问题描述
我有一个要画的jpanel。我希望能够使用鼠标滚轮进行放大和缩小,但是我想缩放到鼠标的位置,以使鼠标下方的点保持不变。我找到了一些questions here on stackoverflow,但它们对我没有用。
通过实现here所描述的内容,我几乎可以完成我想做的事情。这是我的代码:
public class MyPanel extends JPanel {
...
private double zoom = 1;
private double zoom_old = 1;
private int zoomPointX;
private int zoomPointY;
...
class CustomMouseWheelListener implements MouseWheelListener {
@Override
public void mouseWheelMoved(MouseWheelEvent e) {
zoomPointX = e.getX();
zoomPointY = e.getY();
if (e.getPreciseWheelRotation() < 0) {
zoom -= 0.1;
} else {
zoom += 0.1;
}
if (zoom < 0.01) {
zoom = 0.01;
}
repaint();
}
}
...
protected void paintComponent(Graphics g) {
Graphics2D g2D = (Graphics2D) g;
super.paintComponent(g2D);
if (zoom != zoom_old) {
double scalechange = zoom - zoom_old;
zoom_old = zoom;
double offsetX = -(zoomPointX * scalechange);
double offsetY = -(zoomPointY * scalechange) ;
AffineTransform at = new AffineTransform();
at.scale(zoom,zoom);
at.translate(offsetX,offsetY);
g2D.setTransform(at);
}
a_different_class_where_i_do_some_drawing.draw(g2D);
}
}
这个ALMOST可以满足我的要求。如果尝试缩放,我会注意到已考虑了鼠标的位置,因此,例如,如果将鼠标放在面板的左侧,则它将在左侧大致放大。但是,它不能完全缩放到鼠标上,因此鼠标下方的点仍会更改。
有人可以帮我解决这个问题吗?
编辑: 这是上面发布的代码所发生的情况的图片:首先,我将鼠标放在蓝色正方形上,然后使用鼠标滚轮滚动。如您所见,如果更改鼠标位置:
解决方法
我通过实施here
解决了问题这是更新的代码:
public class MyPanel extends JPanel {
...
private double zoom = 1;
private int zoomPointX;
private int zoomPointY;
...
class CustomMouseWheelListener implements MouseWheelListener {
@Override
public void mouseWheelMoved(MouseWheelEvent e) {
zoomPointX = e.getX();
zoomPointY = e.getY();
if (e.getPreciseWheelRotation() < 0) {
zoom -= 0.1;
} else {
zoom += 0.1;
}
if (zoom < 0.01) {
zoom = 0.01;
}
repaint();
}
}
...
protected void paintComponent(Graphics g) {
Graphics2D g2D = (Graphics2D) g;
super.paintComponent(g2D);
AffineTransform at = g2D.getTransform();
at.translate(zoomPointX,zoomPointY);
at.scale(zoom,zoom);
at.translate(-zoomPointX,-zoomPointY);
g2D.setTransform(at);
a_different_class_where_i_do_some_drawing.draw(g2D);
}
}