我正在进行一个Xamarin项目,需要使用一个选择器。但是Xamarin的原生选择器没有ItemsSource属性。我找到了一种几乎可以使用的实现方式,如下所示:
using System;
using System.Collections;
using System.Linq;
using Xamarin.Forms;
namespace AnyNameSpace.Mobile.CustomControls
{
public class BindablePicker : Picker
{
public static readonly BindableProperty ItemsSourceProperty =
BindableProperty.Create(
"ItemSource",
typeof (IEnumerable),
typeof (BindablePicker),
default(IEnumerable),
BindingMode.TwoWay,
propertyChanged: OnItemsSourceChanged);
public static BindableProperty SelectedItemBindableProperty =
BindableProperty.Create(
"SelectedItemBindable",
typeof (object),
typeof (BindablePicker),
default(object),
BindingMode.TwoWay,
propertyChanged: OnSelectedItemChanged);
public IEnumerable ItemsSource
{
get { return (IEnumerable) GetValue(ItemsSourceProperty); }
set { SetValue(ItemsSourceProperty, value); }
}
public object SelectedItemBindable
{
get { return GetValue(SelectedItemBindableProperty); }
set { SetValue(SelectedItemBindableProperty, value); }
}
public BindablePicker()
{
SelectedIndexChanged += OnSelectedIndexChanged;
base.Title = "Seleccione"; // Here I want a custom title, but this is ignoring me :(
}
private static void OnItemsSourceChanged(BindableObject bindable, object oldvalue, object newvalue)
{
var picker = bindable as BindablePicker;
if (picker?.Items == null) return;
picker.Items.Clear();
if (newvalue == null) return;
foreach (var item in ((IEnumerable)newvalue).Cast<object>().Where(item => item != null))
picker.Items.Add(item.ToString());
}
private void OnSelectedIndexChanged(object sender, EventArgs eventArgs)
{
if (Items != null && (SelectedIndex < 0 || SelectedIndex > Items.Count - 1))
SelectedItemBindable = null;
else if (Items != null) SelectedItemBindable = Items[SelectedIndex];
}
private static void OnSelectedItemChanged(BindableObject bindable, object oldvalue, object newvalue)
{
var picker = bindable as BindablePicker;
if (newvalue == null) return;
if (picker?.Items != null) picker.SelectedIndex = picker.Items.IndexOf(newvalue.ToString());
}
}
}
所以问题是:当我在XAML或C#中设置标题属性时,标题属性总是显示“选择一个项目”。我已经尝试在构造函数中设置Picker的标题,但没有起作用。
我会非常感激任何帮助,谢谢。