JavaFX with Geotools Tutorial – Part 2: Interacting with the User
Interacting with the user.
Previously we can use Geotools to load a shape file, so now we will implement user interacting.
Listening the mouse event
We will listen mouse event for
- drag map
- double clicked to restore to original state
- scroll to zoom in and out
Create a method initEvent()in MapCanvas class.
private double baseDrageX;
private double baseDrageY;
/*
* initial for mouse event
*/
private void initEvent() {
/*
* setting the original coordinate
*/
canvas.addEventHandler(MouseEvent.MOUSE_PRESSED, new EventHandler<MouseEvent>() {
@Override
public void handle(MouseEvent e) {
baseDrageX = e.getSceneX();
baseDrageY = e.getSceneY();
e.consume();
}
});
/*
* translate according to the mouse drag
*/
canvas.addEventHandler(MouseEvent.MOUSE_DRAGGED, new EventHandler<MouseEvent>() {
@Override
public void handle(MouseEvent e) {
double difX = e.getSceneX() - baseDrageX;
double difY = e.getSceneY() - baseDrageY;
baseDrageX = e.getSceneX();
baseDrageY = e.getSceneY();
DirectPosition2D newPos = new DirectPosition2D(difX, difY);
DirectPosition2D result = new DirectPosition2D();
map.getViewport().getScreenToWorld().transform(newPos, result);
ReferencedEnvelope env = new ReferencedEnvelope(map.getViewport().getBounds());
env.translate(env.getMinimum(0) - result.x, env.getMaximum(1) - result.y);
doSetDisplayArea(env);
e.consume();
}
});
/*
* double clicks to restore to original map
*/
canvas.addEventHandler(MouseEvent.MOUSE_CLICKED, new EventHandler<MouseEvent>() {
@Override
public void handle(MouseEvent t) {
if (t.getClickCount() > 1) {
doSetDisplayArea(map.getMaxBounds());
}
t.consume();
}
});
/*
* scroll for zoom in and out
*/
canvas.addEventHandler(ScrollEvent.SCROLL, new EventHandler<ScrollEvent>() {
@Override
public void handle(ScrollEvent e) {
ReferencedEnvelope envelope = map.getViewport().getBounds();
double percent = e.getDeltaY() / canvas.getWidth();
double width = envelope.getWidth();
double height = envelope.getHeight();
double deltaW = width * percent;
double deltaH = height * percent;
envelope.expandBy(deltaW, deltaH);
doSetDisplayArea(envelope);
e.consume();
}
});
}
protected void doSetDisplayArea(ReferencedEnvelope envelope) {
map.getViewport().setBounds(envelope);
repaint = true;
}
Painting improvement
We do not repaint every events cause it will overload CPU and making the application lagging.
Create ScehduleService to paint for 50.0 hz
private static final double PAINT_HZ = 50.0;
private void initPaintThread() {
ScheduledService<Boolean> svc = new ScheduledService<Boolean>() {
protected Task<Boolean> createTask() {
return new Task<Boolean>() {
protected Boolean call() {
Platform.runLater(() -> {
drawMap(gc);
});
return true;
}
};
}
};
svc.setPeriod(Duration.millis(1000.0 / PAINT_HZ));
svc.start();
}
Update method drawMap(GraphicsContext gc) to redraw when event occur.
private boolean repaint = true;
private void drawMap(GraphicsContext gc) {
if (!repaint) {
return;
}
repaint = false;
StreamingRenderer draw = new StreamingRenderer();
draw.setMapContent(map);
FXGraphics2D graphics = new FXGraphics2D(gc);
graphics.setBackground(java.awt.Color.WHITE);
graphics.clearRect(0, 0, (int) canvas.getWidth(), (int) canvas.getHeight());
Rectangle rectangle = new Rectangle((int) canvas.getWidth(), (int) canvas.getHeight());
draw.paint(graphics, rectangle, map.getViewport().getBounds());
}