HOWTO · Java
How to Use KeyEvent in JavaFX
This tutorial will show how we can create a key event and execute a simple code when a user presses a key in JavaFX.
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The KeyEvent is used to detect keypress and execute a specific code block when the key is pressed.
This article will show how to create a key event and execute a simple code when a user presses a key. We will also see a simple example to make it easier to understand.
Use KeyEvent in JavaFX
The general format for creating key events is shown below.
scene.setOnKeyPressed(
(KeyEvent event)
-> {
// Create a key event that execute when any key pressed from your keyboard
// Add the actions that we are going to take when a key pressed.
});
We will see an example that will detect the user keypress and show a message that a key was pressed.
The source code of our example will be like below, and we will describe each line by providing the necessary commands. Let’s have a look.
import javafx.application.Application; // Package to create application
import javafx.scene.Scene; // Package to create a scene
import javafx.scene.control.Label; // Package to create a label
import javafx.scene.input.KeyEvent; // Package to create a key event
import javafx.scene.layout.HBox; // Package for the Hbox
import javafx.stage.Stage; // Package to create a stage
public class FxKeyListen extends Application {
Label lbl; // Declares a label
HBox _hbox; // Declares a HBox.
public void start(Stage SimpleStage) throws Exception {
SimpleStage.setTitle(
"Detect key event"); // Set the application title which is "Detect key event"
lbl =
new Label("No key is pressed !!!"); // Create a label with default text "No key pressed !!!"
_hbox = new HBox(lbl); // Create a HBox with a label
Scene scene = new Scene(_hbox, 400, 400); // Create a scene with HBox and necessary dimentions.
scene.setOnKeyPressed(
(KeyEvent event)
-> { // Create a key event that execute when any key pressed from your keyboard
lbl.setText("Key press detected !!!"); // The actions that we are going to take when a key
// pressed. In our case we are changing the label
// text to "Key press detected !!!"
});
SimpleStage.setScene(scene); // Set the scene
SimpleStage.show(); // Visualize the scent
}
public static void main(String[] args) {
Application.launch(args); // Run our application
}
}
We already commanded the purpose of each line. Now let’s explain how the code works.
We created a label on our code with the default text of No key pressed !!! by the line lbl = new Label ("No key pressed !!!");. This label aims to show the user that no key is pressed.
Then we created a simple keypress event as an action that will execute when the user presses a key from his keyboard; we change the label’s default text and set it to Key press detected !!!. So for this purpose, the code adds as action is like lbl.setText("Key press detected !!!");.
Now when you run the code after a successful compilation, a window will open with the title Detect key event, and after you press a key from your keyboard, you will see an output like the one below.
Output:
Remember, if your IDE doesn’t support the automatic inclusion of libraries. Then you may need to include necessary library files manually before compiling.
