一個(gè)樹分為：根節(jié)點(diǎn)，樹枝，樹葉，點(diǎn)擊根節(jié)點(diǎn)觸發(fā)一個(gè)事件：展開所有樹枝；點(diǎn)擊樹枝觸發(fā)一個(gè)事件：展開所有樹葉；點(diǎn)擊樹葉觸發(fā)一個(gè)事件：屏幕右方顯示詳細(xì)信息。那么即可說明：樹是一個(gè)組件即被觀察者，事件對(duì)象即觀察者，只要事件源即用戶點(diǎn)擊操作發(fā)生，就通知事件對(duì)象觀察者做出相應(yīng)的動(dòng)作，首先組裝出樹結(jié)構(gòu)，采用安全的合成模式，類示意圖如下：
如果對(duì)樹組件增加監(jiān)聽事件，即增加觀察者ActionListener，那么綜合觀察者模式，增加鼠標(biāo)和鍵盤監(jiān)聽，第二版類圖如下：
先給出代碼:
package observer;
import java.util.ArrayDeque;
import java.util.Collection;
import java.util.Iterator;
public abstract class Component
{
// 監(jiān)聽隊(duì)列
private static ArrayDeque<ActionListener> deque = new ArrayDeque<ActionListener>();
private String componentName;
public Component(String componentName)
{
this.componentName = componentName;
}
public String getComponentName()
{
return componentName;
}
public void setComponentName(String componentName)
{
this.componentName = componentName;
}
protected abstract Component getComponent();
protected void addActionListener(ActionListener actionListener) throws NullPointerException
{
if (actionListener == null)
throw new NullPointerException("the ActionListener is null");
deque.offerLast(actionListener);
}
protected void removeActionListener(ActionListener actionLister)
{
deque.remove(actionLister);
}
protected Collection<ActionListener> getActionListeners()
{
return deque;
}
/**
* 點(diǎn)擊組件事件
*/
protected void clickOperation()
{
for (Iterator<ActionListener> it = deque.iterator(); it.hasNext();)
{
ActionListener listener = it.next();
if (listener instanceof MouseActionListener)
{
((MouseActionListener) listener).clickEvent(this);
}
if (listener instanceof KeyBoardActionListener)
{
((KeyBoardActionListener) listener).keyPressEvent(this);
}
}
}
/**
* 雙擊組件事件
*/
protected void doubleClickOperation()
{
for (Iterator<ActionListener> it = deque.iterator(); it.hasNext();)
{
ActionListener listener = it.next();
if (listener instanceof MouseActionListener)
{
((MouseActionListener) listener).doubleClickEvent(this);
}
if (listener instanceof KeyBoardActionListener)
{
((KeyBoardActionListener) listener).keyPressEvent(this);
}
}
}
/**
* 拖拽組件事件
*/
protected void dragOperation()
{
for (Iterator<ActionListener> it = deque.iterator(); it.hasNext();)
{
ActionListener listener = it.next();
if (listener instanceof MouseActionListener)
{
((MouseActionListener) listener).dragEvent(this);
}
if (listener instanceof KeyBoardActionListener)
{
((KeyBoardActionListener) listener).keyReleaseEvent(this);
}
}
}
/**
* 組合模式葉子和樹枝通用方法，遍歷時(shí)候，可使葉子和樹枝相同對(duì)待
*/
protected abstract void operation();
}
package observer;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
public class Branch extends Component
{
public Branch(String branchName)
{
super(branchName);
}
private ArrayList<Component> components = new ArrayList<Component>();
public void addComponent(Component component)
{
this.components.add(component);
}
public void removeComponent(Component component)
{
this.components.remove(component);
}
public Collection<Component> getComponents()
{
return components;
}
@Override
protected Component getComponent()
{
return this;
}
public void spreadLeaf()
{
System.out.println("樹枝：" + getComponentName() + "展開節(jié)點(diǎn)");
}
@Override
protected void operation()
{
for (Iterator<Component> it = getComponents().iterator(); it.hasNext();)
{
Component component = it.next();
System.out.println("當(dāng)前節(jié)點(diǎn)："+component.getComponentName());
component.operation();
}
}
}
package observer;
public class Leaf extends Component
{
public Leaf(String leafName)
{
super(leafName);
}
@Override
protected Component getComponent()
{
return this;
}
public void clickLeaf()
{
System.out.println("點(diǎn)擊了" + getComponentName() );
}
@Override
protected void operation()
{
System.out.println("leafName:" + getComponentName() + " 節(jié)點(diǎn)");
}
}
package observer;
public interface ActionListener
{
void actionPerformer(Component component);
}
package observer;
public interface MouseActionListener extends ActionListener
{
void clickEvent(Component component);
void doubleClickEvent(Component component);
void dragEvent(Component component);
}
package observer;
public class MouseActionListenerAdapter implements MouseActionListener
{
@Override
public void actionPerformer(Component component)
{
// TODO Auto-generated method stub
}
/** 增加一個(gè)默認(rèn)單擊事件實(shí)現(xiàn) */
@Override
public void clickEvent(Component component)
{
if (component instanceof Branch)
{
((Branch) component).spreadLeaf();
}
if (component instanceof Leaf)
{
((Leaf) component).clickLeaf();
}
}
@Override
public void doubleClickEvent(Component component)
{
// TODO Auto-generated method stub
}
@Override
public void dragEvent(Component component)
{
// TODO Auto-generated method stub
}
}
package observer;
public interface KeyBoardActionListener extends ActionListener
{
void keyPressEvent(Component component);
void keyReleaseEvent(Component component);
}
package observer;
public class KeyBoardActionListenerAdapter implements KeyBoardActionListener
{
@Override
public void actionPerformer(Component component)
{
// TODO Auto-generated method stub
}
@Override
public void keyPressEvent(Component component)
{
// TODO Auto-generated method stub
}
@Override
public void keyReleaseEvent(Component component)
{
// TODO Auto-generated method stub
}
}
package observer;
public class Client
{
public static void main(String[] args)
{
//根節(jié)點(diǎn)
Branch root = new Branch("根節(jié)點(diǎn)");
//葉子節(jié)點(diǎn)
Leaf leaf1 = new Leaf("葉子1");
//增加葉子1監(jiān)聽事件
leaf1.addActionListener(new MouseActionListenerAdapter());
//樹枝節(jié)點(diǎn)
Branch branch1 = new Branch("樹枝1");
//增加樹枝1監(jiān)聽事件
branch1.addActionListener(new MouseActionListenerAdapter());
//給樹枝1再增加一個(gè)葉子和一個(gè)樹枝
Leaf leaf2 = new Leaf("葉子2");
//leaf2增加監(jiān)聽事件
leaf2.addActionListener(new MouseActionListenerAdapter());
Branch branch2 = new Branch("樹枝1-1");
Leaf leaf3 = new Leaf("葉子3");
//增加監(jiān)聽事件
leaf3.addActionListener(new MouseActionListenerAdapter());
branch2.addComponent(leaf3);
//添加到樹枝1 下面
branch1.addComponent(leaf2);
branch1.addComponent(branch2);
//添加到根節(jié)點(diǎn)下面
root.addComponent(leaf1);
root.addComponent(branch1);
//先調(diào)用一次遍歷
root.operation();
//然后 觸發(fā)點(diǎn)擊葉子3事件
System.out.println("
開始觸發(fā)點(diǎn)擊事件");
//葉子3事件連續(xù)觸發(fā)了4次，這就是事件冒泡原理，因?yàn)樯厦鎸?duì)Component組件加了4個(gè)不同監(jiān)聽
//其他組件也捕獲了這次事件，如果阻止冒泡，那么獲取該事件，做一次判斷即可
leaf3.clickOperation();
}
}
輸出結(jié)果：
當(dāng)前節(jié)點(diǎn)：葉子1
leafName:葉子1 節(jié)點(diǎn)
當(dāng)前節(jié)點(diǎn)：樹枝1
當(dāng)前節(jié)點(diǎn)：葉子2
leafName:葉子2 節(jié)點(diǎn)
當(dāng)前節(jié)點(diǎn)：樹枝1-1
當(dāng)前節(jié)點(diǎn)：葉子3
leafName:葉子3 節(jié)點(diǎn)
......開始觸發(fā)點(diǎn)擊事件......
點(diǎn)擊了葉子3
點(diǎn)擊了葉子3
點(diǎn)擊了葉子3
點(diǎn)擊了葉子3