Textarea scrollpane hold in text append - javafx

Question

It is my test code of textarea append text,
public class TextAreaScrollHold extends Application {
TextArea area = new TextArea();
#Override
public void start(Stage primaryStage) {
StackPane root = new StackPane();
root.getChildren().add(area);
Scene scene = new Scene(root, 300, 250);
primaryStage.setTitle("Hello World!");
primaryStage.setScene(scene);
primaryStage.show();
addTextInTextArea();
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
public void addTextInTextArea() {
for (int i = 0; i < 15; i++) {
area.appendText("Hello World " + i + "\n");
}
Task<Void> task = new Task() {
#Override
protected Void call() throws Exception {
for (int i = 15; i < 100; i++) {
area.appendText("Hello World " + i + "\n");
Thread.sleep(1000);
}
return null;
}
};
new Thread(task).start();
}
}
It my code data will update in thread. i need how to hold in scroll bar when data update in textarea. I have ref JavaFX TextArea and autoscroll and Access to TextArea's Scroll Pane or Scroll Bars but how solve this problems.
I need
When data update in textarea, i will scroll the text area scrollbar the bar will hold.
textArea.scrollTopProperty().addListener(new ChangeListener<Number>() {
#Override
public void changed(ObservableValue<? extends Number> observable, Number oldValue, Number newValue) {
textArea.setScrollTop(100);
}
});
I have used this code but scroll bar in not moved bar will fixed in pixel 100 positions

Answer 1

You can use getCaretPostion and postionCaret (yes, that setter's method name is awkward for Java).
I quickly drafted up some code for you, use the scroll lock button to enable/disable scrolling:
import javafx.application.Application;
import javafx.concurrent.Task;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.TextArea;
import javafx.scene.control.ToggleButton;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
public class ConsoleDemo extends Application {
Console console = new Console();
#Override
public void start(Stage primaryStage) {
StackPane root = new StackPane();
root.getChildren().add(console);
Scene scene = new Scene(root, 300, 250);
primaryStage.setTitle("Console Demo");
primaryStage.setScene(scene);
primaryStage.show();
addTextInTextArea();
}
/**
* #param args
* the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
public void addTextInTextArea() {
for (int i = 0; i < 15; i++) {
console.log("Hello World " + i);
}
Task<Void> task = new Task() {
#Override
protected Void call() throws Exception {
for (int i = 15; i < 100; i++) {
console.log("Hello World " + i);
Thread.sleep(1000);
}
return null;
}
};
new Thread(task).start();
}
public class Console extends BorderPane {
TextArea textArea = new TextArea();
int scrollLockPos = -1;
public Console() {
HBox toolbar = new HBox();
ToggleButton scrollLockButton = new ToggleButton("Scroll Lock");
scrollLockButton.setOnAction(e -> {
if (scrollLockButton.isSelected()) {
scrollLockPos = textArea.getCaretPosition();
} else {
scrollLockPos = -1;
}
});
HBox.setMargin(scrollLockButton, new Insets(5, 5, 5, 5));
toolbar.getChildren().add(scrollLockButton);
setCenter(textArea);
setTop(toolbar);
}
public void log(String text) {
textArea.appendText(text + "\n");
if (scrollLockPos != -1) {
textArea.positionCaret(scrollLockPos);
}
}
}
}
Not the nicest solution, but unless you want to use selection in the textarea while it's scrolling is locked, this one works. For a proper solution you'd need access to the skin / scrollpane / scrollbars and with the upcoming Java 9 version and its modularization you don't know what you will have access to since access to them is currently flagged as "restricted".
Edit:
Here's an alternate solution which uses the Range, console component only. With this version you can select text and keep the selection while the Scroll Lock button is down:
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.control.Button;
import javafx.scene.control.IndexRange;
import javafx.scene.control.TextArea;
import javafx.scene.control.ToggleButton;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
/**
* Console which provides a mechanism to lock scrolling. Selecting text and copying it works while scrolling is locked.
*/
public class Console extends BorderPane {
TextArea textArea = new TextArea();
ToggleButton scrollLockButton;
IndexRange range;
public Console() {
initComponents();
}
private void initComponents() {
// toolbar
HBox toolbar = new HBox();
toolbar.setAlignment(Pos.CENTER_RIGHT);
// clear
Button clearButton = new Button("Clear");
clearButton.setOnAction(e -> {
textArea.clear();
});
// scroll lock
scrollLockButton = new ToggleButton("Scroll Lock");
// button positions & layout
Insets insets = new Insets(5, 5, 5, 5);
HBox.setMargin(clearButton, insets);
HBox.setMargin(scrollLockButton, insets);
toolbar.getChildren().addAll(clearButton,scrollLockButton);
// component layout
setCenter(textArea);
setTop(toolbar);
}
public void log(String text) {
if (scrollLockButton.isSelected()) {
range = textArea.getSelection();
}
textArea.appendText(text + "\n");
if (scrollLockButton.isSelected()) {
textArea.selectRange(range.getStart(), range.getEnd());
}
}
}