridBagLayout());

    FPanel zoomPanel = new FPanel();
    containerPanel.add(zoomPanel);

    jf.add(new JScrollPane(containerPanel));
    jf.setVisible(true);
}    

public FPanel() {
    // generate rectangles with pseudo-random coords
    for (int i=0; i<rects.length; i++) {
        rects[i] = new Rectangle2D.Double(
                Math.random()*.8, Math.random()*.8, 
                Math.random()*.2, Math.random()*.2);
    }
    // mouse listener to detect scrollwheel events
    addMouseWheelListener(new MouseWheelListener() {
        @Override
        public void mouseWheelMoved(MouseWheelEvent e) {
            updatePreferredSize(e.getWheelRotation(), e.getPoint());
        }
    });
}

private void updatePreferredSize(int n, Point p) {

    if(n == 0)              // ideally getWheelRotation() should never return 0. 
        n = -1 * prevN;     // but sometimes it returns 0 during changing of zoom 
                            // direction. so if we get 0 just reverse the direction.

    double d = (double) n * 1.08;
    d = (n > 0) ? 1 / d : -d;

    int w = (int) (getWidth() * d);
    int h = (int) (getHeight() * d);
    preferredSize.setSize(w, h);

    int offX = (int)(p.x * d) - p.x;
    int offY = (int)(p.y * d) - p.y;
    getParent().setLocation(getParent().getLocation().x-offX,getParent().getLocation().y-offY); 
    //in the original code, zoomPanel is being shifted. here we are shifting containerPanel

    getParent().doLayout();             // do the layout for containerPanel
    getParent().getParent().doLayout(); // do the layout for jf (JFrame)

    prevN = n;
}

@Override
public Dimension getPreferredSize() {
    return preferredSize;
}

private Rectangle2D r = new Rectangle2D.Float();
public void paint(Graphics g) {
    super.paint(g);
    g.setColor(Color.red);
    int w = getWidth();
    int h = getHeight();
    for (Rectangle2D rect : rects) {
        r.setRect(rect.getX() * w, rect.getY() * h, 
                rect.getWidth() * w, rect.getHeight() * h);
        ((Graphics2D)g).draw(r);
    }       
  }
}

解释：我添加了一个包含containerPanel的额外JPanel（zoomPanel）。 containerPanel将适应zoomPanel大小小于JFrame时创建的空白区域。 此外，位置敏感缩放仅在zoomPanel的大小大于帧的大小之前。 zoomPanel小于JFrame后，它将始终居中（GridBagLayout}。