Develop Reference

Read a file, if it doesn't exist then create

Honestly, I've searched a lot do this task so I ended up trying various methods but nothing worked until I ended up on this code. It works for me perfectly like it should, so I do not want to change my code.
The help I need is to put this code in a such a way that it begins to read a file, but if it the file doesn't exist then it will create a new file.
Code for saving data:
String data = sharedData.getText().toString();
try {
fos = openFileOutput(FILENAME, MODE_PRIVATE);
fos.write(data.getBytes());
fos.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Code for loading data:
FileInputStream fis = null;
String collected = null;
try {
fis = openFileInput(FILENAME);
byte[] dataArray = new byte [fis.available()];
while (fis.read(dataArray) != -1){
collected = new String(dataArray);
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
try {
fis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
So If I add the saving data code in to the "FileNotFoundException" catch of the loading data part then could I achieve what I want?

Add
File file = new File(FILENAME);
if(!file.exists())
{
file.createNewFile()
// write code for saving data to the file
}
above
fis = openFileInput(FILENAME);
This will check if there exists a File for the given FILENAME and if it doesn't it will create a new one.

If you're working on Android, why don't you use the API's solution for saving files?
Quoting:
String filename = "myfile";
String string = "Hello world!";
FileOutputStream outputStream;
try {
outputStream = openFileOutput(filename, Context.MODE_PRIVATE);
outputStream.write(string.getBytes());
outputStream.close();
} catch (Exception e) {
e.printStackTrace();
}
You should really read the whole document, they explain pretty well the basic ways of creating or accessing files, you can also check the different ways of storing data.
But regarding your original question:
So If I add the saving data code in to the "FileNotFoundException"
catch of the loading data part then could I achieve what I want?
Yes, you could achieve it.

Try this one:
public static void readData() throws IOException
{
File file = new File(path, filename);
if (!file.isFile() && !file.createNewFile()){
throw new IOException("Error creating new file: " + file.getAbsolutePath());
}
BufferedReader r = new BufferedReader(new FileReader(file));
try {
// ...
// read data
// ...
}finally{
r.close();
}
}
Ref: Java read a file, if it doesn't exist create it

How to convert ImageIO.write(input, file, cos) to use in Android

Im a getting errors from some code developed in Java that want to use in Android.
ImageIO.write(input, file, cos)
These are my errors for the following code in android, the code works in Java:
BufferedImage cannot be resolved to a type
ImageIO cannot be resolved
public void decryptFile(String key, String typeFile) throws InvalidKeyException,
NoSuchAlgorithmException,
InvalidKeySpecException,
NoSuchPaddingException,
IOException
{
DESKeySpec dks = new DESKeySpec(key.getBytes());
SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
SecretKey desKey = skf.generateSecret(dks);
Cipher pbeCipher = Cipher.getInstance("DES"); // DES/ECB/PKCS5Padding for SunJCE
pbeCipher.init(Cipher.DECRYPT_MODE, desKey);
// Decrypt the ciphertext and then print it out.
FileInputStream output = null;
File encryptedFile = new File(Environment.getExternalStorageDirectory() + "/images/Et1.jpg");
File decryptedFile = new File(Environment.getExternalStorageDirectory() + "/images/Dt1.jpg");
try
{
output = new FileInputStream(encryptedFile);
}
catch (FileNotFoundException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
CipherInputStream cis = new CipherInputStream(output, pbeCipher);
BufferedImage input = null;
try
{
input = ImageIO.read(cis);
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
FileOutputStream out = null;
try
{
out = new FileOutputStream(decryptedFile);
}
catch (FileNotFoundException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
try
{
ImageIO.write(input,typeFile, out);
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
try
{
cis.close();
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}

i had similar problems with
import javax.sound.sampled.*;
You need to find the corresponding import (probably ImageIO)
and find a replacement
for me it was
import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaRecorder;
if thats not the case then post your errors.
Also take in mind it wasnt just a matter of switching the import, i had to port the code to the new library.

Using Dropbox API to upload a file with Android

How can I upload a File (graphic, audio and video file) with Android using the Dropbox API to Dropbox? I followed the tutorial on the Dropbox SDK Android page and could get the sample to work. But now instead of a String I want to upload an actual File object and am struggling.
The sample code works without any problems and looks like this:
String fileContents = "Hello World!";
ByteArrayInputStream inputStream = new ByteArrayInputStream(fileContents.getBytes());
try {
Entry newEntry = mDBApi.putFile("/testing_123456.txt", inputStream, fileContents.length(), null, null);
} catch (DropboxUnlinkedException e) {
Log.e("DbExampleLog", "User has unlinked.");
} catch (DropboxException e) {
Log.e("DbExampleLog", "Something went wrong while uploading.");
}
But when I try to change it and upload an actual file with this code:
File tmpFile = new File(fullPath, "IMG_2012-03-12_10-22-09_thumb.jpg");
// convert File to byte[]
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(tmpFile);
bos.close();
oos.close();
byte[] bytes = bos.toByteArray();
ByteArrayInputStream inputStream = new ByteArrayInputStream(bytes);
try {
Entry newEntry = mDBApi.putFile("/IMG_2012-03-12_10-22-09_thumb.jpg", inputStream, tmpFile.length(), null, null);
} catch (DropboxUnlinkedException e) {
Log.e("DbExampleLog", "User has unlinked.");
} catch (DropboxException e) {
Log.e("DbExampleLog", "Something went wrong while uploading.");
}
I have no success getting a DropboxException error. I think something where I try to convert the File object to the byte-stream must be wrong but this is just an assumption.
Other than the String example there is nothing else documented on the Dropbox page for Android.
Thanks for any help.

I found the solution - if anyone is interested here is the working code:
private DropboxAPI<AndroidAuthSession> mDBApi;//global variable
File tmpFile = new File(fullPath, "IMG_2012-03-12_10-22-09_thumb.jpg");
FileInputStream fis = new FileInputStream(tmpFile);
try {
DropboxAPI.Entry newEntry = mDBApi.putFileOverwrite("IMG_2012-03-12_10-22-09_thumb.jpg", fis, tmpFile.length(), null);
} catch (DropboxUnlinkedException e) {
Log.e("DbExampleLog", "User has unlinked.");
} catch (DropboxException e) {
Log.e("DbExampleLog", "Something went wrong while uploading.");
}

Here is another implementation of Dropbox API to upload and download a file.
This can be implemented for any type of file.
String file_name = "/my_file.txt";
String file_path = Environment.getExternalStorageDirectory()
.getAbsolutePath() + file_name;
AndroidAuthSession session;
public void initDropBox() {
AppKeyPair appKeys = new AppKeyPair(APP_KEY, APP_SECRET);
session = new AndroidAuthSession(appKeys);
mDBApi = new DropboxAPI<AndroidAuthSession>(session);
mDBApi.getSession().startOAuth2Authentication(MyActivity.this);
}
Entry response;
public void uploadFile() {
writeFileContent(file_path);
File file = new File(file_path);
FileInputStream inputStream = null;
try {
inputStream = new FileInputStream(file);
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
response = mDBApi.putFile("/my_file.txt", inputStream,
file.length(), null, null);
Log.i("DbExampleLog", "The uploaded file's rev is: " + response.rev);
} catch (DropboxException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void downloadFile() {
File file = new File(file_path);
FileOutputStream outputStream = null;
try {
outputStream = new FileOutputStream(file);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
DropboxFileInfo info = null;
try {
info = mDBApi.getFile("/my_file.txt", null, outputStream, null);
Log.i("DbExampleLog", "The file's rev is: "
+ info.getMetadata().rev);
} catch (DropboxException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
#Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
if (mDBApi.getSession().authenticationSuccessful()) {
try {
// Required to complete auth, sets the access token on the
// session
mDBApi.getSession().finishAuthentication();
String accessToken = mDBApi.getSession().getOAuth2AccessToken();
/**
* You'll need this token again after your app closes, so it's
* important to save it for future access (though it's not shown
* here). If you don't, the user will have to re-authenticate
* every time they use your app. A common way to implement
* storing keys is through Android's SharedPreferences API.
*/
} catch (IllegalStateException e) {
Log.i("DbAuthLog", "Error authenticating", e);
}
}
}
->Call uploadFile() and downLoadFile() method in child thread otherwise it will give you exception
->For that use AsyncTask and call these above method in doInBackground method.
Hope this will be helpful...Thanks

Here is another example which uses the Dropbox v2 API but a 3rd party SDK. It works exactly the same for Google Drive, OneDrive and Box.com by the way.
// CloudStorage cs = new Box(context, "[clientIdentifier]", "[clientSecret]");
// CloudStorage cs = new OneDrive(context, "[clientIdentifier]", "[clientSecret]");
// CloudStorage cs = new GoogleDrive(context, "[clientIdentifier]", "[clientSecret]");
CloudStorage cs = new Dropbox(context, "[clientIdentifier]", "[clientSecret]");
new Thread() {
#Override
public void run() {
cs.createFolder("/TestFolder"); // <---
InputStream stream = null;
try {
AssetManager assetManager = getAssets();
stream = assetManager.open("UserData.csv");
long size = assetManager.openFd("UserData.csv").getLength();
cs.upload("/TestFolder/Data.csv", stream, size, false); // <---
} catch (Exception e) {
// TODO: handle error
} finally {
// TODO: close stream
}
}
}.start();
It uses the CloudRail Android SDK

#e-nature's answer is more than correct...just thought I'd point everyone to Dropbox's official site that shows how to upload a file and much more.
Also, #e-nature's answer overwrites files with the same name, so if you don't want that behaviour simply use .putFile instead of .putFileOverwrite. .putFile has an extra argument, you can simply add null to to the end. More info.

According to the latest documentation of dropbox API V2:
// Create Dropbox client
val config = DbxRequestConfig.newBuilder("dropbox/java-tutorial").build()
client = DbxClientV2(config, getString(R.string.token))
// Uploading file
FileInputStream(file).use { item ->
val metadata = client.files().uploadBuilder("/${file.absolutePath.substringAfterLast("/")}")
.uploadAndFinish(item)
}
And if you want to overwrite file then add this to client:
.withMode(WriteMode.OVERWRITE)
.uploadAndFinish(item)

Write a List to internal storage onPause(), then read the List onResume()

I'm so confused. After reading this thread, I'm trying to write a List to internal storage onPause(), then read the List onResume(). Just for testing purposes, I'm trying to write a simple string as the example showed. I've got this to write with:
String FILENAME = "hello_file";
String string = "hello world!";
FileOutputStream fos = null;
try {
fos = openFileOutput(FILENAME, Context. MODE_WORLD_READABLE);
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
fos.write(string.getBytes());
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
fos.close();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
And I'm trying to read it in onResume() by calling:
try {
resultText01.setText(readFile("hello_file"));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
resultText01.setText("exception, what went wrong? why doesn't this text say hello world!?");
}
Which of course uses this:
private static String readFile(String path) throws IOException {
FileInputStream stream = new FileInputStream(new File(path));
try {
FileChannel fc = stream.getChannel();
MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
/* Instead of using default, pass in a decoder. */
return Charset.defaultCharset().decode(bb).toString();
}
finally {
stream.close();
}
}
For some reason, resultText01.setText(...) isn't being set to "hello world!", and is instead calling the catch exception. I'm sorry if my lingo isn't correct, I'm new to this. Thanks for any pointers.

Instead of the following in your readFile(...) method...
FileInputStream stream = new FileInputStream(new File(path));
Try...
FileInputStream stream = openFileInput(path);

Reading my Serialized Object from File in Android

This is my first attempt at serializing/deserializing objects on any platform and, to put it mildly, I'm confused.
After implementing Serializable to my game object I output it to a file thus:
public void saveGameState(){
ByteArrayOutputStream bos = new ByteArrayOutputStream();
try {
ObjectOutput out = new ObjectOutputStream(bos);
out.writeObject(theGame);//theGame is an instance of the custom class
//TGame which stores game info.
byte[] buf = bos.toByteArray();
FileOutputStream fos = this.openFileOutput(filename,
Context.MODE_PRIVATE);
fos.write(buf);
fos.close();
} catch(IOException ioe) {
Log.e("serializeObject", "error", ioe);
}
File f =this.getDir(filename, 0);
Log.v("FILE",f.getName());
}
This seems to work, in that I get no exceptions raised. I can only know for sure when I deserialize it. Which is where things go pear shaped.
public God loadSavedGame(){
TGame g=null;
InputStream instream = null;
try {
instream = openFileInput(filename);
} catch (FileNotFoundException e) {
e.printStackTrace();
return null;
}
try {
ObjectInputStream ois = new ObjectInputStream(instream);
try {
g= (TGame) ois.readObject();
return g;
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
} catch (StreamCorruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
I got the basis of this code from here Android Java -- Deserializing a file on the Android platform and tried to modify it for my app. When running I get
05-31 23:30:45.493: ERROR/copybit(1279): copyBits failed (Invalid argument)
When the output should be loaded and the saved game start up from when it was saved.
Any help would be appreciated.

The error you've shown is not at all related to serialization: its actually a video display error. I'd suggest looking at the object BEFORE you serialize to make sure its not null, and I'd also suggest serializing to a file on the SD card to make sure you actually had data output (so use new FileOutputStream("/mnt/sdcard/serializationtest") as the output stream and new FileInputStream("/mnt/sdcard/serializationtest") as the input stream) while you are debugging; you can switch back to the context methods after it works, but make sure your sdcard is plugged in while you are doing this.
Finally, modify your logging to look like this:
try {
ObjectInputStream ois = new ObjectInputStream(instream);
try {
g= (TGame) ois.readObject();
return g;
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
android.util.Log.e("DESERIALIZATION FAILED (CLASS NOT FOUND):"+e.getMessage(), e);
e.printStackTrace();
return null;
}
} catch (StreamCorruptedException e) {
android.util.Log.e("DESERIALIZATION FAILED (CORRUPT):"+e.getMessage(), e);
// TODO Auto-generated catch block
e.printStackTrace();
return null;
} catch (IOException e) {
android.util.Log.e("DESERIALIZATION FAILED (IO EXCEPTION):"+e.getMessage(), e);
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
and see what error gets returned. I expect the serialization is failing somehow.

To seralize or deserialize anything you can use SIMPLE api. It is very easy to use. Download the file and use it in your program
Have a look here
http://simple.sourceforge.net/download/stream/doc/tutorial/tutorial.php#deserialize
Thanks Deepak

I have created below class to do the save and retrieve object.
public class SerializeUtil {
public static <T extends Serializable> void saveObjectToFile(Context context, T object, String fileName){
try {
FileOutputStream fos = context.openFileOutput(fileName, Context.MODE_PRIVATE);
ObjectOutputStream os = new ObjectOutputStream(fos);
os.writeObject(object);
os.close();
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public static<T extends Serializable> T getObjectFromFile(Context context, String fileName){
T object = null;
try {
FileInputStream fis = context.openFileInput(fileName);
ObjectInputStream is = new ObjectInputStream(fis);
object = (T) is.readObject();
is.close();
fis.close();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return object;
}
public static void removeSerializable(Context context, String filename) {
context.deleteFile(filename);
}
}