JavaFX：在实例化控制器类时传递参数 [英] JavaFX : Pass parameters while instantiating controller class

问题描述

我正在研究JavaFX应用程序。我的所有gui都是 .fxml 格式，并通过控制器类管理所有GUI组件。但是，在加载FXML加载器之前，我在 实例化控制器类 时遇到了困难。我无法在stackoverflow上找到其他人的问题的好解决方案，因此这不是一个重复的问题。

I am working on JavaFX application right now. All my gui is in .fxml format and through controller class manages all GUI components. However, I have difficulties with instantiating the controller class before I load FXML loader. I was unable to find a good solution for my question from others on stackoverflow, therefore this is not a duplicate question.

我实例化控制器类的原因是我想 传递一些参数 ，以便这些参数将显示在GUI中。

The reason why I am instantiating the controller class is that I want to pass some parameters so that these parameters will be displayed in GUI.

我正在加载FXML提交以下方式：

I am loading an FXML file the following way:

/*
 * for Work Order button
 */
@FXML
private void pressWorkOrder() throws Exception{ 
    WorkOrderController wo = new WorkOrderController("ashdkjhsahd");    //instantiating constructor     

    Parent parent = FXMLLoader.load(getClass().getResource("/fxml/WorkOrder.fxml"));        
    Scene scene = new Scene(parent);
    Stage stage = new Stage();
    stage.setScene(scene);
    stage.setTitle("Word Order");
    stage.setResizable(false);
    stage.show();
}

这是我的实际控制器类：

And here is my actual Controller class:

public class WorkOrderController implements Initializable{

     @FXML
     private Button summary;
     private String m,n;

     public WorkOrderController(String str) {
         // TODO Auto-generated constructor stub
         m = str;
     }  

     //for testing
     public void set(String str){
         m = str;
     }  

     @FXML
     public void check(){
         System.out.println("Output after constructor was initialized " + m);
     }

     @Override
     public void initialize(URL location, ResourceBundle resources) {
        // TODO Auto-generated method stub
     }
 }

我得到这个例外：

at javafx.fxml.FXMLLoader.processStartElement(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
at javafx.fxml.FXMLLoader.load(Unknown Source)
at MainController.pressWorkOrder(MainController.java:78)
... 57 more
Caused by: java.lang.InstantiationException: WorkOrderController
at java.lang.Class.newInstance(Unknown Source)
at sun.reflect.misc.ReflectUtil.newInstance(Unknown Source)
... 71 more
Caused by: java.lang.NoSuchMethodException: WorkOrderController.<init>()
at java.lang.Class.getConstructor0(Unknown Source)
... 73 more

推荐答案

为小型应用程序执行此操作的两种最简单方法是：

The two easiest ways of doing it for small applications are :

1. 不要指定 fx： fxml中的controller 。通过向其传递数据来创建控制器实例，然后将其传递给FXMLLoader。

1. Do not specify the fx:controller in the fxml. Create a controller instance by passing data to it and then pass it to the FXMLLoader.

指定 fx：controller 在fxml中。从FXMLLoader获取控制器实例并将数据传递给控制器​​。

Specify the fx:controller in the fxml. Fetch the controller instance from the FXMLLoader and pass the data to the controller.

以下是两个示例以上所述类型。每个示例都有3个组件：

The following are the examples for both the above said types. Each of the example have 3 components :

• FXML - FXML文件，没有第一种类型的 fx：controller 声明，并将其用于第二种类型。


• 控制器 - 有一个<第一种类型的code>构造函数。第二种类型的 setter方法。


• Main - 用于加载FXML并将数据传递给控制器​​。对于第一种情况，将控制器设置为FXMLLoader 。在第二个时，从FXMLLoader 获取控制器。

• FXML - The FXML file, which doesn't have the fx:controller declaration for the first type and has it for the second type.
• Controller - Has a constructor for the first type. Has setter methods for the second type.
• Main - Used for loading FXML and pass data to the controller. For first case, it sets the controller to FXMLLoader. While in second, it fetches the controller from the FXMLLoader.

FXML - 不要指定fx：controller

FXML - Do not specify the fx:controller

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

<?import javafx.scene.layout.FlowPane?>
<?import javafx.scene.control.Label?>

<FlowPane fx:id="root" xmlns:fx="http://javafx.com/fxml">
    <children>
        <Label fx:id="firstName" text="" />
        <Label fx:id="lastName" text="" />
    </children>
</FlowPane>

控制器 - 创建一个构造函数以接受默认值

Controller - create a Constructor to accept default values

import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;

import java.net.URL;
import java.util.ResourceBundle;

public class SampleController implements Initializable {

    private StringProperty firstNameString = new SimpleStringProperty();
    private StringProperty lastNameString = new SimpleStringProperty();

    /**
     * Accepts the firstName, lastName and stores them to specific instance variables
     * 
     * @param firstName
     * @param lastName
     */
    public SampleController(String firstName, String lastName) {
        firstNameString.set(firstName);
        lastNameString.set(lastName);
    }

    @FXML
    Label firstName;

    @FXML
    Label lastName;

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        firstName.setText(firstNameString.get());
        lastName.setText(lastNameString.get());
    }
}

Main - 创建一个控制器实例，通过将值传递给它，然后将其传递给FXMLLoader

Main - Create a Controller instance, by passing value into it and then pass it to the FXMLLoader

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.FlowPane;
import javafx.stage.Stage;

public class Main extends Application {
    @Override
    public void start(Stage primaryStage) throws Exception {
        FXMLLoader loader = new FXMLLoader(getClass().getResource("Sample.fxml"));

        // Create a controller instance
        SampleController controller = new SampleController("itachi", "uchiha");
        // Set it in the FXMLLoader
        loader.setController(controller);
        FlowPane flowPane = loader.load();
        Scene scene = new Scene(flowPane, 200, 200);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

---

2。从FXMLLoader获取控制器实例

FXML - 已指定fx：controller

---

2. Fetch a controller instance from FXMLLoader

FXML - Has specified the fx:controller

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

<?import javafx.scene.layout.FlowPane?>
<?import javafx.scene.control.Label?>

<!-- Controller Specified -->
<FlowPane fx:id="root" xmlns:fx="http://javafx.com/fxml" fx:controller="SampleController">
    <children>
        <Label fx:id="firstName" text="" />
        <Label fx:id="lastName" text="" />
    </children>
</FlowPane>

控制器 - 具有接受输入的Setter方法

Controller - Has Setter methods to accept input

import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;

import java.net.URL;
import java.util.ResourceBundle;

public class SampleController implements Initializable {

    @FXML
    Label firstName;

    @FXML
    Label lastName;

    @Override
    public void initialize(URL location, ResourceBundle resources) {

    }

    /**
     * Accepts a String and sets it to the firstName Label
     *
     * @param firstNameString
     */
    public void setFirstName(String firstNameString) {
        firstName.setText(firstNameString);
    }

    /**
     * Accepts a String and sets it to the lastName Label
     *
     * @param lastNameString
     */
    public void setLastName(String lastNameString) {
        lastName.setText(lastNameString);
    }
}

主要 - 获取调用 load（）后调用FXMLLoader中的控制器实例，然后调用setter方法传递数据。

Main - Fetches the Controller instance from FXMLLoader after calling the load() and then calls the setter methods to pass data.

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.FlowPane;
import javafx.stage.Stage;

public class Main extends Application {
    @Override
    public void start(Stage primaryStage) throws Exception {
        FXMLLoader loader = new FXMLLoader(getClass().getResource("Sample.fxml"));
        FlowPane flowPane = loader.load();
        // Get the Controller from the FXMLLoader
        SampleController controller = loader.getController();
        // Set data in the controller
        controller.setFirstName("itachi");
        controller.setLastName("uchiha");
        Scene scene = new Scene(flowPane, 200, 200);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

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