C++ Windows Forms L10 - Instantiate

C++.NET
Windows Forms Course
L10-Instantiate Controls At
Runtime

Mohammad Shaker
mohammadshakergtr.wordpress.com
C++.NET Windows Forms Course
@ZGTRShaker

Instantiate Controls at
Runtime

The Concept of
Instantiating Controls at
Runtime

Instantiating at Runtime
• Let’s have the following form

• Now, let’s have the following code, what does it mean?
It’s just allocating a memory space for a new object (button)
private: System::Void Form1_Load(System::Object^
System::EventArgs^ e)
{
Button ^MyButton = gcnew Button;
}

• Does it show a button?!!!

sender,

• What happens?

{
MyButton->Show();
}

sender,

• Parent! What happens now?

{
MyButton->Parent = this;
}

sender,

• Why?

• What happens?
private: System::Void Form1_Load(System::Object^ sender,
{
MyButton->Location = System::Drawing::Point(10, 20);
MyButton->Name = L"button1";
MyButton->Size = System::Drawing::Size(75, 23);
MyButton->TabIndex = 0;
MyButton->Text = L"MyDynamicButton";
MyButton->UseVisualStyleBackColor = true;
}

How can we fire events on the
newly created button?

The event wire-up in design time
• Consider that we have the following design …

• And we add a button lick event to button1
_
c
private: System::Void button1_Click(System::Object^
{
MessageBox::Show("HiiiIiIIiIIIIIiiii");
}

sender,

• Now, we can see the following …

private: System::Void button1_Click(System::Object^
• Now, let’s add sth
System::EventArgs^ e) else!
{
MessageBox::Show("HiiiIiIIiIIIIIiiii");
}

sender,

• Now, back to our Button:
{
}

• We can do this:
{
MyButton->Click += gcnew System::EventHandler(this,
&Form1::button1_Click_1);
}

• What happens when clicking the created Button “MyButton”
or Button1?
private: System::Void button1_Click_1(System::Object^
sender, System::EventArgs^ e)
{
MessageBox::Show("Wow!!! ");
}

• We can do this?
{
&Form1::Mamy);
}

• And change it accordingly like this?

private: System::Void Mamy(System::Object^ sender,
{
MessageBox::Show("Mamy is a great cook! :D");
}

• Now, Consider we have the following two functions
private: System::Void Mamy(System::Object^
{
this->Text = "Mamy";
}

sender,

private: System::Void Chocolate(System::Object^ sender,
{
MessageBox::Show("There's no chocolate to eat :'( ");
}

• We can do this? Try it out!
{
&Form1::Mamy);
&Form1::Chocolate);
}

Now, let’s see some more
advanced stuff

Event handling
{
MyButton->MouseHover += gcnew System::EventHandler(this,
&Form1::MyProdHover);
}

Event handling
• Compiler error, why?
private: void MyProdHover (System::Object^
{
while (sender->Width < 200)
{
sender->Width+=3;
sender->Height+=1;
Threading::Thread::Sleep(100);
}
}

sender,

dynamic_cast
• We use dynamic_cast
private: void MyProdHover (System::Object^ sender,
{
while ((dynamic_cast<Button^>(sender))->Width < 200)
{
(dynamic_cast<Button^>(sender))->Refresh();
(dynamic_cast<Button^>(sender))->Width+=3;
(dynamic_cast<Button^>(sender))->Height+=1;
}
}

dynamic_cast
• We can do this for sure
{
Button ^TempButton = (dynamic_cast<Button^>(sender));
while (TempButton->Width < 200)
{
TempButton->Width+=3;
TempButton->Height+=1;
}
}

• Now what happens? And what should happen?

Event handling
• Test it yourself. After seconds “without” motion the button
becomes like this:

How can we solve this and see the motion?

Event handling
• Refresh method!
{
Button ^TempButton = (dynamic_cast<Button^>(sender));
while (TempButton->Width < 200)
{
TempButton->Refresh();
TempButton->Width+=3;
TempButton->Height+=1;
}
}

Event handling
• Now, let’s adde) following …
the
System::EventArgs^

sender,

{
MyButton->MouseHover += gcnew System::EventHandler(this,
&Form1::MyProdHover);
MyButton->MouseLeave += gcnew System::EventHandler(this,
&Form1::MyProdLeave);
}

Event handling
• What will happen now?
private: void MyProdLeave (System::Object^ sender,
{
while ((dynamic_cast<Button^>(sender))->Width > 50)
{
(dynamic_cast<Button^>(sender))->Refresh();
(dynamic_cast<Button^>(sender))->Width-=3;
(dynamic_cast<Button^>(sender))->Height+=1;
}
}

Event handling

Mouse still here

Event handling

Now leaving the button area

What you can do now
• Now, you can create
– Any control you want
• textBox, pictureBox, panel, label, …. etc

– How you want it
– Controls its behavior
– With the number you want (Save references in lists, array, dictionary!!,
…etc)

C++ Windows Forms L10 - Instantiate

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