我在编码时遇到问题,当我在任何地方调用重绘时,它不会更新图像但程序仍然在运行:
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.ImageObserver;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class mainMenu extends JPanel implements MouseListener{
Graphics g;
Image playButton = Toolkit.getDefaultToolkit().getImage("game sprites/play_button.png");
private int part = 0;
public static void main(String[] a) {
mainMenu mm = new mainMenu();
mm.makeJFrame();
}
public void makeJFrame(){
JFrame f = new JFrame();
f.setSize(1000, 600);
f.add(new mainMenu());
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
f.addMouseListener(this);
f.setTitle("MAIN MENU");
}
public void paintComponent(Graphics g) {
if(part == 0)
System.out.println("0");
g.drawImage( playButton, 330, 200, 294, 102, this);
if(part == 1)
{
System.out.println("1");
g.setColor(Color.RED);
g.fillRect(0, 0, 40, 40);
}
}
public void mouseClicked(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
public void mousePressed(MouseEvent e) {
int x = e.getX();
int y = e.getY();
if(part == 0)
{
if(x > 330 && x < 624 && y > 232 && y < 334)
{
System.out.println("a");
part = 1;
repaint();
}
}
}
public void mouseReleased(MouseEvent e) {}
}
我测试了很多次,问题在于重绘,程序是否有效,但是图像保持不变。打印出来: 0 0 0 a(当我点击按钮时) 即使单击按钮也不会再打印出“a”,因为部分设置为1,所以不应该打印出来。
答案 0 :(得分:2)
图像是否加载?这看起来很可疑:Image playButton = Toolkit.getDefaultToolkit().getImage("game sprites/play_button.png");
。图像存储在哪里?
这看起来很可疑......
if (part == 0)
System.out.println("0");
g.drawImage(playButton, 330, 200, 294, 102, this);
可能意味着......
if (part == 0) {
System.out.println("0");
g.drawImage(playButton, 330, 200, 294, 102, this);
}
您已经打破了油漆链,在进行任何自定义绘画之前,您必须致电super.paintComponent
...
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
最后,您有两个mainMenu
...
第一个是屏幕上的那个......
f.add(new MainMenu());
第二个是响应鼠标事件并更新part
f.addMouseListener(this);
与第一个无关。
您应该避免在组件中创建窗口(例如JPanel
),而是创建MainMenu
的实例并将其添加到JFrame
的实例中,例如...
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class MainMenu extends JPanel implements MouseListener {
Image playButton = Toolkit.getDefaultToolkit().getImage("...");
private int part = 0;
public static void main(String[] a) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new MainMenu());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public MainMenu() {
addMouseListener(this);
}
@Override
public Dimension getPreferredSize() {
return new Dimension(800, 600);
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
System.out.println(part);
if (part == 0) {
System.out.println("0");
g.drawImage(playButton, 0, 0, this);
} else if (part == 1) {
System.out.println("1");
g.setColor(Color.RED);
g.fillRect(0, 0, 40, 40);
}
}
public void mouseClicked(MouseEvent e) {
}
public void mouseEntered(MouseEvent e) {
}
public void mouseExited(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
int x = e.getX();
int y = e.getY();
if (part == 0) {
System.out.println("a");
part = 1;
repaint();
}
}
public void mouseReleased(MouseEvent e) {
}
}
答案 1 :(得分:0)
在Java中,if语句只影响语句头部之后的一个语句。所以你需要将整个身体放在{}。
if(part == 0){
System.out.println("0");
g.drawImage( playButton, 330, 200, 294, 102, this);
}