Add a loading effect with progress

Question

Often when we download something use the terminal or the command prompt, we get a progress like this:

----------10%

after a while

------------------------------------------33%

after a while

---------------------------------------------------------48%

and then this continues until it is 100% in the same line. Even I tried to do something like this, but ended up getting a result like this:

-1%-2%-3%-4%-5%-6%-7%-8%-9%-10%-11%-12%-13%-14%-15%-16%-17%-18%-19%-20%-21%-22%-23%-24%-25%-26%-27%-28%-29%-30%-31%-32%-33%-34%-35%-36%-37%-38%-39%-40%-41%-42%-43%-44%-45%-46%-47%-48%-49%-50%-51%-52%-53%-54%-55%-56%-57%-58%-59%-60%-61%-62%-63%-64%-65%-66%-67%-68%-69%-70%-71%-72%-73%-74%-75%-76%-77%-78%-79%-80%-81%-82%-83%-84%-85%-86%-87%-88%-89%-90%-91%-92%-93%-94%-95%-96%-97%-98%-99%-100%

So, this happens after every progress. This is what I did to do so:

for (progress in 1..100){
   print("-$progress%")
   Thread.sleep(100)
}

or in java:

for(int i = 0; i < 100; i++){
   System.out.print("-" + i + "%");
}

So, how can I achieve something like that with the progress being in a single line?

I guess you want to print `---10%`, then clear the screen, and then print `-------20%`, so the previous bars aren't visible? Doing that depends on your operating system and the shell - what are you using? — aSemy, May 07 '22 at 10:25
Not clear as I have also printed other data on the screen. But, if we can, I think we can clear that line and then rewrite the line — Sambhav Khandelwal, May 07 '22 at 10:27
Clearing a single line isn't possible, usually - it's all or nothing. See here https://stackoverflow.com/q/2979383/4161471 — aSemy, May 07 '22 at 10:30
It seems there are some libraries that you can use - have you considered these? [ctongfei/progressbar](https://github.com/ctongfei/progressbar), [varabyte/kotter](https://github.com/varabyte/kotter), [Spring Shell](https://agency04.com/developing-cli-application-with-spring-shell-part-3/). — aSemy, May 07 '22 at 10:33

Darth-CodeX · Accepted Answer · 2022-05-08T06:16:25.933

2

Try this here a string is repeated n times, and then it is printed along with its percentage covered.

"\r" is a escape sequence which brings back the cursor to the starting point of the current line.

import java.lang.Thread;

class Main {
    public static void main(String args[]) {
        try {
            for (int i = 0; i <= 100; i++) {
                System.out.print("\r" + "-".repeat(i) + i + "%");
                Thread.sleep(50); // 50 millisecond
            }
            System.out.println();
        } catch (Exception e) {
            System.err.println(e);
        }
    }
}

Here's the kotlin code:

fun main() {
    for( i in 1..100 ){
       print("\r ${"=".repeat(i)}> $i%");
       Thread.sleep(50);
    }
    println()
}

Output JAVA:

Output KOTLIN:

edited May 08 '22 at 06:16

answered May 07 '22 at 10:41

Darth-CodeX

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@Sambhav.K This will work on every modern terminal – Darth-CodeX May 07 '22 at 16:33
`-1% --2% ---3% ----4% -----5% ------6% -------7% --------8% ---------9% ----------10% -----------11% ------------12% -------------13% --------------14% ---------------15%` this is what I get in Kotlin code after run – Sambhav Khandelwal May 07 '22 at 16:57
1

@DarthCoder first I used online compiler. Now I used Intellij and it works fine. Thanks. – Sambhav Khandelwal May 08 '22 at 05:07
Hi @DarthCoderX. It still works in IntelliJ but not in Eclipse :( – Sambhav Khandelwal May 31 '22 at 16:09
1

@Sambhav.K Perhaps, eclipse terminal doesn't support `"\r"` – Darth-CodeX May 31 '22 at 16:11

score 1 · Answer 2 · answered May 07 '22 at 10:31

If you would like to display the loading bar uninterrupted and on one line, you can try using this approach:

        for (int i = 1; i <= 100; i++) {
            Thread.sleep(300);
            String backspaceCharacter = "\b";

            int numberOfCharactersToDelete =  2;
            if (i / 10 > 0) numberOfCharactersToDelete++;
            System.out.print(backspaceCharacter.repeat(numberOfCharactersToDelete) + "-" + i + "%");
        }

It works by printing a backspace character for deleting the previous x%. There are definitely better ways to do this, but I find this way to be the easiest. Warning: I didn't bug check this, it should be used more like an inspiration than a complete solution. It also may not work in some consoles.

I have already accepted another answer but will surely upvote this if it will work for me — Sambhav Khandelwal, May 07 '22 at 12:27

score 1 · Answer 3 · answered May 07 '22 at 13:48

As other answers show, in general the simple way is to print a carriage return (\r) without a newline (\n): this moves the cursor back to the start of the same line, after which you can overwrite the existing line with a new one.

This only works if the new version of the line is at least as long as the previous one — or you append spaces to overwrite the rest.

If you want to do anything more powerful, the usual way is to print ANSI escape codes. Most modern terminal programs will understand these; they let you move the cursor directly to any point in the window, clear a line or even the whole screen, and use colours and effect such as bold, italic, and reverse video.

(Traditionally, you'd have to determine the current terminal type, and then look up the escape sequences it supported in a termcap database — but these days that's overkill unless you need maximal compatibility, and the ANSI escapes are well supported.)

Alternatively, you can use a library which does all that for you; see this question.

Gidds but it works with terminals right? Does it also work for android studio console? Also i m not sure how to implement it correctly — Sambhav Khandelwal, May 07 '22 at 16:21
I don't know anything about Android development, I'm afraid. Implementing ANSI escape sequences is easy enough, e.g. `print("\u001b[2K")` clears the current line without moving the cursor. — gidds, May 07 '22 at 18:53

Joshua Gordon · Answer 4 · 2022-05-07T10:36:07.137

I can answer this for Java.

Assuming you want each progress printed on a new line, use: System.out.println(); instead. Or add \n where relevant.

Also assuming you want to increase the quantity of dashes with each incremental progress point, you'd have to add an inner for loop to repeat the printing of the "-" multiple times, something like this?

for (int i = 0; i < 100; i++) {
    TimeUnit.SECONDS.sleep(1);
    for (int j = 0; j < i; j++) {
        System.out.print("-");
    }
    System.out.print(i + "%\n");
}

Example output

Or if you want it to look like it's clearing the line and then reprinting the new progress bar, to make it look dynamic, you could try something like this (add more or less \n characters to increase or decrease gap):

for (int i = 0; i < 100; i++) {
    TimeUnit.SECONDS.sleep(1);
    System.out.print("\n\n\n\n\n\n\n\n\n\n\n\n\n");
    for (int j = 0; j < i; j++) {
        System.out.print("-");
    }
    System.out.print(i + "%\n");
}

I dont want it in different lines. That is the challenge for me — Sambhav Khandelwal, May 07 '22 at 10:26
Hey @Sambhav.K, I've updated my answer if you want to see if the other solution works better for you. — Joshua Gordon, May 09 '22 at 08:29

Add a loading effect with progress

4 Answers4