How do I create a scrollbar in panel which contain a FillRectangle inside?

Question

2.00/5 (1 vote)

See more:

I already create 2 panel in Form, which Panel1 is set to Auto Scroll. Panel2 is inside Panel1 and contain a Fill Rectangle which is set with Timer so it looks like a progress bar. The problem is, when i scroll Panel1 to right, yes.. it scrolled to right but when I scroll it back to left, the color in left side is back to normal alias to its default color. Then how to preserve this color on the left side when I scroll it to right?

Any response, Thanks :)

VB

'This code is inside Form1_Load
Grafik = Panel2.CreateGraphics
Timer1.Start()

'This code is inside Timer1_Tick
time += 10
If time <= 100 Then
Grafik.FillRectangle(Brushes.BlueViolet, 0, 0, time, 25)
ElseIf time <= 200 Then
Grafik.FillRectangle(Brushes.Brown, 100, 0, time - 100, 25)
ElseIf time <= 300 Then
Grafik.FillRectangle(Brushes.DarkOrange, 200, 0, time - 200, 25)
ElseIf time <= 400 Then
Grafik.FillRectangle(Brushes.DarkSalmon, 300, 0, time - 300, 25)
ElseIf time <= 500 Then
Grafik.FillRectangle(Brushes.DarkSlateGray, 400, 0, time - 400, 25)
End If

http://s15.postimg.org/ix9q15rzv/cap.png[^]

When it scroll to right then scroll back to left, it should be violet color, but it is default like gray..

Posted 18-Jun-15 1:12am

rudy-peto

Updated 18-Jun-15 4:19am

v3

Add a Solution

3 solutions

Solution 2

You problem is that you paint on the Panel only once. Once you scroll the Panel over, everything you painted is lost. You have to do the painting of the Panel in the Panels Paint event. Every time the Panel is scrolled or another window is passed over your panel you will lose everything you painted and have to repaint it. Windows will tell you when you have to repaint by raising your Panels Paint event.

Posted 18-Jun-15 4:35am

Dave Kreskowiak

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sergey Alexandrovich Kryukov · Accepted Answer · 2015-06-18T04:35:00

You cannot "contain a FillRectangle"; this is not a stationary object. You can render rectangle using System.Drawing.Graphics.FillRectangle, but it happens in response to Paint event.

First, scrolling. For scrolling, you can have your control where you render graphics inside some scrollable control, such as Panel, and scroll that panel. Panel is ScrollableControl, so please see:
https://msdn.microsoft.com/en-us/library/system.windows.forms.scrollablecontrol%28v=vs.110%29.aspx[^].

Inner control should render what you want by overriding OnPaint method or handling the Paint event (then you could also use Panel, but OnPaint would require a derived class). But your graphics is not static, it is animated, or is changed in any way.

The idea is: you need to have some data model which describe your graphics, in your case, some data set describing current rectangle color/size/location. You rendering method should not use constant values (using hard-coded immediate constants is bad style anyway, really bad for maintenance of your project anyway), but values from the model. If you change the values and call Invalidate method, it will trigger re-drawing the graphics in the invalidated control. You need to understand how it works. Please see my past answers:
What kind of playful method is Paint? (DataGridViewImageCell.Paint(...))[^],
capture the drawing on a panel[^],
Drawing Lines between mdi child forms[^],
Zoom image in C# .net mouse wheel[^].

Then you can create a separate thread which implements the scenario of the animated sequence. It could be anything, such as rendering "physics" of some game. The scenario in a separate tread is much easier to implement than timers, because it is sequential, logically independent from your UI. There are specific problems with timers you don't want to have. I don't want to waste more time for explanation; just don't use timers. My past answer explains such animation:
How to speed up my vb.net application?[^].

Your thread only changes the data, and the triggers re-drawing by calling Control.Invalidate. But you cannot call this method directly in a non UI thread (the same goes for timers, excluding the timer System.Windows.Forms.Timer which is totally unsuitable for animation due to its prohibitively bad accuracy). It is also explained in my past answer referenced above. You need to use Control.Invoke to delegate the Control.Invalidate call to the UI thread. See also my past answers:
Problem with Treeview Scanner And MD5[^],
Control.Invoke() vs. Control.BeginInvoke()[^].

That's all.

—SA

Ralf Meier · Accepted Answer · 2015-06-18T03:05:00

Solution 1

I don't understand completly what you want to do ... but I would do the following :

You create your own Control.
This Control inherits from Panel (if you wish - I would take Control).
Inside this Control you integrate the Timer.
Inside this Control you override the OnPaint-method. This method gives you a Graphics-Object for the FillRectangle and also this method is re-called by each invalidating of your control.
With your Timer you force an Invalidate for your control.

I hope, this helps you - else response ...

Posted 18-Jun-15 3:05am

Ralf Meier

Comments

rudy-peto 18-Jun-15 10:16am

Thanks for response.. Okay, I upload an image above. Maybe you can take a look to what I mean.

Ralf Meier 18-Jun-15 10:26am

What happens if time exceeds the value of 500 ?
How do you realize (or wish to realize) the "scrolling to back" ?

rudy-peto 18-Jun-15 10:31am

When the time exceeds the value of 500, well..nothing happen.. 'time' just as a counter.. I plan to make the timer stop. But my problem is when scroll back, the color that should be violet, it changes to gray alias default..

Sergey Alexandrovich Kryukov 18-Jun-15 10:36am

Using the timer is a really bad idea here. Please see Solution 2.
—SA

Ralf Meier 18-Jun-15 10:43am

Solution 2 and also Solution 3 are just the same as I suggested in my Solution ... only with more words around ...

Sergey Alexandrovich Kryukov 18-Jun-15 10:56am

No, there are not the same at all. It's not just "more words".
Of course, I could not avoid some valid points you have made; without them, nothing would work.

But your solution is almost unusable. Using a timer is a really bad idea; one can use them, but it's way more difficult and pointless.

You did not tell what type of timer to use. Many will use System.Windows.Forms.Timer, which is unacceptable. Some will use other types of timers, but don't know about Invoke (BeginInvoke) which is critically important.

—SA

Ralf Meier 18-Jun-15 11:04am

You are quiet right, Sergey, and also not ...
I think, the Thread-Starter uses a System.Windows.Forms.Timer as you have said. But I think also that this is not the actual problem at this moment.
Of course this Control would work very much better if it's using a Thread - but with a Timer for the moment it will work too.

I think, the Thread-Starter have to think about Control-Painting and Invalidating and at first about doing this in the right way.
Other thinks could come later (my opinion).

But it is ((almost)) a pleasure to discus with you ... ;)

Sergey Alexandrovich Kryukov 18-Jun-15 11:18am

I already mentioned before that your solution would work, I only listed the problems the reader can face. I hope now you cannot deny that my solution is different.
Pleasure talking to you, without "almost".
—SA

Ralf Meier 18-Jun-15 14:13pm

I corrected "almost" and added +5 (as i have written : "you are quiet right ...")

Sergey Alexandrovich Kryukov 18-Jun-15 15:04pm

Thank you, Ralf.
—SA