JavaFx 2 - Draw line overlap axis - javafx-2

Question

With a left mouse click then mouse moved, a line is drawned on this line chart, and also on axis.
I would like to draw line only on chart so that it does not overlap x or y axis. How to accomplish this?
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.geometry.Side;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.scene.control.Label;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Line;
import javafx.scene.shape.LineTo;
import javafx.scene.shape.MoveTo;
import javafx.scene.shape.Path;
import javafx.stage.Stage;
public class LinesEdit extends Application {
Path path;
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage stage) {
final CategoryAxis xAxis = new CategoryAxis();
final NumberAxis yAxis = new NumberAxis(1, 21, 0.1);
yAxis.setTickUnit(1);
yAxis.setPrefWidth(35);
yAxis.setMinorTickCount(10);
yAxis.setSide(Side.RIGHT);
yAxis.setTickLabelFormatter(new NumberAxis.DefaultFormatter(yAxis) {
#Override
public String toString(Number object) {
String label;
label = String.format("%7.2f", object.floatValue());
return label;
}
});
final LineChart<String, Number> lineChart = new LineChart<String, Number>(xAxis, yAxis);
lineChart.setCreateSymbols(false);
lineChart.setAlternativeRowFillVisible(false);
lineChart.setLegendVisible(false);
XYChart.Series series1 = new XYChart.Series();
series1.getData().add(new XYChart.Data("Jan", 1));
series1.getData().add(new XYChart.Data("Feb", 4));
series1.getData().add(new XYChart.Data("Mar", 2.5));
series1.getData().add(new XYChart.Data("Apr", 5));
series1.getData().add(new XYChart.Data("May", 6));
series1.getData().add(new XYChart.Data("Jun", 8));
series1.getData().add(new XYChart.Data("Jul", 12));
series1.getData().add(new XYChart.Data("Aug", 8));
series1.getData().add(new XYChart.Data("Sep", 11));
series1.getData().add(new XYChart.Data("Oct", 13));
series1.getData().add(new XYChart.Data("Nov", 10));
series1.getData().add(new XYChart.Data("Dec", 20));
BorderPane bp = new BorderPane();
bp.setCenter(lineChart);
Scene scene = new Scene(bp, 800, 600);
lineChart.setAnimated(false);
lineChart.getData().addAll(series1);
LinesEdit.MouseHandler mh = new LinesEdit.MouseHandler( bp );
bp.setOnMouseClicked( mh );
bp.setOnMouseMoved( mh );
stage.setScene(scene);
path = new Path();
path.setStrokeWidth(1);
path.setStroke(Color.BLACK);
scene.setOnMouseDragged(mh);
scene.setOnMousePressed(mh);
bp.getChildren().add(path);
stage.setScene(scene);
stage.show();
}
class MouseHandler implements EventHandler< MouseEvent > {
private boolean gotFirst = false;
private Line line;
private Pane pane;
private double x1, y1, x2, y2;
private LineHandler lineHandler;
public MouseHandler( Pane pane ) {
this.pane = pane;
lineHandler = new LineHandler(pane);
}
class LineHandler implements EventHandler< MouseEvent > {
double x, y;
Pane pane;
public LineHandler(Pane pane){
this.pane = pane;
}
#Override
public void handle( MouseEvent e ) {
Line l = (Line) e.getSource();
// remove line on right click
if( e.getEventType() == MouseEvent.MOUSE_PRESSED
&& e.isSecondaryButtonDown() ) {
pane.getChildren().remove( l );
} else if( e.getEventType() == MouseEvent.MOUSE_DRAGGED
&& e.isPrimaryButtonDown() ) {
double tx = e.getX();
double ty = e.getY();
double dx = tx - x;
double dy = ty - y;
l.setStartX( l.getStartX() + dx );
l.setStartY( l.getStartY() + dy );
l.setEndX( l.getEndX() + dx );
l.setEndY( l.getEndY() + dy );
x = tx;
y = ty;
} else if( e.getEventType() == MouseEvent.MOUSE_ENTERED ) {
// just to show that the line is selected
x = e.getX();
y = e.getY();
l.setStroke( Color.RED );
} else if( e.getEventType() == MouseEvent.MOUSE_EXITED ) {
l.setStroke( Color.BLACK );
}
// should not pass event to the parent
e.consume();
}
}
#Override
public void handle( MouseEvent event ) {
if( event.getEventType() == MouseEvent.MOUSE_CLICKED ) {
if( !gotFirst ) {
x1 = x2 = event.getX();
y1 = y2 = event.getY();
line = new Line( x1, y1, x2, y2 );
pane.getChildren().add( line );
gotFirst = true;
}
else {
line.setOnMouseEntered( lineHandler );
line.setOnMouseExited( lineHandler );
line.setOnMouseDragged( lineHandler );
line.setOnMousePressed( lineHandler );
// to consume the event
line.setOnMouseClicked( lineHandler );
line.setOnMouseReleased( lineHandler );
line = null;
gotFirst = false;
}
}
else {
if( line != null ) {
x2 = event.getX();
y2 = event.getY();
// update line
line.setEndX( x2 );
line.setEndY( y2 );
}
}
}
}
}

Answer 1

The first thing to know is that many JavaFX UI-Element like charts consist of many underlying children. The part where you want to draw is in fact a Region that is part of a Pane that is child of the LineChart. I really recommend you to use ScenicView, because it shows exactly how your scene graph (including built-in UI-Components) looks like.
Back to your problem: your listeners should only apply to the Region which shows the actual representation of the data. That Region ends exactly where the x and y axis are. The following code will get you that Region and make it the target for your listeners:
//your previous code in start()...
Pane p = (Pane) lineChart.getChildrenUnmodifiable().get(1);
Region r = (Region) p.getChildren().get(0);
LinesEdit.MouseHandler mh = new LinesEdit.MouseHandler(r);
r.setOnMouseClicked(mh);
r.setOnMouseMoved(mh);
stage.setScene(scene);
path = new Path();
path.setStrokeWidth(1);
path.setStroke(Color.BLACK);
r.setOnMouseDragged(mh);
r.setOnMousePressed(mh);
bp.getChildren().add(path);
stage.setScene(scene);
//the following code.....
The next steps are:
1. rewrite your handler methods, so that they accept a `Region` object as parameter
2. rewrite a bit of your line-setting code. Background: you cannot add objects into a `Region` because you cannot access the writable `List` of childrens. So you have to put the lines into the `Pane` object which holds the `Region`. Because every JavaFX UI-Element has its own coordinate system, you have to calculate the offset between the `Pane` and the `Region`, because the `Pane` is a bit larger. If you don't do this, your line will be drawn slightly above the mousepointer. You can get the width and height of a `Pane` and/or `Region` by calling `xyz.getBoundsInLocal().getWidth()/height()`.
UPDATE: Full Solution as requested
As requested in the comments i will show one way to solve this problem. Have a look at your GUI in this picture. It shows all graphical elements in ScenicView. As you can see, the Pane is bigger than the inner Region. Important for us is to know that the origin of all coordinate systems in JavaFX start at the upper left corner of an element. In this scenario, you have to add a line to the Pane, but in respect to the borders of the Region. In the code-snippet i showed earlier i added all of your listeners to the region, which means we get the mouse coordinates inside the coordinate system of the region. Now we have to "translate" or better "transform" these coordinates (the points you wish to set the start or endpoints of the line) into the coordinate system of the Pane (the place the line is actually placed, read above why), because we want the line to start exactly where our mouse is. There is a method you can call to get a transformation matrix: r.getLocalToParentTransform(). We need this matrix because we have to get the exact values for the x and y translation that is applied to the Region (you can see that the Region is approximatly 10 pixels moved from the Panes origin in both x and y axes)
I wrote a simple method for getting the x and y translation between the Region and the Pane: getCoordDiff(Region r, Pane p).
The rest of start() method remains unchanged (but with the changes i wrote earlier). But the handle() methods of MouseHandler and LineHandler have to be modified.
public class LinesEdit extends Application
{
Path path;
public double[] getCoordDiff(Region r, Pane p)
{
//Acquires transformation matrix and returns x and y offset/translation from parent
double[] diffs =
{ r.getLocalToParentTransform().getTx(), r.getLocalToParentTransform().getTy() };
return diffs;
}
public static void main(String[] args)
{
launch(args);
}
#Override
public void start(Stage stage)
{
final CategoryAxis xAxis = new CategoryAxis();
final NumberAxis yAxis = new NumberAxis(1, 21, 0.1);
yAxis.setTickUnit(1);
yAxis.setPrefWidth(35);
yAxis.setMinorTickCount(10);
yAxis.setSide(Side.RIGHT);
yAxis.setTickLabelFormatter(new NumberAxis.DefaultFormatter(yAxis)
{
#Override
public String toString(Number object)
{
String label;
label = String.format("%7.2f", object.floatValue());
return label;
}
});
final LineChart<String, Number> lineChart = new LineChart<String, Number>(xAxis, yAxis);
lineChart.setCreateSymbols(false);
lineChart.setAlternativeRowFillVisible(false);
lineChart.setLegendVisible(false);
XYChart.Series series1 = new XYChart.Series();
series1.getData().add(new XYChart.Data("Jan", 1));
series1.getData().add(new XYChart.Data("Feb", 4));
series1.getData().add(new XYChart.Data("Mar", 2.5));
series1.getData().add(new XYChart.Data("Apr", 5));
series1.getData().add(new XYChart.Data("May", 6));
series1.getData().add(new XYChart.Data("Jun", 8));
series1.getData().add(new XYChart.Data("Jul", 12));
series1.getData().add(new XYChart.Data("Aug", 8));
series1.getData().add(new XYChart.Data("Sep", 11));
series1.getData().add(new XYChart.Data("Oct", 13));
series1.getData().add(new XYChart.Data("Nov", 10));
series1.getData().add(new XYChart.Data("Dec", 20));
BorderPane bp = new BorderPane();
bp.setCenter(lineChart);
Scene scene = new Scene(bp, 800, 600);
lineChart.setAnimated(false);
lineChart.getData().addAll(series1);
Pane p = (Pane) lineChart.getChildrenUnmodifiable().get(1);
Region r = (Region) p.getChildren().get(0);
LinesEdit.MouseHandler mh = new LinesEdit.MouseHandler(r);
r.setOnMouseClicked(mh);
r.setOnMouseMoved(mh);
stage.setScene(scene);
path = new Path();
path.setStrokeWidth(1);
path.setStroke(Color.BLACK);
r.setOnMouseDragged(mh);
r.setOnMousePressed(mh);
bp.getChildren().add(path);
stage.setScene(scene);
ScenicView.show(scene);
stage.show();
}
class MouseHandler implements EventHandler<MouseEvent>
{
private boolean gotFirst = false;
private Line line;
private Region reg;
private double x1, y1, x2, y2;
private LineHandler lineHandler;
public MouseHandler(Region reg)
{
this.reg = reg;
lineHandler = new LineHandler(reg);
}
class LineHandler implements EventHandler<MouseEvent>
{
double x, y;
Region reg;
public LineHandler(Region reg)
{
this.reg = reg;
}
#Override
public void handle(MouseEvent e)
{
Line l = (Line) e.getSource();
l.setStrokeWidth(3);
// remove line on right click
if (e.getEventType() == MouseEvent.MOUSE_PRESSED && e.isSecondaryButtonDown())
{
((Pane) reg.getParent()).getChildren().remove(l);
}
else if (e.getEventType() == MouseEvent.MOUSE_DRAGGED && e.isPrimaryButtonDown())
{
double tx = e.getX();
double ty = e.getY();
double dx = tx - x;
double dy = ty - y;
l.setStartX(l.getStartX() + dx);
l.setStartY(l.getStartY() + dy);
l.setEndX(l.getEndX() + dx);
l.setEndY(l.getEndY() + dy);
x = tx;
y = ty;
}
else if (e.getEventType() == MouseEvent.MOUSE_ENTERED)
{
// just to show that the line is selected
x = e.getX();
y = e.getY();
l.setStroke(Color.RED);
}
else if (e.getEventType() == MouseEvent.MOUSE_EXITED)
{
l.setStroke(Color.BLACK);
}
// should not pass event to the parent
e.consume();
}
}
#Override
public void handle(MouseEvent event)
{
if (event.getEventType() == MouseEvent.MOUSE_CLICKED)
{
double[] diff = getCoordDiff(reg, (Pane) reg.getParent());
if (!gotFirst)
{
//add translation to start/endcoordinates
x1 = x2 = event.getX() + diff[0];
y1 = y2 = event.getY() + diff[1];
line = new Line(x1, y1, x2, y2);
line.setStrokeWidth(3);
((Pane) reg.getParent()).getChildren().add(line);
gotFirst = true;
line.setOnMouseClicked(new EventHandler<Event>()
{
#Override
public void handle(Event arg0)
{
line.setOnMouseEntered(lineHandler);
line.setOnMouseExited(lineHandler);
line.setOnMouseDragged(lineHandler);
line.setOnMousePressed(lineHandler);
// to consume the event
line.setOnMouseClicked(lineHandler);
line.setOnMouseReleased(lineHandler);
line = null;
gotFirst = false;
}
});
}
}
else
{
if (line != null)
{
double[] diff = getCoordDiff(reg, (Pane) reg.getParent());
//add translation to end coordinates
x2 = event.getX() + diff[0];
y2 = event.getY() + diff[1];
// update line
line.setEndX(x2);
line.setEndY(y2);
}
}
}
}
}
You can see the parts where i add the translation values to the lines start and endpoints. This is needed so that line really starts and ends at the points where your mouse is. I moved your code that was executed if gotFirst == true, because it prevented the user to place the line (so that it doesn't follow the cursor). Background: your cursor is now always (pixel perfect) at the end of the line , which doesn't have a 'Listener' at the moment you place it the first time. That missing listener prevents the MouseEvent-click from going to the Region. In short: the "Click" event is now always done on the line itself, thats why we need a listener before the line is finally placed.
Remaining bugs: a line cannot be placed on the yellow lines of the graph. Thats because the click-event is not triggerd on the lines. I might fix that bug at a later time, or you try yourself.