How do I write a byte array to a file in Android?

Question

This is my code to create a file.

public void writeToFile(byte[] array) 
{ 
    try 
    { 
        String path = "/data/data/lalallalaa.txt"; 
        FileOutputStream stream = new FileOutputStream(path); 
        stream.write(array); 
    } catch (FileNotFoundException e1) 
    { 
        e1.printStackTrace(); 
    } 
}

When I try to send my file to my server by just calling the path String path = "/data/data/lalallalaa.txt";

I get this logcat error message:

03-26 18:59:37.205: W/System.err(325): java.io.FileNotFoundException: /data/data/lalallalaa.txt

I don't understand why it can't find a file that is "supposedly" created already.

don't forget to close the stream afterwards

ratchet freak
– ratchet freak

2012-03-26 19:08:57 +00:00
Commented Mar 26, 2012 at 19:08 — ratchet freak
– ratchet freak, Commented Mar 26, 2012 at 19:08

shb · Accepted Answer · 2020-05-28 07:10:35Z

21

I think you'd better add close function of FileOutputStream for clear code

It works me perfectly

try {
    if (!file.exists()) {
        file.createNewFile();
    }
    FileOutputStream fos = new FileOutputStream(file);
    fos.write(bytes);
    fos.close();
} catch (Exception e) {
    Log.e(TAG, e.getMessage());
}

edited May 28, 2020 at 7:10

shb

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answered Feb 18, 2016 at 1:13

Trần Thị Diệu My

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Comments

Churk · Accepted Answer · 2012-03-26 19:10:10Z

13

Are you sure the file is created already?

Try adding this:

File file = new File(path);
if (!file.exists()) {
  file.createNewFile();
}

answered Mar 26, 2012 at 19:10

Churk

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2 Comments

EGHDK Over a year ago

Yes, that was correct. I was not actually creating a new file. Did not know about that method and didn't know that it was necessary. Thanks

qwlice Over a year ago

@EGHDK The docs implicitly say that the file will be created: "If the file exists but is a directory rather than a regular file, does not exist but cannot be created, or cannot be opened for any other reason then a FileNotFoundException is thrown."

Tom Meyer · Accepted Answer · 2012-03-26 19:47:18Z

9

/data/data/ is a privileged directory in Android. Apps can't write to this directory or read from it.

Instead, you should use context.getFilesDir() to find a valid filename to use.

answered Mar 26, 2012 at 19:47

Tom Meyer

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Comments

kurra · Accepted Answer · 2012-03-26 19:28:50Z

0

This exception is thrown if either the file does not exist or if you are trying to write to a file that is read-only. Also try using full path name and see if the same exception occurs (to check if you gave the correct relative path).

answered Mar 26, 2012 at 19:28

kurra

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