How to draw straight line instead of curved line??

[Michelle Wang]

Dear friends:
I have following code, which can draw curved lines when mouse moves, but if I only hope to draw stright line, not curved one, How to draw straight line instead of curved line??

If can help advice something, thanks in advance.
Regards

  
package com.draw;
 
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
 
public class DrawLineOnPanel extends JPanel implements ActionListener
{
    DrawingPanel myDrawingPanel;
    JPanel buttonPanel;
    JButton  blackButton;
    JButton clearButton, upSize, downSize;
 
    public JPanel DrawLineOnPanel()
    {
        myDrawingPanel = new DrawingPanel();
        myDrawingPanel.setBorder(BorderFactory.createEtchedBorder(Color.black, Color.blue));
 
        buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(2, 4, 2, 2));
        buttonPanel.setBorder(BorderFactory.createEtchedBorder(Color.white, Color.blue));
 
        blackButton = addButton(Color.black);
        clearButton = addButton(null);
        clearButton.setText("New");
          add("Center", myDrawingPanel);
        add("South", buttonPanel);
        return this;
}
 
    private JButton addButton(Color color)
    {
        JButton button = new JButton();
        button.setBackground(new Color(230,240,250));
        button.setBorder(BorderFactory.createEtchedBorder());
        if (color != null)
        {
            button.setForeground(Color.white);
            button.setBackground(color);
        }
 
        button.setText("Paint");
        buttonPanel.add(button);
        button.addActionListener(this);
 
        return(button);
    }
 
    public void actionPerformed(ActionEvent e)
    {
        String s = e.getActionCommand();
        
        if (s.equals("Paint"))
        {
            JButton button = (JButton)e.getSource();
            myDrawingPanel.setPaintColor(button.getBackground());
        }
        if (s.equals("New"))
        {
            myDrawingPanel.clearPaint();
        }
    }
 
    public static void main(String[] args)
    {
        JFrame frame = new JFrame();
        DrawLineOnPanel dlp = new DrawLineOnPanel();
        frame.add(dlp.DrawLineOnPanel());
        //frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible( true );
    }
 
    public class DrawingPanel extends JPanel implements MouseListener, MouseMotionListener
    {
        Image image;
        Graphics2D g2d;
        int brushSize = 3;
        Point lastPoint;
 
        public DrawingPanel()
        {
            setPreferredSize( new Dimension(300, 300) );
            addMouseListener(this);
            addMouseMotionListener(this);
        }
 
        public void mouseClicked(MouseEvent e) {}
        public void mouseEntered(MouseEvent e) {}
        public void mouseExited(MouseEvent e) {}
        public void mouseReleased(MouseEvent e) {}
        public void mouseMoved(MouseEvent e) {}
 
        public void mousePressed(MouseEvent e)
        {
            lastPoint = e.getPoint();
            draw( lastPoint );
        }
 
        public void mouseDragged(MouseEvent e)
        {
            double xDelta = e.getX() - lastPoint.getX();
            double yDelta = e.getY() - lastPoint.getY();
            double delta = Math.max(Math.abs(xDelta), Math.abs(yDelta));
            double xIncrement = xDelta / delta;
            double yIncrement = yDelta / delta;
 
            double xStart = lastPoint.getX();
            double yStart = lastPoint.getY();
 
            for (int i = 0; i < delta; i++)
            {
                Point interpolated = new Point((int)xStart, (int)yStart);
                draw( interpolated );
                xStart += xIncrement;
                yStart += yIncrement;
            }
 
            draw(e.getPoint());
            lastPoint = e.getPoint();
        }
 
        private void draw(Point start)
        {
            int x = start.x - (brushSize/2) + 1;
            int y = start.y - (brushSize/2) + 1;
            g2d.fillOval(x, y, brushSize, brushSize);
            repaint(x, y, brushSize, brushSize);
        }
 
        public void setPaintColor(Color color)
        {
            g2d.setColor(color);
        }
 
        public void clearPaint()
        {
            g2d.setColor( Color.white );
            g2d.fillRect(0, 0, getWidth(), getHeight());
            repaint();
            g2d.setColor( Color.black );
        }
 
        public void increaseBrushSize()
        {
            brushSize = brushSize + 2;
        }
 
        public void decreaseBrushSize()
        {
            brushSize = brushSize - 2;
 
            if (brushSize <= 0)
                brushSize = 1;
        }
 
        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);
 
            if (image == null)
            {
                image = createImage(getWidth(), getHeight());
                g2d = (Graphics2D)image.getGraphics();
                g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
                g2d.setColor(Color.white);
                g2d.fillRect(0, 0, getWidth(), getHeight());
                g2d.setColor(Color.black);
            }
 
            Rectangle r = g.getClipBounds();
            g.drawImage(image, r.x, r.y, r.width+r.x, r.height+r.y,
            r.x, r.y, r.width+r.x, r.height+r.y, null);
        }
 
    }
}
 

[Craig Wood]

pressMouse -> start line
releaseMouse -> end line

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
public class DLOP extends JPanel implements ActionListener
{
    DrawingPanel myDrawingPanel;
    JPanel buttonPanel;
    JButton blackButton;
    JButton clearButton, upSize, downSize;
 
    public /*JPanel*/ DLOP()
    {
        myDrawingPanel = new DrawingPanel();
        myDrawingPanel.setBorder(BorderFactory.createEtchedBorder(Color.black,
                                                                  Color.blue));
        buttonPanel = new JPanel();
        // See last paragraph in GridLayout api comments section
        // for what happens when you specify both rows and columns.
        buttonPanel.setLayout(new GridLayout(0, 4, 2, 2));
        buttonPanel.setBorder(BorderFactory.createEtchedBorder(Color.white,
                                                               Color.blue));
 
        blackButton = addButton(Color.black);
        addButton(Color.red);
        addButton(Color.green.darker());
        addButton(Color.blue);
        clearButton = addButton(null);
        clearButton.setText("New");
        System.out.println(getClass().getSuperclass().getName() +
                           " default layout is " +
                           getLayout().getClass().getName());
        setLayout(new BorderLayout());
        add("Center", myDrawingPanel);
        add("South", buttonPanel);
//return this;
    }
 
    private JButton addButton(Color color)
    {
        JButton button = new JButton();
        button.setBackground(new Color(230,240,250));
        button.setBorder(BorderFactory.createEtchedBorder());
        if (color != null)
        {
            button.setForeground(Color.white);
            button.setBackground(color);
        }
 
        button.setText("Paint");
        buttonPanel.add(button);
        button.addActionListener(this);
 
        return button;
    }
 
    public void actionPerformed(ActionEvent e)
    {
        String s = e.getActionCommand();
 
        if (s.equals("Paint"))
        {
            JButton button = (JButton)e.getSource();
            myDrawingPanel.setPaintColor(button.getBackground());
        }
        if (s.equals("New"))
        {
            myDrawingPanel.clearPaint();
        }
    }
 
    public static void main(String[] args)
    {
        JFrame frame = new JFrame();
        DLOP dlp = new DLOP();
        // DLOP extends JPanel so an instance of DLOP is (at least) a
        // JPanel. Therefore, we can add an instance of it to our JFrame.
        frame.add(dlp);
        // EXIT_ON_CLOSE is a static constant in the JFrame class. See
        // Field Detail in JFrame class api. If the enclosing class
        // extended JFrame then you could refer to the constant without
        // the "JFrame." prefix, ie, without using static notation.
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible( true );
    }
 
    public class DrawingPanel extends JPanel implements MouseListener,
                                                        MouseMotionListener
    {
        Image image;
        Graphics2D g2d;
        int brushSize = 3;
        Point lastPoint = new Point();
        Point dragPoint = new Point();
        boolean dragging = false;
 
        public DrawingPanel()
        {
            setPreferredSize( new Dimension(300, 300) );
            addMouseListener(this);
            addMouseMotionListener(this);
        }
 
        public void mouseClicked(MouseEvent e) {}
        public void mouseEntered(MouseEvent e) {}
        public void mouseExited(MouseEvent e) {}
//        public void mouseReleased(MouseEvent e) {}
        public void mouseMoved(MouseEvent e) {}
 
        public void mousePressed(MouseEvent e)
        {
            lastPoint = e.getPoint();
            dragging = true;
//            draw( lastPoint );
        }
 
        public void mouseReleased(MouseEvent e)
        {
            draw(e.getPoint());
            dragging = false;
        }
 
        public void mouseDragged(MouseEvent e)
        {
            if(dragging)
            {
                dragPoint = e.getPoint();
                repaint();
            }
        }
 
        private void draw(Point p)
        {
            g2d.setStroke(new BasicStroke(brushSize));
            g2d.drawLine(lastPoint.x, lastPoint.y, p.x, p.y);
            repaint();
        }
 
        public void setPaintColor(Color color)
        {
            g2d.setColor(color);
        }
 
        public void clearPaint()
        {
            g2d.setColor( Color.white );
            g2d.fillRect(0, 0, getWidth(), getHeight());
            repaint();
            g2d.setColor( Color.black );
        }
 
        public void increaseBrushSize()
        {
            brushSize = brushSize + 2;
        }
 
        public void decreaseBrushSize()
        {
            brushSize = brushSize - 2;
 
            if (brushSize <= 0)
                brushSize = 1;
        }
 
//        public void paintComponent(Graphics g)
        protected void paintComponent(Graphics g)
        {
            super.paintComponent(g);
 
            if (image == null)
            {
                image = createImage(getWidth(), getHeight());
                g2d = (Graphics2D)image.getGraphics();
                g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                                     RenderingHints.VALUE_ANTIALIAS_ON);
                g2d.setColor(Color.white);
                g2d.fillRect(0, 0, getWidth(), getHeight());
                g2d.setColor(Color.black);
            }
            g.drawImage(image, 0, 0, this);
            if(dragging)
            {
                g.setColor(Color.pink);
                g.drawLine(lastPoint.x, lastPoint.y, dragPoint.x, dragPoint.y);
            }
        }
    }
}

[Michelle Wang]

Excellent!! Thanks so much!!Super!!
[ June 21, 2007: Message edited by: girl sunny ]

[Michelle Wang]

I have another idea after your wonderful code,
I tried but failed with following code, If I hope to apply your draw method in your reply post to the following code, is it possible or not, last night I tried hours, no success.

    package com.aa;
import java.awt.*;
import java.awt.event.*; 
import java.awt.geom.*;
import java.util.Vector;
import javax.swing.*;
import javax.swing.event.*;
public class ConnectingLines extends JPanel
{
    protected JLabel label1, label2, label3, label4;
    protected JLabel[] labels;
    protected JLabel selectedLabel;
    protected JButton btn  = new JButton("Draw Lines");
    protected JButton btn1 = new JButton("No Draw");
    int cx, cy;
    protected Vector order = new Vector();  
public static void main(String[] args)
    {
        JFrame f = new JFrame("Connecting Lines");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new ConnectingLines());
        f.setSize(400,300);
        f.setLocation(200,200);
        f.setVisible(true);
    }
 
public ConnectingLines ()
{
setLayout(null);
        addLabels();
        label1.setBounds( 25,  50, 125, 25);
        label2.setBounds(225,  50, 125, 25);
        label3.setBounds( 25, 175, 125, 25);
        label4.setBounds(225, 175, 125, 25);
        //add(btn);
        btn.setBounds(10, 5, 125, 25);
        btn1.setBounds(125, 5, 125, 25);
       add(btn);
       add(btn1);
        
        determineCenterOfComponents();
        ComponentMover mover = new ComponentMover();
     ActionListener lst = new ActionListener() {
    public void actionPerformed(ActionEvent e) {
   ComponentMover mover = new ComponentMover();
         addMouseListener(mover);
         addMouseMotionListener(mover);
       }
     };
    ActionListener lst1 = new ActionListener() {
     public void actionPerformed(ActionEvent e) {
        }
      };     
 btn.addActionListener(lst);
btn1.addActionListener(lst1);
    }
 
    public void paintComponent(final Graphics g)
    {
    super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
    Point[] p;
        g2.setStroke(new BasicStroke(4f));
        
       for(int i = 0 ; i < order.size()-1; i++) {
            JLabel l1 = (JLabel)order.elementAt(i);
            JLabel l2 = (JLabel)order.elementAt(i+1);
            p = getCenterPoints(l1, l2);
            g2.setColor(Color.black);
 
            g2.draw(new Line2D.Double(p[0], p[1]));       
       }
 }
    
    private Point[] getCenterPoints(Component c1, Component c2)
    {
        Point
            p1 = new Point(),
            p2 = new Point();
        Rectangle
            r1 = c1.getBounds(),
            r2 = c2.getBounds();
 
        p1.x = r1.x + r1.width/2;
        p1.y = r1.y + r1.height/2;
        p2.x = r2.x + r2.width/2;
        p2.y = r2.y + r2.height/2;
 
        return new Point[] {p1, p2};
    }
 
 
    private void determineCenterOfComponents()
    {
        int
            xMin = Integer.MAX_VALUE,
            yMin = Integer.MAX_VALUE,
            xMax = 0,
            yMax = 0; 
        for(int i = 0; i < labels.length; i++)
        {
            Rectangle r = labels[i].getBounds();
            if(r.x < xMin)
                xMin = r.x;
            if(r.y < yMin)
                yMin = r.y;
            if(r.x + r.width > xMax)
                xMax = r.x + r.width;
            if(r.y + r.height > yMax)
                yMax = r.y + r.height;
        }
        cx = xMin + (xMax - xMin)/2;
        cy = yMin + (yMax - yMin)/2;
    }
 
    private class ComponentMover extends MouseInputAdapter
    {
        Point offsetP = new Point();
        boolean dragging;
 
        public void mousePressed(MouseEvent e)
        {
            Point p = e.getPoint();
            for(int i = 0; i < labels.length; i++)
            {
                Rectangle r = labels[i].getBounds();
                if(r.contains(p))
                {
                    selectedLabel = labels[i];
                    order.addElement(labels[i]);
                    offsetP.x = p.x - r.x;
                    offsetP.y = p.y - r.y;
                    dragging = true;
                    repaint(); //added
                    break;
                }
            }
        }
 
        public void mouseReleased(MouseEvent e)
        {
            dragging = false;
        }
 
        public void mouseDragged(MouseEvent e)
        {
            if(dragging)
            {
                Rectangle r = selectedLabel.getBounds();
                r.x = e.getX() - offsetP.x;
                r.y = e.getY() - offsetP.y;
                selectedLabel.setBounds(r.x, r.y, r.width, r.height);
                //determineCenterOfComponents();
                repaint();
            }
        } 
    }
 
    private void addLabels()
    {
        label1 = new JLabel("Label 1");
        label2 = new JLabel("Label 2");
        label3 = new JLabel("Label 3");
        label4 = new JLabel("Label 4");
        labels = new JLabel[] {
            label1, label2, label3, label4
        };
        //add(btn);
        for(int i = 0; i < labels.length; i++)
        {
            labels[i].setHorizontalAlignment(SwingConstants.CENTER);
            labels[i].setBorder(BorderFactory.createEtchedBorder());
            add(labels[i]);
        }
    }
}
 

[Craig Wood]

import java.awt.*;
import java.awt.event.*; 
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
import javax.swing.event.MouseInputAdapter;
 
public class AddingLines extends JPanel implements ActionListener
{
    // Member variables which require exposure in class scope.
    // It is good practice to keep these to a minimum
    // and hide as much as possible (as local variables).
    protected JLabel[] labels;
    boolean addingLines = false;
    Color color = Color.black;
    List<LineStore> lineStores = new ArrayList<LineStore>();
 
    public AddingLines()
    {
        setLayout(null);
        addLabels();
        ComponentMover mover = new ComponentMover();
        addMouseListener(mover);
        addMouseMotionListener(mover);
    }
 
    public void actionPerformed(ActionEvent e)
    {
        color = ((JButton)e.getSource()).getBackground();
    }
 
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        Stroke orig = g2.getStroke();
        g2.setStroke(new BasicStroke(4f));
 
        for(int j = 0; j < lineStores.size(); j++)
        {
            LineStore store = (LineStore)lineStores.get(j);
            JLabel l1 = labels[store.index1];
            JLabel l2 = labels[store.index2];
            int x1 = l1.getX() + store.p1.x;
            int y1 = l1.getY() + store.p1.y;
            int x2 = l2.getX() + store.p2.x;
            int y2 = l2.getY() + store.p2.y;
            g2.setPaint(store.color);
            g2.drawLine(x1, y1, x2, y2); 
        }
        // Restore g to its original state so we do not
        // affect drawing of components in paint method
        // which is its originator and final user.
        g2.setStroke(orig);
    }
 
    private class ComponentMover extends MouseInputAdapter
    {
        int selectedIndex;
        int firstSelection = -1;
        Point firstLoc = new Point();
        Point offsetP = new Point();
        boolean dragging;
 
        public void mousePressed(MouseEvent e)
        {
            Point p = e.getPoint();
            for(int j = 0; j < labels.length; j++)
            {
                Rectangle r = labels[j].getBounds();
                if(r.contains(p))
                {
                    selectedIndex = j;
                    if(addingLines)
                    {
                        p.x -= labels[j].getX();
                        p.y -= labels[j].getY();
                        if(firstSelection == -1)
                        {
                            firstSelection = j;
                            firstLoc.setLocation(p);
                        }
                        else
                        {
                            addLine(p);
                        }
                    }
                    else         // Must be dragging.
                    {
                        offsetP.x = p.x - r.x;
                        offsetP.y = p.y - r.y;
                        dragging = true;
                    }
                    break;
                }
            }
        }
 
        private void addLine(Point p)
        {
            lineStores.add(new LineStore(firstSelection, selectedIndex,
                                         new Point(firstLoc), p, color));
            firstSelection = -1;
            repaint();
        }
 
        public void mouseReleased(MouseEvent e)
        {
            dragging = false;
        }
 
        public void mouseDragged(MouseEvent e)
        {
            if(dragging)
            {
                Rectangle r = labels[selectedIndex].getBounds();
                r.x = e.getX() - offsetP.x;
                r.y = e.getY() - offsetP.y;
                labels[selectedIndex].setLocation(r.x, r.y);
                repaint();
            }
        } 
    }
 
    private void addLabels()
    {
        int[][] n =
        {
            { 25,  50, 125, 35 }, { 225,  50, 125, 35 },
            { 25, 175, 125, 35 }, { 225, 175, 125, 35 }
        };
        labels = new JLabel[n.length] ;
        for(int j = 0; j < labels.length; j++)
        {
            labels[j] = new JLabel("Label " + (j+1));
            labels[j].setBounds(n[j][0], n[j][1], n[j][2], n[j][3]);
            labels[j].setHorizontalAlignment(SwingConstants.CENTER);
            labels[j].setBorder(BorderFactory.createEtchedBorder());
            add(labels[j]);
        }
    }
 
    private JPanel getControlPanel()
    {
        final JToggleButton addLines = new JToggleButton("add lines");
        addLines.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                addingLines = addLines.isSelected();
            }
        });
        JPanel hiPanel = new JPanel();
        hiPanel.add(addLines);
        Color[] colors =
        {
            Color.black, Color.red, Color.green.darker(), Color.blue
        };
        JPanel loPanel = new JPanel(new GridLayout(1,0));
        for(int j = 0; j < colors.length; j++)
        {
            JButton button = new JButton();
            button.setBackground(colors[j]);
            button.addActionListener(this);
            loPanel.add(button);
        }
        JPanel panel = new JPanel(new GridLayout(0,1));
        panel.add(hiPanel);
        panel.add(loPanel);
        return panel;
    }
 
    public static void main(String[] args)
    {
        AddingLines test = new AddingLines();
        JFrame f = new JFrame("Adding Lines");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(test);
        f.getContentPane().add(test.getControlPanel(), "Last");
        f.setSize(400,350);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}
 
class LineStore
{
    int index1;
    int index2;
    Point p1;
    Point p2;
    Color color;
 
    public LineStore(int n1, int n2, Point p1, Point p2, Color color)
    {
        index1 = n1;
        index2 = n2;
        this.p1 = p1;
        this.p2 = p2;
        this.color = color;
    }
}

Edit:
Changed this line in ComponentMover.addLine

lineStores.add(new LineStore(firstSelection, selectedIndex,
                             firstLoc, p, color));

to this

lineStores.add(new LineStore(firstSelection, selectedIndex,
                             new Point(firstLoc), p, color));

to prevent the member variable firstLoc from changing values passed to previously
created instances of LineStore.
Also, replaced all loop count variables with letter j.
[ June 22, 2007: Message edited by: Craig Wood ]

[Michelle Wang]

Great! Thanks a lot!!

[justin joel]

How to create a simple paint application?