Not able to add custom class to panel in IntelliJ GUI Designer

Question

I've made a child class of JPanel for the graph plotting, added it to Palette, but when I'm trying to add it to the main panel nothing happens. Also if I try to add it as Non-Palette Component the dialog just closes and reopens again, asking to choose the class to add. Here's the class:

import javax.swing.*;
import java.awt.*;

/**
 * Created by gray on 05.11.14.
 */
public class PPanel extends JPanel {
// Object for the class realizing graph function
public Plotter G;
// Internal class for realization of graph function

class Plotter{
    // rane of the coordinats
    private double Xmin=0, Xmax=10.0, Ymin=0, Ymах= 120.0;
    // graph line color:
    private Color clr;
    // grid line color:
    private Color gclr;
    // class constructor
    Plotter(){
// read the text field and convert it into the number:
       /* try{
            Xmax=Double.valueOf(xmaxTF.getText());}
        catch(NumberFormatException е){
            xmaxTF.setText("10");
            Xmax=10;}*/
// initializing grid line color:
        gclr=Color.GRAY;
// initializing graph line color:
        clr=Color.BLACK;
    }
    // the function that is being displayed:
    private double f(double x){
        return (3*Math.exp(0.4*x)); }
    // methode for the grid display
    public void plot(Graphics Fig){
// parameters for the range in which graph is being displayed
        int H,W,h,w,s=20;
        H=getHeight();
        W=getWidth();
        h=H-2*s;
        w=W-2*s;
// clearing the graph
        Fig.clearRect(0,0,W,H);
// index and quantity of grid lines
        int k, nums=10;
        Fig.setColor(Color.BLACK);
// coordinate axis:
        Fig.drawLine(s,s,s,h+s);
        Fig.drawLine(s,s+h,s+w,s+h);
        for(k=0;k<=nums;k++){
            Fig.drawLine(s+k*w/nums, s+h, s+k*w/nums, s+h+5);
            Fig.drawLine(s-5,s+k*h/nums,s,s+k*h/nums);
            Fig.drawString(Double.toString(Xmin+k*(Xmax-Xmin)/nums),
                    s+k*w/nums-5,s+h+15);
            Fig.drawString(Double.toString(Ymin+k*(Ymах-Ymin)/nums),s-17,
                    s+h-1-k*h/nums);
        }
        Fig.setColor(gclr);
// grid lines:
            for(k=1;k<=nums;k++){
                Fig.drawLine(s+k*w/nums,s,s+k*w/nums,h+s);
                Fig.drawLine(s,s+(k-1)*h/nums,s+w,s+(k-1)*h/nums);
            }
// grаph display:
        Fig.setColor(clr);   // setting graph line color
// scaling coefficient:
        double dx=(Xmax-Xmin)/w,dу=(Ymах-Ymin)/h;
        // cartesian coordinates:
        double x1,x2,y1,y2;
// window coordinates:
        int h1,h2,w1,w2;
// initial values
        x1=Xmin;
        y1=0;
        w1=s;
        h1=h+s-(int)Math.round(y1/dу);
        int step=5;
// displaying the dots and connecting them with lines:
        for(int i=step;i<=w;i+=step){
            x2=i*dx;
            y2=y1+(x2-x1)*f(x2) ;
            w2=s+(int)Math.round(x2/dx);
            h2=h+s-(int)Math.round(y2/dу);
            Fig.drawLine(w1,h1,w2,h2);
            Fig.drawRect(w1-2,h1-2,4,4);
// new values:
            x1=x2;
            y1=y2;
            w1=w2;
            h1=h2;
        }
    }
}
// panel constructor
PPanel(){
// creating the object for the plot function:
    G=new Plotter();
    // setting the background color of the panel:
    setBackground(Color.WHITE);
}
// redefinition of the paint method:
public void paint(Graphics g){
// when redrawing the panel redraw graph as well
    G.plot(g);
}
}

And this is how it looks on the palette. But when I drag'n'drop it to the form nothing happens. The default elements are working just fine. What's wrong?

Answer 1

Aaaand I fixed it. Solution: set bytecode and compiler versions to the same one. Solution for the resize problem - set horizontal and vertical aligns to fill. Also had to create and object of that class in createUIComponents()