尝试是在awt画布上用鼠标绘制图形(现在是一条线).我第一次尝试
java图形.所以不确定如何去做.这是我的第一次尝试：
package def.grafi;
import java.awt.Canvas;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
public class Dra {
Frame f = new Frame();
public void disp() {
f.setBounds(100,100,200,200);
MosL ml = new MosL();
Can c = new Can();
f.add(c);
c.addMouseListener(ml);
c.addMouseMotionListener(ml);
f.setVisible(true);
}
public static void main(String[] args) {
Dra d = new Dra();
d.disp();
}
public class MosL extends MouseAdapter {
int sx = 0;
int sy = 0;
boolean onDrag = false;
@Override
public void mouseDragged(MouseEvent e) {
if (onDrag) {
int x = e.getX();
int y = e.getY();
Canvas comp = (Canvas) e.getSource();
Graphics g = comp.getGraphics();
// comp.repaint(); << for cleaning up the intermediate lines : doesnt work :(
g.drawLine(sx,sy,x,y);
return;
}
onDrag = true;
sx = e.getX();
sy = e.getY();
System.out.println("Draggg");
}
@Override
public void mousePressed(MouseEvent e) {
System.out.println("Pressed");
}
@Override
public void mouseReleased(MouseEvent e) {
System.out.println("Released");
if (onDrag)
onDrag = false;
}
}
public class Can extends Canvas {
@Override
public void paint(Graphics g) {
}
}
}
问题 ：
1)当窗口最小化并恢复时,绘制的线条消失(由于重绘)
2)我想要的是线应该跟随鼠标(当它被拖动时).最后一行应该从按压点延伸到鼠标释放点. Rite现在,当鼠标移动时,新线条将被绘制.我不确定如何清理画布中的中间线.
有人可以帮我解决这些问题吗？
解决方法
这是一个这种“绘画”的简单例子：
public static void main ( String[] args )
{
JFrame paint = new JFrame ();
paint.add ( new JComponent ()
{
private List<Shape> shapes = new ArrayList<Shape> ();
private Shape currentShape = null;
{
MouseAdapter mouseAdapter = new MouseAdapter ()
{
public void mousePressed ( MouseEvent e )
{
currentShape = new Line2D.Double ( e.getPoint (),e.getPoint () );
shapes.add ( currentShape );
repaint ();
}
public void mouseDragged ( MouseEvent e )
{
Line2D shape = ( Line2D ) currentShape;
shape.setLine ( shape.getP1 (),e.getPoint () );
repaint ();
}
public void mouseReleased ( MouseEvent e )
{
currentShape = null;
repaint ();
}
};
addMouseListener ( mouseAdapter );
addMouseMotionListener ( mouseAdapter );
}
protected void paintComponent ( Graphics g )
{
Graphics2D g2d = ( Graphics2D ) g;
g2d.setPaint ( Color.BLACK );
for ( Shape shape : shapes )
{
g2d.draw ( shape );
}
}
} );
paint.setSize ( 500,500 );
paint.setLocationRelativeTo ( null );
paint.setVisible ( true );
}
它会记住所有绘制的形状,只需很小的努力就可以扩展它以绘制你喜欢的任何其他形状.
