此帖子继续this post.我的软件基本上基于CardLayout
小组。现在我想从cardLayout
之外更改面板。在提供的链接中,我得到了帮助,并且它有效。现在我在我的软件中添加了一个控制器,它位于内部面板(CardLayout
)和外部面板之间。在外部面板(leftBar
)中,我有一个按钮,如果其actionListener
位于该类内部,则它可以正常工作并打开所选择的CardLayout
内部面板。但是,如果我将ActionListener
带入控制器,它就不起作用了。没有错误出现。
这是我的示例代码: BASE:
public class Base {
JFrame frame = new JFrame("Panel");
BorderLayout bl = new BorderLayout();
public Base(){
MainPanel mainPanel = new MainPanel();
LeftBar leftBar = new LeftBar(mainPanel);
frame.setLayout(bl);
frame.setSize(800, 600);
frame.add(leftBar, BorderLayout.WEST);
frame.add(mainPanel, BorderLayout.CENTER);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
public static void main(String[] args) throws IOException {
new Base();
}
}
MainPanel(CardLAyout base)
public class MainPanel extends JPanel {
private CardLayout cl = new CardLayout();
private JPanel panelHolder = new JPanel(cl);
public MainPanel(){
FirstPage firstPage = new FirstPage(this);
SecondPage secondPage = new SecondPage(this);
LeftBar leftBar = new LeftBar(this);
Controller controller = new Controller(secondPage, leftBar, this);
setLayout(new GridLayout(0,1));
panelHolder.add(firstPage, "firstPage");
panelHolder.add(secondPage, "secondPage");
cl.show(panelHolder, "firstPage");
add(panelHolder);
}
public void showPanel(String panelIdentifier){
cl.show(panelHolder, panelIdentifier);
}
}
LeftBar
public class LeftBar extends JPanel{
private JButton button;
private MainPanel mainPanel;
public LeftBar(MainPanel mainPanel){
this.mainPanel = mainPanel;
setPreferredSize(new Dimension(200, 40));
setLayout(new BorderLayout());
setBackground(Color.black);
button = new JButton("Show Second Page");
add(button, BorderLayout.NORTH);
}
public void addPageListener(ActionListener listenForButton){
button.addActionListener(listenForButton);
}
}
第二页:
public class SecondPage extends JPanel{
MainPanel mainPanel;
JButton button;
public SecondPage(MainPanel mainPanel){
this.mainPanel = mainPanel;
setBackground(Color.white);
add(new JLabel("This is second page"));
}
}
第一页:
public class FirstPage extends JPanel {
MainPanel mainPanel;
JButton button;
public FirstPage(MainPanel mainPanel) {
this.mainPanel = mainPanel;
setBackground(Color.GRAY);
button = new JButton("Show page");
button.addActionListener(new ActionListener(){
@Override
public void actionPerformed(ActionEvent ae) {
mainPanel.showPanel("secondPage");
}
});
add(button);
}
}
和控制器:
public class Controller {
private SecondPage secondPage;
private LeftBar leftBar;
private MainPanel mainPanel;
public Controller(SecondPage secondPage, LeftBar leftBar, MainPanel mainPanel){
this.secondPage=secondPage;
this.leftBar=leftBar;
this.mainPanel=mainPanel;
this.leftBar.addPageListener(new ButtonListener());
}
class ButtonListener implements ActionListener{
@Override
public void actionPerformed(ActionEvent ae) {
System.out.println("Works");
mainPanel.showPanel("secondPage");
}
}
}
正如您在LeftBar
中看到的那样,我有一个按钮的方法,可用作actionListener
。我在控制器中调用该方法并给它一个类。但它不起作用。但是ACtionListener
如果位于LeftBar类(内联)中则有效。
知道怎么解决吗?
答案 0 :(得分:2)
您正在创建LeftBar
的两个实例,其中一个在Base
构造函数中,并添加到屏幕中...
public Base() {
MainPanel mainPanel = new MainPanel();
LeftBar leftBar = new LeftBar(mainPanel);
frame.setLayout(bl);
frame.setSize(800, 600);
frame.add(leftBar, BorderLayout.WEST);
frame.add(mainPanel, BorderLayout.CENTER);
MainPanel
构造函数中的一个传递给控制器......
public class MainPanel extends JPanel {
private CardLayout cl = new CardLayout();
private JPanel panelHolder = new JPanel(cl);
public MainPanel() {
FirstPage firstPage = new FirstPage(this);
SecondPage secondPage = new SecondPage(this);
LeftBar leftBar = new LeftBar(this);
这意味着控制器将ActionListener
附加到屏幕上永远不可见的按钮
我要做的第一件事就是开始解耦你的代码,而不是传递你的类的实例,你需要建立一系列控制器和视图可以同意的合同,例如你的MainPanel
应该提供一种切换视图的方法,LeftBar
应该在用户想要切换视图时提供通知
例如......
public interface Pageable {
public void showView(String name);
}
public interface Navigatable {
public void addActionListener(ActionListener listener);
}
然后您的主视图将实现Pageable
接口
public class MainPanel extends JPanel implements Pageable {
//...
@Override
public void showView(String name) {
cl.show(panelHolder, name);
}
您的LeftBar
将实施Navigatable
界面
public class LeftBar extends JPanel implements Navigatable {
//...
@Override
public void addActionListener(ActionListener listener) {
button.addActionListener(listener);
}
这只是定义了任何实现的契约能力,你的控制器不应该关心任何其他事情(也不应该允许它做它不是意味着的事情,比如从视图中删除所有组件,顽皮的控制器)
然后您的控制器负责管理接口之间的合同......
public class Controller {
private final Navigatable navigatable;
private final Pageable pageable;
public Controller(Navigatable navigatable, Pageable pageable) {
this.navigatable = navigatable;
this.pageable = pageable;
navigatable.addActionListener(new ButtonListener());
}
class ButtonListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent ae) {
pageable.showView("secondPage");
}
}
}
例如......
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class Base {
JFrame frame = new JFrame("Panel");
BorderLayout bl = new BorderLayout();
public Base() {
MainPanel mainPanel = new MainPanel();
LeftBar leftBar = new LeftBar(mainPanel);
frame.setLayout(bl);
frame.setSize(800, 600);
frame.add(leftBar, BorderLayout.WEST);
frame.add(mainPanel, BorderLayout.CENTER);
Controller controller = new Controller(leftBar, mainPanel);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
public static void main(String[] args) throws IOException {
new Base();
}
public interface Pageable {
public void showView(String name);
}
public interface Navigatable {
public void addActionListener(ActionListener listener);
}
public class MainPanel extends JPanel implements Pageable {
private CardLayout cl = new CardLayout();
private JPanel panelHolder = new JPanel(cl);
public MainPanel() {
FirstPage firstPage = new FirstPage(this);
SecondPage secondPage = new SecondPage(this);
setLayout(new GridLayout(0, 1));
panelHolder.add(firstPage, "firstPage");
panelHolder.add(secondPage, "secondPage");
cl.show(panelHolder, "firstPage");
add(panelHolder);
}
public void showPanel(String panelIdentifier) {
cl.show(panelHolder, panelIdentifier);
}
@Override
public void showView(String name) {
cl.show(panelHolder, name);
}
}
public class LeftBar extends JPanel implements Navigatable {
private JButton button;
private MainPanel mainPanel;
public LeftBar(MainPanel mainPanel) {
this.mainPanel = mainPanel;
setPreferredSize(new Dimension(200, 40));
setLayout(new BorderLayout());
setBackground(Color.black);
button = new JButton("Show Second Page");
add(button, BorderLayout.NORTH);
}
@Override
public void addActionListener(ActionListener listener) {
button.addActionListener(listener);
}
}
public class SecondPage extends JPanel {
MainPanel mainPanel;
JButton button;
public SecondPage(MainPanel mainPanel) {
this.mainPanel = mainPanel;
setBackground(Color.white);
add(new JLabel("This is second page"));
}
}
public class FirstPage extends JPanel {
MainPanel mainPanel;
JButton button;
public FirstPage(MainPanel mainPanel) {
this.mainPanel = mainPanel;
setBackground(Color.GRAY);
button = new JButton("Show page");
button.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent ae) {
mainPanel.showPanel("secondPage");
}
});
add(button);
}
}
public class Controller {
private final Navigatable navigatable;
private final Pageable pageable;
public Controller(Navigatable navigatable, Pageable pageable) {
this.navigatable = navigatable;
this.pageable = pageable;
navigatable.addActionListener(new ButtonListener());
}
class ButtonListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent ae) {
pageable.showView("secondPage");
}
}
}
}
就个人而言,这只是对你的代码的一些攻击,个人而言,我宁愿让一个控制器与一个视图/合同进行交互,这使得它变得更加简单......