Greetings everyone -  I'm fairly new to Processing (and programming in general). I'm writing a program that will take an XML feed of weather data, extract the current weather conditions, and return a color based upon the current weather.

I'm having trouble, however, getting the XML feed to update - once the program starts running, it seems to only get data from the XML feed once. When the weather feed updates every hour, the text doesn't update along with it. Ideally, the program will update itself as new information becomes available.

My (admittedly very preliminary) code is below- the if loop has been simplified so that it looks less messy. Is there something that I'm missing re: the XML feed?

thanks for your help!

Code:

import processing.serial.*;

int n;
XMLElement xml;
String cs;
color c;
Serial port;

void setup() {

  String feed = (xml weather feed URL) //actual URL removed
  
  PFont font;

  size(500,300);      //screen size, etc. 
  background(0);

  font = loadFont("Arial-Black-48.vlw");
  fill(255);
  textFont(font, 13);

  String arduinoPort = Serial.list()[2];       
  port = new Serial(this, arduinoPort, 19200);
  
  xml = new XMLElement(this,feed);
  
}

void draw() {
  
    background(0);

    XMLElement lastreading = xml.getChild("observation_time");
    XMLElement weather = xml.getChild("weather");

    String reading = lastreading.getContent(); //last reading time
    String currweather = weather.getContent(); //current weather
    
    text(reading, 10, 215);
    text("Current Weather: "+ currweather, 10, 240);

    StringTokenizer st = new StringTokenizer(currweather, "\"<>,.()[] "); //tokenize each element in incoming string

    while (st.hasMoreTokens()){               

      String currentweather =st.nextToken().toLowerCase();             

        if (currentweather.indexOf("cloudy") >=0) {    
        c = color(153,51,0);
        }
      
        else if (currentweather.indexOf("sunny") >= 0) {
        c=color(153,51,17);
        } 

      cs = "#"+hex(c,6);
      port.write(cs);
    }

 delay(60000);
  
}

catch (Exception ex) {                                 
  ex.printStackTrace();
  System.out.println("ERROR: "+ex.getMessage());

}

 

Quote:


Though bear in mind that IIRC by default draw() runs at 60fps and I doubt your XML feed refreshes that often, so that's perhaps a little inefficient.  A simple way to reduce the rate at which it reads is to use a counter variable:

Code:

int counter;

void setup() {
  size(20,20);
  counter = 0;  
}

void draw() {
  if(counter > 60) {
    // do stuff once per second based on 60fps.
    // ( note this shouldn't be relied on for accurate timing 
    // since actual fps can be dependent on other factors)
    println("foo");
    // reset the counter
    counter = 0;
  }
  // increment the counter each frame
  counter ++;

} 

If you want to be more accurate you could use millis(), or maybe a datetime function but that's probably overkill...

If you knew that the feed was updating at a specific time, preferably every hour for this example, you could test like this:

Code:

if (minute() == 0) {
  // Re-fetch the feed
} 

Or if it's multiple times per hour just expand it...

Code:

if (minute() == 0 || minute() == 15 || minute() == 30 || minute() = 45) {
  // Re-fetch the feed
} 

But I'm new to Processing and I could be doing things inefficiently, but this works for me on my project. Best of luck.

This page: Weather Widget links to two weather API (Yahoo! and Google ones).
There are probably others.