Null Pointer Exception in Processing programming assignment

Programming Questions

wgimson

Null Pointer Exception in Processing programming assignment

in Programming Questions • 2 years ago

So I'm supposed to be passing command-line arguments from the 'args' string array in

public static void main(String[] args

...to arrays in a setup() function so that I can parse them and use them as values for the heights of bar graphs, which are to be drawn on a graphical window. I don't understand why I keep getting a NullPointerException error at line 16...

for(int i = 0; i < tempArgs.length; i++) {
dataArray[i] = Integer.parseInt(tempArgs[i]);
}

.....as I thought the tempArray array should have values in it, which seems to be bourne out by the System.out.println statement I used to test this at the end of the main method. Here's the whole code, it's quite short. Any help would be much appreciated.

public class Main extends PApplet {
int[] dataArray ;
int[] normalizedData;
String[] tempArgs;
@Override
public void setup() {
/*size(dataArray[2], dataArray[3]);
smooth();
background(255);*/
for(int i = 0; i < tempArgs.length; i++) {
dataArray[i] = Integer.parseInt(tempArgs[i]);
}
int max = dataArray[0];
for(int i = 0; i < dataArray.length; i++) {
if(dataArray[i] > max) {
max = dataArray[i];
}
}
for(int i = 0; i < dataArray.length; i++) {
normalizedData[i] = (dataArray[i] / max) * (height - 20);
}
for(int i = 0; i < normalizedData.length; i++) {
fill(255,34,65);
rect(3, 5, 10, normalizedData[i]);
}
size(dataArray[2], dataArray[3]);
smooth();
background(255);
}
public static void main(String[] args) {
String[] tempArgs = new String[args.length + 2];
tempArgs[0] = "--bgcolor=#FFFFFF";
tempArgs[1] = "project1.Main";
for(int i = 2; i < tempArgs.length; i++) {
tempArgs[i] = args[i-2];
}
System.out.println(tempArgs.length);
PApplet.main(tempArgs);
}
}

Replies(1)

PhiLho

Re: Null Pointer Exception in Processing programming assignment

2 years ago

You create a tempArgs array in main(), which is local and has nothing in common (except the name) with the member of your PApplet which remains uninitialized.

You are overcomplicating things... Just declare a static array in the PApplet ("global" variables are "static" in practice, since there is only one instance of PApplet...) and fill it from main().

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