is it possible to create java application that will
work as background process on symbian smartphones?
You can approximate it but J2ME (the version of java on mobile phones) may not be the right technology to do this.
starting a MIDlet (a Java application for mobile phones) when the phone is switched on is tricky at best without coding a small Symbian OS C++ module that will start it for you. If you want to try anyway, look at the PushRegistry class in the MIDP specs
(http://java.sun.com/javame/reference/apis/jsr118/). The Content Handling API might provide some way to do it too (http://java.sun.com/javame/reference/apis/jsr211). When you are ready to give up, do it in C++.
Backgrounding a MIDlet isn't hard. The phone's "menu" key will do it for you. Programatically, Canvas.setCurrent(null) has a good chance of working. Trying to trick the phone by providing a fully transparent GUI and not handling any keypad activity will absolutely not work. Creating and starting a separate Thread in the MIDlet should allow you to keep something running even after your overload of MIDlet.pauseApp() has been called by the application management system.
The real issue is that the MIDlet will not have any Inter Process Communication system unless you make one. The usual way of doing that is a loopback socket connection over which you transfer data. Not a nice or efficient way of simulating IPC. Sharing a RMS record can only be done from within the same MIDlet suite (you can package several MIDlets into the same .jar file), I think. The code to create a provider/consumer data flow over a file connection is even uglier and will raise security issues.
Without any more information about what you want to use it for, my answer is : maybe but you should probably not try.
You will have in-built MIDP support for background MIDlets in MIDP 3.0 (http://jcp.org/en/jsr/detail?id=271). Don't hold your breath for devices to appear, however - might be some time.
(Note that a few Symbian OS devices have more than just MIDP - the S-E p990 for instance, https://developer.sonyericsson.com/site/global/products/phonegallery/p990/p_p990.jsp).
As already pointed out, it might be helpful to have more information on what product functionality you are trying to implement - often more than one way to skin a cat.
Related
The reason why most people would ever make their android project in javafx would be to have the same codebase across different platforms (such as ios, desktop, android, maybe even web using Bck2Brwsr/teavm/doppio)
But my question is, is there any advantage in javafx ui framework itself when compared to android ui framework?
I have never ever written even a hello world application for android, but I intend to do it now. So I am wondering if having the code in javafx is worth the effort when I can develop directly on android apart from the benifit of portability.
This type of question might result in a subjective/opinionated answer but I think it is a good question so I will provide my assessment.
Having the same codebase across all those platforms is huge. Do not dismiss this. I'm using Gluon Mobile to port aspects of the Deep Space Trajectory Explorer (DSTE) to Android and iOS. As you can see from the video its extremely complex application. There's no way I would rewrite that in native Android... it would be a no-go from a cost perspective.
Starting development from JavaFX makes it easier to make complex visuals. I don't just mean traditional 2D GUI forms. Again looking at the DSTE you will see we use Canvas to do dense renderings and JavaFX 3D along with the FXyz library to do 3D renders. These things are easy in JavaFX and again using Gluon simply "just work" on Android/iOS. In fact it only took about a day to get those aspects of the DSTE code base to work on a Pixel C tablet, most of which was getting the Gradle build setup properly. Now imagine having to port 3D code from JavaFX to a Native framework? I'm a 3D guy and I still wouldn't try it.
Testing is so much easier on the desktop than a mobile device. This doesn't mean the testing is 100% on desktop. Sometimes something that works on desktop "doesn't work" on the mobile platform and you have to tweak accordingly. However you can save a LOT of time standing up the application using JavaFX knowing that 90% of it will work the same on your mobile device.
Word of advice though... remember that a desktop application is NOT a mobile application. You will be tempted to just "port" your desktop app to your device. I was my first time. You can get into other issues where the interfaces and layouts you design for a desktop "work" on the mobile device but are not appropriate and so the usability goes down. Start slow when you port. Think of what aspects of your desktop workflow should be mobilized. Only port the things you absolutely belong in a mobile workflow. Save yourself some headaches.
I am talking about components that can be externally attached to a computer system via some port or other means, not about any of the component that is part of or peripheral of computer itself.
Actually, working on a college project for controlling traffic lights and boom barrier at railway crossing. I've got knowledge in Java but I do not know how can I get the traffic lights and boom barrier working on events in a Swing based application?
One thing is I can create a electronic circuit which can read the small output voltages at computer ports such as a USB port and used them as a trigger for controlling the devices. But how can I generate that small voltages using Java application?
Is JavaPOS can be the solution? or something else?
Any ideas? Suggestions? Articles? Samples?
I'd work backwards from the external device. Answer this 1st: What's the easiest way to communicate with it? If you say USB, ok, use usb. Then ask, what's the easiest way to interface with USB. Then build in whatever language you find to be easiest this USB interface. Finally, call from your Java swing application to this USB-wrapping application... it could be that simple invoke the app using something like ProcessBuilder.
In other words, I think it might be a mistake to solve the problem of interfacing to something like this device with Java, unless it's easy to do so directly.
Have you considered communicating with these external devices by sending digital signals to a serial port using Java? It's then a simple matter of either using those digital signals directly, or using an Analog-to-digital converter to get a voltage of desirable magnitude.
Same for input from the serial port. The RXTX library can help you do this (communicate with the serial port).
On the other hand, if you have access to MATLAB, then this sort of stuff is a piece of cake. Take a look at the Data Acquisition Toolbox and Instrument Control Toolbox.
I think your looking at this the wrong way. Most lights are them selves computer controlled. The lights are running on a computer system. If your project is to write this start to end, then you need to write a loaded to the light controller that does many things, one controls light color and direction, also allow connections via an out side computer. This connection could be USB, Ethernet ext. Now write a program facilitating connecting to the lights and pass commands to the light controller.
Here's my requirement:
I often receive calls from unidentified numbers on my mobile phones. I would like an application which would use a reference list like this, and show me the carrier name and the area of origin along with the number on screen.
Mobile make : Sony Ericsson
Model : C902
Operating System: Propreitary
J2ME: MIDP 2.0
Here are my questions:
Is it possible to do something like this? I have installed a lot of java apps on my mobile, and all of them have to be launched seperately, can be run in the background, but they never seem to access anything native.
If it is possible, which area of J2Me should I start with, for creating an application that achieves the above requirement?
If it is not possbile, what are my alternatives?
I'm pretty sure this isn't possible. I dabbled in J2ME for a while, and came to the conclusion that it's basically just a big joke hard to do anything meaningful. Sorry.
can be run in the background? yes using Push Registry. access anything native? it depends on which native thing you want to access.
It is not possible.
On this model, you don't have alternatives, but on Symbian you can try Qt with help of Qt Mobility Project
Hello I want write my own desktop sharing application in Java.
The application should have some very default features:
Capture screen;
Allow a remote connected user to click / edit fields.
I was thinking to use Java Robot class for mouse movements / key pressing.
The problem is i don't know what screen capture strategy to use.
Should I make sequentially screen captures (on the hosting computer) every second, and send those captures with UDP via network, so that the clients can intercept the data-grams ? Isn't this a little overkill for the network ?
What other strategies are available ? (Except trying an already existing app).
PS: If necessary I can even write native code using JNI (still that's the last thing I planning to do).
Later edit:
After some investigation I've come to the conclusion of #Thorbjørn Ravn Andersen . Java is probably not the best choice for this kind of application. I can try to use JNI, but that code will cover 75%+ of my project.
I will try to find other alternatives.
Have a good long look at the Ultra VNC project on SourceForge. Great place to start.
In pure Java you cannot access structured information on system windows, nor monitor all relevant system events, so the performance of the display synchronization will not be optimal. Also there are privileged windows, which do not accept mouse or key events from Robot. Remote video streaming is not an option!
With named restrictions your attempt with the Robot class is valid.
Robot.createScreenCapture(Rectangle) will put a Desktop section into a BufferedImage, which you can send to the client window.
On client side you can capture keyboard and mouse events and send them to a Robot object on the server side.
Without knowing the actual extent of system windows, it will makes sense to work on a grid of Desktop tiles:
captured BufferedImage-s of tiles may fit into the buffer of the transfer protocol.
capturing period may locally be optimized for tiles with high entropy (-> Capturing Strategy).
Further traffic minimization
Consider differences of subsequent Desktop contents, only
Compression of tiles by PNG or a PCX-like method
For sharing over internet, Peer-to-Peer connection may be established by
a public proxy server
UDP hole punching with, for connection establishing, a necessarily public mediator server
In any case the protocol needs to be secured and delivery asserted.
I am looking to create a video training program which records videos - via webcam, user screen capture and captures sound. Now the main problem is that I need a cross-platform (mac and windows) solutions.
I know its possible to use flash to record webcam + audio. But its not possible to record the user's screen via flash.
So am wonder if I should use Java (which i believe will work on mac & windows). I do not want to develop to separate versions because of the cost involved in developing two versions.
Please guide me as I am new to this.
Thank you.
UPDATE
Hello again,
I had a look at the following site: www.screencast-o-matic.com or www.screentoaster.com. I see that they have developed a java applet which helps interact with Windows/Mac to record the screen.
I am wondering how to go about developing something like that and integrating it with Flash (for webcam and audio recording).
Is this a better idea?
This is not an answer to your question, but I strongly recommend against using video for educational programmes. Our company delivers university courses on-line, and we long ago learned that video feeds are only effective under particular scenarios. In general, a talking head is a waste of bandwidth. You're much better off to put together a well designed powerpoint presentation, record a voice-over (and edit it!) and then assemble the whole thing as a flash presentation. This is a non-trivial amount of work, but it provides a much more interesting product for the student.
When to use video:
1) When you are demonstrating something dynamic - Mechanics or Chemistry for example.
2) When you are acting out a scenario or case as an illustration -- For example, threat de-escalation techniques for high school teachers.
When you solve the screen recording problem, seriously consider whether you need full motion or if you can get away with stills. Often the motion is distracting, and a still with good voice over can be more effective. (Hint: Replace mouse pointers with something HUGE before recording -- Like Fox did with hockey pucks)
Try CamStudio. I don't know, if it works on Mac, but on windows, it's the best solution I know. It's open source, so you can use it's source code, if you want to :)
If you're looking to build an application that does all of the recording and screen capture itself, then you might consider using Adobe AIR (essentially, Flash running on the desktop) in combination with Merapi. Merapi is essentially a bridge between Adobe AIR and Java. So for example, for your project, you might use Java to handle the lower-level (but still cross-platform) stuff you can't do natively in AIR, and use Merapi to wire the Java application to your AIR UI.
This is by no means a simple project. Lets get that said and out the way. There are open source (and cross-platform) options for each element, but nothing (I know of) that will do everything for you.
I think the "cleanest" option would be to use Flash for webcam and audio, as you said, and run a VNC server to send the screen video... The only closed-platform code will be the VNC launching code. That should be pretty simple to maintain!
That raises a problem because most people are behind NAT firewalls these days. Setting up port forwarding is a pain in the behind. I've used an app called Gitso before which allows people to connect to me and send their desktop to my screen (for tech support). Its VNC-based and all it really does is add another layer on top of the VNC connection so rather than me connecting to them, they connect to me. That makes the whole business of port forwarding a non-issue.
And once you've recorded everything, there's the final issue of syncing it all back together... Might not be so hard.
Well, Camtasia provides the solution to get your problem done. It can record the onscreen activity and also the webcam video and put them in the same player template. Another screen recorder DemoCreator can publish the screen recording as Flash movie, but can not record the webcam.