Develop Reference

Unable to write to file - why?

I am attempting to save to long term file storage in android as well as create a new file in the process. This code keeps crashing with minimal helpful logcat.
Thanks.
public void save (String text) {
FileOutputStream fos = null;
try {
fos = openFileOutput("logfile.txt", MODE_PRIVATE);
fos.write(text.getBytes());
} catch (FileNotFoundException e)
{} catch (IOException e) {
e.printStackTrace();
} finally {
if(fos != null)
{
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
I expect it to create a file called logfile.txt and print text to it but instead it crashes.

Try something alike this, in order to get a FileOutputStream from a File in tmp / private storage:
// File file = File.createTempFile("logfile", ".txt");
File file = new File(getFilesDir(), "logfile.txt");
FileOutputStream fos = new FileOutputStream(file);
The resulting path should be /data/data/tld.domain.package/files/logfile.txt.
file.getAbsolutePath() has the value.
See Save a file on internal storage.

Where do I find a file I saved on android?

I have successfully been able to save a file to my internal storage on android using the following code in java/android:
public void writeToFile(String filename) {
String code = getIntent().getStringExtra("code_full");
String fullCode = code;
try {
FileOutputStream fileOutputStream = openFileOutput(filename + ".cs", MODE_PRIVATE);
fileOutputStream.write(fullCode.getBytes());
fileOutputStream.close();
Toast.makeText(getApplicationContext(), "Saved as " + filename, Toast.LENGTH_LONG).show();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
I do not know where I can find the saved file in my android's folders (I am trying to find it on my PC with the phone plugged in.)
Anyone know where to find it?

If you saved a file to internal storage and want a String of the path to the file, you would do getFilesDir().getAbsolutePath().

Is .txt extension necessary in File() constructor?

Like in the method i have attached i have used practiceData.txt i am getting same results while using just practiceData in file constructor so is it ok to use file without any extension or txt is better?
private void saveData(String data) {
File file = new File(this.getFilesDir(), "practiceData.txt");
FileOutputStream fileOutputStream = null;
try {
fileOutputStream = new FileOutputStream(file);
fileOutputStream.write(data.getBytes());
saveStatus = "Data was successfully saved.";
} catch (java.io.IOException e) {
e.printStackTrace();
saveStatus = "Error occurred: " + e.toString();
} finally {
if (fileOutputStream != null) {
try {
fileOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}

It doesn't matter what file extension you use, it just tells the OS how to open the file. So yes, you can use no extension and it will work just as well.
If you intend the file to be opened manually via another application, it may be helpful to use a standard extension however.

How to overwrite a file if it already exists in dropbox?

I am uploading a file in dropbox by this method:
public void upload() {
FileInputStream inputStream = null;
try {
File file = new File(Environment.getExternalStorageDirectory()
.toString() + "/write.txt");
inputStream = new FileInputStream(file);
Entry newEntry = mDBApi.putFile("/write.txt", inputStream,
file.length(), null, null);
Log.i("DbExampleLog", "The uploaded file's rev is: " + newEntry.rev);
} catch (DropboxUnlinkedException e) {
// User has unlinked, ask them to link again here.
Log.e("DbExampleLog", "User has unlinked.");
} catch (DropboxException e) {
Log.e("DbExampleLog", "Something went wrong while uploading.");
} catch (FileNotFoundException e) {
Log.e("DbExampleLog", "File not found.");
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
}
}
}
}
but when already this file exists in the folder then the file get renamed to write(1).txt
but I want that if the file already exists in the dropbox share folder then it will be replaced. What should I do now?

You can use mDBApi.putFileOverwrite instead of mDBApi.putFile

Clearing File content in Internal Storage on Android

I have a logging class for writing into a file in the app's internal storage space. Whenever the log file exceeds the size limit. For clearing the contents, I am closing the current FileOutputStream and creating a new stream with Write mode and closing it. Is there a way better way for accomplishing this:
public final void clearLog() throws IOException {
synchronized (this) {
FileOutputStream fos = null;
try {
// close the current log file stream
mFileOutputStream.close();
// create a stream in write mode
fos = mContext.openFileOutput(
LOG_FILE_NAME, Context.MODE_PRIVATE);
fos.close();
// create a new log file in append mode
createLogFile();
} catch (IOException ex) {
Log.e(THIS_FILE,
"Failed to clear log file:" + ex.getMessage());
} finally {
if (fos != null) {
fos.close();
}
}
}
}

You could also overwrite your file with nothing.
UPDATE:
There seems to be a better option with getFilesDir () Have a look at this question How to delete internal storage file in android?

Write empty data into file:
String string1 = "";
FileOutputStream fos ;
try {
fos = new FileOutputStream("/sdcard/filename.txt", false);
FileWriter fWriter;
try {
fWriter = new FileWriter(fos.getFD());
fWriter.write(string1);
fWriter.flush();
fWriter.close();
} catch (Exception e) {
e.printStackTrace();
} finally {
fos.getFD().sync();
fos.close();
}
} catch (Exception e) {
e.printStackTrace();
}
In this code:
fos = new FileOutputStream("/sdcard/filename.txt", false);
FALSE - for write new content. If TRUE - text append to existing file.

public void writetofile(String text){ // text is a string to be saved
try {
FileOutputStream fileout=openFileOutput("mytextfile.txt", false); //false will set the append mode to false
OutputStreamWriter outputWriter=new OutputStreamWriter(fileout);
outputWriter.write(text);
outputWriter.close();
readfromfile();
Toast.makeText(getApplicationContext(), "file saved successfully",
Toast.LENGTH_LONG).show();
}catch (Exception e) {
e.printStackTrace();
}
}