我想实现画图中画直线时的拉线效果。
既在mousePressed()方法中获取初始点，然后在mouseDragged()中不断获取当前点，画线并调用JPanel的repaint()方法,在mouseReleased()方法中得到结束点，并最终画出这条线。
以上拉线的代码都在mouseDragged()方法中完成。但是，当开始拉线后，一旦鼠标不动后（鼠标还没释放），mouseDragged()就停止调用了，似乎这个时候，系统自动调用了repaint()，导致拉出的线不见了，请问这个问题怎么解决，麻烦各位大虾看看
既在mousePressed()方法中获取初始点，然后在mouseDragged()中不断获取当前点，画线并调用JPanel的repaint()方法,在mouseReleased()方法中得到结束点，并最终画出这条线。
以上拉线的代码都在mouseDragged()方法中完成。但是，当开始拉线后，一旦鼠标不动后（鼠标还没释放），mouseDragged()就停止调用了，似乎这个时候，系统自动调用了repaint()，导致拉出的线不见了，请问这个问题怎么解决，麻烦各位大虾看看
(Eastsun is me,also^_^)import java.awt.geom.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
/**
*简单的画图程序
*@author Eastsun
*@version .1
*/
public class DrawPanel extends JFrame{
LinkedList<Shape> shapeList =new LinkedList<Shape>();
Shape shape;
Point start,end;
final String[] type =new String[]{"Line","Rectangle","Ellipse"};
JComboBox comboBox =new JComboBox(type);
public DrawPanel(){
super("DrawPanel");
JPanel panel =new JPanel(){
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2 =(Graphics2D)g;
g2.setColor(Color.white);
g2.fillRect(0,0,getWidth(),getHeight());
g2.setColor(Color.black);
for(Shape s:shapeList) g2.draw(s);
g2.draw(shape);
}
};
panel.addMouseListener(new MouseAdapter(){
public void mousePressed(MouseEvent e){
start =e.getPoint();
}
public void mouseReleased(MouseEvent e){
shapeList.add(shape);
}
});
panel.addMouseMotionListener(new MouseMotionAdapter(){
public void mouseDragged(MouseEvent e){
end =e.getPoint();
Object select =comboBox.getSelectedItem();
if(select.equals(type[0])) shape =new Line2D.Float(start,end);
else{
if(select.equals(type[1])) shape =new Rectangle();
else shape =new Ellipse2D.Float();
((RectangularShape)shape).setFrameFromDiagonal(start,end);
}
repaint();
}
});
panel.setPreferredSize(new Dimension(320,240));
add(panel,BorderLayout.NORTH);
shape =new Rectangle();
add(comboBox,BorderLayout.SOUTH);
pack();
setResizable(false);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
}
public static void main(String[] args){
new DrawPanel();
}
}
import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.geom.CubicCurve2D;
import java.awt.geom.Line2D;
import java.awt.geom.QuadCurve2D;import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;public class CubicCurveMouse extends JFrame {
DrawingCanvas canvas; JLabel label = new JLabel("Mouse Location (x, y): ");
JLabel coords = new JLabel(""); public CubicCurveMouse() {
super();
Container container = getContentPane(); JPanel panel = new JPanel();
panel.setLayout(new GridLayout(1, 2)); panel.add(label);
//panel.add(label);
panel.setOpaque(false); panel.add(coords); container.add(panel, BorderLayout.SOUTH); canvas = new DrawingCanvas();
JPanel jpanel=new JPanel();
jpanel.add(canvas);
container.add(jpanel);
addWindowListener(new WindowEventHandler());
pack();
setSize(300,300);
setVisible(true);
} class WindowEventHandler extends WindowAdapter {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
} public static void main(String arg[]) { new CubicCurveMouse();
} class DrawingCanvas extends Canvas {
//x1,y1涓鸿捣濮嬬偣鍧愭爣锛寈c1cur, yc1cur绗�2娆＄偣鍑绘椂鐐瑰潗鏍囷紝x4new, y4new绗竴娆℃澗鎵�
//鏃剁邯褰曠殑鐐癸紝
float x1, y1, xc1cur, yc1cur, xc1new, yc1new, xc2cur, yc2cur, xc2new,
yc2new, x4cur, y4cur, x4new, y4new; int pressNo = 0; //鐐瑰嚮榧犳爣娆℃暟 int dragFlag1 = -1; int dragFlag2 = -1; boolean clearFlag = false; float dashes[] = { 5f, 5f }; BasicStroke stroke; public DrawingCanvas() {
setBackground(Color.white);
addMouseListener(new MyMouseListener());
addMouseMotionListener(new MyMouseListener());
setSize(400, 400);
stroke = new BasicStroke(1f, BasicStroke.CAP_BUTT,
BasicStroke.JOIN_BEVEL, 10f, dashes, 0f);
} public void update(Graphics g) {
paint(g);
} public void paint(Graphics g) {
Graphics2D g2D = (Graphics2D) g; if (pressNo == 1) {
g2D.setXORMode(getBackground());
g2D.setColor(Color.red);
g2D.setStroke(stroke); // Erase the currently existing line
g2D.draw(new Line2D.Float(x1, y1, x4cur, y4cur));
// Draw the new line
g2D.draw(new Line2D.Float(x1, y1, x4new, y4new)); // Update the currently existing coordinate values
x4cur = x4new;
y4cur = y4new; }else if (pressNo == 2) {
g2D.setXORMode(getBackground());
g2D.setColor(Color.black);
g2D.setStroke(stroke); if (dragFlag1 != -1) {
g2D.draw(new QuadCurve2D.Float(x1, y1, xc1cur, yc1cur,
x4new, y4new));
}
dragFlag1++; // Reset the drag-flag g2D.draw(new QuadCurve2D.Float(x1, y1, xc1new, yc1new, x4new,
y4new)); xc1cur = xc1new;
yc1cur = yc1new;
}else if (pressNo == 3) {
g2D.setXORMode(getBackground());
g2D.setColor(Color.black); if (dragFlag2 != -1) {
g2D.draw(new CubicCurve2D.Float(x1, y1, xc1new, yc1new,
xc2cur, yc2cur, x4new, y4new));
}
dragFlag2++; // Reset the drag flag
g2D.draw(new CubicCurve2D.Float(x1, y1, xc1new, yc1new, xc2new,
yc2new, x4new, y4new));
xc2cur = xc2new;
yc2cur = yc2new;
}
if (clearFlag) {
g2D.setXORMode(getBackground());
g2D.setColor(Color.black);
g2D.setStroke(stroke); g2D.draw(new Line2D.Float(x1, y1, x4new, y4new));
g2D.draw(new QuadCurve2D.Float(x1, y1, xc1new, yc1new, x4new,
y4new));
clearFlag = false;
}
} class MyMouseListener extends MouseAdapter implements MouseMotionListener {
public void mousePressed(MouseEvent e) {
if (pressNo == 0) {
pressNo++;
x1 = x4cur = e.getX();
y1 = y4cur = e.getY();
} else if (pressNo == 1) {
pressNo++;
xc1cur = e.getX();
yc1cur = e.getY();
} else if (pressNo == 2) {
pressNo++;
xc2cur = e.getX();
yc2cur = e.getY();
}
}
public void mouseReleased(MouseEvent e) {
if (pressNo == 1) {
x4new = e.getX();
y4new = e.getY();
canvas.repaint();
} else if (pressNo == 2) {
xc1new = e.getX();
yc1new = e.getY();
canvas.repaint();
} else if (pressNo == 3) {
xc2new = e.getX();
yc2new = e.getY();
canvas.repaint();
pressNo = 0;
dragFlag1 = -1;
dragFlag2 = -1;
clearFlag = true;
}
}
public void mouseDragged(MouseEvent e) {
if (pressNo == 1) {
x4new = e.getX();
y4new = e.getY();
} else if (pressNo == 2) {
xc1new = e.getX();
yc1new = e.getY(); } else if (pressNo == 3) {
xc2new = e.getX();
yc2new = e.getY(); }
String string = "(" + Integer.toString(e.getX()) + ", "
+ Integer.toString(e.getY()) + ")";
coords.setText(string);
canvas.repaint();
} public void mouseMoved(MouseEvent e) {
String string = "(" + Integer.toString(e.getX()) + ", "
+ Integer.toString(e.getY()) + ")";
coords.setText(string);
}
}
}
}