更改其他类中变量的侦听器 [英] change listener for variable in other class
问题描述
已下面是我在此示例中对 SSCCE 的尝试,让您有机会自行编译.我需要:通知 PanelNumber2
类,PanelNumber1
类中的对象 Generator g
已更改.
EDITED: below is my try of SSCCE for this example to give u an opportunity to compile this on your own. I need to: inform class PanelNumber2
that object Generator g
in class PanelNumber1
have been changed.
我尝试使用 ChangeListner
和 ActionPerformed
但是在命令上:
I tried with ChangeListner
and ActionPerformed
however on command:
listener.stateChanged(new ChangeEvent(this));
我有空指针异常.如果你有这个问题的任何解决方案,请纠正我.或任何更好的方法来做到这一点
i have got nullpointer exception. correct me if u have got any solution of this problem. or any better way to do this
import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class MainFrame extends JFrame{
private PanelNumber1 p1;
private PanelNumber2 p2;
public MainFrame(){
super("Frame");
JPanel panel = new JPanel(new BorderLayout());
this.getContentPane().add(panel);
p1 = new PanelNumber1();
Generator g = p1.getGenerator();
p2 = new PanelNumber2(g);
panel.add(p1,BorderLayout.CENTER);
panel.add(p2,BorderLayout.EAST);
this.setExtendedState(JFrame.MAXIMIZED_BOTH);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
this.setResizable(true);
}
public static void main(String[] args) {
// TODO Auto-generated method stub
new MainFrame();
}
}
class PanelNumber2 extends JPanel implements ChangeListener{
public PanelNumber2(Generator g){
super();
setLayout(new GridLayout(7,1));
g.addListener(this);
}
@Override
public void stateChanged(ChangeEvent e) {
// TODO Auto-generated method stub
this.repaint();
}
}
class PanelNumber1 extends JPanel{
Generator g;
BufferedImage mapa;
File imageFile;
public PanelNumber1(){
super();
g = new Generator();
g.setPanel(this);
imageFile = new File("C:\\Users\\Katie\\Documents\\Eclipse\\Samolot\\src\\Pics\\img_ww1.png");
try {
mapa = ImageIO.read(imageFile);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.drawImage(mapa, 0, 0, getWidth(), getHeight(), null);
}
public Generator getGenerator(){
return g;
}
}
class Generator{
ChangeListener listener;
ArrayList<String> s;
JPanel p;
Timer generatorTimer;
public Generator(){
this.s = new ArrayList<String>();
generatorTimer = new Timer(40, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
addItem();
p.repaint();
}
});
generatorTimer.start();
}
private void addItem(){
s.add(new String("string"));
listener.stateChanged(new ChangeEvent(this));
}
public void setPanel(JPanel p){
this.p = p;
}
public ArrayList<String> getArray(){
return s;
}
public void addListener(ChangeListener list){
this.listener = list;
}
}
需要帮助的人:(
推荐答案
解决方案!
我的天啊,几个小时后弄清楚出了什么问题,我明白了!:P
Oh my God, after few hours figuiring out whats wrong i got it! :P
我需要做的只是在 timer
public void actionPerformed(ActionEvent e) {
if(p != null){ //becouse after creating Generator object im doing setPanel(this) a short while after :)
addItem();
p.repaint();
}
}
现在完美运行.感谢 MadProgrammer 试图帮助我和 YMY - 他发现了那个错误.话题可以关闭
now it works perfectly. Thanks going for MadProgrammer for trying to help me and for YMY - he find that mistake. topic can be closed
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