Subforms

Angela solves a few day-to-day form and report problems, including how to stop dangerous right-clickers and how to dynamically add line numbers.

In Access 95 and 97, I’ve noticed that when I have a form with multiple subforms, I sometimes have a peculiar viewing problem — it seems that when I change records on the main form, some of my related subform records seem to disappear! They don’t actually disappear, but they’re not visible until I scroll or Shift-Tab up to view them. How can I fix this?


Annoying, isn’t it? This problem occurs on forms with one or more related subforms. When you change the current record on the parent form, the child forms are requeried as expected in order to synchronize their data, but not all the records are visible.

You can see a great example of the problem in Northwind. Open the Customer Orders form, and go to customer “Save-a-lot Markets” (record number 71, if you don’t feel like hunting). The parent form (Customer Orders) only has a little customer information — name and country. The parent form also has the Customers table as its RecordSource, which includes the [CustomerID] field. No surprises here.

The first subform, Customer Orders Subform1, lists all the Orders for the Customer currently displayed on the parent form. The two forms are linked by straightforward master/child links on the [CustomerID] field. No surprises here, either.

The second subform, Customer Orders Subform2, lists the details of the Order that’s currently active in Customer Orders Subform1. The master/child links are from [CustomerID] on the child form to [Customer Orders Subform1].Form![OrderID] on the master form. In English, that means the second subform links to the [OrderID] on the first subform. Still no surprises.

So while you’re looking at the order history for Save-a-lot Markets, try browsing through order 10607, which has five items. The last one is for “Uncle Bob’s Organic Dried Pears” — see for yourself. While the fifth record (Uncle Bob’s) is still active in the second subform, click on the next order number in the first subform, order 10612. The items for order 10612 are displayed, but notice which record is active in the item subform — it’s the fifth order item, “Ikura”, and you can’t see the first record. If you were unobservant, you’d think that order 10612 only had three items, since that’s what it looks like. But that’s not true — there are five items, you just can’t see the first two without scrolling or navigating up to them (see Figure 2).


Figure 2

This phenomenon is especially problematic when dealing with subforms without record navigation buttons. The two subforms on the Customer Orders are a perfect example: The only visual clue that there could be some records that aren’t displayed is that the button on the scroll bar isn’t resting at the top of the bar. I don’t know about your intended audience, but about half my clients can’t be trusted to know how to use a scroll bar at all, so I’m not enthusiastic about trusting them to know how to scroll up to see more records. Scroll down is plenty tricky enough.

So that’s the problem. How do you solve it? The most difficult part of the solution is remembering to use it — I have a bad habit of not remembering to put it into my forms until the testing phase. Fortunately, it just takes a few lines of code. Your code will need to switch to the “problem” subform, move to the first record there, and then set the focus back to the appropriate place in the original form. You’ll also need to trap for a particular error when the form loads: your OnCurrent event will occur before the GoToRecord command is available.

Using generic names, the three lines of code you need to add are:

The error-handling code you need to put in the routine is:

In the Customer Orders form in Northwind, the code will need to be put in the OnCurrent event of Customer Orders Subform1. It would read as follows (complete with the stamped-in code that was already there):The error-handling code you need to put in the routine is:

Now the form works exactly as expected, and when you view a new customer or a new invoice, the affected subforms all have their first record made active.

In closing

As much as I enjoy venturing into fun stuff like ActiveX controls or OLE graphing, I keep finding that most of my customers just need solid working forms and easy-to-read, accurate reports. All four of these questions are things I run across all the time, and the answers are immediately usable for most developers.

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