通常需要根据另一个GUI对象的状态更改其他GUI对象的行为.例如.按下按钮时,标签应更改其名称.但是,当我使用像JButton这样的AbstractAction对象时myButton = new JButton(myButtonAction);我需要对继承自AbstractAction的对象中的GUI对象的引用.我应该只是在GUI中创建AbstractAction对象,然后将所有必要的GUI引用传递给AbstractAction对象,还是可以认为是坏样式？
为了使它更具体：
// AbstractAction
public class MyAction extends AbstractAction {
public MyAction(String name,String description,Integer mnemonic,JLabel) {
super(name);
putValue(SHORT_DESCRIPTION,description);
putValue(MNEMONIC_KEY,mnemonic);
}
public void actionPerformed(ActionEvent e) {
// do something
}
}
}
public class GUI{
public Action myAction = null;
public GUI(){
JLabel label = new JLabel("text");
//This is not a good idea:
myAction = new MyAction("some text",desc,new Integer(KeyEvent.VK_Q),label);
JButton myButton = new JButton(myAction);
}
}
解决方法
你想尽可能地松开耦合,而不是像你的问题所暗示的那样收紧耦合,为了做到这一点,我认为你应该进一步抽象,通过将部分进一步分离成一个成熟的MVC程序.然后,侦听器(Action)可以更改模型,作为GUI的视图可以监听模型的更改并进行相应的响应.
例如：
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.*;
import javax.swing.event.SwingPropertyChangeSupport;
public class MvcEg {
private static void createAndShowGui() {
View view = new MvcEgView();
Model model = new MvcEgModel();
new MvcEgControl(model,view);
JFrame frame = new JFrame("MvcEg");
frame.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(view.getMainPanel());
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
interface View {
void setMyButtonAction(Action action);
Component getMainPanel();
void setStatusLabelText(String text);
}
@SuppressWarnings("serial")
class MvcEgView implements View {
private static final int PREF_W = 500;
private static final int PREF_H = 400;
private static final String STATUS_TEXT = "Status: ";
private JPanel mainPanel = new JPanel() {
@Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W,PREF_H);
}
};
private JLabel statusLabel = new JLabel(STATUS_TEXT,SwingConstants.CENTER);
private JButton myButton = new JButton();
public MvcEgView() {
JPanel btnPanel = new JPanel(new GridBagLayout());
btnPanel.add(myButton);
mainPanel.setLayout(new BorderLayout());
mainPanel.add(btnPanel,BorderLayout.CENTER);
mainPanel.add(statusLabel,BorderLayout.SOUTH);
}
@Override
public void setMyButtonAction(Action action) {
myButton.setAction(action);
}
@Override
public void setStatusLabelText(String text) {
statusLabel.setText(STATUS_TEXT + text);
}
@Override
public Component getMainPanel() {
return mainPanel;
}
}
interface Model {
public static final String MOD_FIVE_STATUS = "mod five status";
void incrementStatus();
ModFiveStatus getModFiveStatus();
void removePropertyChangeListener(PropertyChangeListener listener);
void addPropertyChangeListener(PropertyChangeListener listener);
void setModFiveStatus(ModFiveStatus modFiveStatus);
}
class MvcEgModel implements Model {
private ModFiveStatus modFiveStatus = ModFiveStatus.ZERO;
private SwingPropertyChangeSupport pcSupport = new SwingPropertyChangeSupport(
this);
@Override
public void incrementStatus() {
int value = modFiveStatus.getValue();
value++;
value %= ModFiveStatus.values().length;
setModFiveStatus(ModFiveStatus.getValuesStatus(value));
}
@Override
public void setModFiveStatus(ModFiveStatus modFiveStatus) {
ModFiveStatus oldValue = this.modFiveStatus;
ModFiveStatus newValue = modFiveStatus;
this.modFiveStatus = modFiveStatus;
pcSupport.firePropertyChange(MOD_FIVE_STATUS,oldValue,newValue);
}
@Override
public ModFiveStatus getModFiveStatus() {
return modFiveStatus;
}
@Override
public void addPropertyChangeListener(PropertyChangeListener listener) {
pcSupport.addPropertyChangeListener(listener);
}
@Override
public void removePropertyChangeListener(PropertyChangeListener listener) {
pcSupport.removePropertyChangeListener(listener);
}
}
enum ModFiveStatus {
ZERO(0,"Zero"),ONE(1,"One"),TWO(2,"Two"),THREE(3,"Three"),FOUR(4,"Four");
private int value;
private String text;
private ModFiveStatus(int value,String text) {
this.value = value;
this.text = text;
}
public int getValue() {
return value;
}
public String getText() {
return text;
}
public static ModFiveStatus getValuesStatus(int value) {
if (value < 0 || value >= values().length) {
throw new ArrayIndexOutOfBoundsException(value);
}
for (ModFiveStatus modFiveStatus : ModFiveStatus.values()) {
if (modFiveStatus.getValue() == value) {
return modFiveStatus;
}
}
// default that should never happen
return null;
}
}
@SuppressWarnings("serial")
class MvcEgControl {
private Model model;
private View view;
public MvcEgControl(final Model model,final View view) {
this.model = model;
this.view = view;
view.setMyButtonAction(new MyButtonAction("My Button",KeyEvent.VK_B));
view.setStatusLabelText(model.getModFiveStatus().getText());
System.out.println("model's status: " + model.getModFiveStatus());
System.out.println("model's status text: " + model.getModFiveStatus().getText());
model.addPropertyChangeListener(new ModelListener());
}
private class MyButtonAction extends AbstractAction {
public MyButtonAction(String text,int mnemonic) {
super(text);
putValue(MNEMONIC_KEY,mnemonic);
}
@Override
public void actionPerformed(ActionEvent e) {
model.incrementStatus();
System.out.println("button pressed");
}
}
private class ModelListener implements PropertyChangeListener {
@Override
public void propertyChange(PropertyChangeEvent evt) {
if (evt.getPropertyName().equals(Model.MOD_FIVE_STATUS)) {
String status = model.getModFiveStatus().getText();
view.setStatusLabelText(status);
System.out.println("status is: " + status);
}
}
}
}
在我看来,关键是模型对视图一无所知,并且视图对模型知之甚少(这里没有).
