Add values from Code to Menu Item

Need Help With My Project
1

Is it possible to add some values to menu item within my code.

Example: i read all usb devices. If i found a device which have some files on it i would like to change the list and add only the usb devices which have some file on it.

Is that possible?

2

This is not possible at the moment. But idea is nice. We didn’t think in that direction.

3

+1 for this idea. In my scenario, I want to scan for a list of WiFi access points (looking for a FlashAir card) and populate the results in a menu list.

I also have other values that are programatically determined from lookups and calculations that would be great to have in a menu, but it doesn’t look like there’s a way to pass those dynamically - I’d have to know the list at compile-time.

While we’re at it, it would be super cool if the Menu control could hold both Label and Value, and if it were wrapped in a widget.

Basically, I want a Table widget that presents itself in the UI like a Menu. I might use a table for now as a workaround.

Thanks for considering!

4

You mean like this…

//change MENU labels
Blynk.setProperty(V0, "labels", "Menu Item 1", "Menu Item 2", "Menu Item 3");

Pete.

5

Maybe this is a gap in my knowledge of C/C++, but how can I do that if I don’t have those values as literals at compile-time?

In my simplest scenario, I have a CSV of Name/Value pairs that I’m storing on an SD card. I want to populate that list to the menu. Given the syntax, how would I pass this list of values, since the length of the list is not known ahead of time?

In the Table Widget, this is easy - there’s an AddRow().

Is there a way to achieve the same with the Menu?

6

You can create BlynkParamAllocated object, populate it with your values and pass to setProperty function. Check the example called SetProperty_MultiValue

2 Likes
7

I’d assume that it works with variables as well as string literals, but I don’t use menus in Blynk, so I’ve never tried it.

Pete.

8

Thanks, all - that’s exactly what I was looking for! In case it’s helpful to others, here is my routine as a snippet.

I’m reading a 2-column CSV from the SD card where column 0 is a string label and column 1 is a float value.

//
//	Reading from a CSV stored on the SD card
//	File structure in this example is 2 columns: String,Float
//

File file;

//from https://arduino.stackexchange.com/a/1237
String explode(String data, char separator, int index)
{
	int found = 0;
	int strIndex[] = { 0, -1 };
	int maxIndex = data.length() - 1;

	for (int i = 0; i <= maxIndex && found <= index; i++) {
		if (data.charAt(i) == separator || i == maxIndex) {
			found++;
			strIndex[0] = strIndex[1] + 1;
			strIndex[1] = (i == maxIndex) ? i + 1 : i;
		}
	}
	return found > index ? data.substring(strIndex[0], strIndex[1]) : "";
}

void PopulateMenuFromCSV()
{

	file = SD.open("/myFile.csv", FILE_READ);

	if (!file) {
		Serial.println("Error opening file.");
		return;
	}

	//first we need to count the number of lines in the file so we know how large to allocate the colleciton
	int numlines = 0;
	while (file.available())
	{
		file.readStringUntil('\n'); //in this CSV, each line is terminated with a newline character
		numlines++;
	}

	String line;
	file.seek(0); //seek back to the beginning of the file

	//Use the BlynkParamAllocated object to contain the menu labels we want to add
	BlynkParamAllocated items(sizeof(String)*numlines);

	for (int i = 0; i< numlines; i++)
	{
		line = file.readStringUntil('\n');
		
		//split the line at a comma, expecting line format of String,Float
		String name = explode(line, ',', 0); //this will get the item in the first column
		String value = explode(line, ',', 1); //this will get the item in the 2nd column
		float floatval = value.toFloat(); //we expect the second column to contain floats
		if (floatval != 0) //only add a line if we got a valid float (we don't expect 0 as a value in this list)
		{
			items.add(name); //add it to the collection of menu items
		}
	}

	Blynk.setProperty(V30, "labels", items); //push it back to our menu, in this case, Pin 30

	file.close();
}

float GetValueFromMenuSelection(int selectedIndex)
{
	//Blynk menus return 1-based index, so we need to decrement
	selectedIndex = selectedIndex - 1;

	file = SD.open("/myFile.csv", FILE_READ);
	if (!file) {
		Serial.println("Error opening file.");
		return -1;
	}

	for (int i = 0; i < selectedIndex; i++)
	{
		if (file.available())
		{
			file.readStringUntil('\n');
		}
		else
		{
			Serial.println("Error seeking to " + String(selectedIndex));
		}
	}
	//the next line we read should be the selected index line
	String line = file.readStringUntil('\n');
	file.close();

	String name = explode(line, ',', 0);
	String value = explode(line, ',', 1);
	float floatval = value.toFloat();
	if (floatval != 0) { //again, a test to see if we got a valid float and we're not expecting a 0
		Serial.print("Menu item set to " + name + " : ");
		Serial.println(value);
		return floatval;
	}

	else return -1;
}

There’s likely a more efficient way to do this, but hopefully this snippet will help others.

Still, it’d be super awesome to have a menu Widget wrapper that could store both key and value for scenarios like this. The WidgetTable class is so easy to work with in this way - if only I could bind it to a menu :slight_smile:

Anyhow, thanks again. The Blynk platform and community are so awesome.

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