private bool IsTileNext(TileSpecifier specifier)
{
lock (SleepingDownloads)
{
return(specifier.IsEqualTo(SleepingDownloads.Last()));
}
}
private void SetTileDownloading(TileSpecifier specifier)
{
lock (CurrentDownloads)
{
CurrentDownloads.Add(specifier);
}
}
private void EnqueueTile(TileSpecifier specifier)
{
lock (SleepingDownloads)
{
SleepingDownloads.Add(specifier);
}
}
private async Task <ImageSource> GetImageAsyncImpl(TileSpecifier specifier)
{
byte[] image = await GetCachedImageAsync(specifier);
if (image == null)
{
EnqueueTile(specifier);
while (GetCountDownloading() >= MAX_DOWNLOADS || !IsTileNext(specifier))
{
await Task.Delay(500);
}
SetTileDownloading(specifier);
DequeueTile(specifier);
Task <byte[]> downloadedImage = DownloadImageAsync(specifier);
CacheImageAsync(specifier, await downloadedImage);
image = await downloadedImage;
SetTileFinishedDownloading(specifier);
}
MemoryStream imageStream = new MemoryStream(image);
BitmapImage bitmap = new BitmapImage();
bitmap.BeginInit();
bitmap.StreamSource = imageStream;
bitmap.EndInit();
return(bitmap);
}
private void SetTileFinishedDownloading(TileSpecifier specifier)
{
lock (CurrentDownloads)
{
CurrentDownloads.Remove(specifier);
}
}
public bool IsEqualTo(TileSpecifier other)
{
return(Coordinate == other.Coordinate &&
MapType == other.MapType &&
Size == other.Size &&
Zoom == other.Zoom);
}
private void DequeueTile(TileSpecifier specifier)
{
lock (SleepingDownloads)
{
if (SleepingDownloads.Contains(specifier))
{
SleepingDownloads.Remove(specifier);
}
}
}
private async Task <byte[]> DownloadImageAsync(TileSpecifier spec)
{
StringBuilder uriBuilder = new StringBuilder("https://maps.googleapis.com/maps/api/staticmap");
uriBuilder.AppendFormat("?key={0}", API_KEY);
uriBuilder.AppendFormat("¢er={0},{1}", spec.Coordinate.Latitude, spec.Coordinate.Longitude);
uriBuilder.AppendFormat("&maptype={0}", spec.MapType.ToString().ToLower());
uriBuilder.AppendFormat("&size={0}x{1}", spec.Size.Width, spec.Size.Height);
uriBuilder.AppendFormat("&zoom={0}", spec.Zoom);
var client = new WebClient();
var data = client.DownloadDataTaskAsync(uriBuilder.ToString());
return(await data);
}
private void CacheImageAsync(TileSpecifier spec, byte[] image)
{
Task ignore = Task.Run(() =>
{
using (SQLiteCommand command = new SQLiteCommand(SqlStrings.WRITE_IMAGE, DbConnection))
{
command.Parameters.AddWithValue("@latitude", spec.Coordinate.Latitude);
command.Parameters.AddWithValue("@longitude", spec.Coordinate.Longitude);
command.Parameters.AddWithValue("@width", spec.Size.Width);
command.Parameters.AddWithValue("@height", spec.Size.Height);
command.Parameters.AddWithValue("@zoom", spec.Zoom);
command.Parameters.AddWithValue("@mapType", spec.MapType);
command.Parameters.AddWithValue("@pngData", image);
command.Parameters.AddWithValue("@pngDataLen", image.Length);
command.ExecuteNonQuery();
}
});
}
public async Task <ImageSource> GetImageAsync(TileSpecifier specifier)
{
if (!specifier.IsValidCoordinate())
{
return(null);
}
if (Cache.ContainsKey(specifier))
{
RequeueTile(specifier);
return(await Cache[specifier]);
}
Task <ImageSource> task = GetImageAsyncImpl(specifier);
Cache.Add(specifier, task);
return(await task);
}
private async Task <byte[]> GetCachedImageAsync(TileSpecifier spec)
{
byte[] buffer = null;
using (SQLiteCommand command = new SQLiteCommand(SqlStrings.GET_IMAGE, DbConnection))
{
command.Parameters.AddWithValue("@latitude", spec.Coordinate.Latitude);
command.Parameters.AddWithValue("@longitude", spec.Coordinate.Longitude);
command.Parameters.AddWithValue("@width", spec.Size.Width);
command.Parameters.AddWithValue("@height", spec.Size.Height);
command.Parameters.AddWithValue("@zoom", spec.Zoom);
command.Parameters.AddWithValue("@mapType", spec.MapType);
using (SQLiteDataReader reader = await Task.Run(() => command.ExecuteReader()))
{
if (reader.Read())
{
int length = reader.GetInt32(1);
buffer = new byte[length];
reader.GetBytes(0, 0, buffer, 0, length);
}
}
}
return(buffer);
}
