有一个问题，javafx对象一旦被放入数组就会丢失引用 [英] Having an issue with javafx objects losing reference once they're put into an array

问题描述

所以我试图在我的控制器类中修改一些圈子，并且我将圈子链接到我的fxml文件圈子但是当我尝试将它们添加到圆圈阵列以便于管理时，他们似乎失去了他们的参考。例如，我有：

So I'm trying to modify some circles in my controller class, and i've linked the circles to my fxml file circles but when i try to add them to a circle array for easy management, they seem to lose their reference. For example I have:

@FXML
private Circle circle1 = new Circle();

public void addNumber(ActionEvent event){
circle1.setLayoutX(355.0);
circle1.setLayoutY(100.0);
circle1.setVisbility(true);
}

上述方法成功地在给定坐标中弹出一个圆圈。但是以下方法不起作用：

The above method successfully makes a circle pop up in the given coordinates. However the following doesnt work:

@FXML
private Circle circle1 = new Circle();

@FXML
private Circle[] c = {circle1};

public void addNumber(ActionEvent event){
c[0].setLayoutX(355.0);
c[0].setLayoutY(100.0);
c[0].setVisbility(true);
}

这不起作用！尝试过阵列试过arraylist尝试过的链表，对circle1的引用就是迷失了。我是JAVAFX的菜鸟，所以这可能是一个简单的修复，但我试图研究一下，尝试了不同的实现，让它工作，我似乎无法找到解决方案。
我们非常感谢任何帮助！

This doesn't work! Tried array tried arraylist tried linkedlist, the reference to circle1 just gets lost. I'm a noob at JAVAFX so this might be a simple fix but i've tried to research a bit, tried different implementations to get it to work and i cant seem to find the solution. Any help would be much appreciated!

推荐答案

这 SSCCE 应提供足够的信息以帮助您入门。

This SSCCE should provide enough information to get you started.

给出以下FXML文件：

Given the following FXML file:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.shape.*?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>


<Pane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" 
      prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" 
      xmlns:fx="http://javafx.com/fxml/1" 
      fx:controller="yourapplication.FXMLDocumentController">

    <children>
        <Button layoutX="22.0" layoutY="31.0" mnemonicParsing="false" 
         onAction="#addNumber" text="Button" />

        <Circle fx:id="circle1" fill="DODGERBLUE" layoutX="56.0" layoutY="118.0" 
                radius="34.0" stroke="BLACK" strokeType="INSIDE" visible="false" />
    </children>
</Pane>

以下控制器代码：

public class FXMLDocumentController {

    @FXML
    private Circle circle1;
    private Circle[] c;

    public void initialize() {
        c = new Circle[] { circle1 };
    }

    public void addNumber(ActionEvent event) {
        c[0].setLayoutX(355.0);
        c[0].setLayoutY(100.0);
        c[0].setVisible(true);
    }
}

你应该得到你想要的结果。

you should get the results you desire.

注意：

• 使用 FXML 用于将变量绑定到FXML文件中同名元素的注释。


• 变量不需要 FXML 注释在FXML文件中没有定义。


• 我不认为数组等基元可以定义为FXML。


• 对圆圈的引用应该在初始化方法中设置，因为在将变量绑定到FXML文件中的元素之后调用它。


• 如果你使用 FXML 注释标记 Node 变量，您不需要在控制器代码中设置引用，因为这样做加载FXML文件时会被覆盖（这是问题的根源，请参阅Tomsontoms答案）。

• Use the FXML annotation to bind your variables to elements of the same name within your FXML file.
• An FXML annotation is not required for variables that are not defined in the FXML file.
• I don't think primitives such as arrays can be defined FXML.
• the reference to the circle should be set in the initialize method as this is called after the variable is bound to the element in the FXML file.
• if you mark a Node variable with the FXML annotation you don't need to set a reference in the controller code as this will be overwritten when the FXML file is loaded (which is the root of your problem, see Tomsontoms answer).

这篇关于有一个问题，javafx对象一旦被放入数组就会丢失引用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！