Java Java.util.Observable.deleteObserver()用法及代碼示例

描述

這個java.util.Observable.deleteObserver(Observer o)方法刪除指定的觀察者o來自該對象的觀察者集合。

聲明

以下是聲明java.util.Observable.deleteObserver()方法

public void deleteObserver(Observer o)

參數

o─ 要從觀察者集合中刪除的觀察者。

返回值

NA

異常

NA

示例

下麵的例子展示了 java.util.Observable.deleteObserver(Observer) 方法的用法。

package com.tutorialspoint;

import java.util.Observable;
import java.util.Observer;

class ObservedObject extends Observable {
   private String watchedValue;
   
   public ObservedObject(String value) {
      watchedValue = value;
   }
   
   public void setValue(String value) {
      
      // if value has changed notify observers
      if(!watchedValue.equals(value)) {
         System.out.println("Value changed to new value:"+value);
         watchedValue = value;

         // mark as value changed
         setChanged();

         // trigger notification
         notifyObservers(value);
      }
   }
}
public class ObservableDemo implements Observer {
   public static void main(String[] args) {
      
      // create watched and watcher objects
      ObservedObject watched = new ObservedObject("Original Value");
      
      // watcher object listens to object change
      ObservableDemo watcher = new ObservableDemo();

      // trigger value change
      watched.setValue("Value before addObserver");
      
      // add observer to the watched object
      watched.addObserver(watcher);
      
      // trigger value change
      watched.setValue("Value after addObserver");
      
      // delete observer
      watched.deleteObserver(watcher);
      
      // trigger value change
      watched.setValue("Value after deleteObserver");
   }
   
   public void update(Observable obj, Object arg) {
      System.out.println("Update called with Arguments:"+arg);
   }
}

讓我們編譯並運行上麵的程序，這將產生以下結果——

Value changed to new value:Value before addObserver
Value changed to new value:Value after addObserver
Update called with Arguments:Value after addObserver
Value changed to new value:Value after deleteObserver