What is strict mode policy violation in Android - android-permissions

Question

public static void write(byte[] aInput, String aOutputFileName, String dirName) {
(new File(dirName)).mkdir();
try {
OutputStream output = null;
try {
output = new BufferedOutputStream(new FileOutputStream(dirName + "/" + aOutputFileName));
output.write(aInput);
} finally {
output.close();
}
} catch (FileNotFoundException ex) {
System.out.println("File not found.");
} catch (IOException ex) {
System.out.println(ex);
}
}
The code above is from a library i'm using and it is supposed to create an output file and write a byte array to it. I checked logcat and saw the Strict Mode Policy violation Write.toDisk. I understand what it is supposed to be for my questions are: (1) Does Strict mode prevent you from doing disk reads and write on the main thread? (2) Does that mean that the file or folder were not actually created? (3) How then would I go about creating a folder or file within my App that doesn't trigger this? (4) What is the recommended way to handle disk read / write off the main ui thread, a real world example would be appreciated
Thanks in Advance

Answer 1

(1) It turns out that Strict mode doesn't actually prevent you from making writes to the disk it just gives a warning. From Android Developer "StrictMode is a developer tool which detects things you might be doing by accident and brings them to your attention so you can fix them". https://developer.android.com/reference/android/os/StrictMode
(2) The files were actually being created it's just that I was just not familiar with writing and reading from disk
(3) There are numerous ways to go about creating files (i) first you get a hold of a file directory to write the file to:
context.getFilesDir()
(ii) then you get an outputstream writer (iii) then you write out the data with the writer
public void makeFile(String filename){
//Create temp file for filename
FileOutputStream fos = null;
try {
fos = new FileOutputStream(new File(filename));
fos.write(filename.getBytes());//Write the contents of the file to app folder
fos.flush();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
if(fos != null) {
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
(iv) finally you close the outputstream writer
(4) The recommended way is to use either an AsyncTask or some other background running class like FutureTask or to use Threads or Runnable:
public class DownloadFileThread implements Runnable{
public void run(){
//your code here
}
}