您好我是这里的新手，也是Java编程的新手。最近我试图在JPanel中编写绘图函数。问题是，当我添加新的drawRect时（只需在JRadiobutton中选择draw Rect然后在白色空间上拖动）它工作正常但是当我按下undo按钮时，原点上有一个点。绘制椭圆和绘制折线工作正常。谁能帮我吗？
（抱歉我的英语很差，如果你不能得到我的问题，我很抱歉你可以尝试运行代码 - ＆gt;绘制矩形 - ＆gt;点击撤消 - ＆gt;在原点得到了dot（这是我试图解释的问题））
package com.jetbrains;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.image.BufferedImage;
public class Main
{
private BufferedImage buffPNG = new BufferedImage(900,550,BufferedImage.TYPE_INT_ARGB);
private Main()
{
draw_Image img = new draw_Image();
JFrame frame = new JFrame("Ken's Paint");
JButton undo_Button = new JButton("Undo");
JRadioButton rb1 = new JRadioButton("Free Hand");
JRadioButton rb2 = new JRadioButton("Draw Rect");
JRadioButton rb3 = new JRadioButton("Draw Oval");
JMenuBar menu_Bar = new JMenuBar();
undo_Button.setContentAreaFilled(false);
undo_Button.setFocusPainted(false);
ButtonGroup mode_Group = new ButtonGroup();
mode_Group.add(rb1);
mode_Group.add(rb2);
mode_Group.add(rb3);
img.setDraw_Mode(1);
rb1.setSelected(true);
menu_Bar.add(rb1);
menu_Bar.add(rb2);
menu_Bar.add(rb3);
menu_Bar.add(undo_Button);
frameCreate(frame);
frame.setJMenuBar(menu_Bar);
frame.add(img);
rb1.addActionListener(e -> img.setDraw_Mode(1));
rb2.addActionListener(e -> img.setDraw_Mode(2));
rb3.addActionListener(e -> img.setDraw_Mode(3));
undo_Button.addActionListener(e -> img.undo_Pressed());
}
class draw_Image extends JPanel
{
int layerX = 0;
int layerY = 0;
int[] polyX = new int[3000];
int[] polyY = new int[3000];
int[] thick = new int[10000];
int[] nPoint = new int[10000];
int[] draw_Mode = new int[10000];
int[][] x = new int[10000][3000];
int[][] y = new int[10000][3000];
Color[] color = new Color[10000];
boolean dragged = false;
draw_Image()
{
setLayout(null);
setBounds(0,0,900,550);
setBackground(Color.lightGray);
for(int p = 0; p < 10000; p++)
{
draw_Mode[p] = 1;
thick[p] = 3;
color[p] = Color.black;
}
addMouseListener(new MouseAdapter()
{
@Override
public void mouseClicked(MouseEvent e) {super.mouseReleased(e);}
@Override
public void mouseReleased(MouseEvent e)
{
super.mouseReleased(e);
if(dragged)
{
layerX++;
dragged = false;
}
layerY = 0;
}
});
addMouseMotionListener(new MouseMotionListener()
{
@Override
public void mouseDragged(MouseEvent e)
{
dragged = true;
for(int k = layerY; k < 3000; k++)
{
x[layerX][k] = e.getX();
y[layerX][k] = e.getY();
}
nPoint[layerX]++;
layerY++;
repaint();
}
@Override
public void mouseMoved(MouseEvent e){}
});
}
@Override
public void paint(Graphics g)
{
super.paint(g);
Graphics2D g2 = (Graphics2D)g;
Graphics2D g3 = buffPNG.createGraphics();
g2.setColor(Color.white);
g2.fillRect(0,0,900,550);
g3.setColor(Color.white);
g3.fillRect(0,0,900,550);
/* Draw the image in polyline form (implemented multidimensional array (2D is used)) */
for(int i = 0; i <= layerX; i++)
{
for(int j = 0; j < 3000; j++)
{
polyX[j] = x[i][j];
polyY[j] = y[i][j];
}
g2.setColor(color[i]); /* Set the line color (g2 is for display) */
g3.setColor(color[i]); /* Set the line color (g3 is for buffered image) */
g2.setStroke(new BasicStroke(thick[i])); /* Set line thickness (g2 is for display) */
g3.setStroke(new BasicStroke(thick[i])); /* Set line thickness (g3 is for buffered image) */
if(draw_Mode[i] == 1) /* free hand */
{
g2.drawPolyline(polyX,polyY,nPoint[i]);
g3.drawPolyline(polyX,polyY,nPoint[i]);
}
else if(draw_Mode[i] == 2) /* draw rect */
{
g2.drawRect(polyX[0],polyY[0],(polyX[2999] - polyX[0]),(polyY[2999] - polyY[0]));
g3.drawRect(polyX[0],polyY[0],(polyX[2999] - polyX[0]),(polyY[2999] - polyY[0]));
}
else if(draw_Mode[i] == 3) /* draw oval */
{
g2.drawOval(polyX[0],polyY[0],(polyX[2999] - polyX[0]),(polyY[2999] - polyY[0]));
g3.drawOval(polyX[0],polyY[0],(polyX[2999] - polyX[0]),(polyY[2999] - polyY[0]));
}
}
}
void setDraw_Mode(int mode) /* Method to set draw mode */
{
for(int q = layerX; q < 10000; q++)
{
draw_Mode[q] = mode;
}
}
void undo_Pressed() /* Undo an action / Return to previous line drawing */
{
if(layerX > 0)layerX--;
for(int j = 0; j < 3000; j++)
{
x[layerX][j] = 0;
y[layerX][j] = 0;
}
nPoint[layerX] = 0;
setDraw_Mode(draw_Mode[layerX+1]);
repaint();
}
}
private void frameCreate(JFrame frame)
{
frame.pack();
Insets insetValue = frame.getInsets();
int height = insetValue.top + insetValue.bottom + 600 - 10;
int width = insetValue.left + insetValue.right + 900 - 10;
frame.setSize(width,height); /* Set the frame size */
frame.setLocation(195,50); /* Set the frame start up location */
frame.setResizable(false); /* Disable frame resize & full window option */
frame.setLayout(null); /* Set the layout to null */
frame.setVisible(true); /* Set the frame visible */
frame.getContentPane().setBackground(Color.white); /* Set the frame background color */
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE); /* Specify the default behavior upon closing */
}
public static void main(String[] args)
{
new Main();
}
}
答案 0 :(得分：1)
无法解决您的问题，但有些常规提示：
class draw_Image extends JPanel
使用API作为类命名约定的指南。
int[] polyX = new int[3000];
int[] polyY = new int[3000];
int[] thick = new int[10000];
int[] nPoint = new int[10000];
不要在整个程序中使用硬编码。至少使用变量：
private static int SMALLER_SIZE = 3000;
private static int LARGER_SIZE = 10000;
...
int[] polyX = new int[SMALLER_SIZE];
int[] polyY = new int[SMALLER_SIZE];
int[] thick = new int[LARGER_SIZE];
int[] nPoint = new int[LARGER_SIZE];
更好的是，不要使用数组。而是使用ArrayList。那么你不需要为数组的大小选择一些随机大数。
int[] polyX = new int[SMALLER_SIZE];
int[] polyY = new int[SMALLER_SIZE];
不要保留两个数组。如果数据是相关的，则数据应存储在对象中。在上面的例子中，您可以使用属于JDK的Point对象。因此，使用ArrayList（而不是数组）的代码将类似于：
private ArrayList<Point> points = new ArrayList<Point>();
然后使用以下代码将Point对象添加到ArrayList：
points.add( new Point(...) );
现在您的循环代码没有硬编码值：
for (int i = 0; i < points.getSize(); I++
{
Point p = points.get(i);
// do something with the Point
}
一些绘画技巧：
public void paint(Graphics g)
不要覆盖油漆（...）。自定义绘画是通过覆盖paintComponent(...)
g2.setColor(Color.white);
g2.fillRect(0,0,900,550);
g3.setColor(Color.white);
g3.fillRect(0,0,900,550);
不要硬编码尺寸。你不知道屏幕尺寸是多少。相反，当您创建组件时，您只需执行以下操作：
DrawImage panel= new DrawImage();
panel.setBackground(Color.WHITE);
现在调用super.paintComponent（...）时，面板的背景将被涂成白色。
我也不知道你为什么使用透明的BufferedImage。只需直接在面板上绘画。
如果您真的想知道如何在面板上的随机位置绘制矩形，那么您可以查看Custom Painting Approaches。它演示了两种常见的方法。您可能会使用Draw On Component示例，因为它允许您“撤消”绘制矩形。当然你需要实现这个逻辑，但是如果在ArrayList中保留所有信息，这很简单就是删除列表中的最后一项。