Rome Feeder - arrays & NPE - Processing Forum

brodrost

Rome Feeder - arrays & NPE

in Contributed Library Questions • 5 months ago

Hi! So I'm really new to Processing, and I've run smack into a wall that I can't find my way around. I'm using rome feeder to read an rss-feed, and I want to use the data from that rss-feed to create an array. However, I can't seem to get the variables from the array I make.

Here is my code:

//romefeeder
import com.wyldco.romefeeder.*;
import com.sun.syndication.feed.synd.*;
Feeder feeder; // the feeder
SyndEntry entry; // a feed entry
String content;
FeederClass[]feedercontent = new FeederClass[10];
void setup(){
size(displayWidth, displayHeight, P3D);
background(255);
//create the feeder
feeder = new Feeder(this);
//turn on output to the console (useful for debugging)
feeder.verbose = true;
//set sort by published date
//default is unsorted (i.e. as ordered in the feed)
feeder.sortByPublishedDate();
//load the feed
feeder.load("http://monstercirkus.wordpress.com/feed/");
}
void draw(){
background(255);
while (feeder.hasNext()) {
for (int i = 0; i < feedercontent.length ; i ++) {
entry = feeder.next();
content = entry.getTitle();
feedercontent[i] = new FeederClass (content);
println(feedercontent[i].s); // This works
}
}
println(feedercontent[2].s); // This gets and NullPointerException-error.
}
// Feeder class
class FeederClass {
String s;
FeederClass(String sval){
this.s = sval;
}
}

Replies(4)

PhiLho

Re: Rome Feeder - arrays & NPE

5 months ago

I don't know this library, but I have one advice: put the reading of the feed in setup(): you don't need to read the feed 60 times per second!

brodrost

Re: Rome Feeder - arrays & NPE

5 months ago

PhiLo: Thank you for your answer! I thought so as well, but the code simply won't work in setup();. I don't know why though - in the example given in the library it's in draw(); as well.

PhiLho

Re: Rome Feeder - arrays & NPE

5 months ago

Well, you can also put a noLoop() in setup() to avoid calling draw() too often. Or perhaps the feed is read only once, then next() just return null...

Looking again your code, there is a flaw in the logic: you use feeder.hasNext() to see if there is data to read, but then you force read feedercontent.length times feed.next(), without checking if there is actually a positive .hasNext() for each time.
So the .next() can indeed return null.

You say " // This works" without telling what is the output, so I supposed it was OK, but perhaps you have only one or two entries.

brodrost

Re: Rome Feeder - arrays & NPE

5 months ago

PhiLo, thank you so much for your time! I actually found the solution to my own problem, which was that the loading to the feeder actually took a lot of time, so the print outside the while(feederHasNext) executed before the feeder was done loading; hence the NPE. I solved with a simple boolean making sure the feed was done loading before executing any other commands.