Вам необходимо сохранить нарисованные элементы в некоторой структуре данных и убедиться, что каждый элемент в структуре нарисован на холсте при перерисовке.
Кроме того, вам нужно добавить перерисовку для каждого события мыши.
Например: (предполагается, что вы хотите сохранить ВСЕ прямоугольники) - вы можете использовать один прямоугольник, исключив массив и заменив его единственным экземпляром прямоугольника.
import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingConstants;
public class MouseTracker4July extends JFrame implements MouseListener, MouseMotionListener {
private static final long serialVersionUID = 1L;
private final JLabel mousePosition;
int x1, x2, y1, y2;
int w, h;
private final JLabel recStart;
private final JLabel recStop;
private final JLabel cords; // set up GUI and register mouse event handlers
private final ArrayList< Rectangle > rectangles = new ArrayList< Rectangle >();
private boolean isNewRect = true;
public MouseTracker4July() {
super( "Rectangle Drawer" );
this.mousePosition = new JLabel();
this.mousePosition.setHorizontalAlignment( SwingConstants.CENTER );
getContentPane().add( this.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 );
this.recStart = new JLabel();
getContentPane().add( this.recStart, BorderLayout.WEST );
this.recStop = new JLabel();
getContentPane().add( this.recStop, BorderLayout.EAST );
this.cords = new JLabel();
getContentPane().add( this.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( final MouseEvent event ) {
this.mousePosition.setText( "Clicked at [" + event.getX() + ", " + event.getY() + "]" );
repaint();
}
// handle event when mouse pressed
public void mousePressed( final MouseEvent event ) {
this.mousePosition.setText( "Pressed at [" + ( this.x1 = event.getX() ) + ", " + ( this.y1 = event.getY() ) + "]" );
this.recStart.setText( "Start: [" + this.x1 + ", " + this.y1 + "]" );
repaint();
}
// handle event when mouse released after dragging
public void mouseReleased( final MouseEvent event ) {
this.mousePosition.setText( "Released at [" + ( this.x2 = event.getX() ) + ", " + ( this.y2 = event.getY() ) + "]" );
this.recStop.setText( "End: [" + this.x2 + ", " + this.y2 + "]" );
Rectangle rectangle = getRectangleFromPoints();
this.rectangles.add( rectangle );
this.w = this.h = this.x1 = this.y1 = this.x2 = this.y2 = 0;
this.isNewRect = true;
repaint();
}
private Rectangle getRectangleFromPoints() {
int width = this.x1 - this.x2;
int height = this.y1 - this.y2;
Rectangle rectangle = new Rectangle( width < 0 ? this.x1
: this.x2, height < 0 ? this.y1
: this.y2, Math.abs( width ), Math.abs( height ) );
return rectangle;
}
// handle event when mouse enters area
public void mouseEntered( final MouseEvent event ) {
this.mousePosition.setText( "Mouse entered at [" + event.getX() + ", " + event.getY() + "]" );
repaint();
}
// handle event when mouse exits area
public void mouseExited( final MouseEvent event ) {
this.mousePosition.setText( "Mouse outside window" );
repaint();
}
// MouseMotionListener event handlers // handle event when user drags mouse with button pressed
public void mouseDragged( final MouseEvent event ) {
this.mousePosition.setText( "Dragged at [" + ( this.x2 = event.getX() ) + ", " + ( this.y2 = event.getY() ) + "]" ); // call repaint which calls paint repaint();
this.isNewRect = false;
repaint();
}
// handle event when user moves mouse
public void mouseMoved( final MouseEvent event ) {
this.mousePosition.setText( "Moved at [" + event.getX() + ", " + event.getY() + "]" );
repaint();
}
@Override
public void paint( final Graphics g ) {
super.paint( g ); // clear the frame surface
g.drawString( "Start Rec Here", this.x1, this.y1 );
g.drawString( "End Rec Here", this.x2, this.y2 );
Rectangle newRectangle = getRectangleFromPoints();
if ( !this.isNewRect ) {
g.drawRect( newRectangle.x, newRectangle.y, newRectangle.width, newRectangle.height );
}
for( Rectangle rectangle : this.rectangles ) {
g.drawRect( rectangle.x, rectangle.y, rectangle.width, rectangle.height );
}
this.cords.setText( "w = " + this.w + ", h = " + this.h );
}
public static void main( final String args[] ) {
MouseTracker4July application = new MouseTracker4July();
application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
}
} // end class MouseTracker