Develop Reference

How to create a shared folder usable by my android app?

I've got a question that probably borders on opinion, but I've not any related questions or documentation that answers, so I feel like it's a fair one to ask.
I'm trying to build an android app which modifies music files, and what I'd like to do is have a shared folder so that the files and the results can be accessible and shared. I'd like it if it was among the other folders like Music, Downloads, Movies, etc, or even under Music since it's music related. However this seems like it's a security no no in Android, as after I've made something and put it in there I have to use an intent to access it again, where as I'd rather just be able to open the files and not have a permissions based fiasco. Maybe some type of symbolic link like in Linux that pointed to my apps internal folder could be used, but of this I'm still uncertain.
In any case, is there a way I should go about this? If so, are there some resources I could be pointed to?
Thank you in advance to anyone who takes this up!
Edit for CommonsWare:
I used the following to create the folder:
File mediaStorageDir = new File(Environment.getExternalStorageDirectory(), APP_NAME);
And this to copy files from elsewhere to there:
public void copyFileToHomeDirectory(Uri uri)
{
try
{
ContentResolver contentResolver = getApplicationContext().getContentResolver();
String fileName = queryName(contentResolver, uri);
//Get file extension
String fileType = fileName.substring(fileName.length() - 4, fileName.length());
if(fileType.equalsIgnoreCase(MP3_EXTENSION))
{
String path = Environment.getExternalStorageDirectory() + APP_FOLDER;
InputStream in = contentResolver.openInputStream(uri);
File outputFile = new File(path + File.separator + fileName);
outputFile.createNewFile();
OutputStream out = new FileOutputStream(outputFile);
//First we crack open the file to copy it's contents:
byte[] buffer = new byte[KB_SIZE];
int read;
while ((read = in.read(buffer)) != -1)
{
out.write(buffer, 0, read);
}
in.close();
in = null;
// write the output file (You have now copied the file)
out.flush();
out.close();
out = null;
}
}
catch(FileNotFoundException fnfe)
{
Log.e(TAG, "FileNotFoundException");
Log.e(TAG, Log.getStackTraceString(fnfe));
}
catch(IOException ioe)
{
Log.e(TAG, "IOException");
Log.e(TAG, Log.getStackTraceString(ioe));
}
catch(Exception e)
{
Log.e(TAG, "General Exception");
Log.e(TAG, Log.getStackTraceString(e));
}
}
I've tried other methods that I've overwritten in the process, but accessing the files to be used again I need something like this:
public void openDirectory(View view)
{
// Choose a directory using the system's file picker.
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
// Provide read access to files and sub-directories in the user-selected
// directory.
//intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
//intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
//intent.addCategory(Intent.CATEGORY_OPENABLE);
// Optionally, specify a URI for the directory that should be opened in
// the system file picker when it loads.
//intent.putExtra(DocumentsContract.EXTRA_INITIAL_URI, uriToLoad);
intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
intent.addCategory(Intent.CATEGORY_OPENABLE);
intent.setType("*/*"); //use image/* for photos, etc.
//The result of this code will be calling the onActivityResult function below
startActivityForResult(intent, REQUEST_MUSIC_DIR);
}
Edit2:
I've reorganized the folders to what I think I should be doing so that I can work with the files freely, however, even in my internal cache storage (getCacheDir() + folder_name) either isn't letting me create the files (outputFile.createNewFile doesn't throw an error) or it isn't letting me open them when I go to get a directory listing.
Here's my code for creating the file:
String path = getCacheDir() + MY_SUB_FOLDER;
//uri is obtained through ACTION_OPEN_DOCUMENT intent
InputStream in = contentResolver.openInputStream(uri);
File outputFile = new File(path + "/" + fileName);
outputFile.createNewFile();
Log.i(TAG, "The new file's directory/path is: " + outputFile.getAbsolutePath());
//NOTE: This is returning /data/user/0/com.example.myapplication/cache/MY_SUB_FOLDER/file_name.mp3
OutputStream out = new FileOutputStream(outputFile);
byte[] buffer = new byte[1024];
int read;
while ((read = in.read(buffer)) != -1)
{
out.write(buffer, 0, read);
}
in.close();
in = null;
out.flush();
out.close();
out = null;
This is my code for attempting to open and read these newly created files
File directory = new File(getCacheDir(), MY_SUB_FOLDER);
Log.i(TAG, "This is the directory we're trying to get the files from: " + directory.getAbsolutePath());
//NOTE: This returns /data/user/0/com.example.myapplication/cache/MY_SUB_FOLDER
File[] files = directory.listFiles();
if(files != null)
{
for(int i = 0; i < files.length; i++)
{
Log.d(TAG, "Files found: " + files[i].getAbsolutePath());
}
}
The files variable isn't null but it's length is 0 and no files are found.
Edit3:
I am catching the exceptions and logging any stack traces, which currently returns nothing.
catch(FileNotFoundException fnfe)
{
Log.i(TAG, "FileNotFoundException");
Log.i(TAG, Log.getStackTraceString(fnfe));
}
catch(IOException ioe)
{
Log.i(TAG, "IOException");
Log.i(TAG, Log.getStackTraceString(ioe));
}
catch(Exception e)
{
Log.i(TAG, "General Exception");
Log.i(TAG, Log.getStackTraceString(e));
}

My app can't open internal storage file

Android app: Newly created files on internal storage appear in the listing of files, but trying to open the files creates an exception 'No such file or directory'. (Android 8.0, tested on several devices.)
//create a file in internal storage
FileOutputStream output = null;
output = openFileOutput("xxxyyy.txt", Context.MODE_PRIVATE);
String str = "Just any string";
byte[] bytes = str.getBytes();
output.write(bytes, 0, bytes.length);
output.close();
//list the files
String lst[] = fileList();
for (int i = 0; i < lst.length; i++)
{ Log.v("MM" , "INTERNAL FILES: "+lst[i]); }
//system reply: INTERNAL FILES: xxxyyy.txt, ......
//check if file exists and try to open it for reading
File file = new File("xxxyyy.txt");
Log.v("XX" , "TEST: file exists? " + file.exists());
//system reply: TEST: file exists? false
//try to open it for reading
FileInputStream input = null;
try {
input = new FileInputStream("xxxyyy.txt");
} catch (IOException e) {
Log.v("XX" , "TEST: " + e.getMessage());
}
//system reply: TEST: xxxyyy.txt (No such file or directory)
Many variations have been tried.
Any suggestion greatly appreciated!

If you need to access a file created with openFileOutput, you need to specify the correct directory when creating the File object, in this case:
File file = new File(getFilesDir(), "xxxyyy.txt");

What path does "getApplicationContext().getFilesDir()" return?

I'm doing a simple app in Android and in a certain part of the app I would like to create an Excel file and write in it. I've already prepared everything to use jexcel library to edit an excel using Java, but the thing is I can't find the Excel file I created. I've tried to find it in my own device executing the app, but I couldn't.
String fileName = "hours.xls";
File file = new File(getApplicationContext().getFilesDir() + fileName);
Can anybody help me please?
Thanks in advance :)

On Android KitKat, it returns /data/data/{your package name}/files, however I imagine this could change depending on your platform version. Thus if you're just trying to dig through your filesystem and see a file, it's safe to use this path, but if you're using this path for some functionality across multiple platform versions, you should only reference it using getFilesDir().

What are you planning on using this file for? Do you want it usable by other apps too? Using getApplicationContext().getFilesDir() will give you /data/data/com.package/files but if you want a file that's easily accessible by yourself and other apps, you're better off using something like getExternalFilesDir()

If you want to access your file via your PC (with an usb cable) or via a file manager on your device, prefer:
new File(getExternalFilesDir(null), fileName);
This folder is created in .../Android/data/ ... com.yoursociety.yourapp/files ...
null means that you do not want to store files in predefined folders like Movies, Pictures and so on.
(See documentation for more info)

This worked:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context = getApplicationContext();
b = (Brain)load("brain.txt");
if (b == null) {
b = new Brain();
}
vocabulary = (ArrayList <String>) load("vocabulary.txt");
if (vocabulary == null) {
vocabulary = new ArrayList <String> ();
vocabulary.add("I love you.");
vocabulary.add("Hi!");
}
b.setRunning(true);
}
public Object load(String fileName) {
File file = new File("/storage/emulated/0/Android/data/com.cobalttechnology.myfirstapplication/files/" + fileName);
if (!file.exists()) {
return null;
}
try {
Object o;
FileInputStream fis = new FileInputStream(file);
ObjectInputStream ois = new ObjectInputStream(fis);
o = ois.readObject();
if (o == null) {
System.out.println(fileName + " = null");
}
ois.close();
fis.close();
System.out.println("Loaded: " + fileName);
return o;
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException cnfe) {
cnfe.printStackTrace();
}
return null;
}
public void save(Object o, String fileName) {
File file = new File("/storage/emulated/0/Android/data/com.cobalttechnology.myfirstapplication/files/" + fileName);
try {
if (!file.exists()) {
file.createNewFile();
}
FileOutputStream fos = new FileOutputStream(file);
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(o);
oos.close();
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}

Read the documentation, this method reads the files stored in the internal storage that were created with
with openFileOutput():
getFilesDir()
Returns the absolute path to the directory on the filesystem where
files created with openFileOutput(String, int) are stored.

Android work with db file from SD card

I wrote an app which logged data and saved it via SQL into a .db File. I had a method copying it from internal memory to SD card.
Now i wrote a second app, which needs to work with this particular .db file. As i think, that apps can't get access to package files from other apps
(in this case
/data/data/app1_package/databases/my_database.db
)
i need somehow to work with my DB on the SD Card. How do i do that?
Can i use this path in my SQLiteHelper class? Should i copy it from SD to my package, is that even possible (access rights etc.)?
I'm a beginner in databases, some help would be nice.

You can open any readable file path as a database:
File dbFile = new File( Environment.getExternalStorageDirectory(), "myfile.db" );
SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase(dbFile,null,null);
Note: check if sd-card is mounted before using this code.

yes place the DB file in your assets folder and get it this way :
DB_PATH="/data/data/app1_package/databases/my_database.db"
in your create :
is = getAssets().open("Meaniningss.db");
write(is);
the method :
public void write(InputStream is) {
try {
OutputStream out = new FileOutputStream(new File(DB_PATH));
int read = 0;
byte[] bytes = new byte[1024];
while ((read = is.read(bytes)) != -1) {
out.write(bytes, 0, read);
}
is.close();
out.flush();
out.close();
System.err.println(out + "\n");
} catch (IOException e) {
e.printStackTrace();
}
}

I need to be able to store sound files for my application on sdcard

I've read a lot of topics but none seem to cover what I need.
I basically have a load of sound files and I want to be able to play them in the application from the sdcard.
I also want to be able to install them there in the first place when the application is installed.
I am using Eclipse with the android SDK and currently my Target project is v1.6
Can anyone help?
Thanks

OK so I found the answer!
First we need to get the external Storage Directory to a variable called baseDir.
String baseDir = Environment.getExternalStorageDirectory().getAbsolutePath();
Then Create the directory mysounds on the SDcard
File folder = new File(Environment.getExternalStorageDirectory() + "/mysounds");
boolean success = false;
if(!folder.exists())
{
success = folder.mkdir();
}
if (!success)
{
// Do something on success
}
else
{
// Do something else on failure
}
Then This following bit of code will copy all the files with sound at the beginning of the name from the assets directory to the mysounds directory you have already created.
try {
AssetManager am = getAssets();
String[] list = am.list("");
for (String s:list) {
if (s.startsWith("sound")) {
Log.d("Notice", "Copying asset file " + s);
InputStream inStream = am.open(s);
int size = inStream.available();
byte[] buffer = new byte[size];
inStream.read(buffer);
inStream.close();
FileOutputStream fos = new FileOutputStream(baseDir + "/mysounds/" + s);
fos.write(buffer);
fos.close();
}
}
}
Hope this helps someone!