Could not repaint the drawn area?

Question

1.00/5 (1 vote)

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I have 2 user control added to the main form.
1.UserControl1 -Take Input from UserControl2 and display message by using drawString
2.UserControl2 have TextBox,User can enter the text on it causes UserControl1 to display user entered text
PaintEvent is registered with UserControl1.
Upadate ,refresh and invalidate could not redraw the user entered text

[edit]

C#

// UserControl1
{
    private void textBox1_TextChanged(object sender, EventArgs e)
    {
        _titleText = textBox1.Text;
        _mainform = new MainForm();
        this.titleChanged += new TitleChangedHAndler(_mainform.onTitleChanged);
        if (titleChanged != null)
        {
            titleChanged(_titleText);
        }
    }     
}

// MainForm
    public void onTitleChanged(string strText)
    {
       UserControl2.setText(strText);
       ;
    }

// UserControl2
    private void paint(object sender, PaintEventArgs e)
    {
        drawString(Text,...);
    }
    public void setText(theText)
    {
        Text = theText;
        this.Invalidate();
        this.Update();
    }
}

[/edit]

Posted 24-Mar-15 3:43am

Sarita S

Updated 24-Mar-15 4:43am

v5

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Comments

Richard MacCutchan 24-Mar-15 9:49am

Well that is sad. But if you want someone to help you you will need to show the relevant parts of your code.

Dave Kreskowiak 24-Mar-15 9:53am

Well that is sad.

LOL!

Sarita S 24-Mar-15 9:55am

content moved to question

Richard MacCutchan 24-Mar-15 10:07am

I have moved your code to the original question, where it belongs.
I cannot see when or where the various parts of the code are called; I suggest you use your debugger, set some breakpoints, and check what is happening.

Sarita S 24-Mar-15 10:32am

I debug the code it reach upto.
public void setText(theText)
{
Text = theText;
this.invalidate();
}
this.invalidate() line simple get scanned without calling the paint();

Richard MacCutchan 24-Mar-15 10:40am

You spelled Invalidate wrong; see https://msdn.microsoft.com/en-us/library/598t492a%28v=vs.110%29.aspx.

Timberbird 24-Mar-15 10:48am

_mainform = new MainForm();
Do you really create new MainForm object on client event? It looks somewhat messy. I hope this is not your main form where both user controls are placed?

Sarita S 24-Mar-15 10:50am

Yup..Its MainForm where I added those 2 user control.

Timberbird 24-Mar-15 10:59am

And you're creating a new instance of this class (i.e. new form) each time text is changes in one of the controls, then attach control to its handler... no wonder text is not changed. You should access current form instead - the one your controls are placed on - for example, by traversing control parents. Also, don't attach event in textBox1_TextChanged() (otherwise it'll be called billion times) - do that in initializer.

Sarita S 24-Mar-15 11:18am

Yeah.I did it.Whats the problem related to Invalidate??
It didnt call the paint

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Adam Zgagacz · Answer 1 · 2015-03-24T06:42:00

Solution 1

your

C#

paint

method is just private method. It will never be called unless you cal it specifically in your code. You need to override OnPaint and place your painting code there. It will be trigerred by on Invalidate.

C#

protected override void OnPaint(PaintEventArgs e)
{

    //Add your painting code  here
    base.OnPaint(e);
}

Posted 24-Mar-15 6:42am

Adam Zgagacz

Comments

Sarita S 25-Mar-15 4:44am

I used the onPaint() still could not call the paint.

Sarita S 25-Mar-15 4:46am

// UserControl1
{
private void textBox1_TextChanged(object sender, EventArgs e)
{
_titleText = textBox1.Text;
_mainform = new MainForm();
this.titleChanged += new TitleChangedHAndler(UserControl2.onTitleChanged);
if (titleChanged != null)
{
titleChanged(_titleText);
}
}
}
// UserControl2
private void paint(object sender, PaintEventArgs e)
{
drawString(Text,...);
}
public void onTitleChanged(text)
{
Text = text;
this.invalidate
}
I did this changes..still could not cal the paint again.

Adam Zgagacz 25-Mar-15 9:19am

Hmm... I dont see any OnPaint override in code in your comment. Are you sure you added it?

protected override void OnPaint(PaintEventArgs e)
{

//Add your painting code here
paint(this, e);
base.OnPaint(e);
}

Adam Zgagacz 25-Mar-15 9:21am

Set the breakpoint in fist line of OnPaint. You should see how often it is called.

Sarita S 25-Mar-15 10:22am

// UserControl1
{
private void textBox1_TextChanged(object sender, EventArgs e)
{
_titleText = textBox1.Text;
_mainform = new MainForm();
this.titleChanged += new TitleChangedHAndler(UserControl2.onTitleChanged);
if (titleChanged != null)
{
titleChanged(_titleText);
}
}
}
// UserControl2
protected override void OnPaint(PaintEventArgs e)
{
drawString(Text,...);
paint(this, e);
base.OnPaint(e);
}
public void onTitleChanged(text)
{
Text = text;
this.invalidate
}
Actually this is the new code.
Set the breakpoint at first line it get called only once.

Sarita S 25-Mar-15 10:30am

Overall on my observation we could not call the invalide,update and refresh from the method which get called outside the the class where paint is actually registered.