JavaFX学习：Observable Collections（观察集合）

JavaFX中的观察集合（Observable Collections）继承自Java的集合（Collections）。Java集合提供了List、Map、Set三种集合接口。JavaFX在Java集合基础上派生出可以监听集合内容变化的三种集合接口。接口如下：

ObservableList
ObservableSet
ObservableMap

Java的集合接口不仅继承Java的List、Map、Set接口，同时还继承JavaFX中的Observable接口。继承关系如下图所示：

相较于Java中的集合，JavaFX中继承Observable接口的集合有以下新功能：

支持监听失效事件。
支持监听改变事件。可以给继承Observable接口的类注册改变监听器，当集合内容发生变化是进行通知。

ObservableList接口的继承关系如下：

ObservableList接口的addListener()、removeListener()方法注册/注销ListChangeListener事件（ListChangeListener实例），当ObservableList发生改变事件时触发ListChangedListener事件。

void addListener(ListChangeListener<? super E> listener);
void removeListener(ListChangeListener<? super E> listener);

注意，ObservableList接口重写了（Override）Observable接口中的addListener()、removeListener()方法，在Observable接口中，addListener()、removeListener()方法注册/注销InvalidationListener接口。

void addListener(InvalidationListener listener);
void removeListener(InvalidationListener listener);

测试ObservableList注册InvalidationListener接口：

package learnjavafx8.ch03;

import javafx.beans.Observable;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;

/**
 * @copyright 2023-2022
 * @package   learnjavafx8.ch03
 * @file      ListInvalidationTest.java
 * @date      2023-06-16 23:13
 * @author    qiao wei
 * @version   1.0
 * @brief     Test invalidation event. Invalidation event includes add, remove, replace and sort.
 * @history
 */
public class ListInvalidationTest {

    public static void main(String[] args) {
        String one = "one";
        
        // Create a list with some elements without changelistener
        ObservableList<String> list = FXCollections.observableArrayList(one, "two");
        System.out.println(list);
        
        // ObservableList implements Observable interface, Register an InvalidationListener to 
        // the list
        list.addListener(ListInvalidationTest::invalidated);

        System.out.println("Before adding element three.------------------------------------");        
        // Add element to list, list fire invalidation event
        list.add("three");
//        System.out.println(list);
        System.out.println("After adding element three------------------------------------\n");
        
        System.out.println("Before adding elements four and five.---------------------------");
        list.addAll("four", "five");
//        System.out.println(list);
        System.out.println("Before adding elements four and five.-------------------------\n");
        
        
        // Replace the element in 0 index
        System.out.println("Before replacing one in index 0.--------------------------------");
        list.set(3, one);
//        System.out.println(list);
        System.out.println("After replacing one in index 0.-------------------------------\n");
    }
    
    /**
     * @class   ListInvalidationTest
     * @date    2023-06-16 23:14
     * @author  qiao wei
     * @version 1.0
     * @brief   Invalidate event. This method is called if an Observable becomes invalid.
     * @param   list The Observable that became invalid.
     * @return  
     * @throws
     */
    public static void invalidated(Observable list) {
        System.out.println("++++++Invalidation event is fired+++++++.");
        System.out.println(list);
    }
}

运行结果：

[one, two]
Before adding element three.------------------------------------
++++++Invalidation event is fired+++++++.
[one, two, three]
After adding element three------------------------------------

Before adding elements four and five.---------------------------
++++++Invalidation event is fired+++++++.
[one, two, three, four, five]
Before adding elements four and five.-------------------------

Before replacing one in index 0.--------------------------------
++++++Invalidation event is fired+++++++.
[one, two, three, one, five]
After replacing one in index 0.-------------------------------


Process finished with exit code 0

测试ObservableList接口注册InvalidationListener接口和ListChangeListener接口。

package learnjavafx8.ch03;

import javafx.beans.Observable;
import javafx.beans.property.IntegerProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.collections.ListChangeListener;
import javafx.collections.ObservableList;

/**
 * @copyright 2023-2022
 * @package   learnjavafx8.ch03
 * @file      ListInvalidationTest01.java
 * @date      2023-06-12 16:42
 * @author    qiao wei
 * @version   1.0
 * @brief     ObservableList实例对invalidated和onChanged事件的处理。注意区别ObservableList中保存的属性的
 *             invalidated和changed事件处理，ObservableList增删Property触发ObservableList的invalidated
 *             事件和changed事件，Property改变自己的值触发Property的invalidated事件和changed事件。
 * @history
 */
public class ListInvalidationTest01 {

    public static void main(String[] args) {
        ObservableList<IntegerProperty> properties = FXCollections.observableArrayList();
        
        // ObservableList添加invalidated事件和changed事件监听器
        properties.addListener(ListInvalidationTest01::onChanged);
        properties.addListener(ListInvalidationTest01::invalidated);
        
        IntegerProperty property01 = new SimpleIntegerProperty(22);        
//        IntegerProperty property02 = new SimpleIntegerProperty(301);
        
        // Property添加invalidated事件监听器，当Property“失效”时触发
        property01.addListener(ListInvalidationTest01::invalidatedForProperty);
//        property02.addListener(ListInvalidationTest01::invalidatedForProperty);
        
        // Property添加changed事件监听器，当属性“改变”时触发
        property01.addListener(ListInvalidationTest01::changedForProperty);
//        property02.addListener(ListInvalidationTest01::changedForProperty);

        // ObservableList添加元素。触发ObservableList的invalidated事件和changed事件。没有失效或改变
        // property01和property02，不会触发Property的invalidated和changed事件
        properties.add(property01);
//        properties.add(property02);
        
        // 修改Property数值，触发invalidated事件和changed事件。不会触发Property所在的ObservableList的
        // invalidated事件和changed事件
        System.out.println("----------------Property test------------------------");
        properties.get(0).set(10);
        System.out.println("----------------Property test------------------------\n");

        // 删除ObservableList中元素，触发ObservableList的invali事件（如果注册changed事件，同时也会触发）
        System.out.println("============ObservableList test======================");
        properties.remove(0);
        System.out.println("============ObservableList test==================\n");
    }
    
    /**
     * @class   ListInvalidationTest01
     * @date    2023-06-12 19:00
     * @author  qiao wei
     * @version 1.0
     * @brief   Property invalidated event.
     * @param   
     * @return  
     * @throws
     */
    public static void invalidatedForProperty(Observable observable) {
        System.out.println("Property invalidated event   &&&&&&&&&&&&&&&&&&&&&&");
        System.out.println(observable.toString());
        System.out.println("Property invalidated event   &&&&&&&&&&&&&&&&&&&&&&\n");
    }
    
    /**********************************************************************************************
     * @class   ListInvalidationTest01
     * @date    2023-02-01 14:49
     * @author  qiao wei
     * @version 1.0
     * @brief   Property changed event
     * @param   
     * @return  
     * @throws
     *********************************************************************************************/
    public static void changedForProperty(ObservableValue<? extends Number> observable,
                                          Number oldValue,
                                          Number newValue) {
        System.out.println("&&&&&&&&&&&&&&&&&&&&&&   Property changed event");
        // Observable instance's value is the new value
        System.out.println("Property's value : " + observable.getValue().intValue());
        System.out.println("Number changed : ");
        System.out.println("Old = " + oldValue.toString() + ", New = " + newValue.toString());
        System.out.println("&&&&&&&&&&&&&&&&&&&&&&   Property changed event\n");
    }
    
    /**********************************************************************************************
     * @class   ListInvalidationTest01
     * @date    2023-01-31 18:11
     * @author  qiao wei
     * @version 1.0
     * @brief   ObservableList invalidated event
     * @param   
     * @return  
     * @throws
     *********************************************************************************************/
    public static void invalidated(Observable observable) {
        System.out.println("ObservableList invalidated event ----------------------------");
        System.out.println(observable.toString());
        System.out.println("ObservableList invalidated event ----------------------------\n");
    }
    
    /**********************************************************************************************
     * @class   ListInvalidationTest01
     * @date    2023-01-31 18:11
     * @author  qiao wei
     * @version 1.0
     * @brief   ObservableList onChanged event
     * @param   
     * @return  
     * @throws
     *********************************************************************************************/
    public static void onChanged(ListChangeListener.Change<? extends IntegerProperty> change) {
        System.out.println("-------------------------------ObservableList onChanged event");
        if (change.next()) {
            System.out.println("&&&" + change.toString());
        }
        System.out.println("-------------------------------ObservableList onChanged event\n");
    }
}

运行结果：

ObservableList invalidated event ----------------------------
[IntegerProperty [value: 22]]
ObservableList invalidated event ----------------------------

-------------------------------ObservableList onChanged event
&&&{ [IntegerProperty [value: 22]] added at 0 }
-------------------------------ObservableList onChanged event

----------------Property test------------------------
Property invalidated event   &&&&&&&&&&&&&&&&&&&&&&
IntegerProperty [value: 10]
Property invalidated event   &&&&&&&&&&&&&&&&&&&&&&

&&&&&&&&&&&&&&&&&&&&&&   Property changed event
Property's value : 10
Number changed : 
Old = 22, New = 10
&&&&&&&&&&&&&&&&&&&&&&   Property changed event

----------------Property test------------------------

============ObservableList test======================
ObservableList invalidated event ----------------------------
[]
ObservableList invalidated event ----------------------------

-------------------------------ObservableList onChanged event
&&&{ [IntegerProperty [value: 10]] removed at 0 }
-------------------------------ObservableList onChanged event

============ObservableList test==================


Process finished with exit code 0