更改 JPanel Graphics g 彩色绘图线 [英] Changing JPanel Graphics g color drawing line
问题描述
我有一个类似于绘画的程序.并且我正在尝试实现更改笔颜色但是当我更改颜色时，当前绘制的所有内容都更改为红色，例如在我的程序中，我如何才能使它不会重新绘制当前绘制的所有内容颜色变了?下面的代码会编译运行
i have a program similar to paint. and that i am trying to implement a change pen color however when i change the color, everything currently drawn is changed to the color RED for example in my program,how can i make it such that it will not repaint everything currently drawn to the currently changed color?Below code will compile and run
JPanel 绘图区的类
Class for the JPanel drawing area
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import javax.swing.BorderFactory;
import javax.swing.JPanel;
//refer to http://jkost.ergoway.gr/jnkjavaconnection/freedraw.html for the algorithm.
public class STDrawingArea extends JPanel {
/**
*
*/
private static final long serialVersionUID = 1L;
ArrayList<Rectangle> dPoint = new ArrayList<Rectangle>();
Point point = new Point(-1,-1);
private Color currentColor;
public STDrawingArea()
{
setBorder(BorderFactory.createLineBorder(Color.black));
setBackground(Color.WHITE);
addMouseMotionListener(new MouseAdapter() {
public void mouseDragged(MouseEvent e)
{
dPoint.add(new Rectangle(point.x,point.y,e.getX(),e.getY()));
point.x = e.getX();
point.y = e.getY();
repaint();
}
});
addMouseListener(new MouseAdapter(){
public void mousePressed(MouseEvent e)
{
System.out.println("mousePressed X: "+e.getX()+"mousePressed Y: "+e.getY());
dPoint.add(new Rectangle(e.getX(),e.getY(),-1,-1));
point.x = e.getX();
point.y = e.getY();
}
});
addMouseListener(new MouseAdapter(){
public void mouseReleased(MouseEvent e)
{
System.out.println("mouseReleased X: "+e.getX()+"mouseReleased Y: "+e.getY());
repaint();
}
});
}
@Override
public Dimension getPreferredSize() {
return new Dimension(700,500);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(getCurrentColor());
for (int i=0; i < dPoint.size(); i++) {
Rectangle r = dPoint.get(i);
if (r.width != -1)
{
g.drawLine(r.x, r.y, r.width, r.height);
}
}
/* Draw current point.*/
g.drawLine(point.x, point.y, point.x, point.y);
}
//set current drawing color
public void changePenColor(Color color)
{
if (color == null)
setCurrentColor(Color.BLACK);
else
setCurrentColor(color);
}
//clear drawings method
public void clearDrawings()
{
if(!(dPoint==null))
{
dPoint.clear();
repaint();
}
}
private void setCurrentColor(Color currentColor) {
this.currentColor = currentColor;
}
private Color getCurrentColor() {
return currentColor;
}
}
测试主类.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class STTestMain extends JFrame {
STDrawingArea drawingArea = new STDrawingArea();
public STTestMain()
{
//JFrame settings
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("Spelling Trainer");
setResizable(false);
setVisible(true);
//Panel of buttons
JPanel buttonContainer = new JPanel();
JButton btnPenColor = new JButton("Red Pen");
buttonContainer.add(btnPenColor);
//Drawing Area instantiation
//Adding things to JFrame
getContentPane().add(drawingArea);
getContentPane().add(buttonContainer,BorderLayout.PAGE_END);
pack();
//button listener
btnPenColor.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
drawingArea.changePenColor(Color.RED);
}
});
}
public static void main(String args[])
{
STTestMain test = new STTestMain();
}
}
推荐答案
一种方式:
- 使用您的 ArrayList 绘制当前正在绘制的曲线，但是
- 使用 BufferedImage 绘制完整的曲线
- 您将在 mouseReleased 上执行此操作，并使用当前颜色将当前曲线绘制到 BufferedImage.
- 在绘制到 BufferedImage 后，您还需要重新初始化点的 ArrayList.
- 不要忘记在使用完 BufferedImage 的 Graphics 对象后处理它.
- 在 super.paintComponent 之后但在绘制当前曲线之前，在您的paintComponent 方法中绘制BufferedImage.
- 这样，当您更改绘图颜色时，只会影响当前曲线.
编辑
您在评论中提到您不熟悉 BufferedImage，并且正在寻找另一种方式.我想您可以创建一个类，该类包含一个点的 ArrayList 和一个颜色，然后在每个 mouseReleased 上创建此类的一个对象并将其添加到绘图面板中的 ArrayList 中.然后，您的paintComponent 方法可以遍历该ArrayList，绘制带有关联颜色的Points 列表，但我的直觉告诉我，您是一个聪明的人，并且您很快就会学会如何使用BufferedImage.我真的认为这是最好的解决方案.如果您尝试并失败，请向我们展示您的代码，我们可能会帮助您.
EDIT
You've mentioned in a comment that you're not familiar with BufferedImage, and are looking for another way. I suppose you could create a class that holds an ArrayList of Points together with a Color, and then on each mouseReleased create an object of this class and add it to an ArrayList in your drawing panel. Then your paintComponent method could iterate through that ArrayList, drawing the list of Points with their associated color, but my gut tells me that you're an intelligent guy and that you'd pick up on how to use a BufferedImage in no time. I really think it's the best solution. And if you try it and it flops, show us your code, and we'll likely be able to help you.
编辑 2
BufferedImage 构造函数将需要图像宽度、高度和图像类型——我不是 100% 熟悉.我通常将 BufferedImage.TYPE_INT_RGB 用于通用绘图，将 BufferedImage.TYPE_INT_ARGB 用于需要 alpha 的通用绘图.然后你将从 BufferedImage 中提取一个 Graphics 对象，如果你需要的只是一个 Graphics 对象而不是一个 Graphics2D 对象，那么说 getGraphics() .然后当你在你的构造函数中初始化 BufferedImage 时，用 Color.white 填充它，就像你的 JPanel 一样.然后处理 Graphics 对象.然后每次要绘制的时候，获取Graphics，用它绘制，就像在paintComponent方法中一样，完成后处理Graphics，最后通过drawImage方法在paintComponent中绘制BufferedImage.
EDIT 2
The BufferedImage constructor will need the image width, height and an image type -- something I'm not 100% familiar with. I usually use BufferedImage.TYPE_INT_RGB for general purpose drawing, and BufferedImage.TYPE_INT_ARGB for general purpose that needs an alpha too. Then you'll extract a Graphics object out of the BufferedImage, say getGraphics() if all you need is a Graphics object and not a Graphics2D object. Then when you initialize the BufferedImage in your constructor, fill it with a Color.white, just as you for your JPanel. Then dispose the Graphics object. Then each time you want to draw, you getGraphics, draw with it, just like you do in the paintComponent method, dispose of the Graphics when done, and finally draw the BufferedImage in the paintComponent via the drawImage method.
编辑 3
示例程序并不完全符合您的要求，但确实说明了 BufferedImage 与绘图的使用.每次绘制新路径或曲线时，此程序都会更改颜色.
EDIT 3
Example program that doesn't do quite what you are trying to do but does illustrate use of a BufferedImage with drawing. This program changes the color each time a new path or curve is drawn.
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.util.ArrayList;
import javax.swing.*;
public class STTestSimple {
private static void createAndShowUI() {
STDrawPanel drawPanel = new STDrawPanel();
STMouseAdapter mAdapter = new STMouseAdapter(drawPanel);
drawPanel.addMouseListener(mAdapter);
drawPanel.addMouseMotionListener(mAdapter);
JFrame frame = new JFrame("Drawing");
frame.getContentPane().add(drawPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(false);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
createAndShowUI();
}
});
}
}
@SuppressWarnings("serial")
class STDrawPanel extends JPanel {
private static final int ST_WIDTH = 700;
private static final int ST_HEIGHT = 500;
private static final Color BACKGROUND_COLOR = Color.white;
private static final float STROKE_WIDTH = 6f;
private static final Stroke STROKE = new BasicStroke(STROKE_WIDTH,
BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
private static final Color[] colors = {Color.black, Color.blue, Color.red,
Color.green, Color.orange, Color.MAGENTA};
private BufferedImage bImage = new BufferedImage(ST_WIDTH, ST_HEIGHT,
BufferedImage.TYPE_INT_RGB);
private Color color = Color.black;
private ArrayList<Point> points = new ArrayList<Point>();
private int colorIndex = 0;
public STDrawPanel() {
Graphics g = bImage.getGraphics();
g.setColor(BACKGROUND_COLOR);
g.fillRect(0, 0, ST_WIDTH, ST_HEIGHT);
g.dispose();
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(bImage, 0, 0, null);
Graphics2D g2 = (Graphics2D) g;
drawCurve(g2);
}
private void addCurveToBufferedImage() {
Graphics2D g2 = bImage.createGraphics();
drawCurve(g2);
g2.dispose();
}
private void drawCurve(Graphics2D g2) {
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(STROKE);
g2.setColor(color);
if (points != null && points.size() > 1) {
for (int i = 0; i < points.size() - 1; i++) {
int x1 = points.get(i).x;
int y1 = points.get(i).y;
int x2 = points.get(i + 1).x;
int y2 = points.get(i + 1).y;
g2.drawLine(x1, y1, x2, y2);
}
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(ST_WIDTH, ST_HEIGHT);
}
public void curveStart(Point point) {
points.clear();
points.add(point);
}
public void curveEnd(Point point) {
points.add(point);
addCurveToBufferedImage();
points.clear();
repaint();
colorIndex++;
colorIndex %= colors.length;
setColor(colors[colorIndex]);
}
public void curveAdd(Point point) {
points.add(point);
repaint();
}
public void setColor(Color color) {
this.color = color;
}
}
class STMouseAdapter extends MouseAdapter {
private STDrawPanel drawPanel;
public STMouseAdapter(STDrawPanel drawPanel) {
this.drawPanel = drawPanel;
}
@Override
public void mousePressed(MouseEvent e) {
drawPanel.curveStart(e.getPoint());
}
@Override
public void mouseReleased(MouseEvent e) {
drawPanel.curveEnd(e.getPoint());
}
@Override
public void mouseDragged(MouseEvent e) {
drawPanel.curveAdd(e.getPoint());
}
}
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