packages/google_maps_flutter/google_maps_flutter/example/lib/tile_overlay.dart

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// ignore_for_file: public_member_api_docs

import 'dart:typed_data';
import 'dart:ui' as ui;

import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

import 'page.dart';

class TileOverlayPage extends GoogleMapExampleAppPage {
  const TileOverlayPage({Key? key})
      : super(const Icon(Icons.map), 'Tile overlay', key: key);

  @override
  Widget build(BuildContext context) {
    return const TileOverlayBody();
  }
}

class TileOverlayBody extends StatefulWidget {
  const TileOverlayBody({Key? key}) : super(key: key);

  @override
  State<StatefulWidget> createState() => TileOverlayBodyState();
}

class TileOverlayBodyState extends State<TileOverlayBody> {
  TileOverlayBodyState();

  GoogleMapController? controller;
  TileOverlay? _tileOverlay;

  // ignore: use_setters_to_change_properties
  void _onMapCreated(GoogleMapController controller) {
    this.controller = controller;
  }

  @override
  void dispose() {
    super.dispose();
  }

  void _removeTileOverlay() {
    setState(() {
      _tileOverlay = null;
    });
  }

  void _addTileOverlay() {
    final TileOverlay tileOverlay = TileOverlay(
      tileOverlayId: const TileOverlayId('tile_overlay_1'),
      tileProvider: _DebugTileProvider(),
    );
    setState(() {
      _tileOverlay = tileOverlay;
    });
  }

  void _clearTileCache() {
    if (_tileOverlay != null && controller != null) {
      controller!.clearTileCache(_tileOverlay!.tileOverlayId);
    }
  }

  @override
  Widget build(BuildContext context) {
    final Set<TileOverlay> overlays = <TileOverlay>{
      if (_tileOverlay != null) _tileOverlay!,
    };
    return Column(
      mainAxisSize: MainAxisSize.min,
      mainAxisAlignment: MainAxisAlignment.spaceEvenly,
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: <Widget>[
        Center(
          child: SizedBox(
            width: 350.0,
            height: 300.0,
            child: GoogleMap(
              initialCameraPosition: const CameraPosition(
                target: LatLng(59.935460, 30.325177),
                zoom: 7.0,
              ),
              tileOverlays: overlays,
              onMapCreated: _onMapCreated,
            ),
          ),
        ),
        TextButton(
          onPressed: _addTileOverlay,
          child: const Text('Add tile overlay'),
        ),
        TextButton(
          onPressed: _removeTileOverlay,
          child: const Text('Remove tile overlay'),
        ),
        TextButton(
          onPressed: _clearTileCache,
          child: const Text('Clear tile cache'),
        ),
      ],
    );
  }
}

class _DebugTileProvider implements TileProvider {
  _DebugTileProvider() {
    boxPaint.isAntiAlias = true;
    boxPaint.color = Colors.blue;
    boxPaint.strokeWidth = 2.0;
    boxPaint.style = PaintingStyle.stroke;
  }

  static const int width = 100;
  static const int height = 100;
  static final Paint boxPaint = Paint();
  static const TextStyle textStyle = TextStyle(
    color: Colors.red,
    fontSize: 20,
  );

  @override
  Future<Tile> getTile(int x, int y, int? zoom) async {
    final ui.PictureRecorder recorder = ui.PictureRecorder();
    final Canvas canvas = Canvas(recorder);
    final TextSpan textSpan = TextSpan(
      text: '$x,$y',
      style: textStyle,
    );
    final TextPainter textPainter = TextPainter(
      text: textSpan,
      textDirection: TextDirection.ltr,
    );
    textPainter.layout(
      maxWidth: width.toDouble(),
    );
    textPainter.paint(canvas, Offset.zero);
    canvas.drawRect(
        Rect.fromLTRB(0, 0, width.toDouble(), width.toDouble()), boxPaint);
    final ui.Picture picture = recorder.endRecording();
    final Uint8List byteData = await picture
        .toImage(width, height)
        .then((ui.Image image) =>
            image.toByteData(format: ui.ImageByteFormat.png))
        .then((ByteData? byteData) => byteData!.buffer.asUint8List());
    return Tile(width, height, byteData);
  }
}