Working with Callbacks

[gfxfloro]

Hi,

I am trying to get a simple numpad on screen working by using callbacks, rather than virtual functions.

Here is the Screen1View.cpp.

#include <gui/screen1_screen/Screen1View.hpp>
 
Screen1View::Screen1View() :
//	TextClickedCallback(this, &Screen1View::editTextClickHandler){}
	numpadCallback(this, &Screen1View::numpadClickHandler){}
 
 
void Screen1View::setupScreen()
{
    Screen1ViewBase::setupScreen();
//    editText.setClickAction(TextClickedCallback);
    Button_0.setClickAction(numpadCallback);
    Button_1.setClickAction(numpadCallback);
    Button_2.setClickAction(numpadCallback);
    Button_3.setClickAction(numpadCallback);
    Button_4.setClickAction(numpadCallback);
    Button_5.setClickAction(numpadCallback);
    Button_6.setClickAction(numpadCallback);
    Button_7.setClickAction(numpadCallback);
    Button_8.setClickAction(numpadCallback);
    Button_9.setClickAction(numpadCallback);
    Button_neg.setClickAction(numpadCallback);
    Button_back.setClickAction(numpadCallback);
    Button_dec.setClickAction(numpadCallback);
    Button_OK.setClickAction(numpadCallback);
 
}
 
void Screen1View::tearDownScreen()
{
    Screen1ViewBase::tearDownScreen();
}
 
/*
void Screen1View::editTextClickHandler(const TextAreaWithOneWildcard& t, const ClickEvent& evt)
{
	if (&t == &editText)
	{
		remove(keyboard);
		keyboard.setPosition(380, 240, 400, 220);
		add(keyboard);
		keyboard.invalidate();
	}
}
*/
 
void Screen1View::numpadClickHandler(const ButtonWithLabel& b, const ClickEvent& evt)
{
 TypedText h = *&b.getLabel();
 
}

What I would like to know is, how do I determine the label of the button clicked to know which it is, and how do I implement multiple Callbacks on one screen? I don't get this syntax

Screen1View::Screen1View() :
	numpadCallback(this, &Screen1View::numpadClickHandler){}

How would I implement the second TextClickedCallback like in the code above?

[Martin KJELDSEN]

Hi @gfxfloro​,

You could determine which button was clicked and do something with the typed text (h) in the case of each.

void Screen1View::numpadClickHandler(const ButtonWithLabel& b, const ClickEvent& evt)
{
    TypedText h = *&b.getLabel();
 
    if(&b == &myButton)
    {
        ....
    }
}

Or you could inspect the TypedText ID and learn something from that, or you could extract the unicodes for that ID and inspect those. Not sure what you want to do here.

The correct syntax for initializing callbacks is this - You're linking a handler to the callback which is then called when someone calls callback->execute();

Screen1View::Screen1View() :
numpadCallback(this, &Screen1View::numpadClickHandler),
numpadCallback2(this, &Screen1View::numpadClickHandler2),
...
{
    ....
}

Does that answer your question?

/Martin

[gfxfloro]

Ah, thank you, the callback syntax does make sense, it seemed like the braces belonged to the callback function.

Regarding the buttons, for some reason this line

TypedText h = *&b.getLabel();

doesn't work. The most elegant way would be a switch case in which I read, the labels from the buttons and differentiate from those. From the TouchGFX Documentation the getLabel() function should work, but I seem to have misunderstood something there.

Edit: And is there a way to have multiple ClickHandlers on the screen? the ClickHandlers for the buttons don't respond, when there is already a ClickEvent that triggered for the entire screen.

[Martin KJELDSEN]

If you re-direct the event from the View-global handleClickEvent() method, your buttons will have their handlers triggered.

void MyView::handleClickEvent(const ClickEvent& evt)
{
    ...
    View::handleClickEvent(evt);
}

/Martin

[Martin KJELDSEN · Accepted solution]

Sorry, i missed the non-functional code, haha =)

Here are a few things you can do with a button with label. Here i just added a button with label ("New Text") and wrote some code.

TypedText lblText = buttonWithLabel1.getLabelText();
TypedTextId id = lblText.getId();
Unicode::UnicodeChar buf[20];
Unicode::strncpy(buf, lblText.getText(), 20);

Here you have the TypedText, the ID of the typed text and the contents of the buffer (unicode values) associated with that ButtonWithLabel.

/Martin

[gfxfloro]

Thanks Martin, that did the trick!

[Martin KJELDSEN]

Great! Let me know if there's anything else ^_^

/Martin