JavaFX 2: Making a ScrollPane automatically scroll to the edge after adding content
Solution 1
you can bind to Hbox widthproperty chnages .
Sample Code :
//in start method add this code
DoubleProperty wProperty = new SimpleDoubleProperty();
wProperty.bind(chatBox.widthProperty()); // bind to Hbox width chnages
wProperty.addListener(new ChangeListener() {
@Override
public void changed(ObservableValue ov, Object t, Object t1) {
//when ever Hbox width chnages set ScrollPane Hvalue
chatBoxScrollPane.setHvalue(chatBoxScrollPane.getHmax());
}
}) ;
and
// remove below line from your addChatItem() method
chatBoxScrollPane.setHvalue(chatBoxScrollPane.getHmax());
Result :yes added numbering for fun ;)
Solution 2
In my case I needed to enclose a HBox called labels inside a ScrollPane called msgs and here is the way I handled autoscroll.
NOTE: The changeListener added to labels HBox is implemented via Lambda syntax(available in JDK8)
labels.heightProperty().addListener((observable, oldVal, newVal) ->{
msgs.setVvalue(((Double) newVal).doubleValue());
});
user1298572
Updated on August 22, 2022Comments
-
user1298572 almost 2 years
Using JavaFX 2, I have a basic example of a
ScrollPane
that contains anHBox
ofLabel
s. I want to be able to add aLabel
to theHBox
, and simultaneously scroll to the right edge of theScrollPane
so that the newly addedLabel
is visible. My current method uses thesetHvalue()
to set the scroll position andgetHmax()
to get the maximum scrolling distance allowed.The problem is that when I set the scroll position using
getHmax()
, it is as if the just-addedLabel
is not computed in theScrollPanel
's scroll width. Is there a way that I can update this inner width before tryingsetHvalue
?Please see this simple example code which exhibits the issue.
In particular, please notice the
addChatItem(String item)
method, which contains the logic for scrolling to the edge of theScrollPane
.import java.util.Timer; import java.util.TimerTask; import javafx.application.Application; import javafx.application.Platform; import javafx.scene.Scene; import javafx.scene.control.Label; import javafx.scene.control.ScrollPane; import javafx.scene.layout.BorderPane; import javafx.scene.layout.HBox; import javafx.scene.layout.StackPane; import javafx.scene.text.Font; import javafx.stage.Stage; public class ScrollPaneTest extends Application { static int defaultFontSize = 30; ScrollPaneTest scrollPaneTest = this; ScrollPane chatBoxScrollPane = new ScrollPane(); HBox chatBox = new HBox(); Chatter chatter = new Chatter(); public static void main(String[] args) { launch(args);//default } @Override public void stop() throws Exception { super.stop(); System.exit(0); } @Override public void start(Stage primaryStage) { BorderPane borderPane = new BorderPane(); StackPane chatBoxStackPane = new StackPane(); chatBoxScrollPane.setContent(chatBox); //chatBoxScrollPane.setHbarPolicy(ScrollBarPolicy.NEVER); chatBoxScrollPane.setMaxHeight(50); chatBoxStackPane.getChildren().add(chatBoxScrollPane); borderPane.setCenter(chatBoxStackPane); Scene scene = new Scene(borderPane, 800, 600); primaryStage.setScene(scene); primaryStage.setTitle("Scroll Demo"); primaryStage.show(); new Thread("mainGameControlThread") { public void run() { chatter.chatLoop(scrollPaneTest); } }.start(); } public void addChatItem(String chatString) { Label title = new Label(chatString); title.setFont(new Font("Verdana", defaultFontSize)); chatBox.getChildren().add(title); chatBoxScrollPane.setHvalue(chatBoxScrollPane.getHmax()); } class Chatter { public void chatLoop(final ScrollPaneTest test) { Timer closingCeremonyTimer = new Timer(); closingCeremonyTimer.schedule(new TimerTask() { public void run() { Platform.runLater(new Runnable() { @Override public void run() { test.addChatItem("Hello World. "); } }); chatLoop(test); } }, (long) (0.5*1000)); } } }
Here is an image of issue, notice how the
ScrollPane
has not scrolled to the right edge.Edit:
I've come up with a workaround but it is very far from ideal. My solution is to start a timer which will use
setHvalue()
after enough time has passed for theScrollPane
to discover the true width of its content. myaddChatItem()
method now looks like this:public void addChatItem(String chatString) { Label title = new Label(chatString); title.setFont(new Font("Verdana", defaultFontSize)); chatBox.getChildren().add(title); Timer closingCeremonyTimer = new Timer(); closingCeremonyTimer.schedule(new TimerTask() { public void run() { chatBoxScrollPane.setHvalue(chatBoxScrollPane.getHmax()); } }, (long) 50); }
Unfortunately, the number 50 in that method needs to be greater than the time that it takes the
ScrollPane
to update its inner content's width, and that seems to be far from guaranteed.