I am writing simple socket chat using console to output messages. The problem is that when one user types a message, and at the same time getting one, his input interrupted:
I: writing my input here, but
Other_user: hi! here is a message for you.
I: it splits to different lines, which is 1) very inconvenient 2) cannot see which simbols i deleted if press backspace
So, what i am asking is, how can I avoid this
(something like: if message is received, check input for symbols; if there are, remember them, delete last stroke in console, print message, and then recreate that stroke).
EDIT: attached picture
hard to tell without specific code, but an option is to use two threads, one to handle the socket input, one for output. attach these to System.in and System.out respectively. it seems like you might be using only one thread to do both.
Related
i have two threads: one of them (server) is printing something to the console and the other (user) one is taking input from console. The problem occurs if the first thread prints something while user is typing into console. it looks like for example
command from usermessage from server
or if the user hasn't typed the command fully
commmessage from server
and it messes up the command from the user
is there a way to make it look like
message from server
command from user
or
message from server
comm
so to print one line above the currently typed text in the console and maintain the user input. i still want the first thread to print while the user is typing so locking this thread untill user enters the command isn't an option
[I want] to print one line above the currently typed text in the console and maintain the user input.
There are no easy answers here unfortunately. The user input being entered is actually being echoed by the terminal and not by the Java program. You have no control over the input and can't reprint it once the standard output is displayed.
The only way to do this otherwise is to turn off terminal echoing and control the user keystrokes in your program, but that makes it a lot more complicated. See: How to disable console echoing
You could also use some sort of Java dialog box and then pop the standard out message in another dialog or let it go to standard out.
i still want the first thread to print while the user is typing so locking this thread until user enters the command isn't an option
Yeah I fear that locking out the standard output messages is only way for you to do this unless you want to use a different mechanism to get your user input.
I'm writing a multithreaded socket chat. Is there any way to get the console input at a given time before the user has hit enter?
Let's say I'm typing a message, and while I'm typing it, the server sends a message to me. The server's message will get printed right after the message I'm currently writing.
How it looks:
Me>Hey!
Server>Heya!
Me>How are yServer>Hello!
If possible, I want to save the "How are y" string, remove it and paste it again after the server output:
Me>Hey!
Server>Heya!
Server>Hello!
Me>How are y
your problems boils down to two separate issues. number one is reading input from stdin or console character by character. this is tricky by itself, since most common approaches to reading input only do entire lines.
the second issues you're facing is going back and forth on the screenm because you have to update the current input and the new incoming messages this is quite possible, but the way to do it depends heavily on your terminal type and it's capabilities:
http://unix.stackexchange.com/questions/43945/whats-the-difference-between-various-term-variables
doing this correctly for all possible $TERM values on all OSs is rather tricky as well. you might do better using a library such as jcurses:
https://github.com/sunhong/jcurses
that abstracts this away from you.
I get that this isn't possible to do with normal java, although if there are any libraries out this it would be very useful.
Essentially, I'm designing a console app and running into an issue that when output happens while something is typed in the input line, that input text will move up and appear before the line that just got output. Is it possible to fix this in some form so that the text you are inputting that stays at the bottom?
EX:
I'm typing something as input into my commandline app, and then the program prints something WHILE I'm typing - this causes what was originally on the input line to be scrolled up with whatever the output text was. When you are trying to type something in this can obviously be detrimental. I know it's possible to prevent this.. (Other programs have done it... EX: Minecraft Server)
(If I need to be more descriptive I can.)
You could use the help of threads. One that listens to user input, the other process the actual output. This problem is similar to basic race condition problems when multiple threads attempt to read and write to a shared resource.
Your shared resource is that console. You need to keep the Input/Output operations synchronized. Have a look at race condition.
I want to create a cross platform solution for providing access to the input, error and output streams of a Process in Java.
Basically, what I want to create is a text area that displays the Process' output and error streams, and allows you to supply data to the input stream. In other words, pretty much what Eclipse is already providing with its Console when you run an application.
Now, a basic implementation of this was easy, I simply send all key presses to the input stream. But, of course, I ran into trouble with pasting, backspace and arrow keys, handling ctrl-C and so on.
It seems I should wait before sending data to the Process' input stream. But wait for what? Should I send all entered (and pasted) text at each return key? Or after an interval? What about ctrl-C, ctrl-X and so on. Do I send arrow key movement to the input stream?
The easiest and most user-friendly solution is to have a "Send" button which sends the entire contents of the text area and clears it. Think instant messenger apps or SO comment editor.
You should not wait for anything, simply send - but send in a separate Thread, not your GUI-Event-thread, so the latter one does not block.
For handling the special characters, look what you would get when these signs are entered in a text console.
I want to add a "history" function to my java programm, like known from bash etc, so pressing the arrow keys should show previous send commands.
It's no problem to write the past commands to the default output, which will in three new lines if arrow up is hit three times and in not editable output. I want the output of the programm to be written in the input field so i just have to hit enter, to resend the command.
Is this possible?
Kind Regards
Take a look at JLine, which provides command history, tab completion and line editing.
If you want to roll your own solution, this will get you started.
You want to change from using a buffered input into a direct input. You can do this by interfacing with System.in directly. You should create a thread to handle this, and have it block on a call to System.in.read() in a loop, reading one byte at a time.
Each time a byte is read, keep your own buffer updated with the current command that's being read. Every character that gets typed, add it to the buffer. If the character is a \b, delete the last character in the buffer. When you detect a \r or \n, execute the command in the buffer and clear it.
If you receive an up or down arrow, send a number of \bs to System.out equal to the length of the buffer. This will erase the local copy of any current command being entered. Then print out the new command to System.out and enter it into the buffer, replacing whatever was there. This will allow the user to delete it, add to it, or just press enter to submit it. This mimics the functionality of bash.
You can also detect a \t (tab) character and implement a tab-completion function.