Manually scrolling through a TComboBox

Question

I have not been able to figure out why I am unable to manually scroll through a TComboBox component when I programatically cause the drop down pick list to appear. Here is the code I am using:

SendMessage(ComboBox1.handle, CB_SHOWDROPDOWN, Integer(True), 0);

This causes the drop down pick list to appear. However, if I try to use my keyboard and use the up and down arrow keys, the drop down pick list immediately closes. How do I keep the list from auto-closing when using the keyboard up/down navigation keys?

Sertac Akyuz · Accepted Answer · 2013-06-21 21:14:05Z

5

Activate the ComboBox. And you'd better use the DroppedDown property, which also invalidates the combobox to reflect the change.

ActiveControl := ComboBox1; ComboBox1.DroppedDown := True;

edited Jun 21, 2013 at 21:14

answered Jun 21, 2013 at 20:29

Sertac Akyuz

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4 Comments

J... Over a year ago

Worth noting that OP's CB_SHOWDROPDOWN is only one of a larger set of window messages required to recreate the full sequence of activating and dropping down a combobox (which is why it doesn't work on its own). Agreed that this is preferable approach.

user1527613 Over a year ago

Adding ActiveControl := ComboBox1; and ComboBox1.DroppedDown := True; to the code makes no difference. The drop down list still continues to auto-close as soon as the down arrow key is touched.

Sertac Akyuz Over a year ago

@user - With my test here, with a brand new form having a button and a combobox, activating the combobox makes the difference. Actually if I don't activate it, the items cannot be changed with the keyboard but the dropdown doesn't close either. I suggest you to do the same and try this with a new project.

Sertac Akyuz Over a year ago

@J... Either will end up in SetActiveControl. To the first comment - Yeah, DroppedDown also invalidates the combo client rectangle. Incorporated to the answer.

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