我知道这个问题被多次询问并且经常回答,我在这个主题上读了几个小时试图继续工作,但无法让它运行起来。
我想向用户显示一个面板,他或她可以点击该面板来选择点,记住坐标并稍后用它们做一些事情。
我想在点击时显示点数,但它们只是没有显示出来。
我在面板周围绘制的框架确实显示出来,但我设置的点没有显示。
对于给出的任何建议都很高兴,我对java GUI编程非常陌生。
//in main class
SwingUtilities.invokeLater(() -> {
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
drawBoard = new DrawBoard();
drawBoard.setOpaque(true);
container conti = getContentPane();
conti.setLayout(new BorderLayout());
conti.add(drawBoard, BorderLayout.CENTER);
setLocation(400, 200);
setSize(1000, 600);
setVisible(true);
setResizable(false);
});
int timerDelay = 200;
new Timer(timerDelay, e -> {
drawBoard.repaint();
}).start();
//end of main class
public class drawBoard extends JPanel {
int n = 0;
MyPoint[] myPoints = new MyPoint[5];
public drawBoard(){
MyMouseAdapter ma = new MyMouseAdapter(this);
this.addMouseListener(ma);
}
public void addMyPoint(Point p){
this.myPoints[this.n] = new MyPoint(p);
add(myPoints[this.n]);
n++; // overflow ignored cause example
}
@Override
public void paint(Graphics g) {
super.paint(g);
g.drawRect(0,0,600,500);
}
}
public class MyMouseAdapter extends MouseAdapter{
drawBoard owner;
public MyMouseAdapter(drawBoard owner){
this.owner = owner;
}
public void mouseClicked(MouseEvent b) {
owner.addMyPoint(b.getPoint());
owner.invalidate();
owner.repaint();
}
}
public class MyPoint extends Component {
public int x;
public int y;
public MyPoint(Point p){
x = (int)p.getX();
y = (int)p.getY();
}
@Override
public void paint(Graphics g) {
super.paint(g);
g.drawOval(x - 3, y - 3, 6, 6);
}
}
使用此代码,我看到矩形,但没有点椭圆。我错了的任何线索?
答案 0 :(得分:2)
椭圆不应该在扩展Component或任何其他GUI类的类中,而应该在"逻辑"类,换句话说,非GUI类。让DrawBoard完成所有绘图,包括迭代MyPoint对象的ArrayList(不是数组),并绘制它们。此外,所有绘图都应该在paintComponent覆盖范围内完成,而不是绘制覆盖。
如,
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
public class MainFoo {
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
createAndShowGui();
});
}
private static void createAndShowGui() {
DrawBoard mainPanel = new DrawBoard();
JFrame frame = new JFrame("Main Foo");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.add(mainPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
// DrawBoard should start with a capital letter
class DrawBoard extends JPanel {
private static final int PREF_W = 1000;
private static final int PREF_H = 600;
int n = 0;
List<MyPoint> myPoints = new ArrayList<>();
public DrawBoard() {
MyMouseAdapter ma = new MyMouseAdapter(this);
this.addMouseListener(ma);
}
@Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
} else {
return new Dimension(PREF_W, PREF_H);
}
}
public void addMyPoint(Point p) {
MyPoint myPoint = new MyPoint(p);
myPoints.add(myPoint);
repaint();
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawRect(0, 0, 600, 500);
// use Graphics2D to allow for smoothing
Graphics2D g2 = (Graphics2D) g;
// smooth with rendering hiints
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// iterate through each MyPoint in the list
for (MyPoint myPoint : myPoints) {
myPoint.draw(g2); // and draw it
}
}
}
class MyMouseAdapter extends MouseAdapter {
DrawBoard owner;
public MyMouseAdapter(DrawBoard owner) {
this.owner = owner;
}
// btetter to use mousePressed, not mouseClicked
@Override
public void mousePressed(MouseEvent b) {
owner.addMyPoint(b.getPoint());
}
}
class MyPoint {
public int x;
public int y;
public MyPoint(Point p) {
x = (int) p.getX();
y = (int) p.getY();
}
public void draw(Graphics2D g2) {
g2.drawOval(x - 3, y - 3, 6, 6);
}
}