Apps call read and write file in class from fragment over mainActivity

[alex_92]

hi,
after wasting a complete evening of useless trying I really need some help.
I have an Activity with fragments and want to write and read files by clicking an a button or any other event from a fragment.
The problem is, that I have to place the read and write methods in the mainActivity to get all variables. But I can't call them because the static/non-static problem. I don't know how to fix this. And when I try to put the mothods to a extern class it doesn't compile because "openFileOutput()" is undefined. Here is my code that worked in an app without fragments.

[HIGH]
public void writeData (String s)
{
BufferedWriter bufferWriter = null;
try {
FileOutputStream fileOutputStream = openFileOutput("testFile", Context.MODE_PRIVATE);
bufferWriter = new BufferedWriter(new OutputStreamWriter(fileOutputStream));
bufferWriter.write(s);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
bufferWriter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

public String readData()
{
BufferedReader bufferReader = null;
StringBuilder result = new StringBuilder();
try {
FileInputStream fileInputStream = openFileInput("testFile");
bufferReader = new BufferedReader(new InputStreamReader(fileInputStream));
String line;
while ((line = bufferReader.readLine()) != null) {
result.append(line + "\r\n");
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
bufferReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Log.d("fileAccess", "" + result.toString());
return (result.toString());
}
[/HIGH]

 

[deprogram]

There are probably an infinite number of ways to solve this problem, but here's the absolute simplest:

Put this class anywhere in the project.

public static class FileInterface {
public static void writeData (Context c, String s)
{
BufferedWriter bufferWriter = null;
try {
FileOutputStream fileOutputStream = c.openFileOutput("testFile", Context.MODE_PRIVATE);
bufferWriter = new BufferedWriter(new OutputStreamWriter(fileOutputStream));
bufferWriter.write(s);
bufferWriter.close();
} catch (Exception e) {
e.printStackTrace();
}
}

public static String readData(Context c)
{
BufferedReader bufferReader = null;
StringBuilder result = new StringBuilder();
try {
FileInputStream fileInputStream = c.openFileInput("testFile");
bufferReader = new BufferedReader(new InputStreamReader(fileInputStream));
String line;
while ((line = bufferReader.readLine()) != null) {
result.append(line + "\n");
}
bufferReader.close();
} catch (Exception e) {
e.printStackTrace();
}
return (result.toString());
}
}

Then call it like this, from within your activity or fragment:

FileInterface.writeData(getApplicationContext(), "some string");

The application context should be appropriate for what you're trying to do.

I wish this forum didn't have broken code formatting. Really annoying.

 

[alex_92]

first thank you, for your hep.
but your way isn't possible.
Because the file access methods like openFileOutput need the context of the main-activity. But I can't pass the context from a static function.
This was my problem.
But I solved it.
I put a variable in the file access class to store the context, which is passed at the onCreate of the main-activity over the constructor of the class.
This way I don't have to pass the context when calling the file access methods.
Now I can read and write files from fragment events.