如何将带有完成按钮的工具栏添加到 UIPickerView？

Question

我想在 Xamarin.iOS 项目中有一个 UIPickerView。我需要的 UIPicker 必须是这样的（默认隐藏并带有工具栏和完成按钮）：

这是 Xamarin.forms 的一个示例！

我已经看到了关于堆栈溢出的所有问题，但它们不是我的情况，或者它们不是为此目的的完整解释。

为了证明我已经尝试过创建完成工具栏，这是我的代码：

public class TestPickerViewController : UIViewController
    {
        PickerModel picker_model;
        UIPickerView picker;

        public TestPickerViewController()

        {
            Title = Texts.Home;
            View.BackgroundColor = UIColor.White;
            this.EdgesForExtendedLayout = UIRectEdge.None;

        }

        public override void DidReceiveMemoryWarning()
        {
            // Releases the view if it doesn't have a superview.
            base.DidReceiveMemoryWarning();

            // Release any cached data, images, etc that aren't in use.
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();

            List<Object> state_list = new List<Object>();
            state_list.Add("1");
            state_list.Add("2");
            state_list.Add("3");
            state_list.Add("4");
            picker_model = new PickerModel(state_list);

            picker = new UIPickerView();
            picker.Model = picker_model;
            picker.ShowSelectionIndicator = true;



            UIToolbar toolbar = new UIToolbar();
            toolbar.BarStyle = UIBarStyle.Black;
            toolbar.Translucent = true;
            toolbar.SizeToFit();

            UIBarButtonItem doneButton = new UIBarButtonItem("Done", UIBarButtonItemStyle.Done, (s, e) =>
            {
                foreach (UIView view in this.View.Subviews)
                {
                    if (view.IsFirstResponder)
                    {
                        UITextField textview = (UITextField)view;
                        textview.Text = picker_model.values[(int)picker.SelectedRowInComponent(0)].ToString();
                        textview.ResignFirstResponder();
                    }
                }

            });
            toolbar.SetItems(new UIBarButtonItem[] { doneButton }, true);


            View.AddSubviews(picker);

            //How to add toolbar, action for opening toolbar and hide by default the list 
        }

        public override void ViewDidLayoutSubviews()
        {
            base.ViewDidLayoutSubviews();
            View.SubviewsDoNotTranslateAutoresizingMaskIntoConstraints();

            View.AddConstraints(

                picker.AtTopOf(View, 90),
                picker.AtLeftOf(View, 50),
                picker.WithSameWidth(View).Minus(100)
            );
        }


        private void SetPicker(object sender, EventArgs e)
        {
            UITextField field = (UITextField)sender;
            picker.Select(picker_model.values.IndexOf(field.Text), 0, true);
        }
    }

    public class PickerModel : UIPickerViewModel
    {
        public IList<Object> values;

        public event EventHandler<PickerChangedEventArgs> PickerChanged;

        public PickerModel(IList<Object> values)
        {
            this.values = values;
        }

        public override nint GetComponentCount(UIPickerView picker)
        {
            return 1;
        }

        public override nint GetRowsInComponent(UIPickerView picker, nint component)
        {
            return values.Count;
        }

        public override string GetTitle(UIPickerView picker, nint row, nint component)
        {
            return values[(int)row].ToString();
        }

        public override nfloat GetRowHeight(UIPickerView picker, nint component)
        {
            return 40f;
        }

        public override void Selected(UIPickerView picker, nint row, nint component)
        {
            if (this.PickerChanged != null)
            {
                this.PickerChanged(this, new PickerChangedEventArgs { SelectedValue = values[(int)row] });
            }
        }
    }

    public class PickerChangedEventArgs : EventArgs
    {
        public object SelectedValue { get; set; }
    }

我知道我必须将工具栏添加到已完成按钮的某处。而且我还需要隐藏默认选择器并在我们单击选择部分等时显示列表的操作...

Answer 1

只需将UIToolbar 分配给UITextField 的InputAccessoryView 属性即可。下面是一个代码 sn-p 示例：

UIToolbar toolBar = new UIToolbar(new CGRect(0, 0, 320, 44));
UIBarButtonItem flexibleSpaceLeft = new UIBarButtonItem(UIBarButtonSystemItem.FlexibleSpace,null,null);
UIBarButtonItem doneButton = new UIBarButtonItem("OK",UIBarButtonItemStyle.Done,this, new ObjCRuntime.Selector("DoneAction"));
UIBarButtonItem[] list = new UIBarButtonItem[] { flexibleSpaceLeft, doneButton };
toolBar.SetItems(list, false);

UIPickerView pickerView = new UIPickerView(new CGRect(0, 44, 320, 216));
pickerView.DataSource = new MyUIPickerViewDataSource();
pickerView.Delegate = new MyUIPickerViewDelegate();
pickerView.ShowSelectionIndicator = true;

//Assign the toolBar to InputAccessoryView 
textField.InputAccessoryView = toolBar;

textField.InputView = pickerView;

并像这样实现Action：

    [Export("DoneAction")]
    private void DoneAction()
    {
        Console.WriteLine("Your Action!");
    }

它是这样工作的：