C# how to write code for next and previous buttons in flowlayoutpanel

Question

3.00/5 (1 vote)

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i have page's buttons in flowlayoutpanel`1,2,3,4 and next and previous buttons,if i'm on second page and i click on next button it will moved on 3 page, and if i click on button previous it will moved 1 page.

Who can help me, I think i must declare any variable on top for example int index,then it write in my next and previous functions.i tried it but it doesn't work.

What I have tried:

Suggested by Phil.o`

int currentPage;
int pageCount;

public Gallery()
       {
           InitializeComponent();
           for (int i = 1; i <= Controller.books.Count / 4 + 1; i++)
           {
               Button btn = new Button();
               btn.Text = i.ToString();
               flowLayoutPanel2.Controls.Add(btn);
               btn.Click += new EventHandler(show);
           }
       }

public void show(object sender, EventArgs e)
        {
            Button ays = sender as Button;
            int a = (int.Parse(ays.Text) - 1) * 4;
            int b = a + 4;
            this.Sharel(a, b);
        }

and my next and previous buttons.

Button button = new Button();
           button.Text = "previous";
           flowLayoutPanel2.Controls.Add(button);
           button.Click += new EventHandler(prev);
           Button bt = new Button();
           bt.Text = "next";
           flowLayoutPanel2.Controls.Add(bt);
           bt.Click += new EventHandler(next);

 public void prev(object sender,EventArgs e)
        {
            int a = Math.Max(0, currentPage - 1); 
            int b = Math.Min(pageCount, a + 4);   
            Sharel(a, b);
        }
public void next(object sender, EventArgs e)
        {
           int a = Math.Min(pageCount, currentPage + 1);        
            int b = Math.Min(pageCount, a + 4);           
            Sharel(a, b);
        }

public void Sharel(int start = 0, int end = 0)
       {
           currentPage = start;
           flowLayoutPanel1.Controls.Clear();
           for (int i = start; i < end; i++)
           {
               if (i >= Controller.books.Count)
               {
                   break;
               }
               if (end == 0)
               {
                   end = Controller.books.Count;
               }
               Book item = Controller.books[i];
               FlowLayoutPanel flp = new FlowLayoutPanel();
               flp.BackColor = Color.PaleGoldenrod;
               flp.AutoSize = true;
               flp.MinimumSize = new Size(10, 100);
               Label lb = new Label();
               lb.Text = "Title: " + item.title + "\n" + "Autor: " + item.author + "\n" + "Count: " + item.count + "\n" + "Price: " + item.price;
               lb.ForeColor = Color.Black;
               lb.AutoSize = true;
               flp.Controls.Add(lb);
               if (item.image != String.Empty)
               {
                   PictureBox pb = new PictureBox();
                   pb.Location = new Point(20, 80);
                   pb.Image = Image.FromFile("Nkarners/" + item.image);
                   pb.SizeMode = PictureBoxSizeMode.StretchImage;
                   flp.Controls.Add(pb);
               }
               Button bt = new Button();
               bt.Location = new Point(30, 30);
               bt.MinimumSize = new Size(10, 40);
               bt.Text = "Delete";
               flp.Controls.Add(bt);
               bt.Click += new EventHandler(delete);
               flowLayoutPanel1.Controls.Add(flp);
               bt.Tag = item.id.ToString();
               Button b = new Button();
               b.AutoSize = true;
               b.MinimumSize = new Size(10, 40);
               b.Text = "Edit";
               flp.Controls.Add(b);
               b.Click += new EventHandler(edit);
               b.Tag = item.id.ToString();
               button2.Tag = b.Tag;
               Button button = new Button();
               button.AutoSize = true;
               button.MinimumSize = new Size(10, 40);
               button.Text = "Order";
               flp.Controls.Add(button);
               button.Click += new EventHandler(order);
               button.Tag = item.id.ToString();

           }
       }

Posted 1-Mar-18 2:27am

Suren97

Updated 2-Mar-18 0:34am

v4

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Comments

phil.o 1-Mar-18 8:30am

The only FlowLayoutPanel class that I found is in System.Windows.Forms namespace, and does not seem to be fit to display pages. Could it be possible you need a TabControl instead?

Suren97 1-Mar-18 8:34am

no, i need flowlayoutpanel, my pages are working, for example when i click on button 1 page it shows me datas of 1 page,when i click on button 2 page it shows me datas of 2 page and so on.Now i need add prev and next buttons

phil.o 1-Mar-18 8:37am

Then, maybe showing the code which executes when you are clicking on button 1, for example, would help us understand how to help you :)

Suren97 1-Mar-18 8:43am

I have written code of Pages`1,2,3,4,5 and so on, in every page has 4 datas,for example if i have 10 datas it will be 3 page`4+4+2, i just need write function for prev and next buttons.i must say when i click on next button or previous, it will moved on next page or previous.

phil.o 1-Mar-18 8:50am

More specificaly, could you show us the code in the Sharel(int a, int b) method, please?

Suren97 1-Mar-18 8:52am

yes of course, i will add it in my question now

Suren97 1-Mar-18 8:54am

i updated, you can look

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phil.o · Answer 1 · 2018-03-01T03:14:00

Solution 1

Ok, the way things are organized, the Sharel displays 4 pages.
There are several things you need:
- first, you need a way to remember which page is actually displayed. Since existing buttons deal with static values, you are using these values as the start parameter. But, with previous and next buttons, you do not have static data; you need a value so that the compiler know which previous or next page to deal with.
You could add a private member variable in your form, something like

C#

int currentPage;

- second, when you create this member variable, you must then affect it a useful value when a page is actually displayed. For example, you could add:

C#

currentPage = start;

somewhere in the Sharel method.
- finally, from here you ahev an actual value which you can use in the next and previous methods. But, you also have to take care of the edge cases where you are displaying the first and last pages. For the first page, this is simple since its index is zero. For the last page, again you need a way to have an actual, valid value for the number of pages which you are actually displaying. This could be declared this way

C#

int pageCount;

You will have to give it a meaningful value yourself, at the time you are loading the pages in the control; because you will be able to get this value at that time. Then you could write the methods this way:

C#

public void prev(object sender,EventArgs e)
{
   int a = Math.Max(0, currentPage - 1); // Lower limit of start to zero
   int b = Math.Min(pageCount, a + 4);   // Upper limit of end to page count
   Sharel(a, b);
}

public void next(object sender, EventArgs e)
{
   int a = Math.Min(pageCount, currentPage + 1); // Upper limit of start
                                                 // to page count
   int b = Math.Min(pageCount, a + 4);           // Upper limit of end
                                                 // to page count
   Sharel(a, b);
}

Posted 1-Mar-18 3:14am

phil.o

Updated 1-Mar-18 3:28am

v2

Comments

Suren97 1-Mar-18 9:33am

But i need also create like this in function`
Button prev = sender as Button;

phil.o 1-Mar-18 9:36am

Why? Are there two buttons in a glocal space, or do you have two previous and next buttons in each page?

Suren97 1-Mar-18 9:38am

how can i send you picture?

phil.o 1-Mar-18 9:42am

You cannot, sorry.

Suren97 1-Mar-18 9:43am

don't you have fb?

phil.o 1-Mar-18 11:51am

Whether or not I have fb is not the question; I would never accept any file from someone on a public forum. Neither should you.

Suren97 1-Mar-18 9:51am

Where should i write currentPage = start?

phil.o 1-Mar-18 11:55am

At the biginning of the Sharel method would be a possibility.
Did you actually write any of that code yourself, or did you just copy it from somewhere? Because I have the feeling that you do not have any idea of how this code is doing its job...

Suren97 1-Mar-18 12:03pm

i have written it by myself, but your offered code is not working

Ralf Meier 2-Mar-18 6:22am

Show the code where you tried to realize what Phil.o has suggested to you.
If you have realized it as suggest (by Phil) it should work ...

Suren97 2-Mar-18 6:34am

Ok, you can look, i updated it which suggested by phil.o.

Ralf Meier 2-Mar-18 6:39am

The Variable Currentpage must be defined outside the methods.
Also you show assign here the value of the page which is currently displayed - I suppose that in the Moment the assignment isn't correct.
But ... you have written that the suggestion doesn't work - so what happens exactly ?

Suren97 2-Mar-18 6:43am

The variable currentPage i have defined outside the method.Problem is that when i click on next or previous buttons it shows me nothing,empty page,for example if i'm on second page then i click on next button it shows me empty page

Ralf Meier 2-Mar-18 6:49am

OK ... because I'm not sitting beside you :
If you set a Breakpoint into the Sharel-method at the beginning - what values do you get for 'a' and 'b' ?
2nd question : to get it work - what values do you write manually into 'a' and 'b' ?

Suren97 2-Mar-18 6:51am

start and end

phil.o 2-Mar-18 7:16am

There you have to use your debugger :)
Do you know what a debugger is, what it is for and how to use it?

Suren97 2-Mar-18 7:18am

no , idon't know, what is it?

phil.o 2-Mar-18 7:29am

Ok, this is a very common issue, to which CP's quick answers forum has already brought very good answers.
Here is a link to a solution of @ppolymorphe which will provide you with some links to understand what debugging is for and how it can be done. Do not focus on the question which is answered, just read the part of solution 3 which begins with Since arguing with computers....
Really, do it; debugging is far from optional if you want to make progress in development field. You may even enjoy it, as it allows you to have an in-deep perception of what is going on under the hoods.
Solution 3

Suren97 2-Mar-18 7:42am

Thank you so much)))

phil.o 2-Mar-18 8:18am

You are welcome.

Ralf Meier 2-Mar-18 8:04am

@Phil: Thumbs up ... ;)

phil.o 2-Mar-18 8:18am

Thanks :)