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tutorial - Icursor -> Unbound1.vbp ' General declarations Option Explicit ' Special Note: Variables that store Row indices will be ' of data type Long (It is reasonable to assume there may ' be larger than 32,767 rows). Those storing Column ' indices will be of type Integer. (It is very unlikely ' there will be more than 32,767 columns.) Dim MaxCol As Integer ' Number of columns Dim MaxRow As Long ' Number of rows Dim GridArray() As Variant ' Array to store the data Private Sub Form_Load() ' Initialize the data array. Data must be ready ' before the grid is loaded. Form_Load or Main is a ' good place to initialize the data. Dim I As Integer ' column index Dim J As Long ' row index Dim C As TrueDBGrid70.Column Dim Col2 As TrueDBGrid70.Column Dim Col3 As TrueDBGrid70.Column ' Use a 4 columns by 100 rows array as data source. ' Since user will be allowed to add data to the grid, ' the array may grow in size. ' This tutorial project assumes there are 3 columns in ' the grid for simplicity. If you wish to change this ' number, you will need to modify the code below to ' add the correct number of columns. MaxCol = 4 ' You can change MaxRow to show a different number of ' rows when the program loads. MaxRow must be >= 0. MaxRow = 100 If MaxRow > 0 Then ' If MaxRow = 0, then (MaxRow - 1) equals -1. This ' causes an error in the statement below, so we ' handle this special case in the Else clause. ReDim GridArray(0 To MaxCol - 1, 0 To MaxRow - 1) Else ReDim GridArray(0 To MaxCol - 1, 0) End If For I = 0 To MaxCol - 1 For J = 0 To MaxRow - 1 GridArray(I, J) = "Row" + Str$(J) + ", Col" + Str$(I) Next J Next I ' You can configure the grid either at design time or ' run time. Assuming you have not done this at ' design-time, the following code configures a grid ' with 4 columns. By default, the grid already has 2 ' columns, so we just need to add 2 more (don't forget ' to make the new column visible). The existing ' columns are numbered 0 and 1, so we will add new ' columns at positions 2 and 3. Set C = TDBGrid1.Columns.Add(2) C.Visible = True Set C = TDBGrid1.Columns.Add(3) C.Visible = True ' For the sake of efficiency, we use Column objects ' to reference column properties instead of repeatedly ' going through the grid's Columns collection object. Set Col2 = TDBGrid1.Columns(2) Set Col3 = TDBGrid1.Columns(3) ' Set column heading text Col2.Caption = "Column 2" Col3.Caption = "Column 3" ' Inform the grid of how many rows are in the data set. ' This helps with scroll bar positioning. TDBGrid1.ApproxCount = MaxRow End Sub Private Function StoreUserData(Bookmark As Variant, _ Col As Integer, Userval As Variant) As Boolean ' StoreUserData is called from UnboundWriteData to ' write the newly changed information in the grid to ' the array. This function is called once for each ' field that needs to be stored. The grid cell that ' this function is called to store is specified in ' the same way as in GetUserData. Dim Index As Long ' Figure out which row the bookmark refers to Index = IndexFromBookmark(Bookmark, False) If Index < 0 Or Index >= MaxRow Or Col < 0 Or _ Col >= MaxCol Then ' Cell position is invalid, so just return null ' to indicate failure StoreUserData = False Else StoreUserData = True GridArray(Col, Index) = Userval End If End Function ' ByVal RowBuf As TrueDBGrid60.RowBuffer, WriteLocation As Variant) Private Sub TDBGrid1_UnboundWriteData(ByVal RowBuf As TrueDBGrid70.RowBuffer, WriteLocation As Variant) ' The UnboundWriteData event is fired when the user ' modifies an existing row within an unbound grid and ' attempts to commit the changes by moving to another ' row or calling the Update method of the grid. This ' notifies the program that data has changed in the ' grid and it needs to be stored in the data source. ' RowBuf is the row buffer from which you retrieve the ' data to be stored in the data source. Since only one ' row can be updated at a time, RowBuf.RowCount always ' equals 1 here. If a particular column in the row has ' not been changed, its element in the RowBuf.Value ' array will be Null. ' WriteLocation is a bookmark that identifies the row ' to be updated. ' Assume that a function StoreUserData(bookmark, col, ' value) takes a row bookmark, a column index, and a ' variant with the appropriate data to be stored in an ' array or database. The function returns True if the ' data is acceptable and can be stored, False otherwise. ' Loop over all the columns of the row, storing non-Null ' values Dim I As Integer For I = 0 To RowBuf.ColumnCount - 1 If Not IsNull(RowBuf.Value(0, I)) Then If Not StoreUserData(WriteLocation, I, _ RowBuf.Value(0, I)) Then RowBuf.RowCount = 0 ' Tell the grid the ' update failed. so Exit Sub ' so exit the event. End If End If Next I End Sub ' NewRowBookmark As Variant) Private Sub TDBGrid1_UnboundAddData(ByVal RowBuf As TrueDBGrid70.RowBuffer, NewRowBookmark As Variant) ' UnboundAddData is fired when the user adds a new row ' of data to an unbound grid to alert your application ' that it must add a new row of data to its unbound ' dataset. This event will NOT be fired if the grid's ' AllowAddNew property is set to False. ' Assume that a function StoreUserData(bookmark, col, ' value) takes a row bookmark, a column index, and a ' variant with the appropriate data to be stored in ' an array or database. The function returns True if ' the data is acceptable and can be stored, False ' otherwise. ' First, get a bookmark for the new row. Do this with ' a function, GetNewBookmark. This function allocates ' a new row of data in the storage medium (array or ' database), and returns a variant containing a ' bookmark for the added row. Dim I As Integer Dim NewVal As Variant ' Create a new row in the array and get a bookmark ' for the new row NewRowBookmark = GetNewBookmark() ' Loop over all the columns of the row, storing ' non-Null values For I = 0 To RowBuf.ColumnCount - 1 ' Note that since only one row of data may be ' added at a time, the first index of the row ' buffer Value array is always 0. NewVal = RowBuf.Value(0, I) If IsNull(NewVal) Then ' The row buffer does not contain a value for ' this column. A default value should be set. ' A convenient value is the default value for ' the column. NewVal = TDBGrid1.Columns(I).DefaultValue End If ' Now store the new values. If Not StoreUserData(NewRowBookmark, I, NewVal) Then ' Storage of the data has failed. Delete the ' added row using a function, DeleteRow, which ' takes a bookmark as an argument. Also, ' indicate that the update has failed by ' setting RowCount to 0. DeleteRow NewRowBookmark RowBuf.RowCount = 0 Exit Sub ' It failed, so exit the event. End If Next I End Sub Private Function GetNewBookmark() As Variant ' GetNewBookmark is called when we need to create a ' bookmark for a newly added record (row). ' Reserve space for the new row in the array ReDim Preserve GridArray(0 To MaxCol - 1, 0 To MaxRow) ' Since the row index of the last record is (MaxRow - 1), ' the next available index for the row to be added is ' (MaxRow), so create a bookmark for the new row using ' MaxRow as an index. GetNewBookmark = MakeBookmark(MaxRow) ' Increment the number of rows in our dataset MaxRow = MaxRow + 1 ' Calibrate the scroll bars based on the new dataset ' size. TDBGrid1.ApproxCount = MaxRow End Function Private Sub TDBGrid1_UnboundDeleteRow(Bookmark As Variant) ' UnboundDeleteRow is fired when the user deletes an ' existing row in the Unbound grid. This event ' alerts the user that the program must delete the ' row specified by the Bookmark parameter from the ' dataset. Here, an auxiliary function (DeleteRow) ' is used to do this. If Not DeleteRow(Bookmark) Then Bookmark = Null End Sub Private Function DeleteRow(Bookmark As Variant) As Boolean ' DeleteRow is called to logically delete a record ' (row) from the array. The row to be deleted is ' specified by the Bookmark parameter. Dim I As Long, Index As Long Dim J As Integer ' Figure out which row index the bookmark refers to Index = IndexFromBookmark(Bookmark, False) If Index < 0 Or Index >= MaxRow Then ' Row index is invalid, so exit the delete, ' indicating failure. DeleteRow = False Exit Function End If ' Decrement the number of rows in the dataset MaxRow = MaxRow - 1 ' Shift the data in the array to fill the empty space ' vacated by the deleted row For I = Index To MaxRow - 1 For J = 0 To MaxCol - 1 GridArray(J, I) = GridArray(J, I + 1) Next J Next I ' Resize array to free storage space used by deleted ' row If MaxRow > 0 Then ' If MaxRow = 0, then (MaxRow - 1) equals -1. ' This causes an error in the statement below, so ' we handle this special case in the Else clause. ReDim Preserve GridArray(0 To MaxCol - 1, 0 _ To MaxRow - 1) Else ReDim Preserve GridArray(0 To MaxCol - 1, 0) End If DeleteRow = True ' Calibrate scroll bars based on new dataset size TDBGrid1.ApproxCount = MaxRow End Function Private Sub TDBGrid1_UnboundReadData(ByVal RowBuf As TrueDBGrid70.RowBuffer, StartLocation As Variant, ByVal ReadPriorRows As Boolean) ' UnboundReadData is fired by an unbound grid whenever ' it requires data for display. This event will fire ' when the grid is first shown, when Refresh or ReBind ' is used, when the grid is scrolled, and after a ' record in the grid is modified and the user commits ' the change by moving off of the current row. The ' grid fetches data in "chunks", and the number of rows ' the grid is asking for is given by RowBuf.RowCount. ' RowBuf is the row buffer where you place the data and ' the bookmarks for the rows that the grid is requesting ' to display. It will also hold the number of rows that ' were successfully supplied to the grid. ' StartLocation is a bookmark which specifies the row ' before or after the desired data, depending on the ' value of ReadPriorRows. If we are reading rows after ' StartLocation (ReadPriorRows = False), then the first ' row of data the grid wants is the row after ' StartLocation, and if we are reading rows before ' StartLocation (ReadPriorRows = True) then the first ' row of data the grid wants is the row before ' StartLocation. ' ReadPriorRows is a boolean value indicating whether ' we are reading rows before (ReadPriorRows = True) or ' after (ReadPriorRows = False) StartLocation. Dim Bookmark As Variant Dim I As Long, RelPos As Long Dim J As Integer, RowsFetched As Integer ' Get a bookmark for the start location Bookmark = StartLocation If ReadPriorRows Then RelPos = -1 ' Requesting data in rows prior to ' StartLocation Else RelPos = 1 ' Requesting data in rows after ' StartLocation End If RowsFetched = 0 For I = 0 To RowBuf.RowCount - 1 ' Get the bookmark of the next available row Bookmark = GetRelativeBookmark(Bookmark, RelPos) ' If the next row is BOF or EOF, then stop ' fetching and return any rows fetched up to this ' point. If IsNull(Bookmark) Then Exit For ' Place the record data into the row buffer For J = 0 To RowBuf.ColumnCount - 1 RowBuf.Value(I, J) = GetUserData(Bookmark, J) Next J ' Set the bookmark for the row RowBuf.Bookmark(I) = Bookmark ' Increment the count of fetched rows RowsFetched = RowsFetched + 1 Next I ' Tell the grid how many rows we fetched RowBuf.RowCount = RowsFetched End Sub Private Sub TDBGrid1_UnboundGetRelativeBookmark( _ StartLocation As Variant, ByVal Offset As Long, _ NewLocation As Variant, ApproximatePosition As Long) Dim Index As Long ' TDBGrid1 calls this routine each time it needs to ' reposition itself. StartLocation is a bookmark ' supplied by the grid to indicate the "current" ' position -- the row we are moving from. Offset is ' the number of rows we must move from StartLocation ' in order to arrive at the desired destination row. ' A positive offset means the desired record is after ' the StartLocation, and a negative offset means the ' desired record is before StartLocation. ' If StartLocation is NULL, then we are positioning ' from either BOF or EOF. Once we determine the ' correct index for StartLocation, we will simply add ' the offset to get the correct destination row. If IsNull(StartLocation) Then If Offset < 0 Then ' The row to position to is before the current ' one, therefore we must be at EOF (There are ' no rows before BOF). Since (MaxRow-1) is ' the index of the last record, we can use an ' index of (MaxRow) to represent EOF. Index = MaxRow + Offset Else ' The row to position to is after the current ' one, therefore we must be at BOF (There are ' no rows after EOF). Since 0 is the index of ' the first record, we can use an index of -1 ' to represent BOF. Index = -1 + Offset End If Else ' We are not at BOF or EOF, so just get the index ' of the current row and add the offset to it. Index = Val(StartLocation) + Offset End If ' Is the new Index valid? If Index >= 0 And Index < MaxRow Then ' Here, 0 <= Index < MaxRow, so the new location is ' valid. ApproximatePosition = Index NewLocation = MakeBookmark(Index) Else ' The new index is out-of-bounds -- the new location ' refers to a position before the first record or ' after the last one. Thus the index is invalid, ' and we return Null. NewLocation = Null End If End Sub Private Function MakeBookmark(Index As Long) As Variant ' This support function is used only by the remaining ' support functions. It is not used directly by the ' unbound events. It is a good idea to create a ' MakeBookmark function such that all bookmarks can be ' created in the same way. Thus the method by which ' bookmarks are created is consistent and easy to ' modify. This function creates a bookmark when given ' an array row index. ' Since we have data stored in an array, we will just ' use the array index as our bookmark. We will convert ' it to a string first, using the CStr function. MakeBookmark = CStr(Index) End Function Private Function IndexFromBookmark(Bookmark As Variant, _ ReadPriorRows As Boolean) As Long ' This support function is used only by the remaining ' support functions. It is not used directly by the ' unbound events. ' This function is the inverse of MakeBookmark. Given ' a bookmark, IndexFromBookmark returns the row index ' that the given bookmark refers to. If the given ' bookmark is Null, then it refers to BOF or EOF. In ' such a case, we need to use ReadPriorRows to ' distinguish between the two. If ReadPriorRows = True, ' the grid is requesting rows before the current ' location, so we must be at EOF, because no rows exist ' before BOF. Conversely, if ReadPriorRows = False, ' we must be at BOF. Dim Index As Long If IsNull(Bookmark) Then If ReadPriorRows Then ' Bookmark refers to EOF. Since (MaxRow - 1) ' is the index of the last record, we can use ' an index of (MaxRow) to represent EOF. IndexFromBookmark = MaxRow Else ' Bookmark refers to BOF. Since 0 is the ' index of the first record, we can use an ' index of -1 to represent BOF. IndexFromBookmark = -1 End If Else ' Convert string to long integer Index = Val(Bookmark) ' Check to see if the row index is valid: ' (0 <= Index < MaxRow). ' If not, set it to a large negative number to ' indicate that the bookmark is invalid. If Index < 0 Or Index >= MaxRow Then Index = -9999 IndexFromBookmark = Index End If End Function Private Function GetRelativeBookmark(Bookmark As Variant, _ RelPos As Long) As Variant ' GetRelativeBookmark is used to get a bookmark for a ' row that is a given number of rows away from the given ' row. This specific example will always use either -1 ' or +1 for a relative position, since we will always be ' retrieving either the row previous to the current one, ' or the row following the current one. ' IndexFromBookmark expects a Bookmark and a Boolean ' value: this Boolean value is True if the next row to ' read is before the current one [in this case, ' (RelPos < 0) is True], or False if the next row to ' read is after the current one [(RelPos < 0) is False]. ' This is necessary to distinguish between BOF and EOF ' in the IndexFromBookmark function if our bookmark is ' Null. Once we get the correct row index from ' IndexFromBookmark, we simply add RelPos to it to get ' the desired row index and create a bookmark using ' that index. Dim Index As Long Index = IndexFromBookmark(Bookmark, RelPos < 0) + RelPos If Index < 0 Or Index >= MaxRow Then ' Index refers to a row before the first or after ' the last, so just return Null. GetRelativeBookmark = Null Else GetRelativeBookmark = MakeBookmark(Index) End If End Function Private Function GetUserData(Bookmark As Variant, _ Col As Integer) As Variant ' In this example, GetUserData is called by ' UnboundReadData to ask the user what data should be ' displayed in a specific cell in the grid. The grid ' row the cell is in is the one referred to by the ' Bookmark parameter, and the column it is in it given ' by the Col parameter. GetUserData is called on a ' cell-by-cell basis. Dim Index As Long ' Figure out which row the bookmark refers to Index = IndexFromBookmark(Bookmark, False) If Index < 0 Or Index >= MaxRow Or _ Col < 0 Or Col >= MaxCol Then ' Cell position is invalid, so just return null ' to indicate failure GetUserData = Null Else GetUserData = GridArray(Col, Index) End If End Function tutorial - Icursor -> Unbound1.vbp ' General declarations Option Explicit ' Special Note: Variables that store Row indices will be ' of data type Long (It is reasonable to assume there may ' be larger than 32,767 rows). Those storing Column ' indices will be of type Integer. (It is very unlikely ' there will be more than 32,767 columns.) Dim MaxCol As Integer ' Number of columns Dim MaxRow As Long ' Number of rows Dim GridArray() As Variant ' Array to store the data Private Sub Form_Load() ' Initialize the data array. Data must be ready ' before the grid is loaded. Form_Load or Main is a ' good place to initialize the data. Dim I As Integer ' column index Dim J As Long ' row index Dim C As TrueDBGrid70.Column Dim Col2 As TrueDBGrid70.Column Dim Col3 As TrueDBGrid70.Column ' Use a 4 columns by 100 rows array as data source. ' Since user will be allowed to add data to the grid, ' the array may grow in size. ' This tutorial project assumes there are 3 columns in ' the grid for simplicity. If you wish to change this ' number, you will need to modify the code below to ' add the correct number of columns. MaxCol = 4 ' You can change MaxRow to show a different number of ' rows when the program loads. MaxRow must be >= 0. MaxRow = 100 If MaxRow > 0 Then ' If MaxRow = 0, then (MaxRow - 1) equals -1. This ' causes an error in the statement below, so we ' handle this special case in the Else clause. ReDim GridArray(0 To MaxCol - 1, 0 To MaxRow - 1) Else ReDim GridArray(0 To MaxCol - 1, 0) End If For I = 0 To MaxCol - 1 For J = 0 To MaxRow - 1 GridArray(I, J) = "Row" + Str$(J) + ", Col" + Str$(I) Next J Next I ' You can configure the grid either at design time or ' run time. Assuming you have not done this at ' design-time, the following code configures a grid ' with 4 columns. By default, the grid already has 2 ' columns, so we just need to add 2 more (don't forget ' to make the new column visible). The existing ' columns are numbered 0 and 1, so we will add new ' columns at positions 2 and 3. Set C = TDBGrid1.Columns.Add(2) C.Visible = True Set C = TDBGrid1.Columns.Add(3) C.Visible = True ' For the sake of efficiency, we use Column objects ' to reference column properties instead of repeatedly ' going through the grid's Columns collection object. Set Col2 = TDBGrid1.Columns(2) Set Col3 = TDBGrid1.Columns(3) ' Set column heading text Col2.Caption = "Column 2" Col3.Caption = "Column 3" ' Inform the grid of how many rows are in the data set. ' This helps with scroll bar positioning. TDBGrid1.ApproxCount = MaxRow End Sub Private Function StoreUserData(Bookmark As Variant, _ Col As Integer, Userval As Variant) As Boolean ' StoreUserData is called from UnboundWriteData to ' write the newly changed information in the grid to ' the array. This function is called once for each ' field that needs to be stored. The grid cell that ' this function is called to store is specified in ' the same way as in GetUserData. Dim Index As Long ' Figure out which row the bookmark refers to Index = IndexFromBookmark(Bookmark, False) If Index < 0 Or Index >= MaxRow Or Col < 0 Or _ Col >= MaxCol Then ' Cell position is invalid, so just return null ' to indicate failure StoreUserData = False Else StoreUserData = True GridArray(Col, Index) = Userval End If End Function ' ByVal RowBuf As TrueDBGrid60.RowBuffer, WriteLocation As Variant) Private Sub TDBGrid1_UnboundWriteData(ByVal RowBuf As TrueDBGrid70.RowBuffer, WriteLocation As Variant) ' The UnboundWriteData event is fired when the user ' modifies an existing row within an unbound grid and ' attempts to commit the changes by moving to another ' row or calling the Update method of the grid. This ' notifies the program that data has changed in the ' grid and it needs to be stored in the data source. ' RowBuf is the row buffer from which you retrieve the ' data to be stored in the data source. Since only one ' row can be updated at a time, RowBuf.RowCount always ' equals 1 here. If a particular column in the row has ' not been changed, its element in the RowBuf.Value ' array will be Null. ' WriteLocation is a bookmark that identifies the row ' to be updated. ' Assume that a function StoreUserData(bookmark, col, ' value) takes a row bookmark, a column index, and a ' variant with the appropriate data to be stored in an ' array or database. The function returns True if the ' data is acceptable and can be stored, False otherwise. ' Loop over all the columns of the row, storing non-Null ' values Dim I As Integer For I = 0 To RowBuf.ColumnCount - 1 If Not IsNull(RowBuf.Value(0, I)) Then If Not StoreUserData(WriteLocation, I, _ RowBuf.Value(0, I)) Then RowBuf.RowCount = 0 ' Tell the grid the ' update failed. so Exit Sub ' so exit the event. End If End If Next I End Sub ' NewRowBookmark As Variant) Private Sub TDBGrid1_UnboundAddData(ByVal RowBuf As TrueDBGrid70.RowBuffer, NewRowBookmark As Variant) ' UnboundAddData is fired when the user adds a new row ' of data to an unbound grid to alert your application ' that it must add a new row of data to its unbound ' dataset. This event will NOT be fired if the grid's ' AllowAddNew property is set to False. ' Assume that a function StoreUserData(bookmark, col, ' value) takes a row bookmark, a column index, and a ' variant with the appropriate data to be stored in ' an array or database. The function returns True if ' the data is acceptable and can be stored, False ' otherwise. ' First, get a bookmark for the new row. Do this with ' a function, GetNewBookmark. This function allocates ' a new row of data in the storage medium (array or ' database), and returns a variant containing a ' bookmark for the added row. Dim I As Integer Dim NewVal As Variant ' Create a new row in the array and get a bookmark ' for the new row NewRowBookmark = GetNewBookmark() ' Loop over all the columns of the row, storing ' non-Null values For I = 0 To RowBuf.ColumnCount - 1 ' Note that since only one row of data may be ' added at a time, the first index of the row ' buffer Value array is always 0. NewVal = RowBuf.Value(0, I) If IsNull(NewVal) Then ' The row buffer does not contain a value for ' this column. A default value should be set. ' A convenient value is the default value for ' the column. NewVal = TDBGrid1.Columns(I).DefaultValue End If ' Now store the new values. If Not StoreUserData(NewRowBookmark, I, NewVal) Then ' Storage of the data has failed. Delete the ' added row using a function, DeleteRow, which ' takes a bookmark as an argument. Also, ' indicate that the update has failed by ' setting RowCount to 0. DeleteRow NewRowBookmark RowBuf.RowCount = 0 Exit Sub ' It failed, so exit the event. End If Next I End Sub Private Function GetNewBookmark() As Variant ' GetNewBookmark is called when we need to create a ' bookmark for a newly added record (row). ' Reserve space for the new row in the array ReDim Preserve GridArray(0 To MaxCol - 1, 0 To MaxRow) ' Since the row index of the last record is (MaxRow - 1), ' the next available index for the row to be added is ' (MaxRow), so create a bookmark for the new row using ' MaxRow as an index. GetNewBookmark = MakeBookmark(MaxRow) ' Increment the number of rows in our dataset MaxRow = MaxRow + 1 ' Calibrate the scroll bars based on the new dataset ' size. TDBGrid1.ApproxCount = MaxRow End Function Private Sub TDBGrid1_UnboundDeleteRow(Bookmark As Variant) ' UnboundDeleteRow is fired when the user deletes an ' existing row in the Unbound grid. This event ' alerts the user that the program must delete the ' row specified by the Bookmark parameter from the ' dataset. Here, an auxiliary function (DeleteRow) ' is used to do this. If Not DeleteRow(Bookmark) Then Bookmark = Null End Sub Private Function DeleteRow(Bookmark As Variant) As Boolean ' DeleteRow is called to logically delete a record ' (row) from the array. The row to be deleted is ' specified by the Bookmark parameter. Dim I As Long, Index As Long Dim J As Integer ' Figure out which row index the bookmark refers to Index = IndexFromBookmark(Bookmark, False) If Index < 0 Or Index >= MaxRow Then ' Row index is invalid, so exit the delete, ' indicating failure. DeleteRow = False Exit Function End If ' Decrement the number of rows in the dataset MaxRow = MaxRow - 1 ' Shift the data in the array to fill the empty space ' vacated by the deleted row For I = Index To MaxRow - 1 For J = 0 To MaxCol - 1 GridArray(J, I) = GridArray(J, I + 1) Next J Next I ' Resize array to free storage space used by deleted ' row If MaxRow > 0 Then ' If MaxRow = 0, then (MaxRow - 1) equals -1. ' This causes an error in the statement below, so ' we handle this special case in the Else clause. ReDim Preserve GridArray(0 To MaxCol - 1, 0 _ To MaxRow - 1) Else ReDim Preserve GridArray(0 To MaxCol - 1, 0) End If DeleteRow = True ' Calibrate scroll bars based on new dataset size TDBGrid1.ApproxCount = MaxRow End Function Private Sub TDBGrid1_UnboundReadData(ByVal RowBuf As TrueDBGrid70.RowBuffer, StartLocation As Variant, ByVal ReadPriorRows As Boolean) ' UnboundReadData is fired by an unbound grid whenever ' it requires data for display. This event will fire ' when the grid is first shown, when Refresh or ReBind ' is used, when the grid is scrolled, and after a ' record in the grid is modified and the user commits ' the change by moving off of the current row. The ' grid fetches data in "chunks", and the number of rows ' the grid is asking for is given by RowBuf.RowCount. ' RowBuf is the row buffer where you place the data and ' the bookmarks for the rows that the grid is requesting ' to display. It will also hold the number of rows that ' were successfully supplied to the grid. ' StartLocation is a bookmark which specifies the row ' before or after the desired data, depending on the ' value of ReadPriorRows. If we are reading rows after ' StartLocation (ReadPriorRows = False), then the first ' row of data the grid wants is the row after ' StartLocation, and if we are reading rows before ' StartLocation (ReadPriorRows = True) then the first ' row of data the grid wants is the row before ' StartLocation. ' ReadPriorRows is a boolean value indicating whether ' we are reading rows before (ReadPriorRows = True) or ' after (ReadPriorRows = False) StartLocation. Dim Bookmark As Variant Dim I As Long, RelPos As Long Dim J As Integer, RowsFetched As Integer ' Get a bookmark for the start location Bookmark = StartLocation If ReadPriorRows Then RelPos = -1 ' Requesting data in rows prior to ' StartLocation Else RelPos = 1 ' Requesting data in rows after ' StartLocation End If RowsFetched = 0 For I = 0 To RowBuf.RowCount - 1 ' Get the bookmark of the next available row Bookmark = GetRelativeBookmark(Bookmark, RelPos) ' If the next row is BOF or EOF, then stop ' fetching and return any rows fetched up to this ' point. If IsNull(Bookmark) Then Exit For ' Place the record data into the row buffer For J = 0 To RowBuf.ColumnCount - 1 RowBuf.Value(I, J) = GetUserData(Bookmark, J) Next J ' Set the bookmark for the row RowBuf.Bookmark(I) = Bookmark ' Increment the count of fetched rows RowsFetched = RowsFetched + 1 Next I ' Tell the grid how many rows we fetched RowBuf.RowCount = RowsFetched End Sub Private Sub TDBGrid1_UnboundGetRelativeBookmark( _ StartLocation As Variant, ByVal Offset As Long, _ NewLocation As Variant, ApproximatePosition As Long) Dim Index As Long ' TDBGrid1 calls this routine each time it needs to ' reposition itself. StartLocation is a bookmark ' supplied by the grid to indicate the "current" ' position -- the row we are moving from. Offset is ' the number of rows we must move from StartLocation ' in order to arrive at the desired destination row. ' A positive offset means the desired record is after ' the StartLocation, and a negative offset means the ' desired record is before StartLocation. ' If StartLocation is NULL, then we are positioning ' from either BOF or EOF. Once we determine the ' correct index for StartLocation, we will simply add ' the offset to get the correct destination row. If IsNull(StartLocation) Then If Offset < 0 Then ' The row to position to is before the current ' one, therefore we must be at EOF (There are ' no rows before BOF). Since (MaxRow-1) is ' the index of the last record, we can use an ' index of (MaxRow) to represent EOF. Index = MaxRow + Offset Else ' The row to position to is after the current ' one, therefore we must be at BOF (There are ' no rows after EOF). Since 0 is the index of ' the first record, we can use an index of -1 ' to represent BOF. Index = -1 + Offset End If Else ' We are not at BOF or EOF, so just get the index ' of the current row and add the offset to it. Index = Val(StartLocation) + Offset End If ' Is the new Index valid? If Index >= 0 And Index < MaxRow Then ' Here, 0 <= Index < MaxRow, so the new location is ' valid. ApproximatePosition = Index NewLocation = MakeBookmark(Index) Else ' The new index is out-of-bounds -- the new location ' refers to a position before the first record or ' after the last one. Thus the index is invalid, ' and we return Null. NewLocation = Null End If End Sub Private Function MakeBookmark(Index As Long) As Variant ' This support function is used only by the remaining ' support functions. It is not used directly by the ' unbound events. It is a good idea to create a ' MakeBookmark function such that all bookmarks can be ' created in the same way. Thus the method by which ' bookmarks are created is consistent and easy to ' modify. This function creates a bookmark when given ' an array row index. ' Since we have data stored in an array, we will just ' use the array index as our bookmark. We will convert ' it to a string first, using the CStr function. MakeBookmark = CStr(Index) End Function Private Function IndexFromBookmark(Bookmark As Variant, _ ReadPriorRows As Boolean) As Long ' This support function is used only by the remaining ' support functions. It is not used directly by the ' unbound events. ' This function is the inverse of MakeBookmark. Given ' a bookmark, IndexFromBookmark returns the row index ' that the given bookmark refers to. If the given ' bookmark is Null, then it refers to BOF or EOF. In ' such a case, we need to use ReadPriorRows to ' distinguish between the two. If ReadPriorRows = True, ' the grid is requesting rows before the current ' location, so we must be at EOF, because no rows exist ' before BOF. Conversely, if ReadPriorRows = False, ' we must be at BOF. Dim Index As Long If IsNull(Bookmark) Then If ReadPriorRows Then ' Bookmark refers to EOF. Since (MaxRow - 1) ' is the index of the last record, we can use ' an index of (MaxRow) to represent EOF. IndexFromBookmark = MaxRow Else ' Bookmark refers to BOF. Since 0 is the ' index of the first record, we can use an ' index of -1 to represent BOF. IndexFromBookmark = -1 End If Else ' Convert string to long integer Index = Val(Bookmark) ' Check to see if the row index is valid: ' (0 <= Index < MaxRow). ' If not, set it to a large negative number to ' indicate that the bookmark is invalid. If Index < 0 Or Index >= MaxRow Then Index = -9999 IndexFromBookmark = Index End If End Function Private Function GetRelativeBookmark(Bookmark As Variant, _ RelPos As Long) As Variant ' GetRelativeBookmark is used to get a bookmark for a ' row that is a given number of rows away from the given ' row. This specific example will always use either -1 ' or +1 for a relative position, since we will always be ' retrieving either the row previous to the current one, ' or the row following the current one. ' IndexFromBookmark expects a Bookmark and a Boolean ' value: this Boolean value is True if the next row to ' read is before the current one [in this case, ' (RelPos < 0) is True], or False if the next row to ' read is after the current one [(RelPos < 0) is False]. ' This is necessary to distinguish between BOF and EOF ' in the IndexFromBookmark function if our bookmark is ' Null. Once we get the correct row index from ' IndexFromBookmark, we simply add RelPos to it to get ' the desired row index and create a bookmark using ' that index. Dim Index As Long Index = IndexFromBookmark(Bookmark, RelPos < 0) + RelPos If Index < 0 Or Index >= MaxRow Then ' Index refers to a row before the first or after ' the last, so just return Null. GetRelativeBookmark = Null Else GetRelativeBookmark = MakeBookmark(Index) End If End Function Private Function GetUserData(Bookmark As Variant, _ Col As Integer) As Variant ' In this example, GetUserData is called by ' UnboundReadData to ask the user what data should be ' displayed in a specific cell in the grid. The grid ' row the cell is in is the one referred to by the ' Bookmark parameter, and the column it is in it given ' by the Col parameter. GetUserData is called on a ' cell-by-cell basis. Dim Index As Long ' Figure out which row the bookmark refers to Index = IndexFromBookmark(Bookmark, False) If Index < 0 Or Index >= MaxRow Or _ Col < 0 Or Col >= MaxCol Then ' Cell position is invalid, so just return null ' to indicate failure GetUserData = Null Else GetUserData = GridArray(Col, Index) End If End Function |