Develop Reference

Is there a way to export realm database to CSV/JSON?

I want to export my realm database to CSV/JSON in Android. Is there some in-build method in the realm database which can do this?
There is a iOS way of converting realm to CSV link. I want a similar method in Android.

I was able to cobble together the following solution in my project:
// Grab all data from the DB in question (TaskDB):
RealmResults<TaskDB> resultsDB = realm.where(TaskDB.class).findAll();
// Here we need to put in header fields
String dataP = null;
String header = DataExport.grabHeader(realm, "TaskDB");
// We write the header to file
savBak(header);
// Now we write all the data corresponding to the fields grabbed above:
for (TaskDB taskitems: resultsDB) {
dataP = taskitems.toString();
// We process the data obtained and add commas and formatting:
dataP = dataProcess(dataP);
// Workaround to remove the last comma from final string
int total = dataP.length() - 1;
dataP = dataP.substring(0,total);
// We write the data to file
savBak(dataP);
}
I will explain what it is doing as best I can and include all corresponding code(all in reference to the first code block).
The first I did is grab the header using the following method I wrote in a separate class (DataExport.grabHeader). It takes 2 arguments: the realm object in question and the DB object model name:
public static String grabHeader(Realm realm, String model){
final RealmSchema schema = realm.getSchema();
final RealmObjectSchema testSchema = schema.get(model);
final String header = testSchema.getFieldNames().toString();
String dataProcessed = new String();
Pattern p = Pattern.compile("\\[(.*?)\\]");
Matcher m = p.matcher(header);
while(m.find()) {
dataProcessed += m.group(1).trim().replaceAll("\\p{Z}","");
}
return dataProcessed;
Within grabHeader, I apply some regex magic and spit out a string that will be used as the header with the appropriate commas in place (String dataProcessed).
In this scenario, after I obtained the data needed, I used another method (savBak) to write the information to a file which takes 1 string argument:
#Override
public void savBak(String data){
FileOutputStream fos = null;
try {
fos = openFileOutput(FILE_NAME, MODE_PRIVATE | MODE_APPEND);
fos.write(data.getBytes());
fos.write("\n".getBytes());
Log.d("tester", "saved to: " + getFilesDir() + "/" + FILE_NAME);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fos != null) {
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
The "savBak" method writes the information to a FILE_NAME specified in a variable and we have our header information. After the header is written, we do the basically the same process with the DB using a forloop but I also had to include 2 lines to remove the trailing comma after the line was processed. Each line is appended to the file and viola, CSV formatted goodness.
From here, you can use other existing methods of converting CSV to JSON and whatever else as well as putting the information back into realm via JSON. When it comes to more advanced elements like primary keys and such, I am not sure but it worked for my particular project needs.
Please excuse any "bad code" practice as I'm new to Java/Android in general coming from a "barely intermediate" Python background so hopefully this makes sense.

I got a reply from Realm support via email.
Unfortunately, we do not have this feature yet. You can see it tracked here: https://github.com/realm/realm-java/issues/2880
You could use a dynamic API and write a script yourself to perform a similar feature.

Load strings.xml from sd card to application android

Is it possible to load strings.xml from sd card instead of application res/values/... Search on the web but didn't find any tutorials. My thought is download the xml to sd card then save the strings element to an array.
public void stringsxml(){
File file = new File(Environment.getExternalStorageDirectory()
+ ".strings.xml");
StringBuilder contents = new StringBuilder();
try {
//use buffering, reading one line at a time
//FileReader always assumes default encoding is OK!
BufferedReader input = new BufferedReader(new FileReader(file));
try {
String line = null; //not declared within while loop
/*
* readLine is a bit quirky :
* it returns the content of a line MINUS the newline.
* it returns null only for the END of the stream.
* it returns an empty String if two newlines appear in a row.
*/
while (( line = input.readLine()) != null){
contents.append(line);
contents.append(System.getProperty("line.separator"));
}
}
finally {
input.close();
}
}
catch (IOException ex){
ex.printStackTrace();
}
String data= contents.toString();
}

Well, actually it is semi-possible, but you have to create a derivate LayoutInflater which will replace string codes with thus read strings.
I have documented my attempts and failings together with initial implementation here.
Summary: simple strings work, string arrays do not

No, this is not possible. Check Android decoumentation about resources:
The Android SDK tools compile your application's resources into the application binary at build time. To use a resource, you must install it correctly in the source tree (inside your project's res/ directory) and build your application.
Resources are built-in into the application binary and you can't read them from a file.

OOM on devices with smaller RAM

I have two json files in the assets folder. The problem is that on devices with smaller memory I get the out of memory error. What can I do to solve this? I have the following code:
Variables to store json
private static JSONObject one;
private static JSONObject two;
Method to set variables
public static void setJSON(Context context){
try {
one = new JSONObject(loadJSON(context,"one.json"));
two = new JSONObject(loadJSON(context,"two.json"));
} catch (JSONException e) {
e.printStackTrace();
}
}
Method to load json
private static String loadJSON(Context context, String filename){
try {
InputStream is = context.getAssets().open(filename);
int size = is.available();
byte[] buffer = new byte[size];
is.read(buffer);
is.close();
String json = new String(buffer, "UTF-8");
return json;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}

There are a couple of ideas which might help here (and it would have helped to show a JSON file snippet)
A) How big are your JSON files? JSON processing is memory heavy, as you need to have RAM for the parser and the objects it creates in memory. Can you shrink the JSONs?
B) Can you load them one at a time? process, and free?
C) If all else fails, try splitting them into bunches of several objects, then load.
D) All in all, JSON is a terrible form of serialization. If you can use Java serialization instead, you'll be looking at a LOT less memory.

Do not use JSON, but convert your data to normal SQLite database and have it prepopulated in your APK file in assets folder. Then on first run you install it to app folder (you can use this tool) and then, finally use normal database and just get data you need at that moment, without need of loading whole JSON

Open raw text recourse and diplay wrong next line

InputStream inputStream = getResources().openRawResource(idtext);
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
String myText = "";
int in;
try {
in = inputStream.read();
while (in != -1) {
byteArrayOutputStream.write(in);
in = inputStream.read();
}
inputStream.close();
myText = byteArrayOutputStream.toString();
} catch (IOException e) {
e.printStackTrace();
}
myTextView.setText(myText); `
My code is used to display long text file in raw res. I don't know why, but some of text file display wrong about next line, any help?

It would be good if you can share some sample display vs your expected output.
From the initial guess, it could be because of couple of reasons:
The encoding used in the text file. So, if you have written the text in ASCII and displaying it while using UTF-8 strings, it would mess up few things. This should be consistent.
Could be a good case of how line feeds are encoding in the file, like \r\n or just \n.
You can also try encapsulating your InputStream to FileReader and line reading streams which are more specialized in directly reading strings, rather than converting it.
You can probably use a library like Apache Commons IO to manage all the stuffs for you.

Problem finding/reading a file

I'm trying to develop a small application, where I was given a JSON file, and I have to extract data from it. As I understood a JSON object takes a string argument, thus I'm trying to access a file and write the data from it to a string.
I've placed that file in a "JSON file" folder, and when I try to read the file, it throws me a file not found exception.
I've tried several ways to find a path to that file, but every attempt was for vain.
It might be that I'm extracting the path wrong, or might be something else, please help me.
Thanks in advance.
here is the code of finding the path:
try
{
path = Environment.getRootDirectory().getCanonicalPath();
}
catch (IOException e)
{
e.printStackTrace(); //To change body of catch statement use File | Settings | File Templates.
}
File jFile = new File(path + /"JSON file/gallery.json");
here is the code for reading from a file :
String str ="";
try
{
BufferedReader in = new BufferedReader(new FileReader(jFile));
while ((str += in.readLine()) != null)
{
}
in.close();
}
catch (IOException e)
{
e.getMessage();
}
return str;
Here more specification:
I want to take the data from the file in order to do that : JSONObject(jString).
when I extract the path of json file I create a file with the path and pass it to the function that reads from the file, and there it throws me a file not found exception, when I try to read from it.
The file does exists in the folder (even visually - I've tried to attach an image but the site won't let me, because I'm new user)
I've tried to open the file through the windows address bar by typing the path like that:
C:\Users\Marat\IdeaProjects\MyTask\JSON file\gallery.json and it opens it.

if you store it in the assets folder you can access it by using
InputStream is = context.getResources().getAssets().open("sample.json");
You can then convert it to a String
public static String inputStreamAsString(InputStream stream)
throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(stream));
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = br.readLine()) != null) {
sb.append(line + "\n");
}
br.close();
return sb.toString();
}

EDIT
You need to put the file in the device, if it is on your computer, it is not accessible from your device. There are some ways to do that, and one of them is to put it in the res/ dir of your application. Please refer to the documentation to see how to do that.
Debug it. I'm pretty sure it will be very easy to find. To start with, look for the following:
Print the path before you create the file, e.g. Log.d("SomeTag", path + "/JSON file/gallery.json")
Observe the full exception details. Maybe there is another problem.
Explore the folders and see if the file exists (in eclipse: window -> show view -> other -> android -> file explorer.
You will probably observe the problem and be able to fix it. If not, post here a question with more details, including the results of those trials.
BTW, GetgetRootDirectory() returns the root directory of android, that's not what you want (you don't have RW permissions there) you probably want to get the applcation directory, you can see how to get it here, in the question I asked a few month ago. But since you didn't give us those details, it will be hard to help you more then that.