我在一個學校專案中遇到問題，我在其中創建了一個多邊形，當我插入點時，在插入每個點后多邊形更新。
例如
我的程式：
我想要的結果：
我的理解是，為了讓它看起來像結果，洗掉 Point3 和 Point1 之間的鏈接，新的鏈接將在 Point4 和 Point1 之間。如果這是解決方案，我不知道要在我的代碼中添加什么來修復它。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.geom.*;
import java.util.*;
public class ShapesByMouseDrag3 extends JFrame {
private static final int FW = 800;
private static final int FH = 600;
private Point p1;
private Point p2;
private int x;
private int y;
ArrayList<Integer> alX = new ArrayList<>();
ArrayList<Integer> alY = new ArrayList<>();
JRadioButton lineRB = new JRadioButton("Line");
JRadioButton rectRB = new JRadioButton("Rectangle");
JRadioButton Ellipse = new JRadioButton("Ellipse");
JRadioButton PolygonRB = new JRadioButton("Polygon");
public static void main(String[] args) {
new ShapesByMouseDrag3();
}
public ShapesByMouseDrag3() {
setSize(FW, FH);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setTitle("Draw Graphics Objects by Mouse Drag");
setLocationRelativeTo(null);
setLayout(new BorderLayout());
PaintPanel paintPanelObj = new PaintPanel(FW, FH);
JPanel chooseShapePanel = new JPanel();
chooseShapePanel.setBackground(Color.WHITE);
chooseShapePanel.setLayout(new GridLayout(4, 1));
chooseShapePanel.setBorder(BorderFactory.createTitledBorder(
BorderFactory.createEtchedBorder(), "Shapes"));
//Create the radio buttons.
//Create a button group and add buttons
ButtonGroup bgroup = new ButtonGroup();
bgroup.add(lineRB);
bgroup.add(rectRB);
bgroup.add(Ellipse);
bgroup.add(PolygonRB);
// add buttons to chooseShapePanel panel
chooseShapePanel.add(lineRB);
chooseShapePanel.add(rectRB);
chooseShapePanel.add(Ellipse);
chooseShapePanel.add(PolygonRB);
add(paintPanelObj, BorderLayout.CENTER);
add(chooseShapePanel, BorderLayout.WEST);
setVisible(true);
pack();
}
private class PaintPanel extends JPanel {
private int PW; // panel-width
private int PH; // panel-height
Collection<Shape> shapeList = new ArrayList<Shape>();
Collection<Shape> shapeListR = new ArrayList<Shape>();
public PaintPanel(int W, int H) {
PW = W;
PH = H;
setPreferredSize(new Dimension(PW, PH)); // set width & height of panel
setBorder(BorderFactory.createTitledBorder(
BorderFactory.createEtchedBorder(), "Canvas"));
addMouseListener(new MouseClickListener());
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setStroke(new BasicStroke(2f));
g2.setColor(Color.blue);
if (lineRB.isSelected()) {
makeLine();
} else if (rectRB.isSelected()) {
makeRectangle();
} else if (Ellipse.isSelected()) {
makeEllipse();
} else if (PolygonRB.isSelected()) {
makePolygon();
}
// draw all the shapes stored in the collection
Iterator itr = shapeList.iterator();
while (itr.hasNext()) {
g2.draw((Shape) itr.next());
}
// reset
p1 = null;
p2 = null;
}
public void makeLine() {
if (p1 != null && p2 != null) {
shapeList.add(new Line2D.Double(p1.x, p1.y, p2.x, p2.y));
}
}
public void makeRectangle() {
double RectangleX = Math.min(p1.x, p2.x);
double RectangleY = Math.min(p1.y, p2.y);
double RectangleW = Math.abs(p1.x - p2.x);
double RectangleH = Math.abs(p1.y - p2.y);
if (p1 != null && p2 != null) {
shapeList.add(new Rectangle2D.Double(RectangleX, RectangleY, RectangleW, RectangleH));
}
}
public void makeEllipse() {
double EllipseX = Math.min(p1.x, p2.x);
double EllipseY = Math.min(p1.y, p2.y);
double EllipseW = Math.abs(p1.x - p2.x);
double EllipseH = Math.abs(p1.y - p2.y);
if (p1 != null && p2 != null) {
shapeList.add(new Ellipse2D.Double(EllipseX, EllipseY, EllipseW, EllipseH));
}
}
public void makePolygon() {
int[] xArray = new int[alX.size()];
int[] yArray = new int[alY.size()];
for (int i = 0; i < alX.size(); i ) {
xArray[i] = alX.get(i);
yArray[i] = alY.get(i);
}
if (p1 != null && p2 != null) {
shapeList.add(new Polygon(xArray, yArray, xArray.length));
}
}
private class MouseClickListener extends MouseAdapter {
public void mousePressed(MouseEvent event) {
p1 = new Point(event.getX(), event.getY());
alX.add(p1.x);
alY.add(p1.y);
}
public void mouseEntered(MouseEvent event) {
alX.clear();
alY.clear();
}
public void mouseReleased(MouseEvent event) {
p2 = new Point(event.getX(), event.getY());
alX.add(p2.x);
alY.add(p2.y);
repaint();
}
}
}
}
uj5u.com熱心網友回復：
不要paintComponent用來構建形狀，這不是paintComponent目的。
當您以更簡單的方式添加新點時，我會使用Path2D(over )。PolygonPath2D
下面是一個簡單的例子，它使用兩個Path2D實體來跟蹤形狀。第一個是“開放”路徑，我們不斷添加點，第二個是第一個的“封閉”副本。這是有意的，就好像您在每次單擊后關閉形狀一樣，它只會繪制從第一個單擊點延伸的線條。
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
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 java.awt.geom.Path2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Main {
public static void main(String[] args) {
new Main();
}
public Main() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
JFrame frame = new JFrame();
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private Path2D polygon = null;
// Give some guidence
private Point lastClickPoint = null;
private Point currentMousePoint = null;
public TestPane() {
MouseAdapter ma = new MouseAdapter() {
// This is the "acutal" shape been draw
// This allows us to "close" the polygon
// without it breaking the underlying shape
private Path2D mouseShape = null;
@Override
public void mouseClicked(MouseEvent e) {
if (mouseShape == null) {
mouseShape = new Path2D.Double();
mouseShape.moveTo(e.getX(), e.getY());
} else {
mouseShape.lineTo(e.getX(), e.getY());
}
polygon = new Path2D.Double();
polygon.append(mouseShape, true);
polygon.closePath();
lastClickPoint = e.getPoint();
repaint();
}
@Override
public void mouseMoved(MouseEvent e) {
currentMousePoint = e.getPoint();
repaint();
}
};
addMouseListener(ma);
addMouseMotionListener(ma);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(Color.BLACK);
if (polygon != null) {
g2d.draw(polygon);
}
if (lastClickPoint != null && currentMousePoint != null) {
g2d.setColor(Color.GRAY);
g2d.draw(new Line2D.Double(lastClickPoint, currentMousePoint));
}
g2d.dispose();
}
}
}
這是一個重點示例，只解決一個問題，您將需要修改代碼以適應它。我會在每次滑鼠單擊時確定您要創建的形狀型別并創建一個可以繪制的“中間”，直到用戶“提交”更改，此時將添加形狀到List，但那是我
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