Embedding PApplet with JFrame/Swing error on JButton

darth_mak..

Embedding PApplet with JFrame/Swing error on JButton

in Integration and Hardware • 4 months ago

I'm building an application which needs to have a Processing PApplet contained in a JFrame. It all works fine unless I try to use a JButton. I broke it down to the smallest code segment possible where I still get the error. Basically, it runs fine until I create the JButton object. Then I get a null pointer exception. Here is the small code. I stuck a BorderLayout in there so that the PApplet panel would play nicely with the button.

import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
public class MainClass extends JFrame
{
EmbeddedProc mEmbed;
//Button mAButton;
JButton mAButton;
public MainClass()
{
super("Embedded Test");
setSize(750, 500);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLayout(new BorderLayout());
mEmbed = new EmbeddedProc();
add(mEmbed, BorderLayout.CENTER);
mEmbed.init();
//mAButton = new Button("A Button");
mAButton = new JButton("A Button");
add(mAButton, BorderLayout.EAST);
setVisible(true);
}
public static void main(String[] args) {
new MainClass();
}
}

The PApplet is bare-bones, so it's not a specific Processing method causing this.

import processing.core.PApplet;
import java.awt.*;
public class EmbeddedProc extends PApplet
{
public void setup() {
}
public void draw() {
}
}

You'll note the two commented lines in MainClass. If you swap JButton out for an AWT Button, everything works fine. This is my backup workaround. I'd rather not do that for consistency.

Here is the exception:

Exception in thread "Animation Thread" java.lang.NullPointerException
at processing.core.PApplet.handleDraw(PApplet.java:2297)
at processing.core.PGraphicsJava2D.requestDraw(PGraphicsJava2D.java:243)
at processing.core.PApplet.run(PApplet.java:2140)
at java.lang.Thread.run(Unknown Source)

So, does anyone know where the issue lies? Is there just a major conflict between JButton and Processing? The inverse might be just as helpful. Has anyone used JButton in a JFrame without getting an exception?

As a side note, don't bother stopping by to tell me I should stop using Swing. I know that that opinion exists. I have my reasons for using Swing, and that's not what this thread is about.

UPDATE:
I just found that I can get the exact same error (while using Button) by commenting out the size() function in the program where I came across this problem. However, size() isn't in the test PApplet, and that works fine if JButton is removed, so I'm not sure how related it is. Is this a generic exception?

Replies(8)

PhiLho

Re: Embedding PApplet with JFrame/Swing error on JButton

4 months ago

Processing is AWT-based and has its own threading model. I never tried to mix AWT components and Swing ones, I know it can be done, but perhaps you need to take some extra steps, like threading or similar.
I know there are also issues when you try to use a Swing component inside a sketch...

quarks

Re: Embedding PApplet with JFrame/Swing error on JButton

4 months ago

I have played with your code in Eclipse and managed to get the JButton in the JFrame without causing the exception error.

In the code below I have modified the EmbodiedProc class by adding the size command to the setup method. The setSize call in MainClass is no longer needed because I have added the call to pack just before making the frame visible.

NOTE: it is better to set the size of the embedded PApplet then allow the JFrame to determine its own size using pack()

import java.awt.*;
import javax.swing.*;
public class MainClass extends JFrame {
EmbeddedProc mEmbed;
JButton mAButton;
public MainClass() {
super("Embedded Test");
// setSize(750, 500);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLayout(new BorderLayout());
mEmbed = new EmbeddedProc();
add(mEmbed, BorderLayout.CENTER);
mEmbed.init();
mAButton = new JButton("A Button");
add(mAButton, BorderLayout.EAST);
pack();
setVisible(true);
}
public static void main(String[] args) {
new MainClass();
}
}

and

import processing.core.PApplet;
public class EmbeddedProc extends PApplet
{
public void setup() {
size(600, 500);
}
public void draw() {
}
}

darth_mak..

Re: Embedding PApplet with JFrame/Swing error on JButton

4 months ago

Thank you for you answers. I'm now setting the size of the PApplet, and using pack.

The only issue this leaves me with is resizing the display. I think it's layout dependent, but I need the PApplet to resize with its container (for fullscreen).

Trying to set resizeable cause the app to throw another null pointer exception.

frame.setResizable(true);

I think this is because the PApplet isn't in the expected type of container. But that's just a guess.

Is there another function I should call? (I am actively looking through the docs myself.)

jane38

Re: Embedding PApplet with JFrame/Swing error on JButton

4 months ago

the problem lies in adding the Papplet to main frame

add it to a Jpanel then add that to the main frame

mEmbed = new EmbeddedProc();
JPanel canvas= new JPanel();
canvas.add(mEmbed );
add(canvas, BorderLayout.CENTER);

darth_mak..

Re: Embedding PApplet with JFrame/Swing error on JButton

4 months ago

Hmm. Ironically, I finally got it to work by doing the exact opposite. The PApplet will resize when directly added to the BorderLayout.CENTER. The initial size still seems to need to be set on the PApplet though.

frame.setResizeable(true) specifically does not work because JPanels do not have that method.

The first problem seems to be generally solved by having the PApplet.init() call after the instantiation of the JButton.

Thanks guys/girls!

kvlinden

Re: Embedding PApplet with JFrame/Swing error on JButton

3 months ago

I've run the code supplied by both quarks and jane38 in Eclipse using Processing v2.0.1 and still get the same (or very similar) null pointer exception:

Exception in thread "Animation Thread" java.lang.NullPointerException
at processing.core.PApplet.handleDraw(PApplet.java:2301)
at processing.core.PGraphicsJava2D.requestDraw(PGraphicsJava2D.java:243)
at processing.core.PApplet.run(PApplet.java:2141)
at java.lang.Thread.run(Unknown Source)

What version of the processing core library were/are you using?

kvlinden

darth_mak..

Re: Embedding PApplet with JFrame/Swing error on JButton

3 months ago

I was running 2.0b9 64bit for Windows (8), which looks like it was the final pre-release before 2.0.

It seems like there are a few different things which can set off errors very similar to these, including placement of init() relative to JButtons, and size() related things.

I compared the sources for our versions, and the errors is on the exact same line.

What are you trying to accomplish? PApplet and JButtons? or PApplet and resizing? Or another issue?

EDIT:

I just tested my (working under 2.0b9) code with the (just downloaded) latest version of the library, and it works fine. Here is a pastebin of the two files:
http://pastebin.com/LuSP5Lxp < Mainclass
http://pastebin.com/ZnGt7ZPg < PApplet
I included 7 files from the core/library/ folder of Processing:

core.jar
gluegen-rt.jar
gluegen-rt-natives-windows-amd64.jar
gluegen-rt-natives-windows-i586.jar
jogl-all.jar
jogl-all-natives-windows-amd64.jar
jogl-all-natives-windows-i586.jar

I don't think you need the i586 files for 64bit windows. If you are on a Mac or Linux machine, you will need the files for those instead. Actually, I don't recall now if you need those other files in the first place, or if that had to do with specific support that I needed.

I'm not normally a Java or Processing dev, so I haven't really looked at any of this stuff since a month ago. I did Java 1 and 2 in college, which was enough to make me dangerous and capable of a lot, but I've been focused on web development since then. This was a side project.

I would assume that this detail does not matter, but I did all of my projects using the Android Development Tools (another side project) version of Eclipse. I already had it on my machine and it's setup for Java because of Android. I'm fairly certain that all the Android stuff is built on top of Java, so I don't think it affects standard Java projects.

kvlinden

Re: Embedding PApplet with JFrame/Swing error on JButton

3 months ago

Thanks - It appears that the key work-around is to move the call to mEbed.init() to the end of the constructor, after the JFrame is loaded. Doing that allows my examples to run without error in v2.0b9 and v2.0.1. quarks's code (see above) didn't do this and it appears that jane38's did.

This is a bit unfortunate given that I'm working with introductory programming students for whom such work-arounds are puzzling at best. I expect that we'll keep v2.0b7 installed in the labs until we can figure out a more permanent solution. With that in place, it's pretty easy to transition new programmers from pure Processing to Java/Swing/Processing.

thanks for your help,

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