Xamarin表单布局创建重叠视图

1 回答

• 0

  我有完全相同的问题，我使用自定义渲染器修复它 . 这允许用户键入以过滤列表选项，然后在用户选择一个时将所选选项放入条目中 . 在您的表单项目中，您将需要一个新的条目子类：

  public class AutofillTextView : Entry
  {
      public static BindableProperty ChoicesSourceProperty = BindableProperty.Create(
              nameof(ChoicesSource), typeof(ObservableCollection<string>), typeof(CustomPicker), 
              default(ObservableCollection<string>), propertyChanged: OnChoicesSourceChanged);
  
      public ObservableCollection<string> ChoicesSource
      {
          get { return (ObservableCollection<string>)GetValue(ChoicesSourceProperty); }
          set { SetValue(ChoicesSourceProperty, value); }
      }
      public AutofillTextView()
      {
          Items = new List<string>();
      }
  
      private void ChoicesChanged(object sender, NotifyCollectionChangedEventArgs args)
      {
          switch (args.Action)
          {
              case NotifyCollectionChangedAction.Add:
                  Items.Add(args.NewItems[0]);
                  break;
  
              default:
                  var itemsList = ChoicesSource.ToList();
                  Items = itemsList;
                  break;
          }
          OnPropertyChanged(nameof(Items));
      }
  
      private static void OnChoicesSourceChanged(BindableObject bindable, object oldValue, object newValue)
      {
          var textView = (AutofillTextView) bindable;
          textView.ChoicesSource.CollectionChanged -= textView.ChoicesChanged;
          textView.ChoicesSource.CollectionChanged += textView.ChoicesChanged;
          textView.Items = newValue == null ? new List<string>() : ((ObservableCollection<string>)newValue).ToList();
      }
  }
  

  您可能需要对此进行扩展，但我从不从列表中删除项目，因此切换对我来说已经足够了 . 我也需要使用可观察的集合，因此您可以通过切换到列表来简化 . 无论如何，接下来你需要在droid中使用自定义渲染器：

  [assembly: ExportRenderer(typeof(AutofillTextView), typeof(AutofillTextViewRenderer))]
  
  namespace Default
  {
      public class AutofillTextViewRenderer : ViewRenderer<AutofillTextView, InstantAutoCompleteTextView>
      {
          protected override void OnElementChanged(ElementChangedEventArgs<AutofillTextView> e)
          {
              base.OnElementChanged(e);
  
              if (Control == null)
              {
                  var control = new InstantAutoCompleteTextView(Forms.Context);
  
                  control.InputType = Android.Text.InputTypes.ClassText | Android.Text.InputTypes.TextFlagNoSuggestions;
                  control.Text = Element.Text;
                  SetNativeControl(control);
              }
  
              if (e.OldElement != null)
              {
  
              }
  
              if (e.NewElement != null)
              {
                  var adapter = new ArrayAdapter<string>(Forms.Context as Android.App.Activity, Resource.Layout.AutofillTextViewItem, e.NewElement.Items.ToArray<string>());
                  Control.Adapter = adapter;
                  Control.Threshold = 0;
                  Control.TextChanged += Control_TextChanged;
                  adapter.NotifyDataSetChanged();
              }
          }
  
          void Control_TextChanged(object sender, Android.Text.TextChangedEventArgs e)
          {
              if (Element.Text != Control.Text)
              {
                  Element.Text = Control.Text;
              }
          }
  
          protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
          {
              base.OnElementPropertyChanged(sender, e);
              if (e.PropertyName == AutofillTextView.ItemsProperty.PropertyName)
              {
                  var adapter = new ArrayAdapter<string>(Forms.Context as Android.App.Activity, Resource.Layout.AutofillTextViewItem, Element.Items.ToArray<string>());
                  Control.Adapter = adapter;
                  adapter.NotifyDataSetChanged();
              } 
              else if(e.PropertyName == AutofillTextView.TextProperty.PropertyName)
              {
                  if(Control.Text != Element.Text)
                  {
                      Control.Text = Element.Text;
                  }
              } else if(e.PropertyName == AutofillTextView.IsFocusedProperty.PropertyName) {
                  if(Element.IsFocused)
                      Control.PerformFiltering();
              }
          }
  
  
      }
  }
  

  这会将您的自定义类（AutofillTextView）连接到Android类（InstantAutoCompleteTextView）以替换默认的条目渲染器 . 我不使用内置AutoCompleteTextView的原因是因为在您键入至少一个字符之前它不会显示下拉列表 . 我更喜欢它在焦点上显示 . 如果你不在乎你可以跳过它 . 这是该观点：

  public class InstantAutoCompleteTextView : AutoCompleteTextView 
  {
  
      public InstantAutoCompleteTextView(Context context) : base(context) {}
  
      public InstantAutoCompleteTextView(Context arg0, IAttributeSet arg1) : base(arg0, arg1){}
  
      public InstantAutoCompleteTextView(Context arg0, IAttributeSet arg1, int arg2) : base(arg0, arg1, arg2){}
  
      public override bool EnoughToFilter() {
          return true;
      }
  
      public void PerformFiltering()
      {
          PerformFiltering(Text, 0);
      }
  }
  

  回复于 2024-05-16T21:53:00+08:00