MIllozzi4

package esercizio4.frame;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

/**
 * Created by stefano on 12/01/16.
 */
public class JFrameColore extends JFrame {
    public final JLabel label_R, label_G, label_B, label_COLORA;
    public final JTextField text_R, text_G, text_B;
    public final JButton button_COLORA;
    public final JPanel panel_COLORE;

    public JFrameColore() throws HeadlessException {
        setLayout(null);
        label_COLORA = set(
                new JLabel("Coloriamo il mondo"),
                50, 50,
                400, 50,
                Color.orange);


        label_R = set(new JLabel("R"), 50, 120, 40, 40, null);
        label_G = set(new JLabel("G"), 50, 170, 40, 40, null);
        label_B = set(new JLabel("B"), 50, 220, 40, 40, null);

        text_R = set(new JTextField(), 100, 120, 150, 40, null);
        text_G = set(new JTextField(), 100, 170, 150, 40, null);
        text_B = set(new JTextField(), 100, 220, 150, 40, null);

        button_COLORA = set(new JButton("colora"), 300, 220, 150, 30, null);


        panel_COLORE = set(new JPanel(), 300, 120, 150, 80, Color.yellow);
        panel_COLORE.setOpaque(true);

        getContentPane().add(label_R);
        getContentPane().add(label_G);
        getContentPane().add(label_B);

        getContentPane().add(text_R);
        getContentPane().add(text_G);
        getContentPane().add(text_B);

        getContentPane().add(button_COLORA);
        getContentPane().add(panel_COLORE);
        getContentPane().add(label_COLORA);

        button_COLORA.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                boolean err = false;
                int r = -1, g = -1, b = -1;

                try {
                    r = Integer.parseInt(text_R.getText());
                    if (r < 0 || r > 255) throw new NumberFormatException();
                } catch (NumberFormatException ex) {
                    text_R.setText("ERR");
                    err = true;
                }

                try {
                    g = Integer.parseInt(text_G.getText());
                    if (g < 0 || g > 255) throw new NumberFormatException();
                } catch (NumberFormatException ex) {
                    text_G.setText("ERR");
                    err = true;
                }

                try {
                    b = Integer.parseInt(text_B.getText());
                    if (b < 0 || b > 255) throw new NumberFormatException();
                } catch (NumberFormatException ex) {
                    text_B.setText("ERR");
                    err = true;
                }

                if (!err) {
                    panel_COLORE.setBackground(new Color(r, g, b));
                }

            }
        });

        setSize(600, 300);
        setVisible(true);
    }

    public static void main(String[] args) {
        new JFrameColore();
    }

    private <T extends JComponent> T set(T c, int x, int y, int dimx, int dimy, Color back) {
        c.setLocation(x, y);
        if (back != null) {
            c.setOpaque(true);
            c.setBackground(back);
        }
        c.setSize(dimx, dimy);
        return c;
    }
}