Zoom in and out of jPanel

问题

I am wondering what is the best way to retrieve the location of a mouse clic after a zoom was made using paintComponent of a panel? (The location relative to this zoom).

Here's the zoom code :

public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g;
    if(zoomer==true){    
        at.scale(zoom,zoom);//at = AffineTransform...
        zoomer=false;
    }
    g2.transform(at);

In my main class, I use a mouse listener private class and override the mouseRelase method :

 @Override
    public void mouseReleased(MouseEvent e) 
     e.getX();//Location of the mouse on the X axis

I am drawing different shapes such as dots. Every dot has it's Pixels locations stored so if a create it at X:20 and Y:30 this never changes. When I call paintComponent, it is scaled either bigger or smaller. My problem is, I can clic on the location of these dots on the panel and it gives me some information in some textFields about the dots I clicked on. If the panel has been zoomed in/out, the location of the clic is still the same so let's say I zoom in, the shapes won't be at x:20 and y:30 but at a random location based on the scale. How can I ajust my clic location to this scale?

Not sure if I am making myselft clear so do not hesitate if you need more information.

Thank you

回答1:

Alright, I have been working all night long and finally figured out how to do this.

First of all here's what happens when I roll the mouse wheel :

 @Override
    public void mouseWheelMoved(MouseWheelEvent e) {

        //Zoom in
        if(e.getWheelRotation()<0){
            mydrawer.setZoomFactor(1.1*mydrawer.getZoomFactor());
            mydrawer.repaint();
        }
        //Zoom out
        if(e.getWheelRotation()>0){
            mydrawer.setZoomFactor(mydrawer.getZoomFactor()/1.1);
            mydrawer.repaint();
        }
    }

The setZoomFactor method does this :

public void setZoomFactor(double factor){        
    if(factor<this.zoomFactor){
        this.zoomFactor=this.zoomFactor/1.1;
    }
    else{
        this.zoomFactor=factor;
    }
    this.zoomer=true;
}

After, when I call repaint() I transform my Graphics2D object to zoom like this :

 @Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g;
    if(zoomer==true){    
        at = new AffineTransform();
        at.scale(zoomFactor,zoomFactor);
        zoomer=false;
        g2.transform(at);
    }
 }

At this point, nothing really new... My problem was when I clicked on a drawn objet after zoom, I needed to ajust the clic location relative to the zoom factor. In my case, I needed the 0 of the Y axis to be at the bottom left corner instead of top left by default which is why I had to reverse the value based on the panel height :

 @Override
    public void mouseReleased(MouseEvent e) {
        int myXLocationWithoutZoom = e.getX()*(1/myDrawer.getZoomFactor());
        int myYLocationWithoutZoom = myPanel.getSize().height-((e.getY())*(1/myDrawer.getZoomFactor()));

If you figure out another way to do this or think I did not do it the good way, let me know.

Thank you

来源：https://stackoverflow.com/questions/33925884/zoom-in-and-out-of-jpanel

标签

java

jpanel

zoom

paintcomponent

affinetransform