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Clear canvas in JavaFX

Im trying to clear simple canvas in JavaFX.
Start function
Canvas canvas = new Canvas();
Group root = new Group(canvas);
Scene scene = new Scene(root, 1400, 1000);
If user want to load game, then loadSave boolean variable sets to 'true'
if(loadSave){
//Clear scene and load new with circles from file
}
Else, it loads new game
else if(!loadSave){
drawSquares(scene, root);
}
I'll really appreciate your help.

I have special group for my Scene - root.
I can delete only this group using
root.getChildren().clear();
This feature has many uses, I can now eg add items that I want to remove into this group.
To remove only e.g Circles from group(where my Canvas is) I used
void clearScene(Group root) {
for (Circle circle : circles) {
root.getChildren().remove(circle);
}
circles.clear();
}

Integrating both canvas and pane with Line objects in JavaFX

Disclaimer: I am using Java and Javafx 11. Just putting it out there :)
I am in the process of trying to create an Interpreter for Logo, but have run into a roadblock. You see, I defaulted to using a canvas to display all the things I needed as that is fitting for what I am doing. However, I did not account for the fact that my Turtle needed to move.
private void drawTurtle()
{
vertices[0] = new Vector2(position.x, position.y + 15); // The three points that make the triangle that is the turtle
vertices[1] = new Vector2(position.x - 15, position.y);
vertices[2] = new Vector2(position.x + 15, position.y);
vertices[1] = Renderer.rotatePoint(vertices[1], position, rotation); // applying rotation to vertices
vertices[2] = Renderer.rotatePoint(vertices[2], position, rotation);
vertices[0] = Renderer.rotatePoint(vertices[0], position, rotation);
Renderer.drawLine(vertices[2], vertices[1], currentPen); // drawing the vertices
Renderer.drawLine(vertices[2], vertices[0], currentPen);
Renderer.drawLine(vertices[1], vertices[0], currentPen);
}
Trails left due to rotating the turtle in realtime.
In order to achieve this without leaving "trails", I tried to erase the existing turtle by drawing with a white pen over it. That gave me... weird results.
This is after rotating the turtle 360 degrees.
Then I came across a post here on SO talking about how I should use a Line object on a Pane if I wanted to move stuff. And well, I tried combining it with a canvas to make a CanvasPane:
public class CanvasPane extends Pane
{
public final Canvas canvas;
public CanvasPane(double width, double height)
{
setWidth(width);
setHeight(height);
canvas = new Canvas(width, height);
getChildren().add(canvas);
canvas.widthProperty().bind(this.widthProperty()); // Change this so this canvas does not scale with the pane, and its size is constant.
canvas.heightProperty().bind(this.heightProperty());
}
}
And added line objects to this so I can then edit their start and end values to make the turtle move, but I got nothing out of it, no line to show, and I am quite confused and don't know what to do. Nothing on the great internet helped my either, so I am now asking this question to see if anyone has ideas on how I can move my turtle flawlessly. And no, I can't use clearRect()
TLDR: My turtle leaves trails when moving on a canvas, and using Line and Pane doesn't work, and I can't use clearRect() on my canvas. Help!

Use one Pane to hold both the Canvas Node and your "turtle" Node.
Canvas canvas = new Canvas(640, 480);
Shape turtle = new Polygon(); // fill in the points
Pane p = new Pane(canvas, turtle);
Now you can control the position of the turtle node by either setting the layout coordinates or applying a translation. As it was added last, it will be drawn over the Canvas. (You could also use a StackPane to make that layering more explicit.)

How do I insert text into a shape in Javafx?

Using JavaFX I have created a simple rectangle object, and I want to be able to put a text object inside that rectangle, and for it to automatically stay aligned within the rectangle. The code I have to draw the rectangle is:
public static Scene createScene() {
Group root = new Group();
Scene scene = new Scene(root, Color.ALICEBLUE);
Rectangle rectangle_red = new Rectangle();
rectangle_red.setFill(Color.TRANSPARENT);
rectangle_red.setStroke(Color.BLACK);
rectangle_red.setX(50);
rectangle_red.setY(50);
rectangle_red.setWidth(200);
rectangle_red.setHeight(100);
rectangle_red.setCursor(Cursor.HAND);
rectangle_red.setOnMousePressed(circleOnMousePressedEventHandler);
rectangle_red.setOnMouseDragged(circleOnMouseDraggedEventHandler);
root.getChildren().add(rectangle_red);
return scene;
}
The Handlers I have attached to the rectangle allow me to drag the rectangles anywhere in the window. How do I place text inside the rectangle such that it stays aligned as I drag the shape around the screen?

As illustrated in the last example seen here, the Animation Basics example TimelineEvents does this by adding a Circle and some Text to a StackPane, which centers its children by default. The stack can then be moved within an enclosing Group as a unit.
final Circle circle = new Circle(…);
final Text text = new Text (…);
final StackPane stack = new StackPane();
stack.getChildren().addAll(circle, text);
…
stack.setLayoutX(30);
stack.setLayoutY(30);

Getting the absolute coordinates of a node in a BorderPane with some null regions

I have a set of custom made "buttons" for the menu screen of my game. It's basically a StackPane with a Rectangle and a Text node stacked. Basically this is similar to how my buttons are structured.
Pane button1 = new StackPane(new Rectangle(100, 50), new Text("Play!"));
Pane button2 = [....];
Then I insert buttons into a VBox and into my menu along with a header text:
VBox buttons = new VBox(button1, button2, button3...);
Pane menuScreen = new BorderPane(buttons, new Text("The Game"), null, null, null);
However, for my custom detection for mouse position compared to the buttons I need to know the buttons' positions...
int x = button1.getLayoutX(); //returns 0
int x = button1.getTranslateX(); //returns 0
int x = button1.localToScene(0, 0).getX(); //returns 0
int x = button1.localToScene(buttons.get(0).getBoundsInLocal()).getMinX(); //returns 0
int x = button1.localToScene(buttons.get(0).getBoundsInLocal()).getMaxX(); //returns the width of the entire scene
int x = buttons.get(0).getTranslateX(); //returns 0
int y = button1.localToScene(buttons.get(0).getBoundsInLocal()).getMinY();
The last case returns 234.0 if I have the VBox set with .setAlignment(Pos.CENTER) and 64.0 if I don't. But for .getMinX() it stays at 0.0 in either case. I believe it's related to the BorderPane's left/right/bot regions being set to null while the top region has the title text.
I cannot find any way of getting the x coordinate when the buttons are in a layout pane other than the Pane class itself. I tried StackPane as well. My suspicion is that there is no fixed coordinate and that properties are involved, but I only get confused from reading about it when I don't know what I'm looking for.
I have tried solutions from this quesion and this seems to be the same but as I mentioned I'm afraid my minX() doesn't have a set value since the VBox is the only thing filling the center row of my BorderPane.
Edit: StackPane seems to give the right values for .getMinX() when I use .setAlignment(Pos.CENTER), but I am not allowed to do that with the text, only with the VBox, so then the text gets stuck on top of the buttons.

My issue was cause by the VBox and my StackPanes taking up all the possible space, not just the area of the visible Rectangle. Problem was solved by calling setMaxWidth(100) on the StackPane which contained the Rectangle and the Text.
Also, the only problem seems to be that you have a zero x-coordinate. Maybe this is "real". Set a background on button1 to see where it is in the layout. – James_D

When adding a second item to my stackpane, the first item loses its Event/MouseOn. Why? How can I fix? JavaFX

I have a stackpane. When I add a second item to my stack pane, both show up, but I can't click on my first item anymore. It becomes 'unclickable'.
what ever I defined in my .setonmouse does not work. It works for my second item. If I switch the order they are in the stack pane, the other one works, but not both.
is there a fix for this? This is what my program looks like:
I want my 'grid' centered ALWAYS. There are buttons to the left centered in a column, there will be buttons on the right later on, and there will be buttons/Text on top of the grid and buttom in the margins later on too.
I want everything to be clickable.
http://img688.imageshack.us/img688/6025/examplerg.png

StackPane orders items in Z-order: latter above the former. So, your second item gots all mouse clicks and first one (being covered by second) doesn't get anything.
For layout you've described you can use BorderPane:
public void start(Stage stage) throws Exception {
BorderPane root = new BorderPane();
root.setCenter(new Rectangle(100,100, Color.RED));
root.setLeft(new Rectangle(10,10, Color.BLUE));
root.setRight(new Rectangle(10,10, Color.CYAN));
stage.setScene(new Scene(root,300,300));
stage.show();
}

You can make any Pane "mouse transparent", so that it doesn't consume any click events, and lets them pass through to the stack under it.
Here's some example code... this example sets up 4 panes in a stack, with just the mainPane accepting clicks to begin with.
StackPane rootPane = new StackPane();
VBox mainPane = new VBox(80);
BorderPane helpOverlayPane = new BorderPane();
helpOverlayPane.setMouseTransparent(true);
Canvas fullScreenOverlayCanvas = new Canvas();
fullScreenOverlayCanvas.setMouseTransparent(true);
VBox debugPane = new VBox();
debugPane.setAlignment(Pos.BASELINE_RIGHT);
AnchorPane debugOverlay = new AnchorPane();
debugOverlay.setMouseTransparent(true);
debugOverlay.getChildren().add(debugPane);
AnchorPane.setBottomAnchor(debugPane, 80.0);
AnchorPane.setRightAnchor(debugPane, 20.0);
rootPane.getChildren().addAll(mainPane, fullScreenOverlayCanvas, debugOverlay, helpOverlayPane);
Now, when you want to use your canvas to draw on top, make sure you change mouse transparent to false for just that stack, and keep all panes on top of it mouse transparent.
fullScreenOverlayCanvas.setMouseTransparent(false);
debugOverlay.setMouseTransparent(true);
fullScreenOverlayCanvas.setVisible(true);
doSomethingWithCanvasThatNeedsMouseClicks();
P.S. I did some editing of the code I had, so it may not run as-is. Also, see discussion of making only parts of panes transparent here:
JavaFX Pass MouseEvents through Transparent Node to Children