如何在不移动中心的情况下放大JPanel：数学还是Swing？ [英] How to zoom in to JPanel without moving the center: math or Swing?
问题描述
我正在尝试使用Swing制作可缩放的地图。该地图是JScrollPane中的JPanel。放大时，地图会更改大小，而paint（）会将元素绘制在不同的位置。这一切都很有效。
I am trying to make a zoomable map with Swing. The map is a JPanel in a JScrollPane. When zoomed in, the map changes size and paint() paints the elements in a different position. This all works great.
但是，ScrollPane在增加图像大小时没有改变视口，因此放大时总是将我正在看的元素移出屏幕。我尝试用 scrollRectToVisible（）来解决这个问题，但是我无法为矩形找到合适的坐标，因为我在做几何图形时失败了，或者因为我没有我不太了解Swing。
However, the ScrollPane didn't change the viewport while increasing the image size, so that zooming in always moved the elements I was looking at out of the screen. I tried to solve this with scrollRectToVisible(), but I don't manage to get the right coordinates for the rectangle, either because I fail at doing the geometry or because I don't understand Swing all that well.
这就是我所拥有的：
public class MapPanel extends JPanel {
[...]
public void setZoom(double zoom) {
// get the current viewport rectangle and its center in the scaled coordinate system
JViewport vp = (JViewport) this.getParent();
Rectangle rect = vp.getViewRect();
Point middle = getMiddle(rect);
Dimension dim = rect.getSize();
// zoom in
scaler.setZoom(zoom);
setPreferredSize(scaler.transform(dim));
this.revalidate();
// calculate the full size of the scaled coordinate system
Dimension fullDim = scaler.transform(dim);
// calculate the non-scaled center of the viewport
Point nMiddle = new Point((int) ((double) (middle.x)/fullDim.width*dim.width),(int) ((double) (middle.y)/fullDim.height*dim.height));
// this should do the trick, but is always a bit off towards the origin
scrollRectToVisible(getRectangleAroundPoint(nMiddle));
// the below alternative always zooms in perfectly to the center of the map
// scrollRectToVisible(getRectangleAroundPoint(new Point(400,300)));
}
private Rectangle getRectangleAroundPoint(Point p){
Point newP = scaler.transform(p);
Dimension d = railMap.getDimension();
Point corner = new Point(newP.x-d.width/2,newP.y-d.height/2);
return new Rectangle(corner,d);
}
private Point getMiddle(Rectangle r){
return new Point(r.x+r.width/2,r.y+r.height/2);
}
}
这里是Scaler类（没什么好吃的） ，我认为）：
And here's the Scaler class (which does nothing very surprising, I think):
public class Scaler {
private double zoom = 1;
public void setZoom(double zoom) {
this.zoom = zoom;
}
public Point transform(Point2D p){
return new Point((int) (p.getX()*zoom), (int) (p.getY()*zoom));
}
public Dimension transform(Dimension d){
return new Dimension((int) (d.width*zoom), (int) (d.height*zoom));
}
}
谁能告诉我东西在哪里出错了？在我看来，我对地图的当前中心进行了有效计算，并且使用固定的缩放点确实有效...
Who can tell me where things are going wrong? It seems to me I did a valid calculation of the current center of the map, and with a fixed zoom point it does work...
编辑：所以这里的难点是根据旧的视口矩形创建新的视口矩形。
so the hard thing here is to create the new viewport rectangle based on the old viewport rectangle.
推荐答案
我刚刚做了这个非常快速的例子，它基本上试图让滚动窗格保持在所提供图像的中间位置
I just did this really quick example, which basically tries to keep the scroll pane center around the middle of the supplied image
public class TestZooming {
public static void main(String[] args) {
new TestZooming();
}
public TestZooming() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException classNotFoundException) {
} catch (InstantiationException instantiationException) {
} catch (IllegalAccessException illegalAccessException) {
} catch (UnsupportedLookAndFeelException unsupportedLookAndFeelException) {
}
JFrame frame = new JFrame();
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 400);
frame.setLocationRelativeTo(null);
frame.setLayout(new BorderLayout());
final ZoomPane pane = new ZoomPane();
frame.add(new JScrollPane(pane));
frame.setVisible(true);
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
pane.centerInViewport();
}
});
}
});
}
protected class ZoomPane extends JPanel {
private Image background;
private Image scaled;
private float zoom = 1f;
private Dimension scaledSize;
private JViewport con;
public ZoomPane() {
try {
background = ImageIO.read(new File("..."));
scaled = background;
scaledSize = new Dimension(background.getWidth(this), background.getHeight(this));
} catch (IOException ex) {
ex.printStackTrace();
}
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_PLUS, 0), "plus");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_EQUALS, InputEvent.SHIFT_DOWN_MASK), "plus");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_MINUS, 0), "minus");
am.put("plus", new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
setZoom(getZoom() + 0.1f);
}
});
am.put("minus", new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
setZoom(getZoom() - 0.1f);
}
});
setFocusable(true);
requestFocusInWindow();
}
@Override
public void addNotify() {
super.addNotify();
}
public float getZoom() {
return zoom;
}
public void setZoom(float value) {
if (zoom != value) {
zoom = value;
if (zoom < 0) {
zoom = 0f;
}
int width = (int) Math.floor(background.getWidth(this) * zoom);
int height = (int) Math.floor(background.getHeight(this) * zoom);
scaled = background.getScaledInstance(width, height, Image.SCALE_SMOOTH);
scaledSize = new Dimension(width, height);
if (getParent() instanceof JViewport) {
int centerX = width / 2;
int centerY = height / 2;
JViewport parent = (JViewport) getParent();
Rectangle viewRect = parent.getViewRect();
viewRect.x = centerX - (viewRect.width / 2);
viewRect.y = centerY - (viewRect.height / 2);
scrollRectToVisible(viewRect);
}
invalidate();
repaint();
}
}
@Override
public Dimension getPreferredSize() {
return scaledSize;
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (scaled != null) {
g.drawImage(scaled, 0, 0, this);
}
}
protected void centerInViewport() {
Container container = getParent();
if (container instanceof JViewport) {
JViewport port = (JViewport) container;
Rectangle viewRect = port.getViewRect();
int width = getWidth();
int height = getHeight();
viewRect.x = (width - viewRect.width) / 2;
viewRect.y = (height - viewRect.height) / 2;
scrollRectToVisible(viewRect);
}
}
}
}
至于为什么你的工作不起作用，我不能说，我不能运行这个例子，但也许这至少会给你一些想法......
As to why yours doesn't work, I can't say, I can't run the example, but maybe this will at least give you some ideas...
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