那些遇到过的问题

基于文本输入的WPF组合框动态滤波器

Bob*_*Bob 5 wpf combobox

我似乎无法找到一种直接的方法来实现将文本输入过滤到WPF组合框中的项目列表中.
通过将IsTextSearchEnabled设置为true,comboBox下拉列表将跳转到第一个匹配项目的任何内容.我需要的是将列表过滤到与文本字符串匹配的任何内容(例如,如果我专注于我的组合框并键入'abc',我希望看到ItemsSource集合中的所有项目以(或最好包含)开头)'abc'作为下拉列表的成员).

我怀疑它有所不同,但我的显示项目模板化为复杂类型的属性:

<ComboBox x:Name="DiagnosisComboBox" Grid.Row="3" Grid.Column="1" Grid.ColumnSpan="3" 
          ItemsSource="{Binding Path = ApacheDxList,
                                UpdateSourceTrigger=PropertyChanged,
                                Mode=OneWay}"
          IsTextSearchEnabled="True"
          ItemTemplate="{StaticResource DxDescriptionTemplate}" 
          SelectedValue="{Binding Path = SelectedEncounterDetails.Diagnosis,
                                  Mode=TwoWay,
                                  UpdateSourceTrigger=PropertyChanged}"/>
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谢谢.

Jor*_*rdi 13

基于这个答案，我补充道：

  • 能够将用户输入限制为InputSourceusingOnlyValuesInList属性中提供的值。
  • 使用 Esc 键清除过滤器
  • 处理向下箭头键打开组合框。
  • 处理退格键不会清除选择，只会过滤文本。
  • 隐藏辅助类和方法
  • 删除了不必要的方法
  • 添加的SelectionEffectivelyChanged事件仅在用户离开控件或按 Enter 键时触发，就像在从标准 ComboBox 中过滤事件的过程中SelectionChanged多次触发一样。
  • 添加的EffectivelySelectedItem属性仅在用户离开控件或按 Enter 键时更改，就像在从标准 ComboBox 中过滤项目的过程中SelectedItem多次更改一样。
public class FilterableComboBox : ComboBox
{
    /// <summary>
    /// If true, on lost focus or enter key pressed, checks the text in the combobox. If the text is not present
    /// in the list, it leaves it blank.
    /// </summary>
    public bool OnlyValuesInList {
        get => (bool)GetValue(OnlyValuesInListProperty);
        set => SetValue(OnlyValuesInListProperty, value);
    }
    public static readonly DependencyProperty OnlyValuesInListProperty =
        DependencyProperty.Register(nameof(OnlyValuesInList), typeof(bool), typeof(FilterableComboBox));

    /// <summary>
    /// Selected item, changes only on lost focus or enter key pressed
    /// </summary>
    public object EffectivelySelectedItem {
        get => (bool)GetValue(EffectivelySelectedItemProperty);
        set => SetValue(EffectivelySelectedItemProperty, value);
    }
    public static readonly DependencyProperty EffectivelySelectedItemProperty =
        DependencyProperty.Register(nameof(EffectivelySelectedItem), typeof(object), typeof(FilterableComboBox));

    private string CurrentFilter = string.Empty;
    private bool TextBoxFreezed;
    protected TextBox EditableTextBox => GetTemplateChild("PART_EditableTextBox") as TextBox;
    private UserChange<bool> IsDropDownOpenUC;

    /// <summary>
    /// Triggers on lost focus or enter key pressed, if the selected item changed since the last time focus was lost or enter was pressed.
    /// </summary>
    public event Action<FilterableComboBox, object> SelectionEffectivelyChanged;

    public FilterableComboBox()
    {
        IsDropDownOpenUC = new UserChange<bool>(v => IsDropDownOpen = v);
        DropDownOpened += FilteredComboBox_DropDownOpened;

        IsEditable = true;
        IsTextSearchEnabled = true;
        StaysOpenOnEdit = true;
        IsReadOnly = false;

        Loaded += (s, e) => {
            if (EditableTextBox != null)
                new TextBoxBaseUserChangeTracker(EditableTextBox).UserTextChanged += FilteredComboBox_UserTextChange;
        };

        SelectionChanged += (_, __) => shouldTriggerSelectedItemChanged = true;

        SelectionEffectivelyChanged += (_, o) => EffectivelySelectedItem = o;
    }

    protected override void OnPreviewKeyDown(KeyEventArgs e)
    {
        base.OnPreviewKeyDown(e);
        if (e.Key == Key.Down && !IsDropDownOpen) {
            IsDropDownOpen = true;
            e.Handled = true;
        }
        else if (e.Key == Key.Escape) {
            ClearFilter();
            Text = "";
            IsDropDownOpen = true;
        }
        else if (e.Key == Key.Enter || e.Key == Key.Tab) {
            CheckSelectedItem();
            TriggerSelectedItemChanged();
        }
    }

    protected override void OnPreviewLostKeyboardFocus(KeyboardFocusChangedEventArgs e)
    {
        base.OnPreviewLostKeyboardFocus(e);
        CheckSelectedItem();
        if ((e.OldFocus == this || e.OldFocus == EditableTextBox) && e.NewFocus != this && e.NewFocus != EditableTextBox)
            TriggerSelectedItemChanged();
    }

    private void CheckSelectedItem()
    {
        if (OnlyValuesInList)
            Text = SelectedItem?.ToString() ?? "";
    }

    private bool shouldTriggerSelectedItemChanged = false;
    private void TriggerSelectedItemChanged()
    {
        if (shouldTriggerSelectedItemChanged) {
            SelectionEffectivelyChanged?.Invoke(this, SelectedItem);
            shouldTriggerSelectedItemChanged = false;
        }
    }

    public void ClearFilter()
    {
        if (string.IsNullOrEmpty(CurrentFilter)) return;
        CurrentFilter = "";
        CollectionViewSource.GetDefaultView(ItemsSource).Refresh();
    }

    private void FilteredComboBox_DropDownOpened(object sender, EventArgs e)
    {
        if (IsDropDownOpenUC.IsUserChange)
            ClearFilter();
    }

    private void FilteredComboBox_UserTextChange(object sender, EventArgs e)
    {
        if (TextBoxFreezed) return;
        var tb = EditableTextBox;
        if (tb.SelectionStart + tb.SelectionLength == tb.Text.Length)
            CurrentFilter = tb.Text.Substring(0, tb.SelectionStart).ToLower();
        else
            CurrentFilter = tb.Text.ToLower();
        RefreshFilter();
    }

    protected override void OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
    {
        if (newValue != null) {
            var view = CollectionViewSource.GetDefaultView(newValue);
            view.Filter += FilterItem;
        }

        if (oldValue != null) {
            var view = CollectionViewSource.GetDefaultView(oldValue);
            if (view != null) view.Filter -= FilterItem;
        }

        base.OnItemsSourceChanged(oldValue, newValue);
    }

    private void RefreshFilter()
    {
        if (ItemsSource == null) return;

        var view = CollectionViewSource.GetDefaultView(ItemsSource);
        FreezTextBoxState(() => {
            var isDropDownOpen = IsDropDownOpen;
            //always hide because showing it enables the user to pick with up and down keys, otherwise it's not working because of the glitch in view.Refresh()
            IsDropDownOpenUC.Set(false);
            view.Refresh();

            if (!string.IsNullOrEmpty(CurrentFilter) || isDropDownOpen)
                IsDropDownOpenUC.Set(true);

            if (SelectedItem == null) {
                foreach (var itm in ItemsSource)
                    if (itm.ToString() == Text) {
                        SelectedItem = itm;
                        break;
                    }
            }
        });
    }

    private void FreezTextBoxState(Action action)
    {
        TextBoxFreezed = true;
        var tb = EditableTextBox;
        var text = Text;
        var selStart = tb.SelectionStart;
        var selLen = tb.SelectionLength;
        action();
        Text = text;
        tb.SelectionStart = selStart;
        tb.SelectionLength = selLen;
        TextBoxFreezed = false;
    }

    private bool FilterItem(object value)
    {
        if (value == null) return false;
        if (CurrentFilter.Length == 0) return true;

        return value.ToString().ToLower().Contains(CurrentFilter);
    }

    private class TextBoxBaseUserChangeTracker
    {
        private bool IsTextInput { get; set; }

        public TextBoxBase TextBoxBase { get; set; }
        private List<Key> PressedKeys = new List<Key>();
        public event EventHandler UserTextChanged;
        private string LastText;

        public TextBoxBaseUserChangeTracker(TextBoxBase textBoxBase)
        {
            TextBoxBase = textBoxBase;
            LastText = TextBoxBase.ToString();

            textBoxBase.PreviewTextInput += (s, e) => {
                IsTextInput = true;
            };

            textBoxBase.TextChanged += (s, e) => {
                var isUserChange = PressedKeys.Count > 0 || IsTextInput || LastText == TextBoxBase.ToString();
                IsTextInput = false;
                LastText = TextBoxBase.ToString();
                if (isUserChange)
                    UserTextChanged?.Invoke(this, e);
            };

            textBoxBase.PreviewKeyDown += (s, e) => {
                switch (e.Key) {
                    case Key.Back:
                    case Key.Space:
                        if (!PressedKeys.Contains(e.Key))
                            PressedKeys.Add(e.Key);
                        break;
                }
                if (e.Key == Key.Back) {
                    var textBox = textBoxBase as TextBox;
                    if (textBox.SelectionStart > 0 && textBox.SelectionLength > 0 && (textBox.SelectionStart + textBox.SelectionLength) == textBox.Text.Length) {
                        textBox.SelectionStart--;
                        textBox.SelectionLength++;
                        e.Handled = true;
                        UserTextChanged?.Invoke(this, e);
                    }
                }
            };

            textBoxBase.PreviewKeyUp += (s, e) => {
                if (PressedKeys.Contains(e.Key))
                    PressedKeys.Remove(e.Key);
            };

            textBoxBase.LostFocus += (s, e) => {
                PressedKeys.Clear();
                IsTextInput = false;
            };
        }
    }

    private class UserChange<T>
    {
        private Action<T> action;

        public bool IsUserChange { get; private set; } = true;

        public UserChange(Action<T> action)
        {
            this.action = action;
        }

        public void Set(T val)
        {
            try {
                IsUserChange = false;
                action(val);
            }
            finally {
                IsUserChange = true;
            }
        }
    }
}
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Kel*_*lly 8

我刚刚在几天前使用本网站代码的修改版本做了这件事:信用到期的信用

我的完整代码如下:

using System.Collections;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Input;

    namespace MyControls
    {
        public class FilteredComboBox : ComboBox
        {
            private string oldFilter = string.Empty;

            private string currentFilter = string.Empty;

            protected TextBox EditableTextBox => GetTemplateChild("PART_EditableTextBox") as TextBox;


            protected override void OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
            {
                if (newValue != null)
                {
                    var view = CollectionViewSource.GetDefaultView(newValue);
                    view.Filter += FilterItem;
                }

                if (oldValue != null)
                {
                    var view = CollectionViewSource.GetDefaultView(oldValue);
                    if (view != null) view.Filter -= FilterItem;
                }

                base.OnItemsSourceChanged(oldValue, newValue);
            }

            protected override void OnPreviewKeyDown(KeyEventArgs e)
            {
                switch (e.Key)
                {
                    case Key.Tab:
                    case Key.Enter:
                        IsDropDownOpen = false;
                        break;
                    case Key.Escape:
                        IsDropDownOpen = false;
                        SelectedIndex = -1;
                        Text = currentFilter;
                        break;
                    default:
                        if (e.Key == Key.Down) IsDropDownOpen = true;

                        base.OnPreviewKeyDown(e);
                        break;
                }

                // Cache text
                oldFilter = Text;
            }

            protected override void OnKeyUp(KeyEventArgs e)
            {
                switch (e.Key)
                {
                    case Key.Up:
                    case Key.Down:
                        break;
                    case Key.Tab:
                    case Key.Enter:

                        ClearFilter();
                        break;
                    default:
                        if (Text != oldFilter)
                        {
                            RefreshFilter();
                            IsDropDownOpen = true;

                            EditableTextBox.SelectionStart = int.MaxValue;
                        }

                        base.OnKeyUp(e);
                        currentFilter = Text;
                        break;
                }
            }

            protected override void OnPreviewLostKeyboardFocus(KeyboardFocusChangedEventArgs e)
            {
                ClearFilter();
                var temp = SelectedIndex;
                SelectedIndex = -1;
                Text = string.Empty;
                SelectedIndex = temp;
                base.OnPreviewLostKeyboardFocus(e);
            }

            private void RefreshFilter()
            {
                if (ItemsSource == null) return;

                var view = CollectionViewSource.GetDefaultView(ItemsSource);
                view.Refresh();
            }

            private void ClearFilter()
            {
                currentFilter = string.Empty;
                RefreshFilter();
            }

            private bool FilterItem(object value)
            {
                if (value == null) return false;
                if (Text.Length == 0) return true;

                return value.ToString().ToLower().Contains(Text.ToLower());
            }
        }
    }
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WPF应该是这样的:

<MyControls:FilteredComboBox ItemsSource="{Binding MyItemsSource}"
    SelectedItem="{Binding MySelectedItem}"
    DisplayMemberPath="Name" 
    IsEditable="True" 
    IsTextSearchEnabled="False" 
    StaysOpenOnEdit="True">

    <MyControls:FilteredComboBox.ItemsPanel>
        <ItemsPanelTemplate>
            <VirtualizingStackPanel VirtualizationMode="Recycling" />
        </ItemsPanelTemplate>
    </MyControls:FilteredComboBox.ItemsPanel>
</MyControls:FilteredComboBox>
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这里有几点需要注意.您会注意到FilterItem实现在对象上执行ToString().这意味着您要显示的对象的属性应该在object.ToString()实现中返回.(或者已经是一个字符串)换句话说就是这样:

public class Customer
{
    public string Name { get; set; }
    public string Address { get; set; }
    public string PhoneNumber { get; set; }

    public override string ToString()
    {
        return Name;
    }
}
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如果这不能满足您的需求,我想您可以获取DisplayMemberPath的值并使用反射来获取属性以使用它,但这样会慢一点,所以除非必要,否则我不建议这样做.

此实现也不会阻止用户在ComboBox的TextBox部分中键入他们喜欢的内容.如果他们输入了一些愚蠢的东西,那么SelectedItem将恢复为NULL,所以要准备好在你的代码中处理它.

此外,如果您有很多项目,我强烈建议您使用VirtualizingStackPanel,就像上面的示例一样,因为它在加载时间方面有很大不同

Yan*_*hen 6

凯利的回答很棒。但是，有一个小错误，如果您在列表中选择一个项目（突出显示输入文本）然后按 BackSpace，输入文本将恢复为所选项目，并且 ComboBox 的 SelectedItem 属性仍然是您之前选择的项目。

下面是修复错误并添加当输入文本匹配时自动选择项目的功能的代码。

using System.Collections;
using System.Diagnostics;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Input;

namespace MyControls
{
    public class FilteredComboBox : ComboBox
    {
        private string oldFilter = string.Empty;

        private string currentFilter = string.Empty;

        protected TextBox EditableTextBox => GetTemplateChild("PART_EditableTextBox") as TextBox;


        protected override void OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
        {
            if (newValue != null)
            {
                var view = CollectionViewSource.GetDefaultView(newValue);
                view.Filter += FilterItem;
            }

            if (oldValue != null)
            {
                var view = CollectionViewSource.GetDefaultView(oldValue);
                if (view != null) view.Filter -= FilterItem;
            }

            base.OnItemsSourceChanged(oldValue, newValue);
        }

        protected override void OnPreviewKeyDown(KeyEventArgs e)
        {
            switch (e.Key)
            {
                case Key.Tab:
                case Key.Enter:
                    IsDropDownOpen = false;
                    break;
                case Key.Escape:
                    IsDropDownOpen = false;
                    SelectedIndex = -1;
                    Text = currentFilter;
                    break;
                default:
                    if (e.Key == Key.Down) IsDropDownOpen = true;

                    base.OnPreviewKeyDown(e);
                    break;
            }

            // Cache text
            oldFilter = Text;
        }

        protected override void OnKeyUp(KeyEventArgs e)
        {
            switch (e.Key)
            {
                case Key.Up:
                case Key.Down:
                    break;
                case Key.Tab:
                case Key.Enter:

                    ClearFilter();
                    break;
                default:                                        
                    if (Text != oldFilter)
                    {
                        var temp = Text;
                        RefreshFilter(); //RefreshFilter will change Text property
                        Text = temp;

                        if (SelectedIndex != -1 && Text != Items[SelectedIndex].ToString())
                        {
                            SelectedIndex = -1; //Clear selection. This line will also clear Text property
                            Text = temp;
                        }


                        IsDropDownOpen = true;

                        EditableTextBox.SelectionStart = int.MaxValue;
                    }

                    //automatically select the item when the input text matches it
                    for (int i = 0; i < Items.Count; i++)
                    {
                        if (Text == Items[i].ToString())
                            SelectedIndex = i;
                    }

                    base.OnKeyUp(e);                    
                    currentFilter = Text;                    
                    break;
            }
        }

        protected override void OnPreviewLostKeyboardFocus(KeyboardFocusChangedEventArgs e)
        {
            ClearFilter();
            var temp = SelectedIndex;
            SelectedIndex = -1;
            Text = string.Empty;
            SelectedIndex = temp;
            base.OnPreviewLostKeyboardFocus(e);
        }

        private void RefreshFilter()
        {
            if (ItemsSource == null) return;

            var view = CollectionViewSource.GetDefaultView(ItemsSource);
            view.Refresh();
        }

        private void ClearFilter()
        {
            currentFilter = string.Empty;
            RefreshFilter();
        }

        private bool FilterItem(object value)
        {
            if (value == null) return false;
            if (Text.Length == 0) return true;

            return value.ToString().ToLower().Contains(Text.ToLower());
        }
    }
}
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Avi*_* P. 1

听起来您真正想要的是类似于自动完成文本框的东西，它在类似于组合框弹出窗口的弹出窗口中提供完成建议。

您可能会发现这篇 CodeProject 文章很有用：

可重用的 WPF 自动完成文本框

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