获取显示方法以返回布尔值？ -JavaFX

Question

我有一个名为 GUI 的类来管理我的应用程序。当用户想在我的程序中删除他的帐户时，我希望弹出一个警告框并要求他确认或取消他的操作，这样他就不会意外删除他的帐户。

 package application;

 import javafx.geometry.Pos;
 import javafx.scene.Scene;
 import javafx.scene.control.Button;
 import javafx.scene.control.Label;
 import javafx.scene.layout.HBox;
 import javafx.scene.layout.VBox;
 import javafx.stage.*;

 /**
  * An Alert Box for the GUI
  * to display errors to the user.
  *
  */
public class AlertBox
{   
Stage window;

public boolean display(String title, String message)
{       
    boolean cancel = false;

    window = new Stage();                                                               // Create the stage.        

    window.initModality(Modality.APPLICATION_MODAL);                                    // If window is up, make user handle it.
    window.setTitle(title);
    window.setMinHeight(350);
    window.setMinWidth(250);

    VBox root = new VBox();                 // Root layout.

    Label warning = new Label(message);     // Message explaining what is wrong.

    HBox buttonLayout = new HBox();         // The yes and cancel button.

    Button yesButton = new Button("Yes");   // Yes button for the user.
    Button noButton = new Button("No");     // No button for the user.

    yesButton.setOnAction(e ->
    {
        cancel = false;
    });

    noButton.setOnAction(e ->
    {
        cancel = true;
    });
    buttonLayout.getChildren().addAll(yesButton, noButton);


    root.getChildren().addAll(warning, buttonLayout);
    root.setAlignment(Pos.CENTER);

    Scene scene = new Scene(root);
    window.setScene(scene);
    window.show();
}

/**
 * Closes the window and returns whether the user said yes or no.
 * @param variable
 * @return
 */
private boolean close(boolean variable)
{
    window.close();
    return variable;
}

}

我希望我的 GUI 类确切地知道当用户在 AlertBox 类中时发生了什么。用户是否单击是或否？所以我想把显示方法设为布尔值。这就是问题所在，我的事件侦听器表达式无法返回任何值，因为它位于 void 类型的回调中。然后我想，“哦，我会让 close 方法返回一个布尔值”。但后来我记得我调用的原始函数是：

AlertBox warning = new AlertBox;
boolean userWantsToDelete = warning.display("Warning!", "You are about to delete your account. Are you sure you would like to do this?");

希望 display 方法返回一个变量，而不是 close 方法。我也不能只打电话 close ，因为那是行不通的。我能做些什么来帮助解决这个问题？非常感谢。

Answer 1

您可以使用 JavaFX 警报轻松执行您的任务：

    Alert alert = new Alert(Alert.AlertType.CONFIRMATION);
    alert.setTitle("Confirmation Dialog");
    alert.setHeaderText("Warning !");
    alert.setContentText("Are you sure you want to perform this action ?");

    Optional<ButtonType> result = alert.showAndWait();
    if (result.get() == ButtonType.OK) {
     // delete user
 }

result.get() 返回一个布尔值。因此，您可以通过在 if 条件内进行比较来检查用户是否单击了ButtonType.OK 或ButtonType.CANCEL。

这里有一个例子供你理解：

使用默认警报，您会得到两个按钮，一个是确定按钮，另一个是取消按钮。但是，如果您想自定义警报，您可以将自己的按钮类型添加到其中，如下所示：

ButtonType buttonTypeOne = new ButtonType("One");
ButtonType buttonTypeTwo = new ButtonType("Two");
ButtonType buttonTypeThree = new ButtonType("Three");

并将它们添加到警报中：

alert.getButtonTypes().setAll(buttonTypeOne, buttonTypeTwo, buttonTypeThree);

所以你可以检查用户按下了哪个按钮

Optional<ButtonType> result = alert.showAndWait();
if (result.get() == buttonTypeOne){
    // ... user chose "One"
} else if (result.get() == buttonTypeTwo) {
    // ... user chose "Two"
} else{
    // ... user chose "Three"
}

Answer 2

如果没有EventHandler，我认为你做不到。如果你真的想使用自己的类，你可以这样做：

AlertBox alert = new AlertBox("title","message");
alert.setYesAction( e -> {
    //TO-DO
});
alert.setNoAction( e -> {
    //TO-DO
});
alert.showAndWait();

如果您想检查cancel的状态，无论用户是否按下按钮，您都可以致电：alert.isCanceled();

import javafx.event.ActionEvent;
import javafx.event.Event;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.*;

/**
 * An Alert Box for the GUI to display errors to the user.
 *
 */
public class AlertBox extends Stage {
    private boolean cancel = false;
    private EventHandler<ActionEvent> yesAction = null;
    private EventHandler<ActionEvent> noAction = null;

    public AlertBox(String title, String message) {
        super();
        initModality(Modality.APPLICATION_MODAL); // If window is up,
        // make user handle
        // it.
        setTitle(title);
        setMinHeight(350);
        setMinWidth(250);

        VBox root = new VBox(); // Root layout.

        Label warning = new Label(message); // Message explaining what is wrong.

        HBox buttonLayout = new HBox(); // The yes and cancel button.

        Button yesButton = new Button("Yes"); // Yes button for the user.
        Button noButton = new Button("No"); // No button for the user.

        yesButton.setOnAction(e -> {
            cancel = false;
            yesAction.handle(new ActionEvent());
        });

        noButton.setOnAction(e -> {
            cancel = true;
            noAction.handle(new ActionEvent());
        });
        buttonLayout.getChildren().addAll(yesButton, noButton);

        root.getChildren().addAll(warning, buttonLayout);
        root.setAlignment(Pos.CENTER);

        Scene scene = new Scene(root);
        setScene(scene);
    }

    public void setYesAction(EventHandler<ActionEvent> yesAction){
        this.yesAction = yesAction;
    }
    public void setNoAction(EventHandler<ActionEvent> noAction){
        this.noAction = noAction;
    }

    public boolean isCanceled(){
        return cancel;
    }
}

Answer 3

您可以添加可变对象（MutableBool 类）作为传递参数。由于 Mutable Object 是作为指针传递的，因此您可以分配一个值以签出该方法。

添加类：

class MutableBool{
    private boolean value;

    public void setValue(boolean value) {
        this.value = value;
    }

    public boolean getValue() {
        return value;
    }
}

对您的代码进行一些更改：

public boolean display(String title, String message, MutableBool answer){
    ...
    answer.setValue(true);
}

Answer 4

或者你可以在主类中处理：

package application;

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;

public class Main extends Application {
    @Override
    public void start(final Stage primaryStage) {
    try {
        final BorderPane root = new BorderPane();
        final Scene scene = new Scene(root, 400, 400);

        final AlertBox warning = new AlertBox("Warning!",
                "You are about to delete your account. Are you sure you  would like to do this?");    

            warning.addCancelListener(new ChangeListener<Boolean>() {

            @Override
            public void changed(final ObservableValue<? extends Boolean> observable, final Boolean oldValue, final Boolean newValue) {
                if (newValue) {
                    System.out.println("Tschüss");
                } else {
                    System.out.println("Thanks for confidence");
                }
            }
        });

        primaryStage.setScene(scene);
        primaryStage.show();
    } catch (final Exception e) {
        e.printStackTrace();
    }
}    

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

package application;

import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.beans.value.ChangeListener;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Modality;
import javafx.stage.Stage;

/**
 * An Alert Box for the GUI
 * to display errors to the user.
 */
public class AlertBox {
    Stage window;
    ObjectProperty<Boolean> cancel = new SimpleObjectProperty<>(null);

    public AlertBox(final String title, final String message) {
        cancel.setValue(null);
        display(title, message);
    }

    private void display(final String title, final String message) {
        window = new Stage(); // Create the stage.

        window.initModality(Modality.APPLICATION_MODAL); // If window is up, make user handle it.
        window.setTitle(title);
        window.setMinHeight(350);
        window.setMinWidth(250);
        window.setAlwaysOnTop(true);

        final VBox root = new VBox(); // Root layout.

        final Label warning = new Label(message); // Message explaining  what is wrong.

        final HBox buttonLayout = new HBox(); // The yes and cancel button.

        final Button yesButton = new Button("Yes"); // Yes button for the user.
        final Button noButton = new Button("No"); // No button for the user.

        yesButton.setOnAction(e -> {
            cancel.set(false);
            close();
        });

        noButton.setOnAction(e -> {
            cancel.set(true);
            close();
        });

        buttonLayout.getChildren().addAll(yesButton, noButton);

        root.getChildren().addAll(warning, buttonLayout);
        root.setAlignment(Pos.CENTER);

        final Scene scene = new Scene(root);
        window.setScene(scene);
        window.show();
    }

    /**
     * Closes the window
     *
     * @param variable
     */
    private void close() {
        window.close();
    }

    public void addCancelListener(final ChangeListener<Boolean> listener) {
        cancel.addListener(listener);
    }
}