xamarin.forms - IOS 中的 Xamarin 表单选择器不会换行
问题描述
我正在尝试在 Xamarin 表单中制作自定义渲染器,以便选择器中的文本将为 IOS 换行。安卓运行良好。从周围阅读看来,我需要使用 UIPickerViewDelegate 来执行此操作。但是,当我这样做时.. 拾取器的损坏程度比以前更严重,并且基本上无法使用。如果我使用委托,那么选择器渲染得很好,但是当你选择一些东西时。任何事物。它始终是第一个被选中的项目。选择第 10 项,UI 显示第 1 项。您选择哪个项目并不重要。不知何故,选择器总是认为它是第一个。我没有故意做任何事情来影响所选项目。感觉就像我应该做的其他事情这些其他解决方案没有告诉我。
这是我的渲染器:
public class CustomPickerRenderer : PickerRenderer {
protected override void OnElementChanged(ElementChangedEventArgs<Picker> e) {
base.OnElementChanged(e);
if (Control != null) {
((UIPickerView)Control.InputView).Delegate = new CustomPickerViewDelegate();
}
}
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e) {
base.OnElementPropertyChanged(sender, e);
if (e.PropertyName.Equals("itemssource", StringComparison.InvariantCultureIgnoreCase)) {
((Control.InputView as UIPickerView).Delegate as CustomPickerViewDelegate).ItemSource = Element.ItemsSource;
}
}
}
这是我的 UIPickerViewDelegate
public class CustomPickerViewDelegate: UIPickerViewDelegate {
public IList ItemSource { get; set; }
public override UIView GetView(UIPickerView pickerView, nint row, nint component, UIView view) {
UILabel label = new UILabel();
label.Text = ItemSource[(int)row].ToString();
label.Lines = 0;
label.LineBreakMode = UILineBreakMode.WordWrap;
return label;
}
public override nfloat GetRowHeight(UIPickerView pickerView, nint component) {
return 48;
}
}
解决方案
我检查了本地站点中的某些代码,还发现单击Done
Button 后没有设置选定的值。为了解决这个问题,我们需要自定义一个UIToolbar来覆盖系统。
另外,当滚动结束时,不能自动选择值。我们需要在Selected
里面添加覆盖方法来为Control ( )CustomPickerViewDelegate
设置选择值。UITextField
CustomPickerRenderer的完整代码如下:
[assembly: ExportRenderer(typeof(Picker), typeof(CustomPickerRenderer))]
namespace MonkeyApp.iOS
{
public class CustomPickerRenderer : PickerRenderer
{
List<string> itemList;
protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
{
base.OnElementChanged(e);
if (Control != null)
{
//Control.BackgroundColor = UIColor.Red;
UITextField textField = Control;
UIPickerView pickerView = textField.InputView as UIPickerView;
Picker myPicker = Element;
itemList = myPicker.Items.ToList();
pickerView.Delegate = new CustomPickerViewDelegate(itemList, textField);
UIToolbar toolbar = new UIToolbar(new CoreGraphics.CGRect(0,0,UIScreen.MainScreen.Bounds.Size.Width,44));
UIBarButtonItem spaceItem = new UIBarButtonItem(UIBarButtonSystemItem.FlexibleSpace);
UIBarButtonItem doneButtonItem = new UIBarButtonItem(UIBarButtonSystemItem.Done);
doneButtonItem.Clicked += DoneButtonItem_Clicked;
var bbs = new UIBarButtonItem[] { spaceItem, doneButtonItem };
toolbar.SetItems(bbs, false);
Control.InputAccessoryView = toolbar;
}
}
private void DoneButtonItem_Clicked(object sender, EventArgs e)
{
Control.ResignFirstResponder();
}
}
internal class CustomPickerViewDelegate : UIPickerViewDelegate
{
private List<string> itemList;
private UITextField textField;
public CustomPickerViewDelegate(List<string> itemList, UITextField textField)
{
this.itemList = itemList;
this.textField = textField;
}
public override UIView GetView(UIPickerView pickerView, nint row, nint component, UIView view)
{
UILabel label = new UILabel();
label.Text = itemList[(int)row];
label.Lines = 0;
label.LineBreakMode = UILineBreakMode.WordWrap;
return label;
}
public override nfloat GetRowHeight(UIPickerView pickerView, nint component)
{
return 48;
}
public override void Selected(UIPickerView pickerView, nint row, nint component)
{
textField.Text = itemList[(int)row];
}
}
}
效果: