JavaFx 更改窗口，无需新的 Controller 构造函数

Question

我有 2 个 fxml 文件。示例 A.fxml。 B.fxml。我有 2 个 Controller 。 A Controller (A.fxml)B Controller (B.fxml)。 A fxml 和 B fxml 具有更改场景或 fxml 的更改按钮。这是按钮代码；

try {
        FXMLLoader loader = new FXMLLoader(getClass().getResource("/infoLibrary/view/A.fxml"));
        Parent root = loader.load();
        Scene scene = new Scene(root);
        Stage stage = (Stage)((Node)event.getSource()).getScene().getWindow();
        stage.setScene(scene);
        stage.show();
    } catch (IOException e) {
        e.printStackTrace();
    }

BContrroller 更改按钮中的代码相同。当我单击更改按钮时，扫描会发生变化。但每次 init 方法和 Controller 构造器也在工作。当用户每次使用新的构造函数更改 fxml javafx 时。如何在没有新 Controller 构造函数的情况下更改窗口？

Answer 1

使用 View 模型:

public class ViewModel {

    public enum View {A, B}

    private final ObjectProperty<View> currentView = new SimpleObjectProperty<>(View.A);

    public ObjectProperty<View> currentViewProperty() {
        return currentView ;
    }

    public final View getCurrentView() {
        return currentViewProperty().get();
    }

    public final View setCurrentView(View view) {
        currentViewProperty().set(view);
    }

}

现在在您的AController中执行以下操作:

public class AController {

    private ViewModel viewModel ;

    public void setViewModel(ViewModel viewModel) {
        this.viewModel = viewModel ;
    }

    // button handler:
    @FXML
    private void goToB(ActionEvent event) {
        viewModel.setCurrentView(ViewModel.View.B);
    }
}

和BController类似。

最后，您可以使用如下所示的内容设置所有内容，该内容仅执行一次(例如在您的 start() 方法中或类似的地方):

Stage stage = ... ; // maybe it's the primary stage in start...
Scene scene = new Scene();
ViewModel viewModel = new ViewModel();

FXMLLoader aLoader = new FXMLLoader(getClass().getResource("/infoLibrary/view/A.fxml"));
Parent a = aLoader.load();
AController aController = aLoader.getController();
aController.setViewModel(viewModel);

FXMLLoader bLoader = new FXMLLoader(getClass().getResource("/infoLibrary/view/B.fxml"));
Parent b = bLoader.load();
BController bController = bLoader.getController();
bController.setViewModel(viewModel);

scene.rootProperty().bind(Bindings.createObjectBinding(() -> {
    if (viewModel.getCurrentView() == ViewModel.View.A) {
        return a ;
    } else if (viewModel.getCurrentView() == ViewModel.View.B) {
        return b ;
    } else {
        return null ;
    }
}, viewModel.currentViewProperty());

stage.setScene(scene);
stage.show();

现在，这两个 FXML 文件仅加载一次(因此 Controller 仅创建一次，并且它们的 initialize() 方法仅调用一次)。通过更改 ViewModel 的状态并观察该状态来管理切换，因此当模型状态更改时场景的根也会更改。

这是一个完整的 SSCCE:

ViewModel.java:

package sceneswitcher;

import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;

public class ViewModel {

    public enum View {A, B}

    private final ObjectProperty<View> currentView = new SimpleObjectProperty<>(View.A);

    public ObjectProperty<View> currentViewProperty() {
        return currentView ;
    }

    public final View getCurrentView() {
        return currentViewProperty().get();
    }

    public final void setCurrentView(View view) {
        currentViewProperty().set(view);
    }

}

AController.java:

package sceneswitcher;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.TextField;

public class AController {

    private ViewModel viewModel ;

    @FXML
    private TextField textField ;

    public void setViewModel(ViewModel viewModel) {
        this.viewModel = viewModel ;
    }

    // button handler:
    @FXML
    private void goToB(ActionEvent event) {
        viewModel.setCurrentView(ViewModel.View.B);
    }

    public String getText() {
        return textField.getText();
    }
}

A.fxml:

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

<?import javafx.scene.layout.VBox?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.control.Button?>

<VBox fx:controller="sceneswitcher.AController" spacing="5" alignment="CENTER" 
        xmlns:fx="http://javafx.com/fxml/1">

    <Label text='This is view A'/>
    <TextField fx:id="textField" />
    <Button onAction="#goToB" text="Go to view B"/>
</VBox>

BController.java:

package sceneswitcher;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.TextArea;

public class BController {
    private ViewModel viewModel ;

    @FXML
    private TextArea textArea ;

    public void setViewModel(ViewModel viewModel) {
        this.viewModel = viewModel ;
    }

    // button handler:
    @FXML
    private void goToA(ActionEvent event) {
        viewModel.setCurrentView(ViewModel.View.A);
    }

    public String getText() {
        return textArea.getText();
    }
}

B.fxml:

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

<?import javafx.scene.layout.VBox?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextArea?>
<?import javafx.scene.control.Button?>

<VBox fx:controller="sceneswitcher.BController" spacing="5" alignment="CENTER"
         xmlns:fx="http://javafx.com/fxml/1">

    <Label text="This is view B"/>
    <TextArea fx:id="textArea" />
    <Button onAction="#goToA" text="Go to View A"/>
</VBox>

Main.java:

package sceneswitcher;

import java.io.IOException;

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws IOException {
        ViewModel viewModel = new ViewModel();

        FXMLLoader aLoader = new FXMLLoader(getClass().getResource("A.fxml"));
        Parent a = aLoader.load();
        AController aController = aLoader.getController();
        aController.setViewModel(viewModel);

        FXMLLoader bLoader = new FXMLLoader(getClass().getResource("B.fxml"));
        Parent b = bLoader.load();
        BController bController = bLoader.getController();
        bController.setViewModel(viewModel);

        Scene scene = new Scene(a, 400, 400);

        scene.rootProperty().bind(Bindings.createObjectBinding(() -> {
            if (viewModel.getCurrentView() == ViewModel.View.A) {
                return a ;
            } else if (viewModel.getCurrentView() == ViewModel.View.B) {
                return b ;
            } else {
                return null ;
            }
        }, viewModel.currentViewProperty()));

        primaryStage.setScene(scene);
        primaryStage.show();
    }

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