Develop Reference

How to write a JSON file on internal storage

I would like to write json file on internal storage but I can not handle it. Here is my code:
String answers_json = data.getExtras().getString("answers");
Log.d("****", "****************** WE HAVE ANSWERS ******************");
Log.v("ANSWERS JSON", answers_json);
Log.d("****", "*****************************************************");
try {
File file = new File (getFilesDir(),"answers.json");
FileWriter fileWriter = new FileWriter(file);
BufferedWriter writer = new BufferedWriter(fileWriter);
writer.write("answers");
writer.flush();
writer.close()
I have tried so many variants, but it ends always with an error "open failed" or whenever everything is fine, no file finds on my phone (that means nothing happened). What is wrong on my side?

I got it. This is working for me...
try {
String FILENAME = "answers.json";
FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_APPEND);
assert answers_json != null;
fos.write(answers_json.getBytes());
fos.close();
}
catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
greets and thank for your help.

This may help you:
private void downloadAndStoreJson(String url,String tag){
JSONParser jParser = new JSONParser();
JSONObject json = jParser.getJSONFromUrl(url);
String jsonString = json.toString();
byte[] jsonArray = jsonString.getBytes();
File fileToSaveJson = new File("/sdcard/appData/LocalJson/",tag);
BufferedOutputStream bos;
try {
bos = new BufferedOutputStream(new FileOutputStream(fileToSaveJson));
bos.write(jsonArray);
bos.flush();
bos.close();
} catch (FileNotFoundException e4) {
// TODO Auto-generated catch block
e4.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally {
jsonArray=null;
jParser=null;
System.gc();
}}

How to perform caching in android?

I am building an articles reading android application like TechChurn. I am fetching data from server in the form of json.
I am parsing Id(unique),title, author name and articles-content from json and displaying it in list-view.
Those parsed content is stored in local for accessing without internet access.
This i have done using a cache function.
Here is my code that is using for caching -
public final class CacheThis {
private CacheThis() {
}
public static void writeObject(Context context, String fileName,
Object object) throws IOException {
FileOutputStream fos;
ObjectOutputStream oos;
if (fileExistance(fileName, context)) {
fos = context.openFileOutput(fileName, Context.MODE_PRIVATE
| Context.MODE_APPEND);
oos = new AppendingObjectOutputStream(fos);
} else {
fos = context.openFileOutput(fileName, Context.MODE_PRIVATE
| Context.MODE_APPEND);
oos = new ObjectOutputStream(fos);
}
oos.writeObject(object);
oos.flush();
oos.close();
fos.close();
}
public static List<Object> readObject(Context context, String fileName) {
List<Object> list = new ArrayList<Object>(0);
FileInputStream fis;
try {
fis = context.openFileInput(fileName);
ObjectInputStream ois = new ObjectInputStream(fis);
Object object;
try {
while (true) {
object = ois.readObject();
list.add(object);
}
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
fis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return list;
}
public static boolean fileExistance(String fname, Context context) {
File file = context.getFileStreamPath(fname);
return file.exists();
}
}
my article should be cached based on id instead its been loaded for every-time when app is started

Use the following methods to store and retrieve the data.. Here you can store the object..
private void writeData(Object data, String fileName) {
try {
FileOutputStream fos = context.openFileOutput(fileName,
Context.MODE_PRIVATE);
ObjectOutputStream os = new ObjectOutputStream(fos);
os.writeObject(data);
os.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public Object readData(String fileName){
Object data = null;
if (context != null) {
try {
FileInputStream fis = context.openFileInput(fileName);
ObjectInputStream is = new ObjectInputStream(fis);
data = is.readObject();
is.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (StreamCorruptedException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
return data;
}
Write the data once you got the response from the server(at first request to the server). Use the id as file name. After that check for the particular file before you want to hit server for data. If the file is available then you can get the data from that file, otherwise hit the server.

Storing a file to internal storage and reading it

What I am trying to do is store a JSON file as a string in internal storage to access it later. The reasoning behind this is to not have to access the server on every request, as this data is constant. Once it is stored once, it doesn't have to be retrieved again unless there is some sort of update. File storage isn't something I've done before, and I was hoping someone could give me a hand. My current code is throwing a null pointer exception at this line:
File file = new File(getFilesDir(), fileName);
My code:
protected String doInBackground(String[] runeId) {
String url = "https://prod.api.pvp.net/api/lol/static-data/" + region + "/v1.2/rune/" + runeId[0] + "?api_key=" + api_key;
JSONParser jsonParser = new JSONParser();
JSONObject runeInfo = jsonParser.getJSONFromUrl(url);
String jsonString = runeInfo.toString();
String fileName = "runeInfo";
File file = new File(getFilesDir(), fileName);
String readJson = null;
if(!runesCached) {
Log.d("Cache", "Caching File");
try {
FileOutputStream os = new FileOutputStream(file);
os.write(jsonString.getBytes());
os.close();
Log.d("Cache", "Cache Complete");
runesCached = true;
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
String name = null;
try {
FileInputStream fis;
File storedRuneInfo = new File(getFilesDir(), fileName);
fis = new FileInputStream(storedRuneInfo);
fis.read(readJson.getBytes());
JSONObject storedJson = new JSONObject(readJson);
try {
name = storedJson.getString("name");
} catch (JSONException e) {
e.printStackTrace();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (StreamCorruptedException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return name;
}
}

Try this, instead:
File file = new File(getFilesDir().toString(), fileName);
getFilesDir() returns a File, not a String, which the File class constructor takes as a parameter.
getFilesDir()toString() should return something like /data/data/com.your.app/
EDIT:
This gives the same error. How about:
try {
FileWriter fstream;
BufferedWriter out;
fstream = new FileWriter(getFilesDir() + "/" + "filename");
out = new BufferedWriter(fstream);
out.write(jsonString.getBytes());
out.close();
} catch (Exception e){}

Concatenate two audio files and play resulting file

I am really facing problem from last couple of days but I am not able to find the exact solution please help me.
I want to merge two .mp3 or any audio file and play final single one mp3 file. But when I am combine two file the final file size is ok but when I am trying to play it just play first file, I have tried this with SequenceInputStream or byte array but I am not able to get exact result please help me.
My code is the following:
public class MerginFileHere extends Activity {
public ArrayList<String> audNames;
byte fileContent[];
byte fileContent1[];
FileInputStream ins,ins1;
FileOutputStream fos = null;
String combined_file_stored_path = Environment
.getExternalStorageDirectory().getPath()
+ "/AudioRecorder/final.mp3";
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
audNames = new ArrayList<String>();
String file1 = Environment.getExternalStorageDirectory().getPath()
+ "/AudioRecorder/one.mp3";
String file2 = Environment.getExternalStorageDirectory().getPath()
+ "/AudioRecorder/two.mp3";
File file = new File(Environment.getExternalStorageDirectory()
.getPath() + "/AudioRecorder/" + "final.mp3");
try {
file.createNewFile();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
audNames.add(file1);
audNames.add(file2);
Button btn = (Button) findViewById(R.id.clickme);
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
createCombineRecFile();
}
});
}
public void createCombineRecFile() {
// String combined_file_stored_path = // File path in String to store
// recorded audio
try {
fos = new FileOutputStream(combined_file_stored_path, true);
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
File f = new File(audNames.get(0));
File f1 = new File(audNames.get(1));
Log.i("Record Message", "File Length=========>>>" + f.length()+"------------->"+f1.length());
fileContent = new byte[(int) f.length()];
ins = new FileInputStream(audNames.get(0));
int r = ins.read(fileContent);// Reads the file content as byte
fileContent1 = new byte[(int) f1.length()];
ins1 = new FileInputStream(audNames.get(1));
int r1 = ins1.read(fileContent1);// Reads the file content as byte
// from the list.
Log.i("Record Message", "Number Of Bytes Readed=====>>>" + r);
//fos.write(fileContent1);// Write the byte into the combine file.
byte[] combined = new byte[fileContent.length + fileContent1.length];
for (int i = 0; i < combined.length; ++i)
{
combined[i] = i < fileContent.length ? fileContent[i] : fileContent1[i - fileContent.length];
}
fos.write(combined);
//fos.write(fileContent1);*
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
fos.close();
Log.v("Record Message", "===== Combine File Closed =====");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

I already published an app with this function... try my method using SequenceInputStream, in my app I just merge 17 MP3 files in one and play it using the JNI Library MPG123, but I tested the file using MediaPlayer without problems.
This code isn't the best, but it works...
private void mergeSongs(File mergedFile,File...mp3Files){
FileInputStream fisToFinal = null;
FileOutputStream fos = null;
try {
fos = new FileOutputStream(mergedFile);
fisToFinal = new FileInputStream(mergedFile);
for(File mp3File:mp3Files){
if(!mp3File.exists())
continue;
FileInputStream fisSong = new FileInputStream(mp3File);
SequenceInputStream sis = new SequenceInputStream(fisToFinal, fisSong);
byte[] buf = new byte[1024];
try {
for (int readNum; (readNum = fisSong.read(buf)) != -1;)
fos.write(buf, 0, readNum);
} finally {
if(fisSong!=null){
fisSong.close();
}
if(sis!=null){
sis.close();
}
}
}
} catch (IOException e) {
e.printStackTrace();
}finally{
try {
if(fos!=null){
fos.flush();
fos.close();
}
if(fisToFinal!=null){
fisToFinal.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}

Mp3 files are some frames.
You can concatenate these files by appending the streams to each other if and only if the bit rate and sample rate of your files are same.
If not, the first file plays because it has truly true encoding but the second file can not decode to an true mp3 file.
Suggestion: convert your files with some specific bit rate and sample rate, then use your function.

Android Sockets always timeout

I have this class which connects to a server through sockets, for some reason it is always timing out from here and I can't figure out why, I thought at first it had to do with it being with onCreate(), thats why doit() even exists. any help would be appreciated. here is my code...
public class Ads extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_ads);
doit();
};
public void doit(){
Socket socket = null;
FileOutputStream fos = null;
DataInputStream dis = null;
BufferedOutputStream buf = null;
DataOutputStream dos = null;
try {
socket = new Socket("192.168.1.106", 4447);
Bundle extras = getIntent().getExtras();
String value = extras.getString("keyName");
dos = new DataOutputStream(
new BufferedOutputStream(socket.getOutputStream()));
dis = new DataInputStream(new BufferedInputStream(
socket.getInputStream()));
//dos.writeChars(value);
int numFiles = dis.readInt();
File sdCard = Environment.getExternalStorageDirectory();
File dir = new File (sdCard.getAbsolutePath() +value);
dir.mkdirs();
if (dir.isDirectory()) {
String[] children = dir.list();
for (int i=0; i<children.length; i++) {
new File(dir, children[i]).delete();
}
}
int n = 0;
int fileLength = 0;
for (int i=0;i<numFiles;i++){
File file = new File(dir, String.valueOf(i)+".png");
Log.d("debug tag","created file "+file);
}
for (int i=0;i<numFiles;i++){
fileLength = dis.readInt();
byte[] temp = new byte[(int) fileLength];
String path = sdCard.getAbsolutePath()+value+"/"+i+".png";
buf = new BufferedOutputStream(new FileOutputStream(path));
while ((fileLength > 0) && (n = dis.read(temp, 0, (int) Math.min(temp.length, fileLength))) != -1) {
buf.write(temp,0,n);
buf.flush();
fileLength -= n;
}
//buf.close();
Log.d("debug tag","the file is "+temp.length+" bytes long");
}
// now read in text files
n = 0;
fileLength = 0;
for (int i=0;i<numFiles;i++){
File file = new File(dir, String.valueOf(i)+".txt");
Log.d("debug tag","created file "+file);
}
for (int i=0;i<numFiles;i++){
fileLength = dis.readInt();
byte[] temp = new byte[(int) fileLength];
String path = sdCard.getAbsolutePath()+value+"/"+i+".txt";
buf = new BufferedOutputStream(new FileOutputStream(path));
while ((fileLength > 0) && (n = dis.read(temp, 0, (int) Math.min(temp.length, fileLength))) != -1) {
buf.write(temp,0,n);
buf.flush();
fileLength -= n;
}
//buf.close();
Log.d("debug tag","the text file is "+temp.length+" bytes long");
}
generateListView(sdCard.getAbsoluteFile()+value+"/");
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally{
if (socket != null){
try {
socket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (fos != null){
try {
fos.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (dis != null){
try {
dis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (dos != null){
try {
dos.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
;

I'm afraid the question lacks some important details (it timeouts when connecting, right?), but my blind guess is that your device is using cellular connection, while 192.168.1.106 is on your WiFi network - IPs in the 192.168.x.x pool are private IP addresses, and obviously you can't connect to any such IP address over Internet.
But there's another serious problem with your code - you're trying to make blocking I/O calls in onCreate() - which is executed in the main thread of the application. You should never do this (actually, as soon as you try it on Android 3.x or higher, you'll get NetworkOnMainThreadException). Network I/O should always happen in another thread, either explicitly, or perhaps using AsyncTask (which runs the background thread for you).
For a good introduction, see this post and Designing for Responsiveness guide.