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POHow to draw a rectangle on a java applet using mouse drag event and make it stay
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copied!<p>I have my program that can draw rectangles. I have two problems I can't solve. After I draw the rectangle it won't stay. The only code I have that clears the canvas in under paint, repaint is only called on mouse drag. Why when I mouse release or mouse move does my canvas clear. The second thing isn't as much a problem, but something I can't figure out, when either the height or width of my rectangle is negative the rectangle is filled in black.</p> <pre><code>package pracpapp2; import java.awt.*; import java.awt.event.*; import javax.swing.*; public class MouseTracker4July extends JFrame implements MouseListener, MouseMotionListener { private static final long serialVersionUID = 1L; private JLabel mousePosition; int x, y; int x1, x2, y1, y2; int w, h; private JLabel recStart; private JLabel recStop; private JLabel cords; // set up GUI and register mouse event handlers public MouseTracker4July() { super( "Rectangle Drawer" ); mousePosition = new JLabel(); mousePosition.setHorizontalAlignment(SwingConstants.CENTER); getContentPane().add( mousePosition, BorderLayout.CENTER ); JLabel text1 = new JLabel(); text1.setText( "At the center the mouse pointer's coordinates will be displayed." ); getContentPane().add( text1, BorderLayout.SOUTH ); recStart = new JLabel(); getContentPane().add(recStart, BorderLayout.WEST); recStop = new JLabel(); getContentPane().add(recStop, BorderLayout.EAST); cords = new JLabel(); getContentPane().add(cords, BorderLayout.NORTH); addMouseListener( this ); // listens for own mouse and addMouseMotionListener( this ); // mouse-motion events setSize( 800, 600 ); setVisible( true ); } // MouseListener event handlers // handle event when mouse released immediately after press public void mouseClicked( MouseEvent event ) { mousePosition.setText( "Clicked at [" + event.getX() + ", " + event.getY() + "]" ); } // handle event when mouse pressed public void mousePressed( MouseEvent event ) { mousePosition.setText( "Pressed at [" +(x1 = event.getX()) + ", " + (y1 = event.getY()) + "]" ); recStart.setText( "Start: [" + x1 + ", " + y1 + "]" ); } // handle event when mouse released after dragging public void mouseReleased( MouseEvent event ) { mousePosition.setText( "Released at [" +(x2 = event.getX()) + ", " + (y2 = event.getY()) + "]" ); recStop.setText( "End: [" + x2 + ", " + y2 + "]" ); } // handle event when mouse enters area public void mouseEntered( MouseEvent event ) { mousePosition.setText( "Mouse entered at [" + event.getX() + ", " + event.getY() + "]" ); } // handle event when mouse exits area public void mouseExited( MouseEvent event ) { mousePosition.setText( "Mouse outside window" ); } // MouseMotionListener event handlers // handle event when user drags mouse with button pressed public void mouseDragged( MouseEvent event ) { mousePosition.setText( "Dragged at [" + (x = event.getX()) + ", " + (y = event.getY()) + "]" ); // call repaint which calls paint repaint(); } // handle event when user moves mouse public void mouseMoved( MouseEvent event ) { mousePosition.setText( "Moved at [" + event.getX() + ", " + event.getY() + "]" ); } public void paint(Graphics g) { super.paint(g); // clear the frame surface g.drawString("Start Rec Here", x1, y1); g.drawString("End Rec Here", x, y); w = x1 - x; h = y1 - y; w = w * -1; h = h * -1; g.drawRect(x1, y1, w, h); cords.setText( "w = " + w + ", h = " + h); } public static void main( String args[] ) { MouseTracker4July application = new MouseTracker4July(); application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE ); } } // end class MouseTracker </code></pre>

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