It is possible to issue java.lang.reflect.Field to javafx.scene.control.TextField? - javafx-8

Question

It is possible to issue java.lang.reflect.Field to javafx.scene.control.TextField?
For example:
Field[] nodes;
nodes = clase.getDeclaredFields();
for (Field n : nodes)
if (n.getType().getSimpleName().equals("TextField"))
((TextField)((Object) n)).setText("Text");

Answer 1

If you want to modify the TextFields, you need to retrieve the value from those fields (and cast this value to TextField).
The following example should demonstrate the approach:
private TextField t1 = new TextField();
private TextField t2 = new TextField();
#Override
public void start(Stage primaryStage) {
Button btn = new Button("Say 'Hello World'");
btn.setOnAction((ActionEvent event) -> {
Object object = this;
Class clazz = object.getClass();
for (Field field : clazz.getDeclaredFields()) {
if (field.getType().getName().equals("javafx.scene.control.TextField")) {
try {
// get field value here
TextField textField = (TextField) field.get(object);
if (textField != null) {
textField.setText("Hello World");
}
} catch (IllegalArgumentException | IllegalAccessException ex) {
Logger.getLogger(ReflectTest.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
});
VBox root = new VBox();
root.getChildren().addAll(btn, t1, t2);
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
}

Answer 2

Reflection is probably a really bad approach to this. Among many problems is that you make the functionality dependent on how the code is written. Specifically, you assume that each text field is stored in a specific instance field in some class. If you change the implementation, e.g. so that you keep the text fields in a data structure instead of maintaining references to them yourself, then your functionality will break. It is bad practice to write code that is so tightly coupled to the actual implementation of the code, for obvious reasons.
One better approach would simply to be to put all the text fields in a list (or other data structure), so you can do whatever you need with them easily. E.g.
public class MyForm {
private GridPane view ;
private String[] messages = {"First name:", "Last name", "Email"} ;
private List<TextField> textFields ;
public MyForm {
view = new GridPane();
textFields = new ArrayList<>();
for (int r = 0; r < messages.length ; r++) {
view.addRow(r, new Label(messages[r]), createTextField(messages[r]));
}
}
private TextField createTextField(String text) {
TextField textField = new TextField();
textField.setPromptText(text);
textFields.add(textField);
return textField ;
}
public void processTextFields() {
textField.forEach(tf -> tf.setText("Hello"));
}
}
Another approach would be to use a CSS lookup. If myForm is some node that is an ancestor of all the text fields:
myForm.lookupAll(".text-field").forEach(node -> {
TextField textField = (TextField)node ;
textField.setText("Hello");
});
but note that CSS lookups will not work until after CSS has been applied (by default, this means after the scene has been rendered for the first time).
Another way, if all the text fields are all contained in a single direct parent (such as the grid pane in the first example), would be to iterate through the child nodes and filter the text fields:
textFieldParentNode.getChildrenUnmodifiable().stream()
.filter(TextField.class::isInstance)
.map(TextField.class::cast)
.forEach(tf -> tf.setText("Hello"));