global variable not updating in draw()

Programming Questions

danielle_..

global variable not updating in draw()

in Programming Questions • 1 year ago

Hi all,

My program has several functions. One of which is getData, it gets data from a server and puts it in a global variable called wind. Every second the getData function connects to the server to get the 10 most recent data points. If I print them in the getData function I get 10 different values in the wind variable.
My draw() function (no frameRate set) should use the wind variable to do its thing. But when I print the value of wind in draw() it only takes the last value of the 10 data points and doesn't update the wind variable value with every draw() execution.
Here's an example of the output:
The 10 different data point printed from getData look fine:
get wind225.0
get wind227.0
get wind238.0
get wind255.0
get wind281.0
get wind290.0
get wind290.0
get wind286.0
get wind280.0
get wind269.0
The wind variable as printed from draw(), only the final value is printed:
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
269.0
etc.
When the next 10 points become available again only the last one gets printed.

Does anyone know where I should look to solve this issue? Thanks very much in advance, d

Replies(5)

PhiLho

Re: global variable not updating in draw()

1 year ago

" Does anyone know where I should look to solve this issue?"
By showing some code?

Now, if you have a float wind value, I don't see how it can hold 10 values! If that's an array, I don't know how you init it. That's why, instead of speculating, we need to see at least relevant fragments of code.

danielle_..

Re: global variable not updating in draw()

1 year ago

OK, PhiLho, no problem, I just didn't want to burden you with all kinds of code that distract from the problem.
Both wind and wind0 are initialised outside of draw() or getData.
I've printed both wind and wind0 as a first line in draw()

void getData(){
long now = System.currentTimeMillis();
double time = (double)now/1000f;
DecimalFormatSymbols symbols = new DecimalFormatSymbols(Locale.ENGLISH);
String timeStr = new DecimalFormat("##########.###", symbols).format(time);
double tmp = time-1;
String getStart = new DecimalFormat("##########.###", symbols).format(tmp);
for(int i = 0; i<allIds.length; i++){
try {
url2 = new URL("http://api.sense-os.nl/sensors/"+allIds[0]+"/data?per_page=10&sort=DESC&session_id="+sessionId);
conn2 = (HttpURLConnection)url2.openConnection();
conn2.setRequestMethod("GET");
conn2.setDoOutput(true);
}
catch( Exception e) {
println(e);
}
// read data
try{
input2 = conn2.getInputStream();
String inputString = "";
while(input2.available() != 0) {
inputString += (char)input2.read();
}
input2.close();
server_data = append(server_data, inputString);
serverData = new JSONObject(inputString);
JSONArray dataArray = serverData.getJSONArray("data");
for(int j=0; j<dataArray.length(); j++){
JSONObject o = dataArray.getJSONObject(j);
String v = o.getString("value");
v = v.replaceAll("\\\\", "");
JSONObject jV = new JSONObject(v);
int w = jV.getInt("wind");
int t = jV.getInt("temp");
String id = o.getString("sensor_id");
wind = (float)w;
temp = (float)t;
if(i==0){
wind0 = wind;
temp0 = temp;
print("get wind");
println(wind0);
// wSensor0 = append(wSensor0, wind);
}
}
}
catch (Exception e){
println(e);
}
}
}

I've just now noticed that when I change the 0 in
url2 = new URL("http://api.sense-os.nl/sensors/"+allIds[0]+"/data?per_page=10&sort=DESC&session_id="+sessionId);
to a i (I did this to keep things more clear) that the results are better but I still get a lot of 183.0 values when I run the program at frameRate(10) which is strange because the actual values vary a lot as you can see from the output above. This is the value of the wind or wind0 value in the latest situation:
183.0
275.0
110.0
265.0
183.0
183.0
183.0
183.0
183.0
183.0
183.0
328.0
110.0
265.0
183.0
183.0
183.0
183.0
183.0
183.0
183.0
300.0
110.0
265.0
183.0
183.0
etc.

Thanks for you help, best, d

PhiLho

Re: global variable not updating in draw()

1 year ago

Well, again, when you do:

for(int j=0; j<dataArray.length(); j++){
[...]
wind = (float)w;

the previous value of wind (in the previous iteration) is overwritten with the new one. Ie., you just overwrite wind a dataArray.length() number of times. And so only the last one is seen by draw().

danielle_..

Re: global variable not updating in draw()

1 year ago

OK, thanks. I didn't realise the for loop was so much faster than the draw function.

Jonny Stu..

Re: global variable not updating in draw()

1 year ago

It's not that the for loop is faster than the draw function. Processing does one thing at a time (with some exceptions that I don't think apply here). When you call getData() the drawing stops until getData() has finished. If the for loop took a couple of minutes you'd still only see the final value of the wind variable.

Top Reply