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openAssetFileDescriptor does not truncate OneDrive file

Using the following code, a text file that lives on Google Drive erases first as expected,leaving only the newly written content in the file. If the file lives on OneDrive the first x bytes are overwritten and the remaining original bytes left intact. Does anyone know of a work around for OneDrive files. I need the old contents erased and only the new content from the write to remain.
According to these docs
openAssetFileDescriptor and
openAssetFile
that is what should happen.
I have tried this using Java/Android Studio and C#/Xamarin, Android phone 9 api 28.
public void saveFile(View view)
{
try
{
AssetFileDescriptor pfd = getContentResolver().openAssetFileDescriptor(fileUri, "w");
FileOutputStream fileOutputStream = new FileOutputStream(pfd.getFileDescriptor());
fileOutputStream.write(("Overwritten again " + System.currentTimeMillis() + "\n").getBytes());
fileOutputStream.close();
pfd.close();
}
catch (FileNotFoundException e) {
e.printStackTrace();
}
catch (IOException e) {
e.printStackTrace();
}
}

Couldn't come up with a why it doesn't work as documented, but I have come up with a work around to simulate expected behavior. Wouldn't mind comments if anyone sees a better way.
public void saveFile(View view)
{
try
{
ParcelFileDescriptor pfd = getContentResolver().openFileDescriptor(fileUri, "w");
FileOutputStream fileOutputStream = new FileOutputStream(pfd.getFileDescriptor());
//Added if-block to simulate automatic truncate when file located on onedrive.
if( (fileUri.toString()).contains("skydrive"))
{
FileChannel fileChannel = fileOutputStream.getChannel();
fileChannel.truncate(0);
}
fileOutputStream.write(("Overwritten again " + System.currentTimeMillis() + "\n").getBytes());
fileOutputStream.close();
pfd.close();
}
catch (FileNotFoundException e) {
e.printStackTrace();
}
catch (IOException e) {
e.printStackTrace();
}
}

try to use following, just replace "w" with "rwt" to truncate the original file.
getContentResolver().openAssetFileDescriptor(fileUri, "rwt")

Android internal Storage error

I am really new to android and writing a simple game for android.
In the game, like in most games you have score,
now, I want the score to be saved in Internal Storage, and for some reason, I manage to save the score, but not load it back.
here is the code:
final TextView best = (TextView) findViewById(R.id.best);
public int read = -1;
public StringBuffer buffer = new StringBuffer();
public String scoreTxt = buffer.substring(0, buffer.indexOf(" ") + 1);
public int score = 0;
// Save
try {
fileOutputStream = openFileOutput("record.txt", Context.MODE_PRIVATE);
fileOutputStream.write(scoreString.getBytes());
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
if (fileOutputStream != null) {
try {
fileOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Toast.makeText(MainActivity.this, "Save() works fine", Toast.LENGTH_SHORT).show();
// load
try {
FileInputStream fileInputStream = openFileInput("record.txt");
while ((read = fileInputStream.read())!= -1){
buffer.append((char)read);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
best.setText("Best: " + scoreTxt);
Toast.makeText(MainActivity.this, "load() is good too " + scoreTxt, Toast.LENGTH_SHORT).show();
when I run the app, there is no crash or anything special in the logcat, but when ever I use scoreTxt the output is nothing, just " ".
can somebody help me solve this problem? Thanks

You never assign scoreTxt a value in your code.

You need to parse buffer after it has being populated.Now when scoreTxt is initialized buffer is null
You need to replace this
best.setText("Best: " + scoreTxt);
with
scoreTxt = buffer.substring(0, buffer.indexOf(" ") + 1);
best.setText("Best: " + scoreTxt);

In addition I wouldn't store game score into a file because score changes frequently and you want to avoid disk access a lot. Store it in SharedPreferences and from time to time flush it to a file on a background thread.

How do I get matcher.find while loop to write to text file? java [duplicate]

This question already has an answer here:
Writing to a file but only last line saved
(1 answer)
Closed 9 years ago.
I'm using a while(matcher.find()) loop to write certain substrings to a file. I get a list of the matched strings occurring in the file in my System.out console just fine, but when I try to use FileWriter to write to a text file, I only get the very last string in the loop written. I've scoured stackoverflow for similar problems (and it lives up to its name), I couldn't find anything that helped me. And just to clarify this isn't being run on the EDT. Can anyone explain where to look for the problem?
try {
String writeThis = inputId1 + count + inputId2 + link + inputId3;
newerFile = new FileWriter(writePath);
//this is only writing the last line from the while(matched.find()) loop
newerFile.write(writeThis);
newerFile.close();
//it prints to console just fine! Why won't it print to a file?
System.out.println(count + " " + show + " " + link);
} catch (IOException e) {
Logger.getLogger(Frame1.class.getName()).log(Level.SEVERE, null, e);
} finally {
try {
newerFile.close();
} catch (IOException e) {
Logger.getLogger(Frame1.class.getName()).log(Level.SEVERE, null, e);
}
}
}

Quick fix:
change
newerFile = new FileWriter(writePath);
to
newerFile = new FileWriter(writePath, true);
This uses the FileWriter(String fileName, boolean append) constructor.
Better fix:
create the FileWriter outside of the while(matcher.find()) loop and close it afterwards (or use it as a try with resources initilzation).
the code would be something like:
try (FileWriter newerFile = new FileWriter(writePath)) {
while (matcher.find()) {
newerFile.write(matcher.group());
}
} ...

You should not create an instance of FileWriter every loop iteration. You need to leave the usage of method write() there and init FileWriter before loop and close it after loop.

Please check as follows:
FileWriter newerFile = new FileWriter(writePath);
while(matcher.find())
{
xxxxx
try {
String writeThis = inputId1 + count + inputId2 + link + inputId3;
//this is only writing the last line from the while(matched.find()) loop
newerFile.write(writeThis);
newerFile.flush();
//it prints to console just fine! Why won't it print to a file?
System.out.println(count + " " + show + " " + link);
} catch (IOException e) {
Logger.getLogger(Frame1.class.getName()).log(Level.SEVERE, null, e);
} finally {
try {
newerFile.close();
} catch (IOException e) {
Logger.getLogger(Frame1.class.getName()).log(Level.SEVERE, null, e);
}
}
}
}

Cannot read file just written to

I am trying to read from a file to which some user credentials were written. I want to write the file to an internal storage location. The code:
private void writeSendDetails(String name, String number, String emailID) {
//This function writes details to userCredentials.txt and also sends it to server.
String text = "Name: " + userName + "\n" + "Number: " + userNumber + "\n" + "Email ID:" + userEmailID;
FileOutputStream fos = null;
try {
fos = openFileOutput(userCredFile, MODE_PRIVATE);
Log.v(this.toString(), fos.toString());
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
if(fos != null) {
OutputStreamWriter osw = new OutputStreamWriter(fos);
try {
osw.write(text);
} catch (IOException e) {
// TODO Auto-generated catch block
Log.v(this.toString(), "IOException caught in osw.write");
e.printStackTrace();
}
try {
osw.flush();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
osw.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Log.v(this.toString(), "Written everything to userCredentials.txt");
readUserCredentials();
//code to send to server should begin here.
}
private void readUserCredentials() {
//function to read name, number and email ID from userCredentials.txt
/* Steps:
* 1. Check if file exists.
* 2. If it does, read all relevant credentials.
*/
File f = new File(userCredFile);
if(f.canRead()) {
Log.v(this.toString(), "Can open userCredentials for reading from.");
}
try {
FileReader fis = new FileReader(f);
Log.v(this.toString(), "Wrapping a buffered reader around file reader.");
BufferedReader bufRead = new BufferedReader(fis, 100);
String line;
try {
while((line = bufRead.readLine()) != null) {
Log.v(this.toString(), "Line read = " + line);
line = bufRead.readLine();
if(line.indexOf("Name: ") != -1) {
Log.v(this.toString(), "Found name in the string.");
userName = line.substring(6);
} else if(line.indexOf("Number: ") != -1) {
Log.v(this.toString(), "Found number in the string.");
userNumber = line.substring(8);
} else if(line.indexOf("Email ID: ") != -1) {
Log.v(this.toString(), "Found email in the string.");
userEmailID = line.substring(10);
}
}
Log.v(this.toString(), "User credentials = " + userName + " " + userNumber + " " + userEmailID);
} catch (IOException e) {
Log.v(this.toString(), "IOException caught.");
}
} catch (FileNotFoundException e1) {
Log.v(this.toString(), "File not found for reading.");
}
}
The LogCat output shows:
04-14 15:20:43.789: V/com.sriram.htmldisplay.htmlDisplay#44c0c660(675): Written everything to userCredentials.txt
04-14 15:20:43.789: V/com.sriram.htmldisplay.htmlDisplay#44c0c660(675): File not found for reading.
04-14 15:20:43.889: V/com.sriram.htmldisplay.fireflymenu#44c401e0(675): File not found for reading.
My question(s):
1. I need to write the file to internal storage. Am I doing it correctly?
2. Why is the file just written not being read?

Some things for your code:
#Oren is correct, you should use Log.e(TAG, "message", e) instead of the auto-created stuff from eclipse!
you should simply merge the 3 try/catch to one. No need to make it 3 times...
you should use Log.e() as said above for your FileNotFoundException too, so see the stacktrace to check the real reason (which currently covers the hint to solve your issue)
If you would have done at least number 3, you would have seen that the file you try to read could not be found. Thats why your log doesn't show the Can open userCredentials for reading from. output from your if statement.
The reason for that is pretty simple: You create the file by using openFileOutput(userCredFile, MODE_PRIVATE);. If you read the documentation of openFileOutput you will stumble upon:
The name of the file to open; can not contain path separators.
That means that userCredFile can only be something like test.txt. Also this method creates a file in a directory that can't be easily access from "outside".
When you now try to read the file via FileReader(userCredFile) it should be obvious, that android will try to open it in the root directory: /text.txt and it will, of course, fail. No non-root app can write/read in the root directory.
The main question, and also the answer to your issue: Why don't you use the corresponding openFileInput(userCredFile) method to read the file?

java saved file disappears (ObjectOutputStream)

well this is a strange one.
The first save attampt usually works (1 more try max).
but in a heavy load (many saves in a row) the saved file disappears.
if uncommenting the "Thread.sleep" the error is captured otherwise the validation passes succesfully
public void save(Object key, T objToSave) throws FileNotFoundException, IOException {
IOException ex = null;
for (int i = 0; i < NUM_OF_RETRIES; i++) {
try {
/* saving */
String filePath = getFilePath(key);
OutputStream outStream = getOutStream(filePath);
ObjectOutputStream os = new ObjectOutputStream(outStream);
os.writeObject(objToSave);
os.close();
/* validations warnings etc. */
if (i>0){
logger.warn(objToSave + " saved on attamped " + i);
/* sleep more on each fail */
Thread.sleep(100+i*8);
}
//Thread.sleep(50);
File doneFile = new File(filePath);
if (! (doneFile.exists())){
logger.error("got here but file was not witten to disk ! id was" + key);
throw new IOException();
}
logger.info("6. start persist " + key + " path=" + new File(filePath).getAbsolutePath() + " exists="+doneFile.exists());
return;
} catch (IOException e) {
logger.error(objToSave + " failed on attamped " + i);
ex = e;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
throw ex;
}

It is not a java writers issue.
I was not using threads explicitly but in my test I was deleting the folder i was saving to using: Runtime.getRuntime("rm -rf saver_directory");
I found out the hard way that it is asynchronous and the exact delete and create time was changing in mili-seconds.
so the solution was adding "sleep" after the delete.
the correct answer would be using java for the delete and not making a shortcuts ;)
Thank you all.