我有一个GUI,其中有一个我绘制的面板。无论我做什么样的鼠标模式都会在每个被两行划分的扇区中重复。但是,我能够这样做,因为我的paintComponen方法不会调用super.paintComponent。如果我实际上调用了方法,每当我拖动鼠标时,我只得到一个点。我应该怎么做呢?
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Line2D;
import javax.swing.JPanel;
public final class DisplayPanel extends JPanel
{
private boolean dragging;
private Point draw;
private Line2D sectorLine;
private int sectors;
public void init()
{
DisplayListener listener = new DisplayListener();
addMouseListener(listener);
addMouseMotionListener(listener);
setOpaque(true);
setBackground(Color.BLACK);
setSize(900,900);
setVisible(true);
}
//performs the drawing on the display panel
public void paintComponent(Graphics g)
{
//super.paintComponent(g);
setBackground(Color.BLACK);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.RED);
sectorLine = new Line2D.Double(getWidth()/2, 0, getWidth()/2, getHeight());
sectors = 12;
//draws the sectors on the screen
for(int i=0; i<sectors; i++)
{
g2d.draw(sectorLine);
g2d.rotate(Math.toRadians(30),getWidth()/2,getHeight()/2);
}
//draws the doilie
if(dragging)
{
for(int i=0; i<sectors; i++)
{
g2d.fillOval((int) draw.getX(), (int) draw.getY(),20, 20);
g2d.rotate(Math.toRadians(30), getWidth()/2, getHeight()/2);
}
}
}
private class DisplayListener extends MouseAdapter
{
public void mouseDragged(MouseEvent event)
{
dragging = true;
draw = event.getPoint();
repaint();
}
public void mouseReleased(MouseEvent event)
{
dragging = false;
}
}
}
答案 0 :(得分:1)
super.paintComponent()
在绘制前删除/清除区域,因此您只能看到当前绘制的点。
如果要绘制拖动鼠标的线条,则必须将每个绘制的坐标存储在列表中,然后在paintComponent()
中再次绘制所有点。请注意,此列表可能会变得非常大,因此会占用大量内存,因此您应该考虑以某种方式限制它。