Language - Java: Difference between revisions

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[[Category:Language]]
[[Category:Language]]
{{OSLang|[[File:icon-Java.png|64x64px|link=|alt=Java]]|Java is a modern, object-oriented programming language maintained by Oracle.}}
__NOTOC__
__TOC__


==Introduction==
We provide support for the Java language in all major operating systems. We also provide instructions on how to get your project started in a number of common development environments. Select your operating system and preferred development environment below, and follow the instructions to get your project running with Phidgets.


{{LanguageSupport|Java|the complete Phidget API, including events|all Phidget devices.|the {{Code|javac}} command line compiler as well as in integrated development environments(IDEs) such as [[#NetBeans | NetBeans]] and [[#Eclipse | Eclipse]]|}}
If you do not know which development environment you want to use, or your development environment of choice is not listed, we recommend starting with javac as the simplest path to getting your code running.


==Quick Downloads==
General information of how to use Phidgets with Java can be found in the '''Write Code''' section of each development environment page. This information is consistent across all pages.


{{QuickDownloads|Java|
==Choose Your Development Environment:==
{{APIQuickDownloads|http://www.phidgets.com/documentation/JavaDoc.zip}}|
{{ExampleQuickDownloads|http://www.phidgets.com/downloads/examples/JavaJNI.zip|}}|
{{ExtraLibraryQuickDownloads|http://www.phidgets.com/downloads/libraries/phidget21jar.zip|Java|(phidget21.jar)}}
{{WindowsQuickDownloads}}
{{MacQuickDownloads}}
{{LinuxQuickDownloads}}
}}


==Getting started with Java==
{{Language_-_Java_Dev_Environment_Table}}


If you are new to writing code for Phidgets, we recommend starting by running, then modifying existing examples. This will allow you to:
== Quick Downloads ==
{{ExampleCodeReasons}}


Instructions are divided up by operating system. Choose:
If you already know what you're doing and just need the files, you can find them all below.
*[[#Windows(2000/XP/Vista/7)|Windows 2000 / XP / Vista / 7]]
*[[#OS X |OS X]]
*[[#Linux | Linux]] (including PhidgetSBC)


==Windows (2000/XP/Vista/7)==
=== Documentation ===


===Description of Library Files===
*{{Phidget22API}}  (select Java from the drop-down menu)
Java programs on Windows depend on two files, which the installers in the [[#Libraries and Drivers | Quick Downloads]] section put onto your system:
* <b>{{Code|phidget21.dll}}</b> contains the actual Phidget library, which is used at run-time. By default, it is placed in {{Code|C:\Windows\System32}}. 
* <b>{{Code|phidget21.jar}}</b> is the Phidget Java library for JDK <i><b>1.4.2</b></i> or higher. Your compiler has to know where this file is. By default, it is placed into {{Code|C:\Program Files\Phidgets}}. So, you can either point your compiler to that location, or copy and link to it in a directory for your project workspace. For more information, please see the section for your specific compiler/environment.


If you do not want to use our installer, you can download the [http://www.phidgets.com/downloads/libraries/phidget21-x86.zip {{Code|phidget21.dll}}] as well as the [http://www.phidgets.com/downloads/libraries/phidget21jar_2.1.8.20120131.zip {{Code|phidget21.jar}}] and manually install them where you want; refer to our [[OS_-_Windows#Manual_File_Installation|Manual Installation Instructions]].
=== Example Code ===


Running the examples and writing your own code can be fairly compiler-specific, so we include instructions for each compiler below.
*{{SampleCode|Java|Java Examples}}


You can program Phidgets with Java in command line with the {{Code|javac}} compiler as well as in IDEs such as NetBeans and Eclipse.
===Libraries===


===Javac (Command Line)===
{{AllQuickDownloads}}
 
====Use Our Examples====
 
Download the [http://www.phidgets.com/downloads/examples/JavaJNI.zip example] and unpack them into a folder. Here, you can find an example program called HelloWorld which will work with any Phidget.  You can also find example programs for all the devices. {{FindYourDevice}} Please only use the simple examples. The full examples are intended for the [[#NetBeans | NetBeans IDE]].
 
Ensure that the {{Code|phidget21.jar}} is in the same directory as the source code.
 
To compile in Windows command prompt:
<div class="source">
<syntaxhighlight lang=bash>
javac -classpath .;phidget21.jar example.java
</syntaxhighlight>
</div>
 
This will create Java bytecode in the form of {{Code|.class}} files. Type the following to run the program:
<div class="source">
<syntaxhighlight lang=bash>
java -classpath .;phidget21.jar example
</syntaxhighlight>
</div>
 
 
If you wish, you can compile the project as a {{Code|.jar}} so there are fewer files to maintain. The [http://www.oracle.com/java Java SDK] provides the {{Code|jar}} utility which packages all the {{Code|.class}} files into a single {{Code|.jar}} file.
To begin, you will have to provide a Manifest file to indicate the program entry point. With your favourite text editor, create a new file with the following content:
<div class="source">
<syntaxhighlight lang=text>
Manifest-Version: 1.0
Class-Path: phidget21.jar
Main-Class: example
</syntaxhighlight>
<br/>
</div> 
Ensure that the file ends in a single new line or a carriage return character.
Save the file as {{Code|example.mf}} and place it in the same directory as the other {{Code|.class}} files.
Next, create the .{{Code|jar}} with:
<div class="source">
<syntaxhighlight lang=bash>
jar -cfm example.jar example.mf *.class
</syntaxhighlight>
</div>
Afterwards, you can run the {{Code|.jar}} with:
<div class="source">
<syntaxhighlight lang=bash>
java -jar example.jar
</syntaxhighlight>
</div>
Once you have the Java examples running, we have a [[#Follow the Examples|teaching]] section below to help you follow them.
 
=====Write Your Own Code=====
 
When you are building a project from scratch, or adding Phidget function calls to an existing project, you'll need to configure your development environment to properly link the Phidget Java library. Please see the [[#Use Our Examples| previous]] section for instructions.
 
In your code, you will need to include the Phidget Java library:
 
<div class="source">
<syntaxhighlight lang=java>
import com.phidgets.*;
import com.phidgets.event.*;
</syntaxhighlight>
</div>
 
The project now has access to the Phidget function calls and you are ready to begin coding.
 
The same [[#Follow the Examples|teaching]] section which describes the examples also has further resources for programming your Phidget.
 
===NetBeans===
 
 
=====Use Our Examples=====
 
You first download the [http://www.phidgets.com/downloads/examples/JavaJNI.zip examples], unpack them into a folder, and then find the source code for your device. {{FindYourDevice}} The full examples were written in NetBeans, so the rest of this section will use these examples. To use the simple examples, you will have to import the source code into a new NetBeans project.
 
[[File:Java NetBeans Open Project.PNG|link=|alt=Open Project]]
 
The only thing left to do is to run the examples! Click on Run &rarr; Run Project. The project, by default tries to find the {{Code|phidget21.jar}} in {{Code|..\..\lib}}.
 
[[File:Java NetBeans Run.PNG|link=|alt=Run]]
 
Once you have the Java examples running, we have a [[#Follow the Examples|teaching]] section below to help you follow them.
 
=====Write Your Own Code=====
 
When you are building a project from scratch, or adding Phidget function calls to an existing project, you'll need to configure your development environment to properly link the Phidget Java library. To begin:
 
1. Create a new Java application project with a descriptive name such as PhidgetTest.
 
[[File:Java NetBeans New Project.PNG|link=|alt=New Project]]
 
2. Add a reference to the Phidget Java library. In the projects pane, right click {{Code|Libraries}} and add the {{Code|jar}}.
 
[[File:Java NetBeans Add Jar.PNG|link=|alt=Add Jar]]
 
3. Find and select {{Code|phidget21.jar}}.
 
[[File:Java NetBeans Add Jar 2.PNG|link=|alt=Add Jar]]
 
4. Then, in your code, you will need to include the Phidget Java library:
 
<div class="source">
<syntaxhighlight lang=java>
import com.phidgets.*;
import com.phidgets.event.*;
</syntaxhighlight>
</div>
 
 
The project now has access to the Phidget function calls and you are ready to begin coding.
 
The same [[#Follow the Examples|teaching]] section which describes the examples also has further resources for programming your Phidget.
 
===Eclipse===
 
=====Use Our Examples=====
 
1. Download the [http://www.phidgets.com/downloads/examples/JavaJNI.zip examples] and unpack them into a folder. Here, you can find an example program called HelloWorld which will work with any Phidget.  You will also find example programs for all the devices. {{FindYourDevice}}
 
Please use the simple examples. The full examples were written in NetBeans, and are not compatible with Eclipse. The rest of this guide will assume that the simple examples are used. The example source code will be copied into your Eclipse project later on. Keep note of the file name of the example as a Java class will be created with the same name.
 
2. Generate a new Java project with a descriptive name such as PhidgetTest. Click next.
 
[[File:Java Eclipse New Project.PNG|link=|alt=New Project]]
 
3. On the next screen, go to the libraries panel and add an external {{Code|jar}}.
 
[[File:Java Eclipse Add Jar 1.PNG|link=|alt=Add Jar]]
 
4. Find and select {{Code|phidget21.jar}}.
 
[[File:Java Eclipse Add Jar 2.PNG|link=|alt=Add Jar]]
 
5. Add a new Java class to the project.
 
[[File:Java Eclipse New Class.PNG|link=|alt=New Class]]
 
6. Name this class with the same name as the simple example's name.
 
[[File:Java Eclipse New Class 2.PNG|link=|alt=New Class]]
 
7. Copy and paste the example source code over to the class you created.
 
[[File:Java Eclipse Source.PNG|link=|alt=Source Code]]
 
8. The only thing left to do is to run the examples!
 
[[File:Java Eclipse Run.PNG|link=|alt=Run]]
 
 
Once you have the Java examples running, we have a [[#Follow the Examples|teaching]] section below to help you follow them.
 
=====Write Your Own Code=====
 
When you are building a project from scratch, or adding Phidget function calls to an existing project, you'll need to configure your development environment to properly link the Phidget Java library. Please see the [[#Use Our Examples 3| Use Our Examples]] section for instructions.
 
In your code, you will need to include the Phidget Java library:
 
<div class="source">
<syntaxhighlight lang=java>
import com.phidgets.*;
import com.phidgets.event.*;
</syntaxhighlight>
</div>
 
The project now has access to the Phidget function calls and you are ready to begin coding.
 
The same [[#Follow the Examples|teaching]] section which describes the examples also has further resources for programming your Phidget.
 
==Mac OS==
 
{{ContentNeeded|This section needs to be filled in}}
 
Java has excellent support on OS X through the Java Compiler.
 
The first step in using Java on Mac is to install the Phidget libraries.  Compile and install them as explained on the [[OS - OS X|main Mac OS page]].  That page also describes the different Phidget files, their installed locations, and their roles.
 
===Use Our Examples===
 
The command to compile in a OS X and Linux terminal are slightly different. Rather than prefixing {{Code|phidget21.jar}} with a semi-colon( {{Code|;}} ), a colon( {{Code|:}} ) is used:
 
<div class="source">
<syntaxhighlight lang=bash>
javac -classpath .:phidget21.jar example.java
</syntaxhighlight>
</div>
 
Then, to run the program:
 
<div class="source">
<syntaxhighlight lang=bash>
java -classpath .:phidget21.jar example
</syntaxhighlight>
</div>
 
Perhaps refer to the Windows section of Eclipse and Netbeans for further information?
 
===Write Your Own Code===
 
==Linux==
 
Java has excellent support on Linux - there is an established implementation of the Java compiler and interpreter, and several Integrated Development Environments (IDEs) including NetBeans and Eclipse.
 
The first step in using Java on Linux is to install the base Phidget libraries.  Compile and install them as explained on the main [[OS - Linux | Linux page]].  That Linux page also describes the different basic Phidget library files, their installed locations, and their roles.
 
You will also need the [http://www.phidgets.com/downloads/libraries/phidget21jar.zip Phidget Java Libraries (phidget21.jar)].
 
Once downloaded, the {{Code|phidget21.jar}} library file does not get 'installed' (i.e. do not run {{Code| java -jar phidget21.jar}}).  Rather, the library file gets put into the path of whatever program you write, and you will link it via both the java compiler and the java interpreter.  We walk you through this below.
 
We have two different types of Phidget examples in Java:
*Simple examples, to be run on the command line, and
*Full examples, to be run in NetBeans
 
Both are contained within the [http://www.phidgets.com/downloads/examples/JavaJNI.zip Phidget Java example download package].
 
===Description of Library Files===
 
The Phidget Java libraries depend on the C libraries being installed as explained on the main [[OS - Linux | Linux page]].  If you browse around within the phidget21.jar archive, you will find Java class files (too many to reasonably list here) that have names related to the devices they provide an API for.
 
These Java class files use the functions available in the ''dynamic'' Phidget21 C-language library on Linux.  Dynamic libraries end with {{Code|.so}}, and so the C library that the Phidget Java class files use is {{Code|/usr/lib/libphidget21.so}}.
 
===Javac (Command Line)===
 
====Use Our Examples====
 
Linux gets somewhat complicated in that two Java compilers exist: {{Code|openjdk}} and {{Code|gcj}}.  Furthermore, a given IDE can ''usually'' use either compiler. That being said, we only offer support here for openJDK and IDEs running openJDK.
 
To find out which type of compiler your computer has, use the {{Code|-version}} option on the command line.  You can use the same option for your runtime environment (interpreter):
 
<div class="source">
<syntaxhighlight lang=text>
$> java -version
java version "1.6.0_23"
OpenJDK Runtime Environment (IcedTea6 1.11pre) (6b23~pre11-0ubuntu1.11.10.1)
OpenJDK 64-Bit Server VM (build 20.0-b11, mixed mode)
 
$> javac -version
javac 1.6.0_23
</syntaxhighlight>
</div>
 
The good news is that you can have both {{Code|openjdk}} and {{Code|gcj}} on your machine, co-habitating happily.  There can be only one linked java and javac in {{Code|/usr/bin/}} however, and so this will correspond to whichever java compiler and interpreter you installed last.
 
If you do not have {{Code|openjdk}} installed already (this is the default Java installation for most Linux machines, so you will probably know), and you choose to install it for Phidget purposes, it is important is that the {{Code|java}} version be greater than the {{Code|javac}} version.  Otherwise, your runtime environment will consider the stuff your compiler produces to be newfangled nonsense.  So when installing Java from a repository, you should install both the jdk and the jre.  These are, unfortunately, usually separate packages in a repository (e.g. {{Code|openjdk-7-jre}} and {{Code|openjdk-7-jdk}}).
 
The simple examples in Java are meant to be compiled and run on the command line.  The example package includes a {{Code|Makefile}} so you can either make all of the examples at once, with:
 
<div class="source">
<syntaxhighlight lang=bash>
make all
</syntaxhighlight>
</div>
 
...Or you can make them individually.  You should pick out the example with the name that corresponds to the family (software object) of your Phidget hardware.  {{FindYourDevice}}  Once you've identified the right example - say, {{Code|HelloWorld.java}}, which will work with any Phidget - compile it on the command line with:
 
<div class="source">
<syntaxhighlight lang=bash>
javac -classpath .:phidget21.jar HelloWorld.java
</syntaxhighlight>
</div>
 
To run the example on a Linux machine [[OS - Linux#Setting udev Rules| without your udev USB rules set]], you will need to run the Java example as root:
 
<div class="source">
<syntaxhighlight lang=bash>
sudo java -classpath .:phidget21.jar HelloWorld
</syntaxhighlight>
</div>
 
====Write Your Own Code====
 
You'll note that the Phidget Java library file {{Code|phidget21.jar}} needs to be explicitly linked at both points in the compile and run process.  Alternatively, you can make a jar file which includes the Phidget Java library.  This process takes two steps, the first of which is creating a text file called {{Code|MyProgram.mf}}, where {{Code|MyProgram}} is replaced by the name of your main class in both the filename and the text below:
 
<div class="source">
<syntaxhighlight lang=text>
Manifest-Version: 1.0
Class-Path: phidget21.jar
Main-Class: MyProgram
 
</syntaxhighlight>
</div>
 
'''Note:''' The manifest file should end with a carriage return. So, there should be an extra line at the bottom of the file.
 
After creating the manifest file, you can use the {{Code|jar}} function to create one self-contained file with your classes and the correct classpath.
 
<div class="source">
<syntaxhighlight lang=bash>
jar –cfm MyProgram.jar MyProgram.mf *.class
</syntaxhighlight>
</div>
 
If porting this for an external system, such as one that your customer would be running, the Phidget library would need to be compiled and distributed along with the {{Code|.jar}}.  Although we do not directly support this, if you are interested in how to construct this, we provide both a distribution example and information on cross-compiling:
* The [[Language - Android Java | Android Java]] libraries have an ARM-compiled {{Code|libphidget21.so}} file included, as an example of distributing a compiled libphidget21.so with the jar file
* The [[OS - Linux#Cross-Compiling with a Custom Toolchain|Linux page]] has more detail for compiling the Phidget C Libraries for an external target.
 
===NetBeans===
 
We offer in-depth tutorials on using our examples in NetBeans and Eclipse in the [[#NetBeans|Windows NetBeans]] and [[#Eclipse|Windows Eclipse]] sections.
 
As our full examples are written with NetBeans, but NetBeans is not part of the standard Linux package repository, we offer installation instructions here before referring to the Windows sections.
 
====Installation====
 
Although Eclipse is standard in the Debian/Ubuntu package repository, NetBeans is no longer standard.  What is more, Netbeans does not install by default into a folder within your path.  As our Phidget full Java examples are written using NetBeans, we provide basic installation instructions here so you can actually run them.
 
To install NetBeans:
 
1. Download the install script from website: [http://netbeans.org/downloads/ http://netbeans.org/downloads/]<br>
2. Change the permissions of the downloaded file to be executable.  Usually, this is something like:
:{{Code|chmod +x netbeans-7.1-ml-javase-linux.sh}}<br>
3. Run the downloaded file as a script. (This will result in a GUI interaction that walks you through installation.)<br>
4. To find the location where the NetBeans installation occurred, run:<br>
:{{Code|updatedb}}
:{{Code|locate netbeans | grep bin}}<br>
5. Usually, the location of the binary is {{Code|/usr/local/netbeans-7.1/bin/netbeans}}, where 7.1 is the installed version.
 
====Use Our Examples====
 
Once you have NetBeans installed, running our examples will be very similar to the process described in the [[#NetBeans|Windows NetBeans]] section.
 
====Write Your Own Code====
 
When you are building a project from scratch, or adding Phidget function calls to an existing project, you'll need to configure your development environment to properly link the Phidget Java library. Please see the [[#NetBeans| Windows NetBeans]] section for instructions if you are unfamiliar with NetBeans.
 
In your code, you will need to include the Phidget Java library:
 
<div class="source">
<syntaxhighlight lang=java>
import com.phidgets.*;
import com.phidgets.event.*;
</syntaxhighlight>
</div>
 
The project now has access to the Phidget function calls and you are ready to begin coding.
 
The [[#Follow the Examples|teaching]] section - which describes the examples - also has further resources for programming your Phidget.
 
==Follow the Examples==
 
By following the instructions for your operating system and compiler above, you probably now have a working example and want to understand it better so you can change it to do what you want.  This teaching section has resources for you to learn from the examples and write your own.
 
Your main reference for writing Java code will be our Java API information, with syntax for all of our functions:
 
{{UsingAPhidgetInCodeGeneral|both of which are available in Java|[http://www.phidgets.com/documentation/JavaDoc.zip Java API]}}
 
===Example Flow===
 
{{ExamplePseudocode|In Java, it is easiest if you name these '''event''' functions the same as in our examples.  You can change the main function pointer variable name, but none of the other names.  Our examples show how to immediately hook these functions into the events that will call them <br> <br>
In the example code, the event functions common to all Phidgets are called things like '''AttachHandler()''' and '''DetachHandler()''', etc.<br>
But some event functions will be specific to each device, like when a tag is read on an RFID board, or when a sensor value changes on an Interface Kit.  Some 'get data' functions are also specific to each device.
|Creating a Phidget software object in Java - when you are not using the Manager - is specific to the Phidget.  For a Phidget Spatial, for example, this would involve creating a {{Code|SpatialPhidget}} object.  The device-specific examples show how to do this and other API functions.<br><br>
The software object provides device specific methods which are available from the API for your specific Phidget.|
[http://www.phidgets.com/documentation/JavaDoc.zip Java API]}}
 
===Code Snippets===
 
When programming in Java, you're in luck.  All of our code snippet examples on our [[General Phidget Programming]] page are in both C++ and Java.  Therefore, we do not include any here, because that page is much more in-depth, and you won't have to have two pages open at once.  So head over there, and start writing code!
 
==Common Problems and Solutions/Workarounds==
 
None yet.

Revision as of 19:17, 13 December 2018


We provide support for the Java language in all major operating systems. We also provide instructions on how to get your project started in a number of common development environments. Select your operating system and preferred development environment below, and follow the instructions to get your project running with Phidgets.

If you do not know which development environment you want to use, or your development environment of choice is not listed, we recommend starting with javac as the simplest path to getting your code running.

General information of how to use Phidgets with Java can be found in the Write Code section of each development environment page. This information is consistent across all pages.

Choose Your Development Environment:

Java Development Environments
OS - Windows Windows

JAVA JC WIN.png JAVA JC WIN on.png

JAVA NETBEANS.png JAVA NETBEANS on.png

JAVA ECLIPSE.png JAVA ECLIPSE on.png

OS - macOS macOS

JAVA JC TRM.png JAVA JC TRM on.png

JAVA NETBEANS.png JAVA NETBEANS on.png

JAVA ECLIPSE.png JAVA ECLIPSE on.png

OS - Linux Linux

JAVA JC TRM.png JAVA JC TRM on.png

JAVA NETBEANS.png JAVA NETBEANS on.png

JAVA ECLIPSE.png JAVA ECLIPSE on.png

OS - Linux Phidget SBC Linux

JAVA JC SBC.png JAVA JC SBC on.png

OS - Android Android

JAVA AS ANDROID.png JAVA AS ANDROID on.png

Quick Downloads

If you already know what you're doing and just need the files, you can find them all below.

Documentation

Example Code

Libraries