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Graphics2D问题

楼主stone_q（Java虫）2003-05-03 09:47:24 在 Java / J2SE / 基础类提问

这两天正在做一个画图程序，快要疯掉了
我是在一个jpanel上作图的，用主界面的“画图”菜单击活，可是当我点击菜单时什么也没有，只有当窗口大小改变时才显示出来，猜想是repaint问题，但是试过repaint和update都没用，还有，当图象显示出来时，如果再弹出一个对话框，连对话框也会重画在界面上，图象被画的一塌糊涂，请那位指点指点，我都快要疯了，不胜感激！问题点数：100、回复次数：10Top

1 楼rocandroc（程序人生）回复于 2003-05-03 11:00:07 得分 50

因为具体程序不清楚什么也没有猜想是不是setlayout的问题。
给你一个源程序参考一下。

// Java core packages
import java.awt.*;
import java.awt.event.*;

// Java extension packages
import javax.swing.*;

public class SelfContainedPanel extends JPanel {
private int x1, y1, x2, y2;

// set up mouse event handling for SelfContainedPanel
public SelfContainedPanel()
{
// set up mouse listener
addMouseListener(

// anonymous inner class for mouse pressed and
// released event handling
new MouseAdapter() {

// handle mouse press event
public void mousePressed( MouseEvent event )
{
x1 = event.getX();
y1 = event.getY();
}

// handle mouse release event
public void mouseReleased( MouseEvent event )
{
x2 = event.getX();
y2 = event.getY();
repaint();
}

} // end anonymous inner class

); // end call to addMouseListener

// set up mouse motion listener
addMouseMotionListener(

// anonymous inner class to handle mouse drag events
new MouseMotionAdapter() {

// handle mouse drag event
public void mouseDragged( MouseEvent event )
{
x2 = event.getX();
y2 = event.getY();
repaint();
}

} // end anonymous inner class

); // end call to addMouseMotionListener

} // end constructor

// return preferred width and height of SelfContainedPanel
public Dimension getPreferredSize()
{
return new Dimension( 150, 100 );
}

// paint an oval at the specified coordinates
public void paintComponent( Graphics g )
{
super.paintComponent( g );

g.drawOval( Math.min( x1, x2 ), Math.min( y1, y2 ),
Math.abs( x1 - x2 ), Math.abs( y1 - y2 ) );
}

} // end class SelfContainedPanel

import java.awt.*;
import java.awt.event.*;

// Java extension packages
import javax.swing.*;

// Deitel packages
import SelfContainedPanel;

public class SelfContainedPanelTest extends JFrame {
private SelfContainedPanel myPanel;

// set up GUI and mouse motion event handlers for
// application window
public SelfContainedPanelTest()
{
// set up a SelfContainedPanel
myPanel = new SelfContainedPanel();
myPanel.setBackground( Color.yellow );

Container container = getContentPane();
container.setLayout( new FlowLayout() );
container.add( myPanel );

// set up mouse motion event handling
addMouseMotionListener(

// anonymous inner class for mouse motion event handling
new MouseMotionListener() {

// handle mouse drag event
public void mouseDragged( MouseEvent event )
{
setTitle( "Dragging: x=" + event.getX() +
"; y=" + event.getY() );
}

// handle mouse move event
public void mouseMoved( MouseEvent event )
{
setTitle( "Moving: x=" + event.getX() +
"; y=" + event.getY() );
}

} // end anonymous inner class

); // end call to addMouseMotionListener

setSize( 300, 200 );
setVisible( true );
}

// execute application
public static void main( String args[] )
{
SelfContainedPanelTest application =
new SelfContainedPanelTest();

application.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE );
}

} // end class SelfContainedPanelTest
Top

2 楼alexll（游文）回复于 2003-05-03 11:10:41 得分 10

试下重载repaint
或者用double bufferingTop

3 楼Eraserpro（叶·飘·零）回复于 2003-05-03 11:12:17 得分 20

你的第一个问题的原因可能是你的JPanel的宿主窗口(你是用JFrame吧!)中setVisible(true)写在setSize(a,b)之前所致.
第二个问题没遇到过,不过你最好用BufferedImage这个类做一下缓冲,画图在图像上画,然后在paint方法中显示这个BufferedImage,这样子会好点.Top

4 楼stone_q（Java虫）回复于 2003-05-04 18:52:53 得分 0

up
Top

5 楼jettyl（菜鸟一个）回复于 2003-05-04 20:10:22 得分 0

是不是repaint的位置写的不对Top

6 楼wangfc（秋水）回复于 2003-05-04 20:25:16 得分 20

通常不直接使用repaint,使用update。Top

7 楼beyond_xiruo（CorruptionException）回复于 2003-05-04 20:30:35 得分 0

没有具体的代码，难道要无的放失？？？！！！Top

8 楼stone_q（Java虫）回复于 2003-05-05 10:53:59 得分 0

代码很普通，就是在paint中画几条线，没有别的操作Top

9 楼stone_q（Java虫）回复于 2003-05-05 21:57:19 得分 0

upTop

10 楼stone_q（Java虫）回复于 2003-05-06 11:10:35 得分 0

为什么没有人理我了？Top