Android Question File.Exists(directory, filename)

luciano deri · Sep 28, 2016

dim namedir, namefile as string
'namedir exists i am sure.
'namefile not valorizzed,
if File.Exists(namedir, namefile) then
'file.exists return true. Why?
'I must check namefile.lenght > 0 also ?
end if

luciano deri · Sep 28, 2016

Most important situation is the file.delete.
The problem is the same, but in this case is deleted the directory !!

luciano deri · Sep 28, 2016

Syd Wright said:
Handling files and directories is a very elementary part of B4A. If a Bug had existed it would have been found years ago.
You did not describe your problem in #1. If you want to delete a file always use:

B4X:

If File.Exists(NameDir, FileName) then File.Delete(NameDir, FileName)

Are you using your code within a Sub? "Return True" won't work outside of a sub. Please show your full code.

Try this

JakeBullet70 · Sep 28, 2016

I find when dealing with files to make everything lowercase. it is Linux after all.

LucaMs · Sep 28, 2016

Luciano wanted to ask another thing (I know it only because I read his post in the Italian forum ).

If he provides an empty string as file name, the function returns True if the directory exists and Luciano thinks this is a bug.

But usually we use that way right to know if a folder exists, since there is not a function like IfDirExists or IfFolderExists.

It is worse when you use the File.Delete command: in this case, you will delete the folder (I have not tried but I trust )

Erel · Sep 29, 2016

I don't see any bug here.

Note that File.Delete will not delete a folder unless it is empty.

luciano deri · Sep 29, 2016

Return to begin. I reading a db that can contain a list of filename that i must delete.
I had made so
If File.Exists(NameDir, FileName) then File.Delete(NameDir, FileName)
Where filename is read from db.
filename = cursors.getstring("nomefile")
But if in filename not is valorized the App delete the folder. In the note of file.exists not specified this, so this is a bug.
Afther discovered this the correct code is
If File.Exists(NameDir, FileName) and FileName.lenght > 0 then
File.Delete(NameDir, FileName)
end if
Yours sincerely

LucaMs · Sep 29, 2016

luciano deri said:
If File.Exists(NameDir, FileName) and FileName.lenght > 0 then

It would be better (a little):
If FileName.lenght > 0 And File.Exists(NameDir, FileName) then

because if the first condition is false, the second one is not evaluated and this one take more time.

LucaMs · Sep 29, 2016

Syd Wright said:
Are you sure the "second one is not evaluated"?

I did some tests in the past and B4A it seems to be so.
However, with the code you posted, you can feel more secure

Erel · Sep 29, 2016

Conditions in B4X are short-circuited. Meaning that the next condition will not be evaluated in the following cases:
False AND expression
True OR expression

Android Question File.Exists(directory, filename)

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