Getting weather data from XML

Programming Questions

Ben Crack..

Getting weather data from XML

in Programming Questions • 1 years ago

Hi, I'm new to processing, but code a lot in other languages (C++, Actionscript, and a few others), and I'm writing some code to get the current weather from yahoo. Here is the page the XML data comes from:

Yahoo

And my code:

XMLElement xml;
void setup() {
PFont font;
size(500,300); //screen size, etc.
background(0);
font = loadFont("Arial-Black-48.vlw");
fill(255);
textFont(font, 13);
}
void draw() {
if(second() == 0) { //Run every minute (Just for testing, will later run every hour
String feed = ("http://weather.yahooapis.com/forecastrss?w=24493874&u=c");
xml = new XMLElement(this,feed);
background(0);
XMLElement yweather = xml.getChild("weather"); //I think the problem is here. What should the child be?
String currweather = yweather.getContent(); //current weather
}
}

This code originally came from Here, and I edited it.

The error is: "NullPointerException"

I think the problem is on line 23, I don't know what should be in the quotes (I have no xml experience)

The information I hope to get from the XLM data is:

<yweather:forecast day="Sat" date="26 Nov 2011" low="9" high="10" text="Showers/Wind" code="11"/>

Thanks for any help!

Replies(7)

Ben Crack..

Re: Getting weather data from XML

1 years ago

Solved, thanks to google. I just needed "channel/item/description" on line 23.

hellochar

Re: Getting weather data from XML

1 years ago

The nullpointer comes from the fact that there is no direct child named "weather" from the xml file. Taking a look at it, there's a "channel" element which holds all of the data; inside this element there's an "item" element which then actually holds the "yweather:forecast" element. So to get yweather:forecast, try:

XMLElement yweather = xml.getChild("channel/item/yweather:forecast");

This will prevent the nullpointer.

But be careful; getContent() won't get the data you want. You have to use the getString method inside XMLElement to grab the attribute you want. For instance:

String currweather = yweather.getContent(); //this returns null!
String text = yweather.getString("text"); //this returns "Showers/Wind"
String date = yweather.getString("date"); //this returns "26 Nov 2011"

Edit: Sounds good. I'll leave this here for others.

Ben Crack..

Re: Getting weather data from XML

1 years ago

Ok, it works great! here is the finished code:

XMLElement xml;
String[] data; //XML data from "channel/item/description" goes here after being split down to just the weather
String todayUnsplit; //Weather of today, jumbled together with high and low temps
String tomorrowUnsplit; //Weather of tomorrow, jumbled together with high and low temps
String[] today; // 0:DAY 2:WEATHER 4:HIGH 6:LOW
String[] tomorrow; // 0:DAY 2:WEATHER 4:HIGH 6:LOW
oneDay thisDay; //Thisday object
oneDay nextDay; //Nextday object
void setup() {
thisDay = new oneDay();
nextDay = new oneDay();
}
void draw() {
if(second() == 0) { //Run every minute (Just for testing, will later run every hour
String feed = ("http://weather.yahooapis.com/forecastrss?w=24493874&u=c"); //Get the feed
xml = new XMLElement(this,feed); //Stick the feed into a variable
XMLElement yweather = xml.getChild("channel/item/description"); //get the forecast part of the feed
String currweather = yweather.getContent(); //convert xml data to string
data = splitTokens(currweather,"<>"); //Split the mass jumble of data into managable parts
todayUnsplit = data[16]; //get the forecast. You may need to change "16" to something else. To find out, use a for loop to print each piece of the array, until you see the forecast.
tomorrowUnsplit = data[18]; //You may need to change this too
today = split(todayUnsplit," "); //split the forecast into individual parts
tomorrow = split(tomorrowUnsplit," ");
thisDay.chosenDay = today[0]; //assign the forecast parts to an object
thisDay.weather = today[2];
thisDay.high = Integer.parseInt(today[4]);
thisDay.low = Integer.parseInt(today[6]);
nextDay.chosenDay = today[0];
nextDay.weather = today[2];
nextDay.high = Integer.parseInt(today[4]);
nextDay.low = Integer.parseInt(today[6]);
println(thisDay.chosenDay);
println(thisDay.weather);
println(thisDay.high);
println(thisDay.low);
}
}
class oneDay {
String chosenDay;
String weather;
int high;
int low;
}

This code may not work later, because yahoo's XML format may change. Now, I'm adding TTS using freeTTS

Ben Crack..

Re: Getting weather data from XML

1 year ago

I made a much more orginized version of the code, using hellochar's code, but I'm having some problems with it.

XMLElement xml;
void setup() {
String feed = ("http://weather.yahooapis.com/forecastrss?w=24493874&u=c"); //Get the feed
xml = new XMLElement(this,feed); //Stick the feed into a variable
XMLElement yweather = xml.getChild("channel/item/yweather:forecast"); //get the forecast part of the feed
String weatherGot = yweather.getString("text"); //this returns "Showers/Wind"
String dateGot = yweather.getString("date"); //this returns "26 Nov 2011"
String dayGot = yweather.getString("day"); //this returns "Mon"
String highGot = yweather.getString("high"); // this returns "10"
String lowGot = yweather.getString("low"); //this reurns "4"
weatherSpeech = weatherGot + " with a high of " + highGot + " degrees celcius, and a low of " + lowGot + " degrees celcius";
println(weatherSpeech);
}

"The function getString(string) does not exist" Is yweather supposed to be a class? I know getString() is a function, why isn't it working?

hellochar

Re: Getting weather data from XML

1 year ago

That's weird. I'll look into it soon. In the meantime, here's the reference page for getString: http://processing.org/reference/XMLElement_getString_.html You might be able to find something in there.

Ben Crack..

Re: Getting weather data from XML

1 year ago

Does that code (the one I just posted) work with anyone?

Ben Crack..

Re: Getting weather data from XML

1 year ago

I found out why it's not working. I was using a very old version of processing

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