我正致力于my Github repository的xamarin解决方案。对于Pins project，我遇到了问题。有一件事，如果您创建一个引脚（又名CustomPin()），然后，您想要编辑该位置。然后，如果更改地址，地址名称将更改并且位置相同，将根据地址名称创建位置。所以从这里开始，这很容易。
但是，当Pin地址/位置发生变化时，我希望我的Map更新本身。但是因为List＆lt;＆gt;属性不会更改，也不会更新地图。
那么，获取指向父列表或地图的指针？
但是这个解决方案似乎不适合我的使用，我想也许，另一个最好的解决方案存在，但我不知道该怎么办..
您可以编译项目，但有三个更新。
CustomPin
public class CustomPin : BindableObject
{
public static readonly BindableProperty AddressProperty =
BindableProperty.Create(nameof(Address), typeof(string), typeof(CustomPin), "",
propertyChanged: OnAddressPropertyChanged);
public string Address
{
get { return (string)GetValue(AddressProperty); }
set { SetValue(AddressProperty, value); }
}
private static async void OnAddressPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
(bindable as CustomPin).SetValue(LocationProperty, await CustomMap.GetAddressPosition(newValue as string));
}
public static readonly BindableProperty LocationProperty =
BindableProperty.Create(nameof(Location), typeof(Position), typeof(CustomPin), new Position(),
propertyChanged: OnLocationPropertyChanged);
public Position Location
{
get { return (Position)GetValue(LocationProperty); }
set { SetValue(LocationProperty, value); }
}
private static async void OnLocationPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
(bindable as CustomPin).SetValue(AddressProperty, await CustomMap.GetAddressName((Position)newValue));
Debug.WriteLine("private static async void OnLocationPropertyChanged(BindableObject bindable, object oldValue, object newValue)");
}
public string Name { get; set; }
public string Details { get; set; }
public string ImagePath { get; set; }
public uint PinSize { get; set; }
public uint PinZoomVisibilityMinimumLimit { get; set; }
public uint PinZoomVisibilityMaximumLimit { get; set; }
public Point AnchorPoint { get; set; }
public Action<CustomPin> PinClickedCallback { get; set; }
public CustomPin(Position location)
{
Location = location;
Name = "";
Details = "";
ImagePath = "";
PinSize = 50;
PinZoomVisibilityMinimumLimit = uint.MinValue;
PinZoomVisibilityMaximumLimit = uint.MaxValue;
AnchorPoint = new Point(0.5, 1);
PinClickedCallback = null;
}
public CustomPin(string address)
{
Address = address;
Name = "";
Details = "";
ImagePath = "";
PinSize = 50;
PinZoomVisibilityMinimumLimit = uint.MinValue;
PinZoomVisibilityMaximumLimit = uint.MaxValue;
AnchorPoint = new Point(0.5, 1);
PinClickedCallback = null;
}
public CustomPin()
{
Address = "";
Location = new Position();
Name = "";
Details = "";
ImagePath = "";
PinSize = 50;
PinZoomVisibilityMinimumLimit = uint.MinValue;
PinZoomVisibilityMaximumLimit = uint.MaxValue;
AnchorPoint = new Point(0.5, 1);
PinClickedCallback = null;
}
}
CustomMap | PS：只需添加这三种方法
#region
public async static Task<string> GetAddressName(Position position)
{
string url = "https://maps.googleapis.com/maps/api/geocode/json";
string additionnal_URL = "?latlng=" + position.Latitude + "," + position.Longitude
+ "&key=" + App.GOOGLE_MAP_API_KEY;
JObject obj = await CustomMap.GoogleAPIHttpRequest(url, additionnal_URL);
string address_name;
try
{
address_name = (obj["results"][0]["formatted_address"]).ToString();
}
catch (Exception)
{
return ("");
}
return (address_name);
}
public async static Task<Position> GetAddressPosition(string name)
{
string url = "https://maps.googleapis.com/maps/api/geocode/json";
string additionnal_URL = "?address=" + name
+ "&key=" + App.GOOGLE_MAP_API_KEY;
JObject obj = await CustomMap.GoogleAPIHttpRequest(url, additionnal_URL);
Position position;
try
{
position = new Position(Double.Parse((obj["results"][0]["geometry"]["location"]["lat"]).ToString()),
Double.Parse((obj["results"][0]["geometry"]["location"]["lng"]).ToString()));
}
catch (Exception)
{
position = new Position();
}
return (position);
}
private static async Task<JObject> GoogleAPIHttpRequest(string url, string additionnal_URL)
{
try
{
var client = new HttpClient();
client.BaseAddress = new Uri(url);
var content = new StringContent("{}", Encoding.UTF8, "application/json");
HttpResponseMessage response = null;
try
{
response = await client.PostAsync(additionnal_URL, content);
}
catch (Exception)
{
return (null);
}
string result = await response.Content.ReadAsStringAsync();
if (result != null)
{
try
{
return JObject.Parse(result);
}
catch (Exception)
{
return (null);
}
}
else
{
return (null);
}
}
catch (Exception)
{
return (null);
}
}
#endregion
MainPage.xaml.cs | PS：PCL部分，只需更改构造函数
即可 public MainPage()
{
base.BindingContext = this;
CustomPins = new List<CustomPin>()
{
new CustomPin("Long Beach") { Name = "Le Mans", Details = "Famous city for race driver !", ImagePath = "CustomIconImage.png", PinZoomVisibilityMinimumLimit = 0, PinZoomVisibilityMaximumLimit = 150, PinSize = 75},
new CustomPin() { Name = "Ruaudin", Details = "Where I'm coming from.", ImagePath = "CustomIconImage.png", PinZoomVisibilityMinimumLimit = 75, PinSize = 65 },
new CustomPin() { Name = "Chelles", Details = "Someone there.", ImagePath = "CustomIconImage.png", PinZoomVisibilityMinimumLimit = 50, PinSize = 70 },
new CustomPin() { Name = "Lille", Details = "Le nord..", ImagePath = "CustomIconImage.png", PinZoomVisibilityMinimumLimit = 44, PinSize = 40 },
new CustomPin() { Name = "Limoges", Details = "I have been there ! :o", ImagePath = "CustomIconImage.png", PinZoomVisibilityMinimumLimit = 65, PinSize = 20 },
new CustomPin() { Name = "Douarnenez", Details = "A trip..", ImagePath = "CustomIconImage.png", PinZoomVisibilityMinimumLimit = 110, PinSize = 50 }
};
Debug.WriteLine("Initialization done.");
PinActionClicked = PinClickedCallback;
PinsSize = Convert.ToUInt32(100);
MinValue = 50;
MaxValue = 100;
InitializeComponent();
Debug.WriteLine("Components done.");
}
也许它很容易，或者说我说它是唯一的方式，但我不知道如果引脚被编辑，如何在地图上更新引脚，因为最后，它仍然是同一个对象，所以列表没有不要改变......
感谢您的帮助！
好的，我做了一些更改，但它仍然无效..我的意思是我的代码按照我的意愿工作，但调用PropertyChanged并没有改变任何东西......
我更改了List<CustomPin>现在ObservableCollection<CustomPin>之类的内容。此外，我将xaml部分更改为：
<control:CustomMap x:Name="MapTest" CustomPins="{Binding CustomPins}" CameraFocusParameter="OnPins"
PinSize="{Binding PinsSize, Converter={StaticResource Uint}}"
PinClickedCallback="{Binding PinActionClicked}"
VerticalOptions="Fill" HorizontalOptions="Fill"/>
我的CustomPin现在就是这样：
public class CustomPin : BindableObject, INotifyPropertyChanged
{
/// <summary>
/// Handler for event of updating or changing the
/// </summary>
public event PropertyChangedEventHandler PropertyChanged;
public static readonly BindableProperty AddressProperty =
BindableProperty.Create(nameof(Address), typeof(string), typeof(CustomPin), "",
propertyChanged: OnAddressPropertyChanged);
public string Address
{
get { return (string)GetValue(AddressProperty); }
set { SetValue(AddressProperty, value); }
}
private static void OnAddressPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
(bindable as CustomPin).SetAddress(newValue as string);
Debug.WriteLine("Address property changed");
}
private async void SetAddress(string address)
{
if (setter == SetFrom.None)
{
setter = SetFrom.Address;
SetLocation(await CustomMap.GetAddressPosition(address));
setter = SetFrom.None;
NotifyChanges();
}
else if (setter == SetFrom.Location)
{
setter = SetFrom.Done;
SetValue(AddressProperty, address);
}
}
private enum SetFrom
{
Address,
Done,
Location,
None,
}
private SetFrom setter;
private async void SetLocation(Position location)
{
if (setter == SetFrom.None)
{
setter = SetFrom.Location;
SetAddress(await CustomMap.GetAddressName(location));
setter = SetFrom.None;
NotifyChanges();
}
else if (setter == SetFrom.Address)
{
setter = SetFrom.Done;
SetValue(LocationProperty, location);
}
}
public static readonly BindableProperty LocationProperty =
BindableProperty.Create(nameof(Location), typeof(Position), typeof(CustomPin), new Position(),
propertyChanged: OnLocationPropertyChanged);
public Position Location
{
get { return (Position)GetValue(LocationProperty); }
set { SetValue(LocationProperty, value); }
}
private static async void OnLocationPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
(bindable as CustomPin).SetLocation((Position)newValue);
Debug.WriteLine("Location property changed");
}
private void NotifyChanges()
{
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Address)));
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Location)));
}
public string Name { get; set; }
public string Details { get; set; }
public string ImagePath { get; set; }
public uint PinSize { get; set; }
public uint PinZoomVisibilityMinimumLimit { get; set; }
public uint PinZoomVisibilityMaximumLimit { get; set; }
public Point AnchorPoint { get; set; }
public Action<CustomPin> PinClickedCallback { get; set; }
public CustomPin(Position location)
{
setter = SetFrom.None;
Location = location;
Name = "";
Details = "";
ImagePath = "";
PinSize = 50;
PinZoomVisibilityMinimumLimit = uint.MinValue;
PinZoomVisibilityMaximumLimit = uint.MaxValue;
AnchorPoint = new Point(0.5, 1);
PinClickedCallback = null;
}
public CustomPin(string address)
{
setter = SetFrom.None;
Address = address;
Name = "";
Details = "";
ImagePath = "";
PinSize = 50;
PinZoomVisibilityMinimumLimit = uint.MinValue;
PinZoomVisibilityMaximumLimit = uint.MaxValue;
AnchorPoint = new Point(0.5, 1);
PinClickedCallback = null;
}
public CustomPin()
{
setter = SetFrom.None;
Address = "";
Location = new Position();
Name = "";
Details = "";
ImagePath = "";
PinSize = 50;
PinZoomVisibilityMinimumLimit = uint.MinValue;
PinZoomVisibilityMaximumLimit = uint.MaxValue;
AnchorPoint = new Point(0.5, 1);
PinClickedCallback = null;
}
}
最后，PropertyChanged的电话没有做任何事情......任何想法？
谢谢！
PS：不要忘记我的github存储库中提供了该解决方案
答案 0 :(得分：0)
您应该在Pin实施中使用INotifyPropertyChanged。这样，当您更新某些参数时，您会通知更改并可以更新地图。
答案 1 :(得分：0)
前一段时间面对类似的问题，为我解决的问题是改变了xaml中的绑定：
CustomPins="{Binding CustomPins}"
到此：
CustomPins="{Binding CustomPins, Mode=TwoWay}"
答案 2 :(得分：0)
我终于有了主意！在Xamarin表单中，App可以从任何地方加入，所以我做的是：
在MainPage.xaml.cs中创建一个调用PropertyChanged事件的方法。你可以这样做：
public void PinsCollectionChanged()
{
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(CustomPins)));
Debug.WriteLine("Updated !!!");
}
然后，从列表中的项目（对我来说，它是CustomPin对象），通过获取应用程序的当前实例来调用此方法。看一下代码来理解：
private void NotifyChanges()
{
(App.Current.MainPage as MainPage).PinsCollectionChanged();
}
PS：不要忘记在对象中添加using MapPinsProject.Page;。
希望它有所帮助！