LocationPicker

LocationPicker picks a geographic coordinate on a map, with GPS tracking and a draggable pin. It follows the picker pattern (see Picker) and returns a LatLon.

🔴 · Package: dev.crossfly.ui.picker · Extends: Picker · Hardware: GPS + map

When to use

Collect a location (delivery address, point of interest) on a map.

Appearance

Top bar with circular buttons (map type Normal/Satellite, back, confirm), the map (FILL) filling the body, a draggable pin with an accuracy circle (green/red according to the PDOP) and a status label at the bottom.

Complete example (copy, paste and run)

LocationPicker opens a full-screen map — trigger it from a Button. The example reuses the basic usage and shows the confirmed coordinate in a Label. LatLon comes from dev.crossfly.map.

package com.exemplo;

import dev.crossfly.map.LatLon;

import dev.crossfly.ui.*;
import dev.crossfly.ui.layout.*;
import dev.crossfly.ui.picker.*;

/** Runnable main screen. Point the launcher (classname) and run: gradlew :lwjgl3:run */
public class MainWindow extends Window
{
   @Override
   public void onShow() throws Exception
   {
      super.onShow();
      setLayout(new VerticalLayout());

      Label saida = new Label("Nenhuma coordenada");
      add(LAY_AUTO, saida);

      Button escolher = new Button("Escolher local no mapa")
         .onAction(c ->
         {
            LocationPicker lp = new LocationPicker(
               coord -> {},   // onCapture from the constructor (optional; can be null)
               10.0,          // minPdop
               true,          // the pin can be dragged
               true,          // high precision
               false);        // no street view

            lp.show(answer ->
            {
               LatLon ll = (LatLon) answer;
               if (ll != null)
                  saida.setText("Local: " + ll.lat + ", " + ll.lon);
            });
         });
      add(LAY_AUTO, escolher);
   }
}

The snippets below show only the core (what goes inside onShow()). To run them, place them in the MainWindow skeleton above.

Basic usage

LocationPicker lp = new LocationPicker(
   coord -> Debug.log("Capturado: " + coord.lat + "," + coord.lon),
   10.0,   // minPdop
   true,   // the pin can be dragged
   true,   // high precision
   false); // no street view

lp.show(answer ->
{
   LatLon ll = (LatLon) answer;
   salvarLocal(ll.lat, ll.lon);
});

Constructors

Constructor	Description
`LocationPicker(RunnableWith<LatLon> onCapture, double minPdop, boolean canDragPin, boolean highPrecision, boolean streetview)`	See parameters below.

Parameter	Type	What it does
`onCapture`	`RunnableWith<LatLon>`	Callback with the `LatLon` on confirmation (may be `null`).
`minPdop`	`double`	Maximum acceptable PDOP; confirm stays hidden until it is reached.
`canDragPin`	`boolean`	Allows dragging the pin to a manual location.
`highPrecision`	`boolean`	Turns on high-precision GPS.
`streetview`	`boolean`	Enables street view on the map.

Callbacks and events

Callback	When it fires
`onCapture` (constructor)	on confirmation, with the `LatLon` (if `!= null`).
`show(onAnswer)`	on closing, delivers the confirmed `LatLon`.

getAnswer() returns the confirmed LatLon, or null if canceled. There are two paths to the result (the constructor’s onCapture and the show’s onAnswer) — both only fire when answer != null.

States

Dragging the pin turns off the GPS (canUpdateGPS = false), marks “Custom Location” and reveals confirm.
The confirm button only appears when the accuracy is acceptable (or on desktop, or after a manual drag).
Resources (GPS thread, Location, map) are released exactly once on close.

Best practices

Choose a realistic minPdop; on mobile the confirm stays hidden until the GPS reaches it.
Do not reuse the instance after hide() — the GPS/map resources are released.

Common mistakes

Confirm never appearing — GPS did not reach minPdop and the user did not drag the pin (on desktop it appears immediately).
Expecting onAnswer on cancellation — it does not fire (answer = null).