Question

如果这是一个错误，或者我在JavaFX MapProperty绑定中遗漏了什么，有人可以解释一下吗？

方案：两个MapProperty实例 - 主和子。

首先我们将孩子绑定到主人
然后我们在master
解除主人的束缚
清除孩子
两个实例都是空的 - 为什么？
在儿童中存储一些值
两个实例都包含相同的值 - 为什么？

代码：

public static void main(String[] args) {

    MapProperty<String, Object> master = new SimpleMapProperty<String, Object>(
            FXCollections.observableMap(new HashMap<String, Object>()));
    MapProperty<String, Object> child = new SimpleMapProperty<String, Object>(
            FXCollections.observableMap(new HashMap<String, Object>()));

    child.bind(master);

    master.put("k1", "v1");

    System.out.println("Java version: " + System.getProperty("java.version"));
    System.out.println("OS version  : " + System.getProperty("os.name") + " - " + System.getProperty("os.arch"));
    System.out.println("------------");
    System.out.println("master: " + master);
    System.out.println("child : " + child);

    // Isn't this supposed to stop change listener ?????
    child.unbind();
    child.clear();

    System.out.println("------------");
    System.out.println("master: " + master);
    System.out.println("child : " + child);

    child.put("k2", "v2");

    System.out.println("------------");
    System.out.println("master: " + master);
    System.out.println("child : " + child);

}

输出：

run:
Java version: 1.8.0_45
OS version  : Windows 7 - amd64
------------
master: MapProperty [value: {k1=v1}]
child : MapProperty [bound, invalid]
------------
master: MapProperty [value: {}]
child : MapProperty [value: {}]
------------
master: MapProperty [value: {k2=v2}]
child : MapProperty [value: {k2=v2}]
BUILD SUCCESSFUL (total time: 0 seconds)

Answer 1

MapProperty的值是ObservableMap，而不是ObservableMap的内容。

执行此代码

MapProperty<String, Object> master = new SimpleMapProperty<String, Object>(
        FXCollections.observableMap(new HashMap<String, Object>()));
MapProperty<String, Object> child = new SimpleMapProperty<String, Object>(
        FXCollections.observableMap(new HashMap<String, Object>()));

ObservableMap<String, Object> childMap = child.get();
ObservableMap<String, Object> masterMap = master.get();

System.out.println("before binding: " + ((childMap == masterMap) ? "childMap == masterMap" : "childMap != masterMap"));

child.bind(master);

childMap = child.get();
masterMap = master.get();

System.out.println("after binding: " + ((childMap == masterMap) ? "childMap == masterMap" : "childMap != masterMap"));

child.unbind();
System.out.println("after unbinding: " + ((childMap == masterMap) ? "childMap == masterMap" : "childMap != masterMap"));

显示绑定后，child和main中的ObservableMap是同一个对象，因为该属性包装了地图而不包含其内容：

before binding: childMap != masterMap
after binding: childMap == masterMap
after unbinding: childMap == masterMap

要绑定地图的内容，请改用bindContent。执行

MapProperty<String, Object> master = new SimpleMapProperty<String, Object>(
        FXCollections.observableMap(new HashMap<String, Object>()));
MapProperty<String, Object> child = new SimpleMapProperty<String, Object>(
        FXCollections.observableMap(new HashMap<String, Object>()));

child.bindContent(master);

master.put("k1", "v1");

System.out.println("Java version: " + System.getProperty("java.version"));
System.out.println("OS version  : " + System.getProperty("os.name") + " - " + System.getProperty("os.arch"));
System.out.println("------------");
System.out.println("master: " + master);
System.out.println("child : " + child);

child.unbindContent(master);
child.clear();

System.out.println("------------");
System.out.println("master: " + master);
System.out.println("child : " + child);

child.put("k2", "v2");

System.out.println("------------");
System.out.println("master: " + master);
System.out.println("child : " + child);

给出以下结果：

Java version: 1.8.0_45
OS version  : Windows 7 - amd64
------------
master: MapProperty [value: {k1=v1}]
child : MapProperty [value: {k1=v1}]
------------
master: MapProperty [value: {k1=v1}]
child : MapProperty [value: {}]
------------
master: MapProperty [value: {k1=v1}]
child : MapProperty [value: {k2=v2}]

JavaFX 8 MapProperty unbind不起作用？

1 个答案: