在“Pro JavaFX 8：构建桌面、移动和嵌入式 Java 客户端的权威指南”的第 3 章中，一个示例说明了如何直接在 FXML 文件中指定对象。
您可以在本文末尾找到完整的 FXML 文件以及示例中的其他文件。
这是我正在讨论的片段。该sizes字段使用该fx:factory属性指示必须使用工厂方法 Utilities.createList() 创建一个整数列表，然后用三个整数填充该列表。
<sizes>
<Utilities fx:factory="createMyCollection">
<Integer fx:value="1"/>
<Integer fx:value="2"/>
<Integer fx:value="3"/>
</Utilities>
</sizes>
这是 Utilities.java：
package projavafx.fxmlbasicfeatures;
import java.util.ArrayList;
import java.util.List;
public class Utilities {
public static final Double TEN_PCT = 0.1d;
public static final Double TWENTY_PCT = 0.2d;
public static final Double THIRTY_PCT = 0.3d;
public static List<Integer> createList() {
return new ArrayList<>();
}
}
我的问题是：使用这些工厂方法的一般机制是什么？
我想了解 FXMLLoader 如何知道需要将三个 Integers 添加到使用该add方法创建的对象中。自然，它必须以某种方式知道List或也许知道Collection，但是该知识在哪里指定？它是内置在 FXMLLoader 中的吗？如果是这样，如何为用户定义的类提供这样的工厂方法？
我实际上尝试将它与用户定义的类一起使用。我在 Utilities.java 中添加了以下代码片段，它创建了一个MyCollection具有单个方法add(Integer)并定义了一个Utilities.createMyCollection方法的类：
public class Utilities {
(...)
public static class MyCollection {
private List<Integer> myList = new LinkedList<>();
public void add(Integer o) {
myList.add(o);
}
public String toString() {
return myList.toString();
}
}
public static MyCollection createMyCollection() {
return new MyCollection();
}
(...)
}
但是，当我在 FXML 文件中替换 createMyCollection 时，我收到消息“MyCollections 没有默认属性。将 MyCollection 内容放在属性元素中。”
这让我想知道如何为用户定义的类声明一个默认属性，以及如何List已经拥有一个。
这是所有文件（除了上面的 Utilities.java）：
FXMLBasicFeatures.fxml：
<?import javafx.scene.paint.Color?>
<?import projavafx.fxmlbasicfeatures.FXMLBasicFeaturesBean?>
<?import projavafx.fxmlbasicfeatures.Utilities?>
<?import java.lang.Double?>
<?import java.lang.Integer?>
<?import java.lang.Long?>
<?import java.util.HashMap?>
<?import java.lang.String?>
<FXMLBasicFeaturesBean name="John Smith"
flag="true"
count="12345"
xmlns:fx="http://javafx.com/fxml/1">
<address>12345 Main St.</address>
<foreground>#ff8800</foreground>
<background>
<Color red="0.0" green="1.0" blue="0.5"/>
</background>
<price>
<Double fx:value="3.1415926"/>
</price>
<discount>
<Utilities fx:constant="TEN_PCT"/>
</discount>
<sizes>
<Utilities fx:factory="createList">
<Integer fx:value="1"/>
<Integer fx:value="2"/>
<Integer fx:value="3"/>
</Utilities>
</sizes>
<profits>
<HashMap q1="1000" q2="1100" q3="1200" a4="1300"/>
</profits>
<fx:define>
<Long fx:id="inv" fx:value="9765625"/>
</fx:define>
<inventory>
<fx:reference source="inv"/>
</inventory>
<products>
<String fx:value="widget"/>
<String fx:value="gadget"/>
<String fx:value="models"/>
</products>
<abbreviations CA="California" NY="New York" FL="Florida" MO="Missouri"/>
</FXMLBasicFeaturesBean>
FXMLBasicFeaturesBean.java：
package projavafx.fxmlbasicfeatures;
import javafx.scene.paint.Color;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class FXMLBasicFeaturesBean {
private String name;
private String address;
private boolean flag;
private int count;
private Color foreground;
private Color background;
private Double price;
private Double discount;
private List<Integer> sizes;
private Map<String, Double> profits;
private Long inventory;
private List<String> products = new ArrayList<String>();
private Map<String, String> abbreviations = new HashMap<>();
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public boolean isFlag() {
return flag;
}
public void setFlag(boolean flag) {
this.flag = flag;
}
public int getCount() {
return count;
}
public void setCount(int count) {
this.count = count;
}
public Color getForeground() {
return foreground;
}
public void setForeground(Color foreground) {
this.foreground = foreground;
}
public Color getBackground() {
return background;
}
public void setBackground(Color background) {
this.background = background;
}
public Double getPrice() {
return price;
}
public void setPrice(Double price) {
this.price = price;
}
public Double getDiscount() {
return discount;
}
public void setDiscount(Double discount) {
this.discount = discount;
}
public List<Integer> getSizes() {
return sizes;
}
public void setSizes(List<Integer> sizes) {
this.sizes = sizes;
}
public Map<String, Double> getProfits() {
return profits;
}
public void setProfits(Map<String, Double> profits) {
this.profits = profits;
}
public Long getInventory() {
return inventory;
}
public void setInventory(Long inventory) {
this.inventory = inventory;
}
public List<String> getProducts() {
return products;
}
public Map<String, String> getAbbreviations() {
return abbreviations;
}
@Override
public String toString() {
return "FXMLBasicFeaturesBean{" +
"name='" + name + '\'' +
",\n\taddress='" + address + '\'' +
",\n\tflag=" + flag +
",\n\tcount=" + count +
",\n\tforeground=" + foreground +
",\n\tbackground=" + background +
",\n\tprice=" + price +
",\n\tdiscount=" + discount +
",\n\tsizes=" + sizes +
",\n\tprofits=" + profits +
",\n\tinventory=" + inventory +
",\n\tproducts=" + products +
",\n\tabbreviations=" + abbreviations +
'}';
}
}
FXMLBasicFeaturesMain.java：
package projavafx.fxmlbasicfeatures;
import javafx.fxml.FXMLLoader;
import java.io.IOException;
public class FXMLBasicFeaturesMain {
public static void main(String[] args) throws IOException {
FXMLBasicFeaturesBean bean = FXMLLoader.load(
FXMLBasicFeaturesMain.class.getResource(
"/projavafx/fxmlbasicfeatures/FXMLBasicFeatures.fxml")
);
System.out.println("bean = " + bean);
}
}