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JavaFX Tutorial

You’ve come to this page to discover how to count number of characters in JavaFX. In this article, we will count number of characters in Java using a JavaFX Textfield. When we type something into the Textfield, it automatically counts the number of characters using the binding API in JavaFX.

The binding API allows you to simplify listeners to just one line of code. It makes interacting with JavaFX components or nodes a lot easier. We will be working with the Property API and bind() method. In addition to getters and setters. JavaFX property API provides almost all to its classes fields. We need a property API to access the property of JavaFX components or nodes. The property has two important APIs it is Observable and Binding.

Observable API allows you to monitor the change event of corresponding property of a JavaFX component or node.

The bind() method comes from the base property. The bind API has the following API methods.

• bind() – Binds a property to observable
• unBind() – To stop the binding
• boolean isBound() – To check whether the property is bound.
• bindBidirectional(Property<T> other) – This is to ties two properties together in both directions
• unbindBidectional(Property<T> other) – This to stop the bidirectional binding

Bidirectional binding connects two properties making them always have the same value. Consider the following example for bidirectional binding.

bindBidirectional binding

Example

Slider slider1 = new Slider(0, 120, 45);
Slider slider2 = new Slider(0, 120, 45);
slider1.valueProperty().bindBidirectional(slider2.valueProperty());

Rules of binding

Binding looks very simple to use but there are several rules that you need to be aware.

1. Read-only properties cannot be bound
2. Only one bind can be active for a property, but several properties can be bound to another one
3. Binding and setters do not work togther
4. Bidirectional binding are less strict

How to count number of characters in JavaFX

We will use the bind() method to count number of characters in JavaFX. Let’s pretend that we have a JavaFX TextField and a Label. When we type something in the TextField, the number of characters in JavaFX TextField is automatically counted. What exactly do we need in order to count number of characters in javafx? Take a look at the bullets below.

• textProperty() – Property of the object to be changed
• bind() – Bind call
• length() – Returns integerBinding type, not just an integer.
• concat() – A constant that will be used as a string

Example

The following sample code is to count the number of characters in JavaFX Textfield. These are the variables are being used in the exampe code below.

• lbl_result – JavaFX Label
• txtfield – JavaFX TextField

lbl_result.textProperty().bind(Bindings.concat(lbl_result.getText(), txtfield.textProperty().length()));

Output

YouTube Video

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