I want to use a single ChangeListener for multiple TextFields in my application.
I know that you can create a listener object and add this to all TextFields, then you can check via the event key which TextField-Object triggered the event.
With lamda expression I could use this for every TextField, unfortunately this isn't suited for my problem. I use the input of all TextFields so one single Listener should be enough.
TextField textField = new TextField();
textField.textProperty().addListener((observable, oldValue, newValue) -> {
System.out.println("textfield changed from " + oldValue + " to " + newValue);
});
As Slaw pointed out in his comment, you can easily create a single ChangeListener
and then apply it to each of your TextField
nodes.
ChangeListener<String> listener = ((observable, oldValue, newValue) -> {
System.out.println("TextField changed from " + oldValue + " to " + newValue + "!");
});
Here is a complete sample you can run to see it in action:
import javafx.application.Application;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.ListView;
import javafx.scene.control.TextField;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import java.util.ArrayList;
import java.util.Arrays;
public class ReusableListenerSample extends Application {
public static void main(String[] args) {
launch(args);
}
@Override
public void start(Stage primaryStage) {
// Simple Interface
VBox root = new VBox(10);
root.setAlignment(Pos.CENTER);
root.setPadding(new Insets(10));
// Create a ChangeListener that we will apply to multiple TextFields
ChangeListener<String> listener = ((observable, oldValue, newValue) -> {
System.out.println("TextField changed from " + oldValue + " to " + newValue + "!");
});
// Create some TextFields
TextField txt1 = new TextField();
TextField txt2 = new TextField();
TextField txt3 = new TextField();
// Now, we can add our preconfigured listener to each of the TextFields
txt1.textProperty().addListener(listener);
txt2.textProperty().addListener(listener);
txt3.textProperty().addListener(listener);
// Add our TextFields to the scene
root.getChildren().addAll(txt1, txt2, txt3);
// Show the stage
primaryStage.setScene(new Scene(root));
primaryStage.setTitle("ListViewSample Sample");
primaryStage.show();
}
}
Now, the above example does not indicate which TextField
was changed. In order to track that, you could create your own inner class that implements ChangeListener<String>
and pass your TextField
(or any other data to it):
class MyChangeListener implements ChangeListener<String> {
private final TextField myTextField;
public MyChangeListener(TextField myTextField) {
this.myTextField = myTextField;
}
@Override
public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
System.out.println(myTextField + " changed from " + oldValue + " to " + newValue + "!");
}
}
Then, just add a new instance of that MyChangeListener
to each TextField
instead:
txt1.textProperty().addListener(new MyChangeListener(txt1));