Google Place Autocomplete in Xamarin.Forms

Question

是否有人使用Xamarin.Forms集成了Google Place自动完成功能？我将在地图上使用它来提供位置建议。我只看到Xamarin.Android和Xamarin.iOS的资源，但实现AutoCompleteView的部分，我也不知道。如果有人能指导我，我会非常感激。谢谢！

Answer 1

通过使用Google Place API可以实现地方自动完成功能，无论何时用户输入一个字符，匹配的位置和输入的字符都会从Google服务器获取并绑定回用户界面。

这里的链接如何使用谷歌地图将API在Xamarin形式： http://www.appliedcodelog.com/2015/05/google-place-api-with-autocomplete-in.html

另外，请阅读谷歌官方Places API的Web服务： https://developers.google.com/places/web-service/autocomplete

Answer 2

对于iOS

[assembly: ExportRenderer(typeof(CustomAutoCompleteLocation), typeof(CustomAutoCompleteRenderer))] 
namespace Aesthetic.iOS.Renderer 
{ 
    public class CustomAutoCompleteProfileRenderer : EntryRenderer 
    { 
     IntPtr inptr; 
     string tx = "1"; 
     CustomAutoCompleteLocation _view; 
     Place place; 
     UITextField textView; 

     public UIWindow Window 
     { 
      get; 
      set; 
     } 
     protected override void OnElementChanged(ElementChangedEventArgs<Entry> e) 
     { 
      base.OnElementChanged(e); 

      _view = (CustomAutoCompleteLocation)Element; 
      if (Control != null) 
      { 
       textView = (UITextField)Control; 
       textView.Font = UIFont.FromName("Lato-Light", textView.Font.PointSize); 
       textView.BorderStyle = UITextBorderStyle.Line; 
       textView.Layer.BorderWidth = 1f; 
       textView.Layer.CornerRadius = 0f; 
       // do whatever you want to the textField here! 

       UIView paddingView = new UIView(new RectangleF(10, 16, 10, 16)); 
       textView.LeftView = paddingView; 
       textView.LeftViewMode = UITextFieldViewMode.Always; 
      } 
     } 
     protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e) 
     { 
      var x = sender as CustomAutoComplete; 

      if (e.PropertyName == "IsFocused") 
      { 
       if (tx == "1") 
       { 
        Device.BeginInvokeOnMainThread(() => 
        { 

         Window = new UIWindow(UIScreen.MainScreen.Bounds); 


         var controller = new LocationViewController(); 

         Window.RootViewController = controller; 
         // make the window visible 
         Window.MakeKeyAndVisible(); 
         controller.PlaceSelected1 += HandlePlaceSelection; 
        }); 
        tx = "2"; 
       } 
       else if (tx == "2") tx = "3"; 
       else if (tx == "3") tx = "4"; 
       else if (tx == "4") tx = "1"; 
      } 
     } 

     private void HandlePlaceSelection(object sender, string locationData) 
     { 

      textView.Text = locationData; 
      Window.Hidden = true; 
     } 
    } 
} 

这是位置视图控制器

public partial class LocationViewController : UIViewController 
    { 
     public delegate void PlaceSelected(object sender, string locationData); 
     UITextField txtLocation; 
     public UIView backgroundView; 
     // UITextView txtLocation; 
     UIImageView googleAttribution; 
     UITableView tableViewLocationAutoComplete; 

     public event PlaceSelected PlaceSelected1; 
     public string strSampleString { get; set; } 
     LocationPredictionClass objAutoCompleteLocationClass; 
     string strAutoCompleteQuery; 
     LocationAutoCompleteTableSource objLocationAutoCompleteTableSource; 

     public LocationViewController() : base() 
     { 

     } 

     public override void ViewDidLoad() 
     { 
      base.ViewDidLoad(); 
      FnInitializeView(); 
      FnClickEventInit(); 
     } 

     void FnInitializeView() 
     { 


      backgroundView = new UIView(View.Frame); 
      backgroundView.BackgroundColor = UIColor.White; 
      View.AddSubview(backgroundView); 

      txtLocation = new UITextField(); 
      txtLocation.Frame = new CoreGraphics.CGRect(20, 20, View.Frame.Width-20, 45.0f); 
      txtLocation.TranslatesAutoresizingMaskIntoConstraints = false; 
      txtLocation.ReturnKeyType = UIReturnKeyType.Done; 
      txtLocation.BackgroundColor = UIColor.FromRGB(221,221,221); 
      txtLocation.TextColor = UIColor.Black; 

      View.AddSubview(txtLocation); 

      txtLocation.BecomeFirstResponder(); 

      tableViewLocationAutoComplete = new UITableView(); 
      tableViewLocationAutoComplete.Frame = new CoreGraphics.CGRect(txtLocation.Frame.X, txtLocation.Frame.Height+ txtLocation.Frame.Y, View.Frame.Width, View.Frame.Height - txtLocation.Frame.Height - txtLocation.Frame.Y); 
      tableViewLocationAutoComplete.BackgroundColor = UIColor.White; 
      tableViewLocationAutoComplete.Source = objLocationAutoCompleteTableSource; 
      View.AddSubview(tableViewLocationAutoComplete); 

      tableViewLocationAutoComplete.Hidden = false; 
      txtLocation.ShouldReturn += (textField) => textField.ResignFirstResponder(); 

      StringBuilder builderLocationAutoComplete = new StringBuilder(Constants.strPlacesAutofillUrl); 
      builderLocationAutoComplete.Append("?input={0}").Append("&key=").Append(Constants.strGooglePlaceAPILey); 
      strAutoCompleteQuery = builderLocationAutoComplete.ToString(); 
      builderLocationAutoComplete.Clear(); 
      builderLocationAutoComplete = null; 
     } 

     void FnClickEventInit() 
     { 
      txtLocation.EditingChanged += async delegate (object sender, EventArgs e) 
      { 
       if (string.IsNullOrWhiteSpace(txtLocation.Text)) 
       { 
        tableViewLocationAutoComplete.Hidden = true; 
       } 
       else 
       { 
        if (txtLocation.Text.Length > 2) 
        { 

         //Autofill 
         string strFullURL = string.Format(strAutoCompleteQuery, txtLocation.Text); 
         objAutoCompleteLocationClass = await RestRequestClass.LocationAutoComplete(strFullURL); 


         if (objAutoCompleteLocationClass != null && objAutoCompleteLocationClass.status == "OK") 
         { 
          if (objAutoCompleteLocationClass.predictions.Count > 0) 
          { 
           if (objLocationAutoCompleteTableSource != null) 
           { 
            objLocationAutoCompleteTableSource.LocationRowSelectedEventAction -= LocationSelectedFromAutoFill; 
            objLocationAutoCompleteTableSource = null; 
           } 

           tableViewLocationAutoComplete.Hidden = false; 
           objLocationAutoCompleteTableSource = new LocationAutoCompleteTableSource(objAutoCompleteLocationClass.predictions); 
           objLocationAutoCompleteTableSource.LocationRowSelectedEventAction += LocationSelectedFromAutoFill; 
           tableViewLocationAutoComplete.Source = objLocationAutoCompleteTableSource; 
           tableViewLocationAutoComplete.ReloadData(); 
          } 
          else 
           tableViewLocationAutoComplete.Hidden = true; 
         } 
         else 
         { 
          tableViewLocationAutoComplete.Hidden = true; 
         } 
        } 
       } 
      }; 

     } 

     void LocationSelectedFromAutoFill(Prediction objPrediction) 
     { 
      DismissViewController(true, null); 
      Console.WriteLine(objPrediction.description); 
      PlaceSelected1(this, objPrediction.description); 
      txtLocation.ResignFirstResponder(); 
     } 
    } 

    public class RestRequestClass 
    { 
     static async Task<string> CallService(string strURL) 
     { 
      WebClient client = new WebClient(); 
      string strResult; 
      try 
      { 
       strResult = await client.DownloadStringTaskAsync(new Uri(strURL)); 
      } 
      catch 
      { 
       strResult = "Exception"; 
      } 
      finally 
      { 
       client.Dispose(); 
       client = null; 
      } 
      return strResult; 
     } 

     internal static async Task<LocationPredictionClass> LocationAutoComplete(string strFullURL) 
     { 
      LocationPredictionClass objLocationPredictClass = null; 
      LocationPredictionClass objLocationPredictClass12 = new LocationPredictionClass(); 
      objLocationPredictClass12.predictions = new List<Prediction>(); 
      string strResult = await CallService(strFullURL); 
      if (strResult != "Exception") 
      { 
       objLocationPredictClass = JsonConvert.DeserializeObject<LocationPredictionClass>(strResult); 
      } 

      foreach (Prediction objPred in objLocationPredictClass.predictions) 
      { 
       if (objPred.types[0] == "country") 
       { 
        objLocationPredictClass12.predictions.Add(objPred); 
        objLocationPredictClass12.status = "OK"; 
       } 
      } 


      // string[] strPredictiveText = new string[data.Count]; 
      //int index = 0; 
      // foreach (Prediction objPred in data) 
      // { 
      //  strPredictiveText[index] = objPred.description; 
      //  index++; 
      // } 

      return objLocationPredictClass12; 
     } 

    } 


    public class MatchedSubstring 
    { 
     public int length { get; set; } 
     public int offset { get; set; } 
    } 

    public class Term 
    { 
     public int offset { get; set; } 
     public string value { get; set; } 
    } 

    public class Prediction 
    { 
     public string description { get; set; } 
     public string id { get; set; } 
     public List<MatchedSubstring> matched_substrings { get; set; } 
     public string place_id { get; set; } 
     public string reference { get; set; } 
     public List<Term> terms { get; set; } 
     public List<string> types { get; set; } 
    } 

    public class LocationPredictionClass 
    { 
     public List<Prediction> predictions { get; set; } 
     public string status { get; set; } 
    } 

    public class Constants 
    { 
     public static string strGooglePlaceAPILey = "AIzaSyBXJntNIs2aAvKIRwrgCEwOGwnigbSWep8"; 
     public static string strPlacesAutofillUrl = "https://maps.googleapis.com/maps/api/place/autocomplete/json"; 
    } 

    public class LocationAutoCompleteTableSource : UITableViewSource 
    { 
     const string strCellIdentifier = "Cell"; 
     readonly List<Prediction> lstLocations; 
     internal event Action<Prediction> LocationRowSelectedEventAction; 

     public LocationAutoCompleteTableSource(List<Prediction> arrItems) 
     { 
      lstLocations = arrItems; 
     } 

     public override nint RowsInSection(UITableView tableview, nint section) 
     { 
      return lstLocations.Count; 

     } 

     public override UIView GetViewForFooter(UITableView tableView, nint section) 
     { 
      return new UIView(); 
     } 

     public override UITableViewCell GetCell(UITableView tableView, Foundation.NSIndexPath indexPath) 
     { 
      UITableViewCell cell = tableView.DequeueReusableCell(strCellIdentifier) ?? new UITableViewCell(UITableViewCellStyle.Default, strCellIdentifier); 
      cell.TextLabel.Text = lstLocations[indexPath.Row].description; 
      cell.TextLabel.Font = UIFont.SystemFontOfSize(12); 
      return cell; 
     } 
     public override void RowSelected(UITableView tableView, Foundation.NSIndexPath indexPath) 
     { 
      if (LocationRowSelectedEventAction != null) 
      { 
       LocationRowSelectedEventAction(lstLocations[indexPath.Row]); 
      } 
      tableView.DeselectRow(indexPath, true); 
     } 
    } 
}