Come disegnare un rettangolo su un applet Java utilizzando evento del mouse trascinare e farlo rimanere

Question

Ho il mio programma in grado di disegnare rettangoli. Ho due problemi che non possono risolvere. Dopo che ho disegnare il rettangolo non rimarrà. L'unico codice che ho che cancella la tela in meno di vernice, ridipingere viene chiamato solo sul trascinamento del mouse. Perché quando il rilascio del mouse o movimento del mouse fa la mia tela chiara. La seconda cosa non è tanto un problema, ma una cosa che non riesco a capire, quando l'altezza o la larghezza del mio rettangolo è negativo il rettangolo è riempito in nero.

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

Answer 1

Ok, dopo aver riletto la tua domanda sembra che si potrebbe importare di meno per avere più rettangoli:)

Ecco una soluzione con una sola alla volta (che è vicino a quello che si doveva cominciare):

import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;

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 x, y, w, h;
    private final JLabel recStart;
    private final JLabel recStop;
    private final JLabel cords; // set up GUI and register mouse event handlers
    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 + "]" );

        this.isNewRect = true;

        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 + "]" );

        repaint();
    }

// 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 );

        int width = this.x1 - this.x2;
        int height = this.y1 - this.y2;

        this.w = Math.abs( width );
        this.h = Math.abs( height );
        this.x = width < 0 ? this.x1
            : this.x2;
        this.y = height < 0 ? this.y1
            : this.y2;

        if ( !this.isNewRect ) {
            g.drawRect( this.x, this.y, this.w, this.h );
        }

        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

Answer 2

È necessario memorizzare i vostri oggetti disegnati in qualche struttura di dati e garantire che ogni elemento nella struttura è dipinto sulla tela il ridisegno.

Inoltre, è necessario aggiungere ridipingere a ciascuno dei vostri eventi del mouse.

In questo modo:. (Questo presuppone che si desidera mantenere tutti rect di) - si può andare con un unico rettangolo eliminando l'ArrayList e la sua sostituzione con una singola istanza rect

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

Answer 3

Leggi su questi due Custom Painting Approcci . Un approccio è descritto sopra e il secondo approccio mostra come utilizzare una BufferedImage. L'esempio utilizzato per entrambi gli approcci permette di aggiungere più rettangoli al telaio.

Answer 4

Se non si cura un po 'di informazioni sul display, basta eliminare ogni "mousePosition.setText (...)" negli ascoltatori del mouse, che comporterà il ridisegno non necessarie () chiamate.

Quindi, aggiungere due campi: "int rx, ry,", aggiungere / modificare diversi metodi, come di seguito:

        public void mouseDragged(MouseEvent event) {
//      mousePosition.setText("Dragged at [" + (x = event.getX()) + ", "
//              + (y = event.getY()) + "]");
        // call repaint which calls paint
        x = event.getX();
        y = event.getY();

        compRectPos();
        repaint();
    }

    private void compRectPos()
    {
        rx = x1;
        ry = y1;

        w = x - x1;
        h = y - y1;

        if ( w < 0)
            rx += w;
        if (h < 0)
            ry += h;

        w = Math.abs(w);
        h = Math.abs(h);

    }

    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);

        g.drawRect(rx, ry, w, h);

        cords.setText("w = " + w + ", h = " + h);
    }

L'unico problema che ho trovato è che il rettangolo non appare quando prima disegnato.