Q141636: How to Set Up a Grid as a Destination for Drag and Drop
Article: Q141636
Product(s): Microsoft FoxPro
Version(s): 3.00 3.00b
Operating System(s):
Keyword(s): kbcode
Last Modified: 20-AUG-1999
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The information in this article applies to:
- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b
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SUMMARY
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By default, if a grid is used for the destination of a drag and drop operation,
the DragDrop method of the grid is called. This does not allow dropping into an
individual grid cell, because the DragDrop method of the cell control is never
called. This article shows how to calculate the destination cell coordinates,
and call the DragDrop method of the appropriate destination.
MORE INFORMATION
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The following code demonstrates how a grid can be set up as the destination of a
drag and drop operation. This example uses the Customer table from the
\VFP\Samples\Data\Testdata database.
Step-by-Step Example
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1. Run the following commands in the Command window to create a table to use as
the RecordSource of the grid that will be the destination of the drag and
drop operation.
USE HOME()+"samples\data\customer.dbf"
COPY TO cust_tmp.dbf
2. Create a new form. Add the Testdata!Customer and Cust_tmp tables to the Data
Environment of the form.
3. Place the source grid on the form by dragging the Customer table from the
Data Environment. Set the ColumnCount of this grid to 5.
4. Place the following code in the MouseDown event for the text box in each of
the columns in the source grid:
THIS.Drag(1) && Starts Drag
5. Place the following code in the MouseUp event for the text box in each of the
columns in the source grid:
THIS.Drag(0) && Ends Drag if mouse button is released
6. Place the destination grid on the form by dragging the Cust_tmp table from
the Data Environment. Set its ColumnCount property to 5.
7. Place the following code in the DragDrop event for the destination grid. The
LPARAMETERS statement will already be present.
LPARAMETERS oSource, nXCoord, nYCoord
PRIVATE nPrevColwidths, nGridLeftwall, nGridRightwall, nRowlevel, ;
nGridBottomEdge, nColCount
* Check destination grid for DeleteMark and RecordMark
nGridLeftWall=1+THIS.Left+IIF(THIS.DeleteMark and THIS.RecordMark,18, ;
IIF(THIS.DeleteMark or THIS.RecordMark,9,0))
* Check destination grid for Vertical Scroll bar
nGridRightWall=THIS.Left+THIS.Width-IIF(THIS.ScrollBars>1,14,0)
* Check destination grid for Horizontal Scroll bar
nGridBottomEdge=THIS.Top+THIS.Height-IIF(THIS.ScrollBars=1 or ;
THIS.ScrollBars=3, 12 ,0)
* Hold sum of ColumnWidths of columns to left of current column
nPrevColwidths=0
* Find out which destination row
nRowlevel=CEILING((nYcoord-THIS.Top-THIS.HeaderHeight)/THIS.RowHeight)
* Necessary if grid RecordSource table is not currently selected
SELECT EVAL('THIS.RecordSource')
* Loop through all visible columns
FOR ni=THIS.LeftColumn to THIS.ColumnCount
* Determine if current column is drop destination
IF BETWEEN(nXCoord, nGridLeftwall+nPrevColWidths, nGridLeftwall + ;
nPrevColwidths+THIS.Columns(ni).Width) and nRowlevel>0 and ;
nYCoord < nGridBottomEdge and nXCoord < nGridRightWall
* If correct column, call DragDrop of textbox in the column
THIS.Columns(ni).Text1.DragDrop(oSource,0,nYCoord, ;
ni+1-THIS.LeftColumn,nRowlevel)
EXIT && After drop, no need to check additional columns
ENDIF
* Add width of current column to sum of widths of previous columns
* and proceed to calculate if next column is drop destination
nPrevColWidths=nPrevColWidths+THIS.Columns(ni).Width
ENDFOR
8. Place the following code in the DragDrop event's method code for the text box
control in each of the columns of the destination grid (Note the two added
parameters in the LPARAMETERS statement).
LPARAMETERS oSource, nXCoord, nYCoord, nDropCol, nDropRow
* Activate cell which is destination for drop
THIS.PARENT.PARENT.ActivateCell(nDropRow,nDropCol)
* Replace ControlSource field with value of dragged object
REPLACE (THIS.ControlSource) WITH oSource.Value
9. Run the form, and drag from the source grid to the destination grid. The
value present in the source grid cell will appear in the destination grid
cell.
Notes
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1. The form ScaleMode property needs to be 3 - Pixels for the determination of
the destination column and row to work properly.
2. If the data types of the source and destination are different, a "Data type
mismatch" error will occur.
3. This example uses a text box in a grid column as the source of the drag
operation, but a text box on a form will work as well, as should any source
where the data type is the same as that of the destination.
Additional query words: VFoxWin
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Keywords : kbcode
Technology : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP300b
Version : 3.00 3.00b
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