我是AWT的新手，这只是一个示例程序，可以看看它是如何工作的。
我的问题是，在调整大小/最小化等事件时，窗口会被清除。
我已经覆盖了许多SO问题中指定的paintComponent，并且实际调用了代码（因为如果我在其中放置println，我会看到输出），但是没有显示任何内容。< / p>
我在Windows和Linux上试过这个，结果是一样的，所以我想我错过了什么。
以下是代码：
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;
class Site {
private Integer x;
private Integer y;
private Integer width;
private Integer height;
private Graphics2D g2d;
private boolean isOpen = false;
private Integer id = null;
private Integer root = null;
public Site(Integer id, Integer x, Integer y, Integer width, Integer height, Graphics2D g2d) {
this.id = id;
this.root = id;
this.x = x;
this.y = y;
this.width = width;
this.height = height;
this.g2d = g2d;
}
public void Draw() {
g2d.setPaint(new Color(0, 0, 0));
g2d.setStroke(new BasicStroke(2));
Integer x_top_corner = x - (width / 2);
Integer y_top_corner = y - (height / 2);
g2d.drawRect(x_top_corner, y_top_corner, width, height);
System.out.println(x_top_corner);
if (isOpen) {
g2d.setPaint(new Color(150, 150, 200));
} else {
g2d.setPaint(new Color(200, 200, 200));
}
g2d.fillRect(x_top_corner + 1, y_top_corner + 1, width - 2, height - 2);
}
public void Open() {
this.isOpen = true;
}
public void Close() {
this.isOpen = false;
}
}
class Surface extends JPanel {
private ArrayList<Site> sites = new ArrayList<Site>();
private Graphics2D g2d = null;
private void initSites() {
Integer width = 30;
Integer height = 30;
Integer index = 0;
for (Integer y = height; y < 800 - height - 30; y += height) {
for (Integer x = width; x < 800 - width; x += width) {
sites.add(new Site(index, x, y, width, height, g2d));
index++;
}
}
Integer x = 20;
Integer y = 3;
sites.get(x + (y * 25)).Open();
sites.get(x + 1 + (y * 25)).Open();
sites.get(x).Open();
sites.get(4).Open();
sites.get(9).Open();
sites.get(13).Open();
sites.get(18).Open();
}
private void doDrawing(Graphics g) {
if (g2d == null) {
g2d = (Graphics2D) g;
}
if (sites.size() == 0) {
initSites();
}
for (Site site : sites) {
site.Draw();
}
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
doDrawing(g);
}
}
public class Squares extends JFrame {
public Squares() {
initUI();
}
private void initUI() {
add(new Surface());
setTitle("Squares demo");
setSize(800, 800);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public static void main(String[] args) {
Squares ex = new Squares();
ex.setVisible(true);
}
}
答案 0 :(得分：5)
您正在使用Graphics2D作为一个字段，假设一个图形对象与下一个图形对象一样好，而不是您如何进行Swing绘图。赋给paintComponent方法的Graphics对象不是长寿命或稳定的，必须使用它并且不能存储到字段中供以后使用。而是仅使用通过paintComponent参数从JVM动态传递到程序中的Graphics对象。例如，如果你给Draw（重命名它绘制）一个Graphics或Graphics2D参数，然后从paintComponent方法传入它：
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
class Site {
private Integer x;
private Integer y;
private Integer width;
private Integer height;
// private Graphics2D g2d;
private boolean isOpen = false;
private Integer id = null;
private Integer root = null;
// !! public Site(Integer id, Integer x, Integer y, Integer width, Integer
// height, Graphics2D g2d) {
public Site(Integer id, Integer x, Integer y, Integer width, Integer height) {
this.id = id;
this.root = id;
this.x = x;
this.y = y;
this.width = width;
this.height = height;
// this.g2d = g2d;
}
public void draw(Graphics2D g2d) {
g2d.setPaint(new Color(0, 0, 0));
g2d.setStroke(new BasicStroke(2));
Integer x_top_corner = x - (width / 2);
Integer y_top_corner = y - (height / 2);
g2d.drawRect(x_top_corner, y_top_corner, width, height);
System.out.println(x_top_corner);
if (isOpen) {
g2d.setPaint(new Color(150, 150, 200));
} else {
g2d.setPaint(new Color(200, 200, 200));
}
g2d.fillRect(x_top_corner + 1, y_top_corner + 1, width - 2, height - 2);
}
public void Open() {
this.isOpen = true;
}
public void Close() {
this.isOpen = false;
}
}
class Surface extends JPanel {
private ArrayList<Site> sites = new ArrayList<Site>();
private Graphics2D g2d = null;
private int width;
private int height;
public Surface(int width, int height) {
this.width = width;
this.height = height;
}
@Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(width, height);
}
private void initSites() {
Integer width = 30;
Integer height = 30;
Integer index = 0;
for (Integer y = height; y < 800 - height - 30; y += height) {
for (Integer x = width; x < 800 - width; x += width) {
// sites.add(new Site(index, x, y, width, height, g2d));
sites.add(new Site(index, x, y, width, height)); // !!
index++;
}
}
Integer x = 20;
Integer y = 3;
sites.get(x + (y * 25)).Open();
sites.get(x + 1 + (y * 25)).Open();
sites.get(x).Open();
sites.get(4).Open();
sites.get(9).Open();
sites.get(13).Open();
sites.get(18).Open();
}
private void doDrawing(Graphics g) {
if (sites.size() == 0) {
initSites();
}
for (Site site : sites) {
site.draw((Graphics2D) g);
}
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
doDrawing(g);
}
}
public class Squares extends JFrame {
private static final int SIDE_LENGTH = 800;
public Squares() {
initUI();
}
private void initUI() {
add(new Surface(SIDE_LENGTH, SIDE_LENGTH));
setTitle("Squares demo");
// setSize(800, 800);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setLocationRelativeTo(null);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
Squares ex = new Squares();
ex.setVisible(true);
});
}
}
另外，