Develop Reference

Load simple JSON file into 2 dimensional Array in Android

Driving myself crazy over the simplest thing. I have a JSON file called config.txt. The file is shown below.
{
"UsePipesInGuestData": true
}
All I want to do is get a 2 dimensional array such that:
Array[0] = UsePipesInGuestData and
Array[1] = true
I have been trying for 4 hours with various attempts, my most recent is shown below:
private void getConfig(){
//Function to read the config information from config.txt
FileInputStream is;
BufferedReader reader;
try {
final File configFile = new File(Environment.getExternalStorageDirectory().getPath() + "/guestlink/config.txt");
if (configFile.exists()) {
is = new FileInputStream(configFile);
reader = new BufferedReader(new InputStreamReader(is));
String line = reader.readLine();
while (line != null) {
line = reader.readLine();
if(line!= null) {
line = line.replace("\"", ""); //Strip out Quotes
line = line.replace(" ", ""); //Strip out Spaces
if ((!line.equals("{")) || (!line.equals("}"))) {
} else {
String[] configValue = line.split(":");
switch (configValue[0]) {
case "UsePipesInGuestData":
if (configValue[1].equals("true")) {
sharedPreferences.edit().putString("UsePipes", "true").apply();
} else {
sharedPreferences.edit().putString("UsePipes", "false").apply();
}
break;
}
}
}
}
reader.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
I cannot seem to ignore the lines with the { and } in them.
Clearly there MUST be an easier way. JAVA just seems to take an extremely large amount of code to do the simplest thing. Any help is greatly appreciated.

I believe your condition is incorrect. You try to read the file in the else of the condition (!line.equals("{")) || (!line.equals("}")). Simplifying, your code will run when the following happens:
!(!{ || !}) => { && } (applying De Morgan's law)
This means you will only run your code when the line is "{" AND it is "}" which is a contradiction. Try using simple conditions, like (!line.equals("{")) && (!line.equals("}")) (this is when you want to execute your code).
Additionally, you may be getting end of line characters (\n) in your string, which will make your condition fail ("{\n" != "{"). I suggest you debug and see the actual values you're getting in those lines.

Randomize array of questions while reading from text file android

This is a android quiz app code snippet which load the question from text file.
I want to shuffle the question and answer after every next click so how can i implement random function ?
https://github.com/gitssk/quizfun/blob/master/src/ssk/quizfun/QuizFunActivity.java
https://github.com/gitssk/quizfun/blob/master/res/raw/questions.txt
private void loadQuestions() throws Exception {
try {
InputStream questions = this.getBaseContext().getResources()
.openRawResource(R.raw.questions);
bReader = new BufferedReader(new InputStreamReader(questions));
StringBuilder quesString = new StringBuilder();
String aJsonLine = null;
while ((aJsonLine = bReader.readLine()) != null) {
quesString.append(aJsonLine);
}
Log.d(this.getClass().toString(), quesString.toString());
JSONObject quesObj = new JSONObject(quesString.toString());
quesList = quesObj.getJSONArray("Questions");
Log.d(this.getClass().getName(),
"Num Questions " + quesList.length());
} catch (Exception e){
} finally {
try {
bReader.close();
} catch (Exception e) {
Log.e("", e.getMessage().toString(), e.getCause());
}
}
}
https://github.com/gitssk/quizfun/blob/master/src/ssk/quizfun/QuizFunActivity.java

I will refrain from posting much code because I think you should attempt it on your own. It is seriously not that tough. I will give you an approach though.
You have quesList = quesObj.getJSONArray("Questions");. So quesList is the list of questions that is a JSONArray. You want to shuffle this. Just do this:
Get the length of the quesList array. Let's call it len.
Create a simple arrayList called quesOrder containing integers 0 to len.
List<Integer> quesOrder = new ArrayList<>();
for (int i = 0; i <= len; i++)
{
quesOrder.add(i);
}
Once you have the quesOrder array. Just do Collections.shuffle(quesOrder);. Now when you get questions from your quesList array, just get the index from quesOrder list. And you will have a randomized selection. Put it together in a function for convenience.

How to escape comma in a CSV file, android

I have a CSV file (the information is with Cyrillic letters, if matters). The CSV class is written so that it reads every row and splits it on a comma:
String[] row = csvLine.split(",");
In the csv I have rows in the following pattern:
ааа,бб, рр, ррр рр тт.
How can I force the CSV be split on the first comma only?
PS: I've already tried using double commas and blackslash in from of the comma, without any success so far.
EDIT:
Here is the whole CSVreader class:
public class CSVReader {
InputStream inputStream;
public CSVReader(InputStream is) {
this.inputStream = is;
}
public List<String[]> read() {
List<String[]> resultList = new ArrayList<String[]>();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
try {
String csvLine;
while((csvLine = reader.readLine()) != null) {
String[] row = csvLine.split(",");
resultList.add(row);
}
} catch(IOException ex) {
throw new RuntimeException("Error in reading CSV file:" + ex);
} finally {
try{
inputStream.close();
} catch(IOException e) {
throw new RuntimeException("Error while closing input stream: " + e);
}
}
return resultList;
}
}
What I need is the above excerpt from the CSV to be split on the first comma only, and the encountered after that to be parsed and shown on the screen.

If you want to split only the first comma of each line, you can use
csvLine.split(",",2);
Where 2 is the limit parameter checking the maximum lenght of the resulting String array. This means that the split will only occur limit-1 times. In your case, 1.
As explained in JavaDocs here.
With input aa,bb,cc,dd you'll get the array {"aa","bb,cc,dd"}

IndexOutOfBoundsException error happening depending on Android OS version

I am desperatly trying to fix a bug that:
always happens in my emulator for Android versions 2.2, 2.3
never happens in emulator android versions 4.*
never happens in a real device (android 4.*)
It is the following IndexOutOfBoundsException exception:
java.lang.RuntimeException: Unable to start activity
ComponentInfo{<myapppackage>}: java.lang.IndexOutOfBoundsException:
Invalid index 39, size is 0
In my app I am fecthing data from a json file that I am displaying as text. I've isoleted where the bug is coming from, it is when I call this method:
public String getItemValue(int id, String s) {
List<JsonItems> list = new ArrayList<JsonItems>();
try {
// CONVERT RESPONSE STRING TO JSON ARRAY
JSONArray ja = new JSONArray(s);
// ITERATE THROUGH AND RETRIEVE
int n = ja.length();
for (int i = 0; i < n; i++) {
// GET INDIVIDUAL JSON OBJECT FROM JSON ARRAY
JSONObject jo = ja.getJSONObject(i);
// RETRIEVE EACH JSON OBJECT'S FIELDS
JsonItems ji = new JsonItems();
ji.id = jo.getInt("id");
ji.text= jo.getString("text");
list.add(ji);
}
} catch (Exception e) {
e.printStackTrace();
}
return list.get(id).text;
}
My class JsonItems is very basic:
public class JsonItems{
int id;
String text;
}
Sample from my json file:
[
{"id":0,"text":"some text 0"},
{"id":1,"text":"some text 1"},
{"id":2,"text":"some text 2"}
]
Here is how I process content of my json file into a String
public static String fromJsonFileToString(String fileName, Context c) {
//JSONArray jArray = null;
String text = "";
try {
InputStream is = c.getAssets().open(fileName);
int size = is.available();
byte[] buffer = new byte[size];
is.read(buffer);
is.close();
text = new String(buffer);
} catch (IOException e) {
throw new RuntimeException(e);
}
return text;
}
Once again I repeat: the IndexOutOfBoundsException NEVER happens on a device with Android 4.* , it only happens when I test the app on emulators with Android 2.*
Any idea where it is coming from?
Thanks

First problem:
You are not reading your input stream correctly. Calling available literally does just that - it returns you the amount of data that is available to be read, when the call is made. This number may, or may not represent the entire content of the file.
Reading material for you:
How to Read a File in Java.
Writing and Creating Files
Note that there are helper libraries like Apache Commons IO that make it possible to read file contents in a single line of code (IOUtils.toString(inputStream)). Android doesn't support Java 7 yet but a noteworthy alternative is available in that release, with the Files.readAllLines method. In any case, you can make the below shown changes to your file reading code and it should work better:
public static String fromFileToString(String fileName, Context context) {
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
context.getAssets().open(fileName)));
String line = null;
StringBuilder builder = new StringBuilder(1024);
while ((line = reader.readLine()) != null) {
builder.append(line);
}
return builder.toString();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
Second problem:
You do not do any bound check, to make sure that the argument you pass into your 'search' method:
public String getItemValue(int id, String s)
Does not exceed the length of the list of items you eventually calculate:
return list.get(id).text;
// ^
// -------------
// 'id' could be larger than the list size!
In any case, your current design doesn't at all match what you are really trying to do, aka, to determine the element in the JSON array that has an 'id' field matching what you supply to the method. You need to process the JSON data as a map, in order to be able to do this.
public String getItemValue(int id, String json) {
if(json == null || json.trim().equals("")) return null;
Map<Integer, JsonItems> map = new HashMap<Integer, JsonItems>(4);
try {
JSONArray ja = new JSONArray(json);
int n = ja.length();
for (int i = 0; i < n; i++) {
JSONObject jo = ja.getJSONObject(i);
JsonItems ji = new JsonItems();
ji.id = jo.getInt("id");
ji.text = jo.getString("text");
map.put(Integer.valueOf(ji.id, ji);
}
} catch(NumberFormatException nfe) {
throw new IllegalArgumentException("Invalid JSON format");
} catch (Exception e) {
throw new RuntimeException(e);
}
JsonItems item = map.get(id);
return item != null ? item.text : null;
}
Some quick notes:
JsonItems should be called JsonItem, to conform to good Java naming standards
You should really parse and store your JSON just once, to improve performance
You are really only using a minimal subset of your JSON data, you could actually determine the matching node within your for loop and directly return its value, without having to use an intermedia Java bean object

Dynamically populating an expandableListView

So All I'm trying to do is create a dynamic expandableListView Currently It works if I just do the groupViews. The problem comes in when I have to populate the children of those groupViews.. I don't know if I'm doing something wrong, or if theres another better way to do it. If anyone knows please let me know. I'm open to anything.
Currently I'm pulling my data off a server and the error I'm getting is java null pointer exception. So I'm thinking it might have something to do with how big I specified my array sizes?
private static String[][] children = new String[7][4];
private static String[] groups = new String[7];
Here is the rest of the code when I try to populate the View.
public void getData(){
try {
int tempGroupCount = 0;
URL food_url = new URL (Constants.SERVER_DINING);
BufferedReader my_buffer = new BufferedReader(new InputStreamReader(food_url.openStream()));
temp = my_buffer.readLine();
// prime read
while (temp != null ){
childrenCount = 0;
// check to see if readline equals Location
//Log.w("HERasdfsafdsafdsafE", temp);
// start a new location
if (temp.equalsIgnoreCase("Location"))
{
temp = my_buffer.readLine();
groups[tempGroupCount] = temp;
tempGroupCount++;
Log.w("HERE IS TEMP", temp);
}
temp = my_buffer.readLine();
while (temp.equalsIgnoreCase("Location") == false){
Log.w("ONMG HEHREHRHERHER", temp);
children[groupCount][childrenCount] = "IAJHSDSAD";
childrenCount++;
temp = my_buffer.readLine();
}
groupCount++;
}
my_buffer.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
Log.e("IO EXCEPTION", "Exception occured in MyExpandableListAdapter:" + e.toString());
}
}

to me it looks like an error in the loop - as you are reading another line without checking is it null
your while loop should look something like this methinks:
// prime read
while (temp != null ){
int childrenCount = 0;
// check to see if readline equals Location
// start a new location
//Log.w("HERasdfsafdsafdsafE", temp);
if (temp.equalsIgnoreCase("Location"))
{
temp = my_buffer.readLine();
groups[tempGroupCount] = temp;
tempGroupCount++;
Log.w("HERE IS TEMP", temp);
}
//>>remove following line as that one isn't checked and
//>>you are loosing on a line that is potentialy a child
//temp = my_buffer.readLine();
//>>check do you have first item to add subitems
else if (tempGroupCount>0){
while (temp.equalsIgnoreCase("Location") == false){
Log.w("ONMG HEHREHRHERHER", temp);
children[tempGroupCount-1][childrenCount] = "IAJHSDSAD";
childrenCount++;
temp = my_buffer.readLine();
}
//>>next counter is probably not need but can't see if you're using it somewhere else
//groupCount++;
}

I would first replace strings array to some 2d collection for example arraylist2d ( you can google it ) so you could easally add and remove data from list. If you created adapter that extends BaseExpandableListAdapter everything should be handled without any problems.
About NULLPointer, could you paste stacktrace or more info on which line it occurs ?