Xamarin 谷歌地图自动完成

Question

我正在尝试在我的 Xamarin 表单映射的 Xamarin 表单上的自定义搜索栏（我正在使用条目）中添加自动完成服务，但我无法这样做。

我已经尝试过使用 XLabs，但没有成功，到目前为止我还没有找到任何其他解决方案。

Xamarin.FormsMaps 是否包含任何自动完成功能？或者我可能会在 Xamarin 上缺少任何自动完成功能？ 你给我推荐什么？如果您需要任何代码或其他任何内容，请告诉我。

Answer 1

这是一个很长的内容，但这里有……显然，您希望将服务调用代码放在服务class 中，并将所有其他代码放在ViewModel 中。您可能还希望在服务调用方法中或周围添加更多的 null 和错误检查。

我忽略的一个重要部分是 Google 要求在执行搜索时显示 Google 徽标。所以下载their icon 并将其添加到用户界面。我只在用户关注Entry 时显示它。

这些是 Places 模型和我自己的 Address 模型：

public class AddressInfo {

    public string Address { get; set; }

    public string City { get; set; }

    public string State { get; set; }

    public string ZipCode { get; set; }

    public double Longitude { get; set; }

    public double Latitude { get; set; }
}

public class PlacesMatchedSubstring {

    [Newtonsoft.Json.JsonProperty("length")]
    public int Length { get; set; }

    [Newtonsoft.Json.JsonProperty("offset")]
    public int Offset { get; set; }
}

public class PlacesTerm {

    [Newtonsoft.Json.JsonProperty("offset")]
    public int Offset { get; set; }

    [Newtonsoft.Json.JsonProperty("value")]
    public string Value { get; set; }
}

public class Prediction {

    [Newtonsoft.Json.JsonProperty("id")]
    public string Id { get; set; }

    [Newtonsoft.Json.JsonProperty("description")]
    public string Description { get; set; }

    [Newtonsoft.Json.JsonProperty("matched_substrings")]
    public List<PlacesMatchedSubstring> MatchedSubstrings { get; set; }

    [Newtonsoft.Json.JsonProperty("place_id")]
    public string PlaceId { get; set; }

    [Newtonsoft.Json.JsonProperty("reference")]
    public string Reference { get; set; }

    [Newtonsoft.Json.JsonProperty("terms")]
    public List<PlacesTerm> Terms { get; set; }

    [Newtonsoft.Json.JsonProperty("types")]
    public List<string> Types { get; set; }
}

public class PlacesLocationPredictions {

    [Newtonsoft.Json.JsonProperty("predictions")]
    public List<Prediction> Predictions { get; set; }

    [Newtonsoft.Json.JsonProperty("status")]
    public string Status { get; set; }
}

这里我们调用 Places API：

public const string GooglePlacesApiAutoCompletePath = "https://maps.googleapis.com/maps/api/place/autocomplete/json?key={0}&input={1}&components=country:us"; //Adding country:us limits results to us

public const string GooglePlacesApiKey = "bTafrOPmO4LpPgAl34r5wQ6LFRWhgTxBW80-3GK";

private static HttpClient _httpClientInstance;
public static HttpClient HttpClientInstance => _httpClientInstance ?? (_httpClientInstance = new HttpClient());

private ObservableCollection<AddressInfo> _addresses;
public  ObservableCollection<AddressInfo> Addresses {
    get => _addresses ?? (_addresses = new ObservableCollection<AddressInfo>());
    set {
        if(_addresses != value) {
            _addresses = value;
            OnPropertyChanged();
        }
    };
}

private string _addressText;
public  string AddressText {
    get => _addressText;
    set {
        if(_addressText != value) {
            _addressText = value;
            OnPropertyChanged();
        }
    };
}

public async Task GetPlacesPredictionsAsync() {

    // TODO: Add throttle logic, Google begins denying requests if too many are made in a short amount of time

    CancellationToken cancellationToken = new CancellationTokenSource(TimeSpan.FromMinutes(2)).Token;

    using(HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, string.Format(GooglePlacesApiAutoCompletePath, ConstantKeys.GooglePlacesApiKey, WebUtility.UrlEncode(_addressText)))) { //Be sure to UrlEncode the search term they enter

        using(HttpResponseMessage message = await HttpClientInstance.SendAsync(request, HttpCompletionOption.ResponseContentRead, cancellationToken).ConfigureAwait(false)) {
            if(message.IsSuccessStatusCode) {
                string json = await message.Content.ReadAsStringAsync().ConfigureAwait(false);

                PlacesLocationPredictions predictionList = await Task.Run(() => JsonConvert.DeserializeObject<PlacesLocationPredictions>(json)).ConfigureAwait(false);

                if(predictionList.Status == "OK") {

                    Addresses.Clear();

                    if(predictionList.Predictions.Count > 0) {
                        foreach(Prediction prediction in predictionList.Predictions) {
                            Addresses.Add(new AddressInfo {
                                Address = prediction.Description
                            });
                        }
                    }
                } else {
                    throw new Exception(predictionList.Status);
                }
            }
        }
    }
}

现在是 UI...

    <Entry Text="{Binding AddressText}"
           TextChanged="OnTextChanged" />

    <ListView ItemsSource="{Binding Addresses}">
      <ListView.ItemTemplate>
        <DataTemplate>
          <TextCell Text="{Binding Address}"/>
        </DataTemplate>
      </ListView.ItemTemplate>
    </ListView>

以及后面的代码：

private async void OnTextChanged(object sender, EventArgs eventArgs) {
    if(!string.IsNullOrWhiteSpace(ViewModel.AddressText)) {
        await ViewModel.GetPlacesPredictionsAsync();
    }
}