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Getting a weird filenotfoundexception

I am currently on the beginner level when it comes to Android & I am currently scratching my head over an issue that I am currently facing.
I am creating an Android app to check if "cache.json" exists in the internal storage:
If it does not exist then first create it & write a string fetched from HTTP API to the file (replaced with fixed string in code below).
Regardless, read the file after writing is done (if necessary) & do appropriate stuff.
This is the code snippet:
public class ShowClasses extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
filename = "cache.json";
file = new File(getApplicationContext().getFilesDir(), filename);
if (file.exists()) {
System.out.println("EXISTS");
} else {
System.out.println("DOES NOT EXIST");
writeFile();
}
readFile();
}
public void writeFile() {
new JsonTask().execute(email);
}
public void readFile() {
FileInputStream fin = null;
try {
fin = new FileInputStream(file);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
int c;
result = "";
try {
while( (c = fin.read()) != -1){
result = result + Character.toString((char)c);
}
} catch (IOException e) {
e.printStackTrace();
}
try {
fin.close();
} catch (IOException e) {
e.printStackTrace();
}
return;
}
private class JsonTask extends AsyncTask<String, Void, String> {
protected void onPreExecute() {
result = ""; // Clear result
super.onPreExecute();
pd.setMessage("Please wait");
pd.setCancelable(false);
pd.show();
}
protected String doInBackground(String... params) {
return "THIS STRING IS GOING TO BE RETURNED " + params[0];
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
FileOutputStream fileout = null;
try {
fileout = new FileOutputStream(file);
fileout.write(result.getBytes());
//display file saved message
msg("File saved successfully!");
} catch (Exception e) {
e.printStackTrace();
}
try {
fileout.close();
} catch (IOException e) {
e.printStackTrace();
}
if (pd.isShowing()){
pd.dismiss();
}
}
}
}
I have tried to remove un-necessary part of the code so that it is smaller in length.
The actual issue I am facing is when writeFile() & readFile() both are called. I get a FileNotFoundException in readFile() when I open the stream even though the file should be created since writeFile() is called before readFile().
If I writeFile on one execution & then call readFile() on the other, it simply works as it should be.
This is the error that I am facing.
System.err: java.io.FileNotFoundException: /data/user/0/host.timetable.timetablenotifier/files/cache.json (No such file or directory)
System.err: at java.io.FileInputStream.open(Native Method)
Any help would be really appreciated.
Thanks

writeFile() is asynchronous. When that method returns, nothing has happened with respect to this file. At most, onPreExecute() of your JsonTask might be called. So, when you call readFile(), the file will not exist yet.
Beyond that:
You have an AsyncTask that you use in writeFile(), but you do your disk I/O in onPostExecute(), and that method is called on the main application thread.
You are doing disk I/O on the main application thread in readFile().
You catch exceptions, log them, but then continue executing your code, when most of those exceptions mean that the later statements are going to fail as well.
Reading in data one int at a time has not been a recommended approach for getting close to 20 years, for performance reasons.
You will have multiple issues related to configuration changes, such as screen rotations, as neither your AsyncTask nor your ProgressDialog account for configuration changes
Also:
getApplicationContext().getFilesDir() could be replaced by getFilesDir() in onCreate()
You do not need createNewFile()

AsyncTask runs in a background thread so the other code in the main thread doesn't wait for the execution to complete. In simpler terms, your readFile() method is executed before writeFile() completes and hence there is a FileNotFoundException. What would work for you is if you put the readFile() method at the end of the onPostExecute() method inside your Asynctask

Android FileObserver onEvent not getting called

Can someone possibly help me with this?
I want to observe a file to see if it gets modified so that I can update the activity. After several tests, I've determined it's just plain not working.
Am I doing something wrong?
I'm creating a FileObserver with an onEvent method to display a Toast and log data just to see if it's working, however the onEvent is never getting called.
I have tried it both with an existing and a new file, but it doesn't seem to work in either case.
Context context = this;
File fileFolder = context.getFilesDir();
String fileName = "quest";
FileObserver questObserver = new FileObserver(fileFolder.getPath()) { // also tried fileFolder.getName()
#Override
public void onEvent(int event, String path) {
Toast.makeText(getApplicationContext(), "onEvent fired", Toast.LENGTH_LONG).show();
Log.d(TAG, "FileObserver().onEvent");
}
};
questObserver.startWatching();
/* create file */
ObjectOutputStream objectOut = null;
try {
FileOutputStream fileOut = context.openFileOutput(fileName, Context.MODE_PRIVATE);
objectOut = new ObjectOutputStream(fileOut);
objectOut.writeObject(new Quest());
fileOut.getFD().sync();
} catch (IOException e) {
Log.d(TAG, e.getMessage());
} finally {
if (objectOut != null) {
try {
objectOut.close();
} catch (IOException e) {
Log.d(TAG, e.getMessage());
}
}
}
/* read file */
ObjectInputStream objectIn = null;
Quest quest = null;
try {
FileInputStream fileIn = context.openFileInput(fileName);
objectIn = new ObjectInputStream(fileIn);
quest = (Quest) objectIn.readObject();
} catch (FileNotFoundException e) {
// Do nothing
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} finally {
if (objectIn != null) {
try {
objectIn.close();
} catch (IOException e) {
Log.d(TAG, e.getMessage());
}
}
}
Toast.makeText(context, quest.getTitle(), Toast.LENGTH_LONG).show();
questObserver.stopWatching();
Any help would be greatly appreciated.

'public abstract void onEvent (int event, String path)" -
This method is invoked on a special FileObserver thread. It runs
independently of any threads, so take care to use appropriate
synchronization! Consider using post(Runnable) to shift event handling
work to the main thread to avoid concurrency problems.
http://developer.android.com/reference/android/os/FileObserver.html
If you put the toast through a handler.post(new Runnable(){...}), that should work.

Assuming your file doesn't (always) exist you should probably put your observer on the files folder, obtained like so:
Context ctx = ...;
File filesFolder = ctx.getFilesDir();
Note that this will also ensure that the filesFolder directory will be created.
Your observer will now be notified whenever a file is written, deleted or updated using for instance Context#.openFileOutput(..) - and you can filter in your FileObserver for the file name, in your example "quest".

Android MediaPlayer - switch to next song

I generate a midi file and write it like this:
File output = new File("exampleout.mid");
I think I might need to change this, so it is in the right folder (just a readable/writable folder, perhaps Music/ )
Next I want to play this midi file with MediaPlayer, but I cannot figure out how to load the file.
mediaPlayer = MediaPlayer.create(this, R.raw.test3);
Only loads from the read only directory /res/raw. But if I try something like:
mediaPlayer = MediaPlayer.create(this, "file://exampleout");
It does not work because create needs an integer as input. I experimented with AssetFileDescriptor, but haven't figured it out yet.
Meanwhile, I want to generate a new midi file and load it in mediaPlayer (chained) to play when the first file finishes playing.
MediaPlayer mediaPlayer = MediaPlayer.create(Activity.this,R.raw.a1);
mediaPlayer.setOnCompletionListener(new musicCompletionListener());
mediaPlayer.start();
private class musicCompletionListener implements OnCompletionListener {
#Override
public void onCompletion(MediaPlayer mediaPlayer) {
mediaPlayer.setDataSource(WHATTOPUTHERE)
mediaPlayer.release();
}
}
My Problem is really how to call the file. I cannot use strings apparantly, and the r.raw directory is not possible due to its read only nature. I feel the solution is not so difficult, but I am just easing into java from c++, any help is much appreciated!

I stored the file in the cache dir, that works!
File output = new File(getCacheDir() + "/exampleout.mid");
And then calling the file:
String filePath = null;
File file = null;
FileInputStream inputStream = null;
try {
filePath = getCacheDir() + "/exampleout.mid";
file = new File(filePath);
inputStream = new FileInputStream(file);
if(inputStream.getFD().valid())
{
System.out.println("Valid!");
}
} catch (Exception e1) {
e1.printStackTrace();
System.exit(-1);
}
try {
mediaPlayer = new MediaPlayer();
mediaPlayer.setDataSource(inputStream.getFD());
inputStream.close();
} catch (Exception e1) {
e1.printStackTrace();
System.exit(-1);
}
try {
mediaPlayer.prepare();
} catch (IllegalStateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

You have to nicely design the Architecture of your app then only you can achieve what you have asked.
According to me you can do the following.
Design an interface with the method midiReady(uri of midi file)
This interface is implemented by your activity which contains mediaplayer
As soon as midi file is generation is completed call the method midiReady(uri of midi file)
Now since your activity implements the interface callback is invoked on your activity and you can set the mediaplayer to play the midi file since in callback you have uri of your midi file.
The above metinoed points are just a faint idea what you can do.With above faint idea you can go forward for implementation.
Hope this will help.
Thanks.

Android MediaPlayer needs file at installation

I am dynamically generating midi files (in cache dir) with an android app.
After generation, I play the file with MediaPlayer within the same app.
When running the app for the first time, it already needs the file to be there in the cache directory (the app crashes). It works on the emulator if I use the filemanager to put a dummy file there first. How can I circumvent this?
I need the app to run on a tablet for the first time, without requiring the file.
I am using these commands now:
try {
filePath = getCacheDir() + "/optimuse" + song + ".mid";
file = new File(filePath);
inputStream = new FileInputStream(file);
if (inputStream.getFD().valid()) {
System.out.println("Valid!");
}
} catch (Exception e1) {
e1.printStackTrace();
System.exit(-1);
}
try {
mediaPlayer = new MediaPlayer();
mediaPlayer.setDataSource(inputStream.getFD());
inputStream.close();
} catch (Exception e1) {
e1.printStackTrace();
System.exit(-1);
}
try {
mediaPlayer.prepare();
} catch (IllegalStateException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
Is there any way around this?
Thanks!

Maybe check whether the file exists before using it? You can achieve this using the File#exists() method.
First, you use the Context#getFileStreamPath(String) method - where the String is the filename of the file you are trying to access. Then you can call File#exists() on the returned object.

Restoring data using AsyncTask

I have a saving method that runs during onPause():
String save = numberValue.getText().toString();
FileInputStream fos;
try {
fos = openFileOutput(FILENAME,Context.MODE_PRIVATE);
fos.write(save.getBytes());
fos.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
Toast.makeText(getBaseContext(), "Save has run", Toast.LENGTH_SHORT).show();
}
and I try to read this file by calling
new Loader().execute(FILENAME);
and my Loader class looks like this:
public class Loader extends AsyncTask<String, Integer, String> {
protected void onPostExecute(String result) {
textview.setText(result);
}
#Override
protected String doInBackground(String... params) {
FileInputStream fis;
String loaded = null;
try {
fis = openFileInput(FILENAME);
byte[] dataArray = new byte[fis.available()];
while (fis.read(dataArray) != -1) {
loaded = new String(dataArray);
}
fis.close();
textview.setText(loaded);
return loaded;
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return loaded;
}
}
And I have no idea as to why the textview does not get set as the bytes from FILENAME. The idea is that the textview is an increasing number, and this number gets saved when the activity is closed and gets restored to the textview when the activity starts up again.
It does start, I know that because after a few minutes, Watch Dog tells me that a background service from this app is consuming about 50% of CPU. I did check /data/data//files and the file that I write to is there with the correct value.

You probably need to call your Loader from onResume() for this to work.

Why not just save the state you need by using the onSavedInstanceState() method? Writing stuff out to the fileSystem on the onPause method is going to making switching out of your application really slow. From the Activity Documentation regarding the onPause method:
Called when the system is about to start resuming a previous activity. This is typically used to commit unsaved changes to persistent data, stop animations and other things that may be consuming CPU, etc. Implementations of this method must be very quick because the next activity will not be resumed until this method returns.
Also, from the android documentation:
In situations where the system needs more memory it may kill paused processes to reclaim resources. Because of this, you should be sure that all of your state is saved by the time you return from this function. In general onSaveInstanceState(Bundle) is used to save per-instance state in the activity and this method is used to store global persistent data (in content providers, files, etc.)
Here's where I got that from.