[英]Why doesn't ActionListener work in the controller?
這篇文章是這篇文章的繼續。 我的軟件基本上是基於CardLayout
面板的。 現在,我想從cardLayout
外部更改面板。 在提供的鏈接中,我得到了幫助,並且可以正常工作。 現在,我在軟件中添加了一個控制器,該控制器位於內部面板( CardLayout
)和外部面板之間。 在外部面板( leftBar
)中,有一個按鈕,如果它的actionListener
位於該類的內部,則它可以正常工作,並打開CardLayout
的選定內部面板。 但是,如果我將ActionListener
放入控制器,它將無法正常工作。 沒有錯誤出現。
這是我的示例代碼: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基座)
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);
}
}
左欄
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);
}
}
第二頁:
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"));
}
}
第一頁:
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");
}
}
}
如您在LeftBar
中看到的,我有一個用作actionListener
的按鈕方法。 然后在控制器中調用該方法並為其提供一個類。 但它不起作用。 但是,如果ACtionListener
位於LeftBar類(內聯)中,則它可以工作。
知道如何解決嗎?
您將在Base
構造函數中創建兩個LeftBar
實例,將其添加到屏幕中。
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);
還有MainPanel
構造函數中的一個傳遞給控制器...
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);
這意味着控制器將ActionListener
附加到在屏幕上永遠不可見的按鈕
我要做的第一件事是開始分離代碼,而不是傳遞類的實例,您需要建立一系列控制器和視圖可以同意的MainPanel
,例如, MainPanel
應該提供一種切換視圖的方法,您的LeftBar
應該在用戶想要切換視圖時提供通知
例如...
public interface Pageable {
public void showView(String name);
}
public interface Navigatable {
public void addActionListener(ActionListener listener);
}
然后您的主視圖將實現Pageable
接口
public class MainPanel extends JPanel implements Pageable {
//...
@Override
public void showView(String name) {
cl.show(panelHolder, name);
}
您的LeftBar
將實現Navigatable
接口
public class LeftBar extends JPanel implements Navigatable {
//...
@Override
public void addActionListener(ActionListener listener) {
button.addActionListener(listener);
}
這只是定義了任何實現的合同功能,您的控制器不應該關心其他任何事情(也不應該允許它執行原本不希望做的事情,例如從您的視圖中刪除頑皮的控制器中的所有組件)
然后,您的控制器僅負責管理接口之間的合同...
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");
}
}
}
}
現在,就個人而言,這只是圍繞您的代碼的一些小技巧,就個人而言,我更希望有一個與單個視圖/合同進行交互的控制器,這使它非常簡單...
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