Why does clicking in a text box cause an AutoScrol

问题:

Finishing up a register form in a C# application and I noticed with the panel if I enable AutoScroll and then have a textbox that is below the scroll and click on it it jumps all the way back up to the top. Is there a way to fix this with some code or is it a propriety?

It's a little difficult for me to explain it in words, so here's a short video that shows the behavior.

回答1:

I have had the same problem. I fixed it with this code in my panel:

protected override Point ScrollToControl(Control activeControl)
{
    return this.AutoScrollPosition;
}

回答2:

I had this exact problem. I had to remove the docking from my panels on the form and this fixed the problem.

回答3:

Since apparently no one has seen this behavior before and could provide a quick answer, I opened up Visual Studio to try and reproduce what you describe.

I created a new WinForms project with a GroupBox containing a Panel whose AutoScroll property is set to "True". Then, I added two new GroupBox controls inside of the Panel, each containing two TextBox controls. The first embedded GroupBox is at the top of the form, entirely visible at startup; the second embedded GroupBox is at the bottom where it must be scrolled into view. This is equivalent to the design/layout that you have as best I can tell from your description and video.

However, when I run the project, scroll down to the second embedded GroupBox and select one of the TextBox controls that it contains, it performs exactly as expected. The TextBox control that I clicked on gets the focus, without scrolling the entire panel back up to the top. I can't seem to reproduce what you're seeing. If you could either tell me what I've done wrong in designing my test sample or post the smallest sample project needed to recreate the behavior you're experiencing, I might be able to help.

Otherwise, here are a few suggestions of things to investigate:

1. The tab order of the objects on your form. This really shouldn't be causing the behavior described because clicking on a control should set the focus to that control, regardless of its position in the tab order, and jumbling up the tab order multiple times in my sample project still doesn't appear to have the same effect. But I suppose it's worth a try anyway. In Design Mode, go to your "View" menu, and click "Tab Order". All of the controls that you can set the tab order for will have a little colored box at their top-left corner, indicating their tab order in each container. To set the tab order, click once on each of the controls in the natural order you want them to be focused.

2. Scour your code for any <Control>.Focus or <Control.Select> statements. Make sure that you don't have any validation code that's altering the tab order in any way during run-time. This could be causing focus to jump back to a control located near the top of your Panel, forcing it to auto-scroll to the new location.

3. Try to reproduce the behavior in a brand new, clean project. Ideally, create a new project in Visual Studio and lay out the controls the exact same way you have them in the project with which you're experiencing difficulties. This is the same thing I did, partly because I don't have your particular project to work with, and also because this is the best way to troubleshoot particularly tricky behavior. It's more likely there is some quirk to your design or source code that's causing this behavior, rather than some kind of bug in the controls themselves. But either way, this will let you know exactly where the problem is occurring, which will get you that much closer to a solution.

回答4:

You can use TableLayoutPanel" instead of "Panel" to avoid scrollbar change its position.