我在Xamarin Forms项目中通过这个精彩的post在右侧成功实现了带有向下图标的选择器，但是当选择器中的文本很长（比选择器控件的宽度）时，文本与向下的图像重叠，这看起来非常糟糕。
基本上，向下图标可绘制图像被设置为背景可绘制，所以我尝试在自定义渲染器中使用Control.Foreground，但是我得到了这个错误 - “Java.Lang.LinkageError：没有非静态方法”。
...
if (Control != null && this.Element != null && !string.IsNullOrEmpty(element.Image))
Control.Background = AddPickerStyles(element.Image);
...
请协助。如果你指出文本省略号的任何解决方案（即...，像iOS这样的选择器中的长文本点）会非常有用，在此先感谢
注意：这显然不是iOS中的问题。
是的，正如LandLu所说，你可以添加SetPadding来解决这个问题：
if (Control != null && this.Element != null && !string.IsNullOrEmpty(element.Image))
{
Control.Background = AddPickerStyles(element.Image);
Control.SetPadding(5, 0, 70, 0); //Add code here
}
或者在AddPickerStyles方法中修改：
public LayerDrawable AddPickerStyles(string imagePath)
{
ShapeDrawable border = new ShapeDrawable();
border.Paint.Color = Android.Graphics.Color.Gray;
border.SetPadding(10,10,10,10);
border.Paint.SetStyle(Paint.Style.Stroke);
Drawable[] layers = { border , GetDrawable(imagePath) };
LayerDrawable layerDrawable = new LayerDrawable(layers);
layerDrawable.SetLayerInset(0, 0, 0, 0, 0);
layerDrawable.SetPadding(5,0,70,0); // Add code here
return layerDrawable;
}
但这隐藏了大量文本，适用于较小分辨率的设备，如Moto E和更大的分辨率设备平板电脑，如Nexus 9 ..任何解决方案..
如果您的意思是弹出对话框视图隐藏部分文本，下面是一种解决方法。您可以自定义弹出对话框，让对话框居中。
IElementController ElementController => Element as IElementController;
private AlertDialog _dialog;
要修改对话框，需要自定义Control click方法：
if (Control != null && this.Element != null && !string.IsNullOrEmpty(element.Image))
{
...
Control.Click += Control_Click
}
...
private void Control_Click(object sender, EventArgs e)
{
var picker = new NumberPicker(Context);
picker.DescendantFocusability = DescendantFocusability.BlockDescendants;
if (model.Items != null && model.Items.Any())
{
// set style here
picker.MaxValue = model.Items.Count - 1;
picker.MinValue = 0;
//picker.SetBackgroundColor(Android.Graphics.Color.Yellow);
picker.SetDisplayedValues(model.Items.ToArray());
picker.WrapSelectorWheel = false;
picker.Value = model.SelectedIndex;
}
var layout = new LinearLayout(Context) { Orientation = Orientation.Vertical };
layout.AddView(picker);
ElementController.SetValueFromRenderer(VisualElement.IsFocusedProperty, true);
var builder = new AlertDialog.Builder(Context);
builder.SetView(layout);
builder.SetTitle(model.Title ?? "");
builder.SetNegativeButton("Cancel ", (s, a) =>
{
ElementController.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
// It is possible for the Content of the Page to be changed when Focus is changed.
// In this case, we'll lose our Control.
Control?.ClearFocus();
_dialog = null;
});
builder.SetPositiveButton("Ok ", (s, a) =>
{
ElementController.SetValueFromRenderer(Picker.SelectedIndexProperty, picker.Value);
// It is possible for the Content of the Page to be changed on SelectedIndexChanged.
// In this case, the Element & Control will no longer exist.
if (Element != null)
{
if (model.Items.Count > 0 && Element.SelectedIndex >= 0)
Control.Text = model.Items[Element.SelectedIndex];
ElementController.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
// It is also possible for the Content of the Page to be changed when Focus is changed.
// In this case, we'll lose our Control.
Control?.ClearFocus();
}
_dialog = null;
});
_dialog = builder.Create();
_dialog.DismissEvent += (ssender, args) =>
{
ElementController?.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
};
_dialog.Show();
var metrics = Resources.DisplayMetrics;
Window dialogWindow = _dialog.Window;
WindowManagerLayoutParams p = dialogWindow.Attributes;
// set width
p.Width = metrics.WidthPixels;
p.Gravity = GravityFlags.Center;
p.Alpha = 0.8f;
dialogWindow.Attributes = p;
}
最后是上述两个问题的完整解决方案代码：
public class CustomPickerRenderer : PickerRenderer
{
CustomPicker element;
IElementController ElementController => Element as IElementController;
private AlertDialog _dialog;
protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
{
base.OnElementChanged(e);
element = (CustomPicker)this.Element;
if (Control != null && this.Element != null && !string.IsNullOrEmpty(element.Image))
{
Control.Background = AddPickerStyles(element.Image);
//Control.SetPadding(5, 0, 70, 0);
Control.Click += Control_Click;
}
}
private void Control_Click(object sender, EventArgs e)
{
//throw new NotImplementedException();
Picker model = Element;
var picker = new NumberPicker(Context);
picker.DescendantFocusability = DescendantFocusability.BlockDescendants;
if (model.Items != null && model.Items.Any())
{
// set style here
picker.MaxValue = model.Items.Count - 1;
picker.MinValue = 0;
//picker.SetBackgroundColor(Android.Graphics.Color.Yellow);
picker.SetDisplayedValues(model.Items.ToArray());
picker.WrapSelectorWheel = false;
picker.Value = model.SelectedIndex;
}
var layout = new LinearLayout(Context) { Orientation = Orientation.Vertical };
layout.AddView(picker);
ElementController.SetValueFromRenderer(VisualElement.IsFocusedProperty, true);
var builder = new AlertDialog.Builder(Context);
builder.SetView(layout);
builder.SetTitle(model.Title ?? "");
builder.SetNegativeButton("Cancel ", (s, a) =>
{
ElementController.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
// It is possible for the Content of the Page to be changed when Focus is changed.
// In this case, we'll lose our Control.
Control?.ClearFocus();
_dialog = null;
});
builder.SetPositiveButton("Ok ", (s, a) =>
{
ElementController.SetValueFromRenderer(Picker.SelectedIndexProperty, picker.Value);
// It is possible for the Content of the Page to be changed on SelectedIndexChanged.
// In this case, the Element & Control will no longer exist.
if (Element != null)
{
if (model.Items.Count > 0 && Element.SelectedIndex >= 0)
Control.Text = model.Items[Element.SelectedIndex];
ElementController.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
// It is also possible for the Content of the Page to be changed when Focus is changed.
// In this case, we'll lose our Control.
Control?.ClearFocus();
}
_dialog = null;
});
_dialog = builder.Create();
_dialog.DismissEvent += (ssender, args) =>
{
ElementController?.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
};
_dialog.Show();
var metrics = Resources.DisplayMetrics;
Window dialogWindow = _dialog.Window;
WindowManagerLayoutParams p = dialogWindow.Attributes;
// set width
p.Width = metrics.WidthPixels;
p.Gravity = GravityFlags.Center;
p.Alpha = 0.8f;
dialogWindow.Attributes = p;
}
public LayerDrawable AddPickerStyles(string imagePath)
{
ShapeDrawable border = new ShapeDrawable();
border.Paint.Color = Android.Graphics.Color.Gray;
border.SetPadding(10,10,10,10);
border.Paint.SetStyle(Paint.Style.Stroke);
Drawable[] layers = { border , GetDrawable(imagePath) };
LayerDrawable layerDrawable = new LayerDrawable(layers);
layerDrawable.SetLayerInset(0, 0, 0, 0, 0);
layerDrawable.SetPadding(5,0,80,0);
return layerDrawable;
}
private BitmapDrawable GetDrawable(string imagePath)
{
int resID = Resources.GetIdentifier(imagePath, "drawable", this.Context.PackageName);
var drawable = ContextCompat.GetDrawable(this.Context, resID);
var bitmap = ((BitmapDrawable)drawable).Bitmap;
var result = new BitmapDrawable(Resources, Bitmap.CreateScaledBitmap(bitmap, 70, 70, true));
result.Gravity = Android.Views.GravityFlags.Right;
return result;
}
protected override void Dispose(bool disposing)
{
Control.Click -= Control_Click;
base.Dispose(disposing);
}
}
我最终使用的网格在每个列中都有一个选择器和图像，如xamarin论坛讨论中所给出的那样。这很好用！
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*"/>
</Grid.ColumnDefinitions>
<userControl:BindablePicker Grid.Row="0" Grid.Column="0" ItemsSource="{Binding x, Mode=TwoWay}" SelectedItem="{Binding x}"/>
<Image Grid.Row="0" Grid.Column="0" Source="arrow.png" HeightRequest="x" WidthRequest="x" InputTransparent="True" HorizontalOptions="End" VerticalOptions="Center"/>
</Grid>
注意：我使用上面的XAML代码来处理我的情况，因为我的下拉数量非常少，也因为我没有任何其他方法可以解决这个问题。