Moving JPasswordField to absolute position

问题:

I have this code:

import java.awt.Color;
import java.awt.Component;
import java.awt.Dialog.ModalityType;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.*;

public class DialogExample extends JPanel {
   private static final int COLUMN_COUNT = 10;
   private static final int I_GAP = 3;
   public static final String BKG_IMG_PATH = "http://upload.wikimedia.org/wikipedia/commons/"
         + "thumb/9/92/Camels_in_Jordan_valley_%284568207363%29.jpg/800px-Camels_in_Jordan_valley_"
         + "%284568207363%29.jpg";

   private BufferedImage backgrndImage;
   private JTextField userNameField = new JTextField();
   private JPasswordField passwordField = new JPasswordField();
   private JPanel mainPanel = new JPanel(new GridBagLayout());
   private JButton okButton = new JButton("OK");
   private JButton cancelButton = new JButton("Cancel");

   public DialogExample(BufferedImage backgrndImage) {
      this.backgrndImage = backgrndImage;
      userNameField.setColumns(COLUMN_COUNT);
      passwordField.setColumns(COLUMN_COUNT);

      JPanel btnPanel = new JPanel(new GridLayout(1, 0, 5, 5));
      btnPanel.setOpaque(false);
      btnPanel.add(okButton);
      btnPanel.add(cancelButton);

      GridBagConstraints gbc = getGbc(0, 0, GridBagConstraints.BOTH);
      mainPanel.add(createLabel("User Name", Color.white), gbc);
      gbc = getGbc(1, 0, GridBagConstraints.HORIZONTAL);
      mainPanel.add(userNameField, gbc);
      gbc = getGbc(0, 1, GridBagConstraints.BOTH);
      mainPanel.add(createLabel("Password:", Color.white), gbc);
      gbc = getGbc(1, 1, GridBagConstraints.HORIZONTAL);
      mainPanel.add(passwordField, gbc);
      gbc = getGbc(0, 2, GridBagConstraints.BOTH, 2, 1);
      mainPanel.add(btnPanel, gbc);

      mainPanel.setOpaque(false);
      add(mainPanel);
   }

   private JLabel createLabel(String text, Color color) {
      JLabel label = new JLabel(text);
      label.setForeground(color);
      return label;
   }

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      if (backgrndImage != null) {
         g.drawImage(backgrndImage, 0, 0, this);
      }
   }

   @Override
   public Dimension getPreferredSize() {
      if (isPreferredSizeSet() || backgrndImage == null) {
         return super.getPreferredSize();
      }
      int imgW = backgrndImage.getWidth();
      int imgH = backgrndImage.getHeight();
      return new Dimension(imgW, imgH);
   }

   public static GridBagConstraints getGbc(int x, int y, int fill) {
      GridBagConstraints gbc = new GridBagConstraints();
      gbc.gridx = x;
      gbc.gridy = y;
      gbc.gridwidth = 1;
      gbc.gridheight = 1;
      gbc.weightx = 1.0;
      gbc.weighty = 1.0;
      gbc.insets = new Insets(I_GAP, I_GAP, I_GAP, I_GAP);
      gbc.fill = fill;

      return gbc;
   }

   public static GridBagConstraints getGbc(int x, int y, int fill, int width,
         int height) {
      GridBagConstraints gbc = getGbc(x, y, fill);
      gbc.gridwidth = width;
      gbc.gridheight = height;

      return gbc;
   }

   private static void createAndShowGui() throws IOException {
      final JFrame frame = new JFrame("Frame");

      final JDialog dialog = new JDialog(frame, "User Sign-In", ModalityType.APPLICATION_MODAL);
      URL imgUrl = new URL(BKG_IMG_PATH);
      BufferedImage img = ImageIO.read(imgUrl);
      final DialogExample dlgExample = new DialogExample(img);
      dialog.add(dlgExample);
      dialog.pack();

      JPanel mainPanel = new JPanel();
      mainPanel.add(new JButton(new AbstractAction("Please Press Me!") {

         @Override
         public void actionPerformed(ActionEvent e) {
            dialog.setVisible(true);
         }
      }));
      mainPanel.setPreferredSize(new Dimension(800, 650));

      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            try {
               createAndShowGui();
            } catch (IOException e) {
               e.printStackTrace();
            }
         }
      });
   }
}

Ho can I move the JPasswordField to a absolute position (X,Y)?? I've been trying different things like setPosition(int X, int Y) and nothing worked. I tryed playing too with the layout but not success either. I would like to have just a JPasswordField object and a button object on his right. that's it

Thank you

回答1:

Start by creating a panel for the password field and button to reside on. Next, randomise a EmptyBorder and the Insets of a GridBagConstraints to define different locations within the parent container. Add the password/button panel to this container with these randomised constraints...

public class TestPane extends JPanel {

    public TestPane() {

        Random rnd = new Random();

        JPanel panel = new JPanel();
        JPasswordField pf = new JPasswordField(10);
        JButton btn = new JButton("Login");
        panel.add(pf);
        panel.add(btn);

        panel.setBorder(new EmptyBorder(rnd.nextInt(10), rnd.nextInt(10), rnd.nextInt(10), rnd.nextInt(10)));
        setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(rnd.nextInt(100), rnd.nextInt(100), rnd.nextInt(100), rnd.nextInt(100));

        add(panel, gbc);

    }

}

The other choice would be to write your own custom layout manager...but if you can avoid it, the above example is MUCH simpler...

ps- You could randomise either the border OR the insets, maybe using a larger random range and get the same effect, I've simpler used both to demonstrate the point ;)

Updated with layout manager example

public class TestPane extends BackgroundImagePane {

    public TestPane() throws IOException {

        super(ImageIO.read(new File("Path/to/your/image")));            

        Random rnd = new Random();

        JPanel panel = new JPanel();
        panel.setOpaque(false);
        JPasswordField pf = new JPasswordField(10);
        JButton btn = new JButton("Login");
        panel.add(pf);
        panel.add(btn);

        setLayout(new RandomLayoutManager());

        Dimension size = getPreferredSize();
        size.width -= panel.getPreferredSize().width;
        size.height -= panel.getPreferredSize().height;

        add(panel, new Point(rnd.nextInt(size.width), rnd.nextInt(size.height)));

    }

}

public class RandomLayoutManager implements LayoutManager2 {

    private Map<Component, Point> mapConstraints;

    public RandomLayoutManager() {
        mapConstraints = new WeakHashMap<>(25);
    }

    @Override
    public void addLayoutComponent(String name, Component comp) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

    @Override
    public void removeLayoutComponent(Component comp) {
        mapConstraints.remove(comp);
    }

    @Override
    public Dimension preferredLayoutSize(Container parent) {
        Area area = new Area();
        for (Component comp : mapConstraints.keySet()) {

            Point p = mapConstraints.get(comp);
            Rectangle bounds = new Rectangle(p, comp.getPreferredSize());
            area.add(new Area(bounds));

        }

        Rectangle bounds = area.getBounds();
        Dimension size = bounds.getSize();
        size.width += bounds.x;
        size.height += bounds.y;

        return size;

    }

    @Override
    public Dimension minimumLayoutSize(Container parent) {
        return preferredLayoutSize(parent);
    }

    @Override
    public void layoutContainer(Container parent) {
        for (Component comp : mapConstraints.keySet()) {
            Point p = mapConstraints.get(comp);
            comp.setLocation(p);
            comp.setSize(comp.getPreferredSize());
        }
    }

    @Override
    public void addLayoutComponent(Component comp, Object constraints) {
        if (constraints instanceof Point) {

            mapConstraints.put(comp, (Point) constraints);

        } else {

            throw new IllegalArgumentException("cannot add to layout: constraint must be a java.awt.Point");

        }
    }

    @Override
    public Dimension maximumLayoutSize(Container target) {
        return preferredLayoutSize(target);
    }

    @Override
    public float getLayoutAlignmentX(Container target) {
        return 0.5f;
    }

    @Override
    public float getLayoutAlignmentY(Container target) {
        return 0.5f;
    }

    @Override
    public void invalidateLayout(Container target) {
    }

}

public class BackgroundImagePane extends JPanel {

    private Image image;

    public BackgroundImagePane(Image img) {

        this.image = img;

    }

    @Override
    public Dimension getPreferredSize() {
        return image == null ? super.getPreferredSize() : new Dimension(image.getWidth(this), image.getHeight(this));
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        if (image != null) {
            int x = (getWidth() - image.getWidth(this)) / 2;
            int y = (getHeight() - image.getHeight(this)) / 2;
            g.drawImage(image, x, y, this);
        }
    }

}

The BackgroundImagePane is based on this example, allowing the background image panel to be the container for the field panel and you should be well on your way...

回答2:

You could use a null layout, but that takes too long and it doesn't re-size with the frame. Like this:

public class TestPane{

public static void main (String[] args) {

    Random rnd = new Random();

    JFrame frame = new JFrame();
    JPasswordField pf = new JPasswordField();
    JButton btn = new JButton("Login");
    frame.setSize(500, 500);
    frame.setLayout(null);
    btn.setBounds(y, x, width, height);
    pf.setBounds(y, x, width, height);
    frame.add(btn);
    frame.add(pf);        
}

}

And that should work. If you want to use a null layout.