How to parse a specific line from xml/rss feed

Programming Questions

bignickk

How to parse a specific line from xml/rss feed

in Programming Questions • 4 months ago

Hello everyone

I've been trying to make a program that makes several LED's turn on and off depending on xml feed's data. Unfortunately i am very new to Processing and i have like a week to finish this project, but problems keep occuring everywhere as usual :) . Anyway to the point so far one of the main problems is that half of the things I am trying to do(such as turn LED on and off) works on Processing version 1.5 and part of my xml parsing code works on version 2+. Currently I am trying to run this code in order to get the xml info I want :

The code:

/**

* Loads RSS feed and visualizes the titles in a very simple manner.

* Color and bar depend on the length of the corresponding title.

// Array to store titles

String[] titles;

XML xml;

XML[] children;

PFont font;

void setup() {

size(700, 300);

background(0);

noStroke();

// Setup font

font = loadFont("Calibri-12.vlw");

textFont(font, 12);

xml = loadXML("http://weather.yahooapis.com/forecastrss?w=27764362");

children = xml.getChildren("channel/yweather:wind"); // the program reads the xml content without yweather:wind, but i need exactly this bit, so thats why i left it so you can see that I've tried

titles = new String[children.length];

for (int i = 0; i < children.length; i++) {

String title = children[i].getContent();

titles[i] = title;

}

void draw() {

background(255);

// Draw all titles with bars and colors depending on its length

for (int i = 0; i < titles.length; i++) {

float y = (i+1) * 15;

fill(255 - constrain(titles[i].length(), 0, 255));

rect(8, y - 11, 14, 14);

fill(127, 100);

rect(23, y - 11, titles[i].length() * 2, 14);

fill(0, 220);

text(titles[i], 26, y);

}

So basically what I need to do is get the "yweather:wind" line of the XML code which it doesn show and get wind speed and wind direction attributes and use those values later in order to control the LED's . I've tried all possible getChild commands such as (channel/yweather:wind, channel/yweather: and etc) Unfortunately this seems to be harder than i expected considering all the version incompatibility. I've connected everything through Arduino I also tried using Firmata library which works only in ver 1.5 sort of :D

PS: as you can probably see one part of the code doesnt do anything specific for xml reading it just colors the text, but this is an example which Im using and if i delete this bit of the code i just get a black screen.

I would appreciate any help since this is my final project and the time is passing by quickly

Thanks

Nick

Replies(18)

PhiLho

Re: How to parse a specific line from xml/rss feed

4 months ago

The problem is that this XML use the yweather namespace, but Processing seems not to handle such namespaces, so with 2.0b9 it fails with the error:
The prefix "yweather" for element "yweather:wind" is not bound

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

Soo this means that i wont be able to call this part specifically?

Ive tried with 2.0b7 and 2.0b9, still not working

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

Is there any way that I can extract the exact wind speed and wind direction from this feed or I need to find another one

Thanks

Nick

PhiLho

Re: How to parse a specific line from xml/rss feed

4 months ago

Try with loadStrings() and extract the information from the specific line, perhaps with split() on double quote.

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

Okay thanks I will try

PhiLho

Re: How to parse a specific line from xml/rss feed

4 months ago

A way to do it. Unorthodox, but seems to work...

// Array to store titles
String[] titles;
PFont font;
void setup() {
size(700, 300);
background(0);
noStroke();
// Setup font
font = createFont("Arial", 12);
textFont(font, 12);
// xml = loadXML("http://weather.yahooapis.com/forecastrss?w=27764362");
String[] xml = loadStrings("G:/Tmp/weather.xml");
println("Weather read");
int i = 0;
for (; i < xml.length; i++)
{
if (xml[i].contains("yweather:wind"))
break;
}
if (i == xml.length)
{
println("Not found");
exit();
}
String[] info = xml[i].split("\\W+"); // Split on everything not alphanumerical
println(info);
titles = new String[3];
for (int j = 0; j < info.length; j++)
{
if (info[j].equals("chill")) titles[0] = "chill = " + info[j+1];
if (info[j].equals("direction")) titles[1] = "direction = " + info[j+1];
if (info[j].equals("speed")) titles[2] = "speed = " + info[j+1];
}
}

Same draw() routine.

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

Hi, it works great even for 1.5 just when I use the original link instead the xml file that you are using, I guess because I don't have this file on my laptop. So now I have to get the string number that represents the wind speed for example and put it into the loop so for example when the speed is more than 8mp/h to turn one LED on right?

Thanks so much Phil, you are the man :)

PhiLho

Re: How to parse a specific line from xml/rss feed

4 months ago

Yes, sorry, I saved the XML file to my hard disk to speed up loading, but it is the same, of course. I just forgot to change the path to the URL.

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

Hey PhiLho can I ask you one more thing, because i just get one error. I've worked a bit more on this code and I am going to use it with Firmata. Also now i got to the point where i need to get string values and make the if statement for different LEDs. Unfortunately I get this error " unexpected token: void" and it highlights the loop line. It is strange because it gave me the same error for void setup before and I fixed it somehow dunno how, but this error is a bit unpleasant. I tried with Ctr+ T but it didnt worked and i tried running the Standard Firmata script from Arduino again, but i still get this error :(

Check the code :

// Array to store titles

String[] titles;

import processing.serial.*;

PFont font;

import cc.arduino.*;

Arduino arduino;

int ledPin = 13;

Serial myPort;

void setup() {

size(700, 300);

background(0);

noStroke();

//println(Arduino.list());

arduino = new Arduino(this, Arduino.list()[0], 57600);

arduino.pinMode(ledPin, Arduino.OUTPUT);

// Setup font

font = createFont("Arial", 12);

textFont(font, 12);

// xml = loadXML("http://weather.yahooapis.com/forecastrss?w=27764362");

String[] xml = loadStrings("http://weather.yahooapis.com/forecastrss?w=27764362");

println("Weather read");

int i = 0;

for (; i < xml.length; i++)

{

if (xml[i].contains("yweather:wind"))

break;

}

if (i == xml.length)

{

println("Not found");

exit();

}

String[] info = xml[i].split("\\W+"); // Split on everything not alphanumerical

println(info);

titles = new String[3];

for (int j = 0; j < info.length; j++)

{

if (info[j].equals("chill")) titles[0] = "chill = " + info[j+1];

if (info[j].equals("direction")) titles[1] = "direction = " + info[j+1];

if (info[j].equals("speed")) titles[2] = "speed = " + info[j+1];

}

println(Serial.list());

int speed = Integer.parseInt(info[8]);

println(""+ speed);

void loop() {

if (speed>11) { //if the value is maxed out or greater than 250

arduino.digitalWrite(ledPin, Arduino.HIGH);

delay(500);

}

Once i go pass this error and see if the led actiually works with the if statement Im gonna add 2 more LED's and include them in the statement. Here is some more about the error if needed :

processing.app.SketchException: unexpected token: void

at processing.mode.java.JavaBuild.preprocess(JavaBuild.java:326)

at processing.mode.java.JavaBuild.preprocess(JavaBuild.java:197)

at processing.mode.java.JavaBuild.build(JavaBuild.java:156)

at processing.mode.java.JavaBuild.build(JavaBuild.java:135)

at processing.mode.java.JavaMode.handleRun(JavaMode.java:176)

at processing.mode.java.JavaEditor$20.run(JavaEditor.java:481)

at java.lang.Thread.run(Thread.java:662)

Thanks Nick

PhiLho

Re: How to parse a specific line from xml/rss feed

4 months ago

Ctrl+T is a good idea...
Once I applied it to your code, I saw that loop() is defined inside setup(), meaning you forgot to close the brace after setup(), before loop().

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

}

void loop() {

if (speed>11) { //if the value is maxed out or greater than 250

arduino.digitalWrite(ledPin, Arduino.HIGH);

delay(500);

}

you mean it should look like this? Because if yes then it gives me: Found one or too many {characters without a} to match it :D

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

Found it there is one brace infront the last comment :D

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

Can I ask you one more thing if you have time and im not too much of pain in the ass. I think this is a bit more important error and is the key to making everything work. It relates to the code that you wrote the 1st time. It works great and everything, but now I need to get the exact wind speed value which is placed on number [8] in the string and I need to make it into int so it can actiually read that its a number, so I can compare in the if statement. I've tried doing it , but now when I call it it gives me the error: Cannot find anything named speed. I'll post the code one more time without the brace errors and u can check it if you have time. So far it gives me only the error that I've just mentioned, although im not sure what is gonna be next after i solve it , if I solve it :d

the code:

// Array to store titles

String[] titles;

import processing.serial.*;

PFont font;

import cc.arduino.*;

Arduino arduino;

int ledPin = 13;

Serial myPort;

void setup() {

size(700, 300);

background(0);

noStroke();

//println(Arduino.list());

arduino = new Arduino(this, Arduino.list()[0], 57600);

arduino.pinMode(ledPin, Arduino.OUTPUT);

// Setup font

font = createFont("Arial", 12);

textFont(font, 12);

// xml = loadXML("http://weather.yahooapis.com/forecastrss?w=27764362");

String[] xml = loadStrings("http://weather.yahooapis.com/forecastrss?w=27764362");

println("Weather read");

int i = 0;

for (; i < xml.length; i++)

{

if (xml[i].contains("yweather:wind"))

break;

}

if (i == xml.length)

{

println("Not found");

exit();

}

String[] info = xml[i].split("\\W+"); // Split on everything not alphanumerical

println(info);

titles = new String[3];

for (int j = 0; j < info.length; j++)

{

if (info[j].equals("chill")) titles[0] = "chill = " + info[j+1];

if (info[j].equals("direction")) titles[1] = "direction = " + info[j+1];

if (info[j].equals("speed")) titles[2] = "speed = " + info[j+1];

}

println(Serial.list());

int speed = Integer.parseInt(info[8]);

println(""+ speed);

}

void loop() {

if (speed > 11) //if the value is maxed out or greater than 250

arduino.digitalWrite(ledPin, Arduino.HIGH);

delay(500);

}

Thanks one more time :)

PhiLho

Re: How to parse a specific line from xml/rss feed

4 months ago

A variable declared between a { and its closing } disappears as soon as the } is reached, and is not reachable from outside (class fields are a different thing!). These are called local variables.
In Processing, you can declare global variables, in your code, these are those declared before setup().
Add a:
int speed;
line there, remove the int part of the assignment of the speed, and you should be good to go.

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

I see but If i just add int speed before the setup, how would it know that it relates to the exact speed from the xml and is exactly [8] from the string?

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

i mean when I add int speed as global var it doesn't give me the error, but its doesn't actiually read the data from the xml it just prints the string numbers and their matching content. And I need to link this if to the current wind speed so if its lets say higher than 5mp/h to turn the LED

PhiLho

Re: How to parse a specific line from xml/rss feed

4 months ago

Looks like I wasn't clear.
Change:

println(Serial.list());

int speed = Integer.parseInt(info[8]);

println(""+ speed);

}

println(Serial.list());

speed = Integer.parseInt(info[8]); // No "int" part, not a declaration, just an assignment

println(""+ speed);

}

in addition to declaring speed at global level.

And, in Processing, you can just write: speed = int(info[8]);

bignickk

Re: How to parse a specific line from xml/rss feed

4 months ago

Now I see what you meant I changed it, but my LED still doesnt turn on if lets say the value is of the wind speed is like 10km/h and i make a statement

void loop() {

if (speed > 5)

arduino.digitalWrite(ledPin, Arduino.HIGH);

delay(500);

}

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