Windows Community Toolkit 4.0 - DataGrid - Part03

概述在上面一篇 Windows Community Toolkit 4.0 - DataGrid - Part02 中，我們針對 DataGrid 控制項的 Utilities 部分做了詳細分享。而在本篇，我們會對控制項中最重要的 DataGrid 文件夾中的類做詳細的分享。下麵是 Windows ...

概述

在上面一篇 Windows Community Toolkit 4.0 - DataGrid - Part02 中，我們針對 DataGrid 控制項的 Utilities 部分做了詳細分享。而在本篇，我們會對控制項中最重要的 DataGrid 文件夾中的類做詳細的分享。

下麵是 Windows Community Toolkit Sample App 的示例截圖和 code/doc 地址：

Windows Community Toolkit Doc - DataGrid

Windows Community Toolkit Source Code - DataGrid

Namespace: Microsoft.Toolkit.Uwp.UI.Controls; Nuget: Microsoft.Toolkit.Uwp.UI.Controls.DataGrid;

開發過程

DataGrid 文件夾中是 DataGrid 控制項最重要的功能，首先我們還是先來看一下類結構：

包括了 Automation；DataGrid，DataGridColumn，DataGridRow，DataGridCell 控制項實現，事件處理參數類和數據類等；

接著我們看幾個重要的類和方法：

1. DataGrid.cs

這個類是 DataGrid 控制項的主要處理類，功能也是比較複雜，單個類的代碼行數是 9001 行，我們只挑兩個方法來看一下。其他方法大家有興趣或用到時可以在 DataGrid.cs 中查閱。

1) DataGrid()

首先看一下 DataGrid 類的構造方法，之所以看這個方法，是想讓大家可以更瞭解 DataGrid 類中變數的初始化方式，這些變數在不同的交互場景下會被賦予不同的值。

public DataGrid()
{
    this.TabNavigation = KeyboardNavigationMode.Once;

    _loadedRows = new List<DataGridRow>();
    _lostFocusActions = new Queue<Action>();
    _selectedItems = new DataGridSelectedItemsCollection(this);
    _rowGroupHeaderPropertyNameAlternative = Properties.Resources.DefaultRowGroupHeaderPropertyNameAlternative;
    _rowGroupHeaderStyles = new ObservableCollection<Style>();
    _rowGroupHeaderStyles.CollectionChanged += RowGroupHeaderStyles_CollectionChanged;
    _rowGroupHeaderStylesOld = new List<Style>();
    this.RowGroupHeadersTable = new IndexToValueTable<DataGridRowGroupInfo>();

    _collapsedSlotsTable = new IndexToValueTable<Visibility>();
    _validationItems = new Dictionary<INotifyDataErrorInfo, string>();
    _validationResults = new List<ValidationResult>();
    _bindingValidationResults = new List<ValidationResult>();
    _propertyValidationResults = new List<ValidationResult>();
    _indeiValidationResults = new List<ValidationResult>();

    this.ColumnHeaderInteractionInfo = new DataGridColumnHeaderInteractionInfo();
    this.DisplayData = new DataGridDisplayData(this);
    this.ColumnsInternal = CreateColumnsInstance();

    this.RowHeightEstimate = DATAGRID_defaultRowHeight;
    this.RowDetailsHeightEstimate = 0;
    _rowHeaderDesiredWidth = 0;

    this.DataConnection = new DataGridDataConnection(this);
    _showDetailsTable = new IndexToValueTable<Visibility>();

    _focusInputDevice = FocusInputDeviceKind.None;
    _proposedScrollBarsState = ScrollBarVisualState.NoIndicator;
    _proposedScrollBarsSeparatorState = ScrollBarsSeparatorVisualState.SeparatorCollapsed;

    this.AnchorSlot = -1;
    _lastEstimatedRow = -1;
    _editingColumnIndex = -1;
    this.CurrentCellCoordinates = new DataGridCellCoordinates(-1, -1);

    this.RowGroupHeaderHeightEstimate = DATAGRID_defaultRowHeight;

    this.LastHandledKeyDown = VirtualKey.None;

    this.DefaultStyleKey = typeof(DataGrid);

    HookDataGridEvents();
}

2) ShowScrollBars()

DataGrid 控制項中滾動條的處理方法。如果 AreAllScrollBarsCollapsed 為 true，則按照該規則簡單處理；如果為 false，先按照 mouse 和 touch 的類型進行判斷處理，再根據 UI 設置里的 AreSettingsEnablingAnimations 和 AreSettingsAutoHidingScrollBars 屬性來切換滾動條的狀態，調用 SwitchScrollBarsVisualStates 方法。

private void ShowScrollBars()
{
    if (this.AreAllScrollBarsCollapsed)
    {
        _proposedScrollBarsState = ScrollBarVisualState.NoIndicator;
        _proposedScrollBarsSeparatorState = ScrollBarsSeparatorVisualState.SeparatorCollapsedWithoutAnimation;
        SwitchScrollBarsVisualStates(_proposedScrollBarsState, _proposedScrollBarsSeparatorState, false /*useTransitions*/);
    }
    else
    {
        if (_hideScrollBarsTimer != null && _hideScrollBarsTimer.IsEnabled)
        {
            _hideScrollBarsTimer.Stop();
            _hideScrollBarsTimer.Start();
        }

        // Mouse indicators dominate if they are already showing or if we have set the flag to prefer them.
        if (_preferMouseIndicators || _showingMouseIndicators)
        {
            if (this.AreBothScrollBarsVisible && (_isPointerOverHorizontalScrollBar || _isPointerOverVerticalScrollBar))
            {
                _proposedScrollBarsState = ScrollBarVisualState.MouseIndicatorFull;
            }
            else
            {
                _proposedScrollBarsState = ScrollBarVisualState.MouseIndicator;
            }

            _showingMouseIndicators = true;
        }
        else
        {
            _proposedScrollBarsState = ScrollBarVisualState.TouchIndicator;
        }

        // Select the proper state for the scroll bars separator square within the GroupScrollBarsSeparator group:
        if (UISettingsHelper.AreSettingsEnablingAnimations)
        {
            // When OS animations are turned on, show the square when a scroll bar is shown unless the DataGrid is disabled, using an animation.
            _proposedScrollBarsSeparatorState =
                this.IsEnabled &&
                _proposedScrollBarsState == ScrollBarVisualState.MouseIndicatorFull ?
                ScrollBarsSeparatorVisualState.SeparatorExpanded : ScrollBarsSeparatorVisualState.SeparatorCollapsed;
        }
        else
        {
            // OS animations are turned off. Show or hide the square depending on the presence of a scroll bars, without an animation.
            // When the DataGrid is disabled, hide the square in sync with the scroll bar(s).
            if (_proposedScrollBarsState == ScrollBarVisualState.MouseIndicatorFull)
            {
                _proposedScrollBarsSeparatorState = this.IsEnabled ? ScrollBarsSeparatorVisualState.SeparatorExpandedWithoutAnimation : ScrollBarsSeparatorVisualState.SeparatorCollapsed;
            }
            else
            {
                _proposedScrollBarsSeparatorState = this.IsEnabled ? ScrollBarsSeparatorVisualState.SeparatorCollapsedWithoutAnimation : ScrollBarsSeparatorVisualState.SeparatorCollapsed;
            }
        }

        if (!UISettingsHelper.AreSettingsAutoHidingScrollBars)
        {
            if (this.AreBothScrollBarsVisible)
            {
                if (UISettingsHelper.AreSettingsEnablingAnimations)
                {
                    SwitchScrollBarsVisualStates(ScrollBarVisualState.MouseIndicatorFull, this.IsEnabled ? ScrollBarsSeparatorVisualState.SeparatorExpanded : ScrollBarsSeparatorVisualState.SeparatorCollapsed, true /*useTransitions*/);
                }
                else
                {
                    SwitchScrollBarsVisualStates(ScrollBarVisualState.MouseIndicatorFull, this.IsEnabled ? ScrollBarsSeparatorVisualState.SeparatorExpandedWithoutAnimation : ScrollBarsSeparatorVisualState.SeparatorCollapsed, true /*useTransitions*/);
                }
            }
            else
            {
                if (UISettingsHelper.AreSettingsEnablingAnimations)
                {
                    SwitchScrollBarsVisualStates(ScrollBarVisualState.MouseIndicator, ScrollBarsSeparatorVisualState.SeparatorCollapsed, true /*useTransitions*/);
                }
                else
                {
                    SwitchScrollBarsVisualStates(ScrollBarVisualState.MouseIndicator, this.IsEnabled ? ScrollBarsSeparatorVisualState.SeparatorCollapsedWithoutAnimation : ScrollBarsSeparatorVisualState.SeparatorCollapsed, true /*useTransitions*/);
                }
            }
        }
        else
        {
            SwitchScrollBarsVisualStates(_proposedScrollBarsState, _proposedScrollBarsSeparatorState, true /*useTransitions*/);
        }
    }
}

2. DataGridCellEditEndedEventArgs.cs

DataGrid 控制項中有很多事件處理參數類，我們只看其中一個 DataGridCellEditEndedEventArgs 吧。很顯然這個事件包含了 column row 和 editAction 三個變數，大家看到其他時間參數時，可以具體再分析。

public class DataGridCellEditEndedEventArgs : EventArgs
{
   public DataGridCellEditEndedEventArgs(DataGridColumn column, DataGridRow row, DataGridEditAction editAction)
    {
        this.Column = column;
        this.Row = row;
        this.EditAction = editAction;
    }

    public DataGridColumn Column
    {
        get;
        private set;
    }

     public DataGridEditAction EditAction
    {
        get;
        private set;
    }

    public DataGridRow Row
    {
        get;
        private set;
    }
}

3. DataGridCellCollection.cs

DataGrid 控制項中有很多數據類，我們看一個單元格集合類，可以看到集合中有 _cells，Count 變數，Insert 和 RemoveAt 方法等，處理邏輯都比較簡單。

internal class DataGridCellCollection
{
    private List<DataGridCell> _cells;
    private DataGridRow _owningRow;

    internal event EventHandler<DataGridCellEventArgs> CellAdded;

    internal event EventHandler<DataGridCellEventArgs> CellRemoved;

    public DataGridCellCollection(DataGridRow owningRow)
    {
        _owningRow = owningRow;
        _cells = new List<DataGridCell>();
    }

    public int Count
    {
        get
        {
            return _cells.Count;
        }
    }

    public IEnumerator GetEnumerator()
    {
        return _cells.GetEnumerator();
    }

    public void Insert(int cellIndex, DataGridCell cell)
    {
        Debug.Assert(cellIndex >= 0 && cellIndex <= _cells.Count, "Expected cellIndex between 0 and _cells.Count inclusive.");
        Debug.Assert(cell != null, "Expected non-null cell.");

        cell.OwningRow = _owningRow;
        _cells.Insert(cellIndex, cell);

        if (CellAdded != null)
        {
            CellAdded(this, new DataGridCellEventArgs(cell));
        }
    }

    public void RemoveAt(int cellIndex)
    {
        DataGridCell dataGridCell = _cells[cellIndex];
        _cells.RemoveAt(cellIndex);
        dataGridCell.OwningRow = null;
        if (CellRemoved != null)
        {
            CellRemoved(this, new DataGridCellEventArgs(dataGridCell));
        }
    }

    public DataGridCell this[int index]
    {
        get
        {
            if (index < 0 || index >= _cells.Count)
            {
                throw DataGridError.DataGrid.ValueMustBeBetween("index", "Index", 0, true, _cells.Count, false);
            }

            return _cells[index];
        }
    }
}

4. DataGridCell.cs

DataGrid 控制項的單元格類，處理比較簡單，我們通過構造方法來看一下類中都涉及到哪些事件的處理；可以看到，游標的一系列處理都有涉及。

public DataGridCell()
{
    this.IsTapEnabled = true;
    this.AddHandler(UIElement.TappedEvent, new TappedEventHandler(DataGridCell_PointerTapped), true /*handledEventsToo*/);

    this.PointerCanceled += new PointerEventHandler(DataGridCell_PointerCanceled);
    this.PointerCaptureLost += new PointerEventHandler(DataGridCell_PointerCaptureLost);
    this.PointerPressed += new PointerEventHandler(DataGridCell_PointerPressed);
    this.PointerReleased += new PointerEventHandler(DataGridCell_PointerReleased);
    this.PointerEntered += new PointerEventHandler(DataGridCell_PointerEntered);
    this.PointerExited += new PointerEventHandler(DataGridCell_PointerExited);
    this.PointerMoved += new PointerEventHandler(DataGridCell_PointerMoved);

    DefaultStyleKey = typeof(DataGridCell);
}

總結

這裡我們把 DataGrid 的 DataGrid 相關類介紹完成了，代碼部分的 CollectionView，Utilities 和 DataGrid 就介紹完了。因為代碼本身比較複雜，量也很大，所以我們只挑選了一小部分代碼來分享，大傢具體用到時可以再具體分析。

接下來我們會就 DataGrid 控制項的各種編輯功能，各種自定義功能等做進一步的使用方式的分享。

最後，再跟大家安利一下 WindowsCommunityToolkit 的官方微博：https://weibo.com/u/6506046490, 大家可以通過微博關註最新動態。

衷心感謝 WindowsCommunityToolkit 的作者們傑出的工作，感謝每一位貢獻者，Thank you so much, ALL WindowsCommunityToolkit AUTHORS !!!