sumber: http://delphi.about.com/od/usedbvcl/l/aa101403b.htm | |||||||
Here's how to place a DBLookupComboBox into a DBGrid. Create visually more attractive user interfaces for editing lookup fields inside a DBGrid - place a DBLookupComboBox into a cell of a DBGrid.
What a great idea! Let's see how to create the best data editing grid ever!
Creating a lookup with a DBLookupComboBoxTo show a DBLookupComboBox inside a cell of a DBGrid we'll need to make one available for us at run time. Select the "Data controls" page on the Component Palette and pick a DBLookupComboBox. Drop one anywhere on the form (leave the default name, "DBLookupComboBox1") - it doesn't matter where, since most of the time it will be invisible or floating over the grid.
Next, you have to add one more DataSource and a DataSet component to "fill" the combo box with values. Drop a TDataSource (name: DataSource2) and a TAdoQuery (name: AdoQuery1) anywhere on the form.
For a DBLookupComboBox to work properly several more properties must be set, these properties are key to the lookup connection:
Here's how to set all the important properties from code (in the form's OnCreate event handler):
Note: when you want to display more than one field in a DBLookupComboBox, as in the example above, you have to make sure that all columns are visible. This is done by setting the DropDownWidth property. However, you'll see that initially you have to set this to a very large value which results in dropped list being too wide in most cases. One workaround is to set the DisplayWidth of a particular Field shown in a drop down list. The next code snippet, placed inside the OnCreate event for the form, ensures that both author name and it's email are displayed inside the drop down list:
AdoQuery1.FieldByName('Email').DisplayWidth:=10; AdoQuery1.FieldByName('Name').DisplayWidth:=10; AdoQuery1.DropDownWidth:=150; Magic...What's left for us to do, is to actually make a combo box hover over a cell (when in edit mode) displaying the AuthorEmail field. We've already discussed the theory - I'll show you only the code here (you'll have the option to download the entire project later):
First, we need to make sure the DBLookupComboBox1 is moved (and sized) over the cell in which the AuthorEmail field is displayed.
Next, when we leave the cell, we have to hide the combo box:
Next, note that when in editing mode, all keystrokes are going to the DBGrid's cell, we have to make sure they are sent to the DBLookupComboBox. In the case of a DBLookupComboBox we are primarily interested in the [Tab] key - [Tab] should move the input focus to the next cell.
That's it. Run the project and voila ... one nicely looking drop down list box (with two columns!) all over the AuthorEmail field's column.
What does happen when you select a value (Name; Email) from the drop down list? When you pick an item ("row") from a DBLookupComboBox, the value or the correspondingKeyField field is stored as the value of the DataField field. |
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Thursday, 29 May 2014
Drop down list (DBLookupComboBox) inside a DBGrid
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