JavaFX Alert Dialogs Tutorial

View more categories:

1- JavaFX Alert

The Alert class subclasses the Dialog class, and provides support for a number of pre-built dialog types that can be easily shown to users to prompt for a response. Therefore, for many users, the Alert class is the most suited class for their needs (as opposed to using Dialog directly). Alternatively, users who want to prompt a user for text input or to make a choice from a list of options would be better served by using TextInputDialog and ChoiceDialog, respectively.
Alert is at default a window with the modelity of  Modelity.WINDOW_MODAL. However, you can change by using  alert.initModality(Modality).
By default, any window that opens an Alert dialog will be the parent window of this Alert.
You can see more explanation about the  Modelity in the following posts:
  • TODO Link!
Below is the illustration of the Alert window structure:

Header Region:

This region is used to display a short notification and icon.

Content Region:

By default, Content Region display a Label, you can set the text for this Label via alert.setContentText(String) method. You can also display another Node in the Content Region via alert.getDialogPane().setContent(Node).

Footer Region:

This region is used to display Buttons. You can customize the displayed buttons.

2- Information Alert

Information Alert means a dialog window, displaying information. Below is an image of a standard  Information Alert:
The image of an  Information Alert with default Header Text:
Image of an  Information Alert without Header Text:

Example:

InformationAlertExample.java
package org.o7planning.javafx.alert;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class InformationAlertExample extends Application {

	// Show a Information Alert with header Text
	private void showAlertWithHeaderText() {
		Alert alert = new Alert(AlertType.INFORMATION);
		alert.setTitle("Test Connection");
		alert.setHeaderText("Results:");
		alert.setContentText("Connect to the database successfully!");

		alert.showAndWait();
	}

	// Show a Information Alert with default header Text
	private void showAlertWithDefaultHeaderText() {
		Alert alert = new Alert(AlertType.INFORMATION);
		alert.setTitle("Test Connection");

		// alert.setHeaderText("Results:");
		alert.setContentText("Connect to the database successfully!");

		alert.showAndWait();
	}

	// Show a Information Alert without Header Text
	private void showAlertWithoutHeaderText() {
		Alert alert = new Alert(AlertType.INFORMATION);
		alert.setTitle("Test Connection");

		// Header Text: null
		alert.setHeaderText(null);
		alert.setContentText("Connect to the database successfully!");

		alert.showAndWait();
	}

	@Override
	public void start(Stage stage) {

		VBox root = new VBox();
		root.setPadding(new Insets(10));
		root.setSpacing(10);

		Button button1 = new Button("Information Alert");
		Button button2 = new Button("Information Alert with default Header Text");
		Button button3 = new Button("Information Alert without Header Text");

		button1.setOnAction(new EventHandler<ActionEvent>() {

			@Override
			public void handle(ActionEvent event) {
				showAlertWithHeaderText();
			}
		});

		button2.setOnAction(new EventHandler<ActionEvent>() {

			@Override
			public void handle(ActionEvent event) {
				showAlertWithDefaultHeaderText();
			}
		});

		button3.setOnAction(new EventHandler<ActionEvent>() {

			@Override
			public void handle(ActionEvent event) {
				showAlertWithoutHeaderText();
			}
		});

		root.getChildren().addAll(button1, button2, button3);

		Scene scene = new Scene(root, 450, 250);
		stage.setTitle("JavaFX Information Alert (o7planning.org)");
		stage.setScene(scene);

		stage.show();

	}

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

}

3- Warning Alert

Warning Alert is similar to an Information Alert, except for its icon and intended use.The  Warning Alert is used to warn an user for potential risks or problems, although it doesn't probably occur.
Image of a standard  Warning Alert :
Image of a  Warning Alert with default  Header Text:
Image of a Warning Alert without  Header Text:

Example:

WarningAlertExample.java
package org.o7planning.javafx.alert;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class WarningAlertExample extends Application {

	// Show a Warning Alert with header Text
	private void showAlertWithHeaderText() {
		Alert alert = new Alert(AlertType.WARNING);
		alert.setTitle("Warning alert");
		alert.setHeaderText("Battery Status:");
		alert.setContentText("The battery charge is low!");

		alert.showAndWait();
	}

	// Show a Warning Alert with default header Text
	private void showAlertWithDefaultHeaderText() {
		Alert alert = new Alert(AlertType.WARNING);
		alert.setTitle("Warning alert");

		// alert.setHeaderText("Battery Status:");
		alert.setContentText("The battery charge is low!");

		alert.showAndWait();
	}

	// Show a Warning Alert without Header Text
	private void showAlertWithoutHeaderText() {
		Alert alert = new Alert(AlertType.WARNING);
		alert.setTitle("Warning alert");

		// Header Text: null
		alert.setHeaderText(null);
		alert.setContentText("The battery charge is low!");

		alert.showAndWait();
	}

	@Override
	public void start(Stage stage) {

		VBox root = new VBox();
		root.setPadding(new Insets(10));
		root.setSpacing(10);

		Button button1 = new Button("Warning Alert");
		Button button2 = new Button("Warning Alert with default Header Text");
		Button button3 = new Button("Warning Alert without Header Text");

		button1.setOnAction(new EventHandler<ActionEvent>() {

			@Override
			public void handle(ActionEvent event) {
				showAlertWithHeaderText();
			}
		});

		button2.setOnAction(new EventHandler<ActionEvent>() {

			@Override
			public void handle(ActionEvent event) {
				showAlertWithDefaultHeaderText();
			}
		});

		button3.setOnAction(new EventHandler<ActionEvent>() {

			@Override
			public void handle(ActionEvent event) {
				showAlertWithoutHeaderText();
			}
		});

		root.getChildren().addAll(button1, button2, button3);

		Scene scene = new Scene(root, 450, 250);
		stage.setTitle("JavaFX Warning Alert (o7planning.org)");
		stage.setScene(scene);

		stage.show();

	}

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

}

4- Error Alert

Error Alert is the same as   Informtion Alert and  Warning Alert, except for icon and intended use. The  Error Alert is used to notify of occurence of a serious matter.
To create an Error Alert,  you need to use   AlertType.ERROR.
* Error Alert *
Alert alert = new Alert(AlertType.ERROR);

alert.setTitle("Error alert");
alert.setHeaderText("Can not add user");
alert.setContentText("The 'abc' user does not exists!");

alert.showAndWait();
In fact, when an error takes place, you display an Error Alert for users to know. It consists of short information and probably details of error in which case, you need to set customizing content for the Content Region.

Example:

ErrorAlertExample2.java
package org.o7planning.javafx.alert;

import java.io.PrintWriter;
import java.io.StringWriter;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextArea;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class ErrorAlertExample2 extends Application {

	private void showError(Exception e) {
		Alert alert = new Alert(AlertType.ERROR);
		alert.setTitle("Error alert");
		alert.setHeaderText(e.getMessage());

		VBox dialogPaneContent = new VBox();

		Label label = new Label("Stack Trace:");

		String stackTrace = this.getStackTrace(e);
		TextArea textArea = new TextArea();
		textArea.setText(stackTrace);

		dialogPaneContent.getChildren().addAll(label, textArea);

		// Set content for Dialog Pane
		alert.getDialogPane().setContent(dialogPaneContent);

		alert.showAndWait();
	}

	private void doSomething() {
		try {
			// An error has occurred here.
			int a = 100 / 0;
		} catch (Exception e) {
			showError(e);
		}
	}

	private String getStackTrace(Exception e) {
		StringWriter sw = new StringWriter();
		PrintWriter pw = new PrintWriter(sw);
		e.printStackTrace(pw);
		String s = sw.toString();
		return s;
	}

	@Override
	public void start(Stage stage) {

		VBox root = new VBox();
		root.setPadding(new Insets(10));
		root.setSpacing(10);

		Button button1 = new Button("Error Alert");

		button1.setOnAction(new EventHandler<ActionEvent>() {

			@Override
			public void handle(ActionEvent event) {
				doSomething();
			}
		});

		root.getChildren().addAll(button1);

		Scene scene = new Scene(root, 450, 250);
		stage.setTitle("JavaFX Error Alert (o7planning.org)");
		stage.setScene(scene);

		stage.show();

	}

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

}

5- Confirmation Alert

Confirmation Alert displays to ask users to confirm that an action will be done or not. It is defaulted that the  Confirmation Alert will have 2 options for users such as  OK or  Cancel.

Example:

ConfirmationAlertExample.java
package org.o7planning.javafx.alert;

import java.util.Optional;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Label;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class ConfirmationAlertExample extends Application {

   private Label label;

   private void showConfirmation() {

      Alert alert = new Alert(AlertType.CONFIRMATION);
      alert.setTitle("Delete File");
      alert.setHeaderText("Are you sure want to move this file to the Recycle Bin?");
      alert.setContentText("C:/MyFile.txt");

      // option != null.
      Optional<ButtonType> option = alert.showAndWait();

      if (option.get() == null) {
         this.label.setText("No selection!");
      } else if (option.get() == ButtonType.OK) {
         this.label.setText("File deleted!");
      } else if (option.get() == ButtonType.CANCEL) {
         this.label.setText("Cancelled!");
      } else {
         this.label.setText("-");
      }
   }

   @Override
   public void start(Stage stage) {

      VBox root = new VBox();
      root.setPadding(new Insets(10));
      root.setSpacing(10);

      this.label = new Label();

      Button button = new Button("Click here to delete file");

      button.setOnAction(new EventHandler<ActionEvent>() {

         @Override
         public void handle(ActionEvent event) {
            showConfirmation();
         }
      });

      root.getChildren().addAll(button, label);

      Scene scene = new Scene(root, 450, 250);
      stage.setTitle("JavaFX Confirmation Alert (o7planning.org)");
      stage.setScene(scene);

      stage.show();

   }

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

}

6- Custom Buttons

The Alert dialog allows you to customize buttons to be displayed on the Footer Region. Below is an example:

Example:

ConfirmationAlertExample2.java
package org.o7planning.javafx.alert;

import java.util.Optional;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Label;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class ConfirmationAlertExample2 extends Application {

	private Label label;

	private void showConfirmation() {

		Alert alert = new Alert(AlertType.CONFIRMATION);
		alert.setTitle("Select");
		alert.setHeaderText("Choose the sport you like:");

		ButtonType football = new ButtonType("Football");
		ButtonType badminton = new ButtonType("Badminton");
		ButtonType volleyball = new ButtonType("Volleyball");

		// Remove default ButtonTypes
		alert.getButtonTypes().clear();

		alert.getButtonTypes().addAll(football, badminton, volleyball);

		// option != null.
		Optional<ButtonType> option = alert.showAndWait();

		if (option.get() == null) {
			this.label.setText("No selection!");
		} else if (option.get() == football) {
			this.label.setText("You like Football");
		} else if (option.get() == badminton) {
			this.label.setText("You like Badminton");
		} else if (option.get() == volleyball) {
			this.label.setText("You like Volleyball");
		} else {
			this.label.setText("-");
		}
	}

	@Override
	public void start(Stage stage) {

		VBox root = new VBox();
		root.setPadding(new Insets(10));
		root.setSpacing(10);

		this.label = new Label();

		Button button = new Button("Click here to select a Sport");

		button.setOnAction(new EventHandler<ActionEvent>() {

			@Override
			public void handle(ActionEvent event) {
				showConfirmation();
			}
		});

		root.getChildren().addAll(button, label);

		Scene scene = new Scene(root, 450, 250);
		stage.setTitle("JavaFX Confirmation Alert (o7planning.org)");
		stage.setScene(scene);

		stage.show();

	}

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

}

View more categories: