Develop Reference

ArrayList size 0 after deserialisation Android Studio Java

Hello I tried to make an app for displaying quote in Android Studio.
But I got stuck when reading.
I created an "ArrayList" with my custom class Quotes.
I seems to work ok when writing the ArrayList to the file, but when reading from it the size of ArrayList is 0.
public class SaveQuote extends AppCompatActivity {
EditText editTextQuote;
EditText editTextAuthor;
Button btnSave;
ArrayList<Quote> arrQuo = new ArrayList<>();
public static ArrayList<Quote> arrayListQuotesSave;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_save_quote);
init();
btnSave.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String quote = editTextQuote.getText().toString();
String author =editTextAuthor.getText().toString();
addQuote(quote,author);
}
});
}
private void init(){
editTextQuote = findViewById(R.id.editTextQuote);
editTextAuthor = findViewById(R.id.editTextAuthor);
btnSave = findViewById(R.id.buttonSave);
arrayListQuotesSave = new ArrayList<>();
}
private void addQuote(String quote, String author){
Quote q = new Quote(quote, author);
arrQuo.add(q);
String path = this.getFilesDir().toString();
try {
FileOutputStream fos = openFileOutput("Quotes.txt",MODE_APPEND);
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(arrQuo);// when I write size = 1
oos.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
FileInputStream fis = openFileInput("Quotes.txt");
ObjectInputStream ois = new ObjectInputStream(fis);
arrQuo =(ArrayList<Quote>) ois.readObject();
ois.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}

I tried to passe a context and call the method openFileOutput on the context
so like this:
enter code here
FileOutputStream fs = context.openFileOutput("Quotes.txt", Context.MODE_PRIVATE);
enter code here
public class SaveQuote extends AppCompatActivity {
EditText editTextQuote;
EditText editTextAuthor;
Button btnSave;
ArrayList<Quote> arrQuo = new ArrayList<>();
public static ArrayList<Quote> arrayListQuotesSave;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_save_quote);
init();
btnSave.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String quote = editTextQuote.getText().toString();
String author =editTextAuthor.getText().toString();
if(quote.isEmpty() || author.isEmpty()){
Toast.makeText(SaveQuote.this,"Fill all fields",Toast.LENGTH_SHORT).show();
}else {
writeToFile(SaveQuote.this, quote, author);
Toast.makeText(SaveQuote.this,"The quote was saved",Toast.LENGTH_SHORT).show();
}
}
});
}
private void init(){
editTextQuote = findViewById(R.id.editTextQuote);
editTextAuthor = findViewById(R.id.editTextAuthor);
btnSave = findViewById(R.id.buttonSave);
arrayListQuotesSave = new ArrayList<>();
}
private void writeToFile(Context context,String quote,String author) {
Quote q = new Quote(quote,author);
MainActivity.arrayListQuotesMain.add(q);
Integer size = MainActivity.arrayListQuotesMain.size();
Log.v("Added","arrayListQuotesMain size is = "+size.toString());
try {
FileOutputStream fs = context.openFileOutput("Quotes.txt", Context.MODE_PRIVATE);
ObjectOutputStream oos = new ObjectOutputStream(fs);
oos.writeObject(MainActivity.arrayListQuotesMain);
oos.close();
}
catch (IOException e) {
Log.e("Exception", "File write failed: " + e.toString());
}
editTextQuote.setText("");
editTextAuthor.setText("");
}
}

How to read text file upon opening an app?

I am making an app where I have my school balance set and can press dedicated buttons to take away certain amounts depending on what I purchase. I am having trouble with the balance. I have a way of updating it to what I want, however after I terminate the application I want it to stay the same in a TextView. I so far was able to make it save it to a file, or at least I hope I was, with the help of a video.
How could I on opening the app read the text file and set the TextView equal to what is in the file?
submitBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String submitAmount = amountEnter.getText().toString();
balance.setText(submitAmount);
String myBalance = balance.getText().toString();
try {
FileOutputStream fou = openFileOutput("balance.txt",
MODE_WORLD_READABLE);
OutputStreamWriter osw = new OutputStreamWriter(fou);
try {
osw.write(myBalance);
osw.flush();
osw.close();
} catch (IOException e) {
e.printStackTrace();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
});

You can save it in SharedPrefs
change it to
submitBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String submitAmount = amountEnter.getText().toString();
balance.setText(submitAmount);
PreferenceManager.getDefaultSharedPreferences(getApplicationContext()).
edit().putString("balance", submitAmount).commit();
}
});
and you can get it by
String balance=PreferenceManager.getDefaultSharedPreferences(getApplicationContext())
.getString("balance","nothing_there");

Seeing your code, i assume that you know how to read/write a file in android. If not, then see it from here . https://stackoverflow.com/questions/12421814/how-can-i-read-a-text-file-in-android/ You can try the following code. THe readfile method is from the upper link. You just have to read the particular line/string from the file at onCreate method of the activity. Get the reference of your desired TextView and then set the text to TextView like below. I hope it helps you
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.your_layout);
String texts = readfile();
TextView textView = findViewById(R.id.text_view);
textView.setText(text);
}
private String readfile() {
File sdcard = Environment.getExternalStorageDirectory();
File file = new File(sdcard, "file.txt");
StringBuilder text = new StringBuilder();
try {
BufferedReader br = new BufferedReader(new FileReader(file));
String line;
while ((line = br.readLine()) != null) {
text.append(line);
text.append('\n');
}
br.close();
} catch (IOException e) {
//You'll need to add proper error handling here
}
return text.toString();
}

How to download a file after clicking a button (Android Studio)

I recently created an activity in my app. Now I wanted the user to download a .pdf file when he/she wants to view the guidelines. I wanted to implement this on a button. Any idea how to do this properly?
Heres my code below:
public class Exhibitor_Registration_Activity extends AppCompatActivity {
Button buttonDownload;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_exhibitor_registration_);
this.setTitle("Buyer Registration");
Toolbar myToolbar = (Toolbar) findViewById(R.id.my_toolbar);
setSupportActionBar(myToolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
myToolbar.setNavigationIcon(R.drawable.ic_arrow_back_white_24dp);
final Button buttonDownload = (Button) findViewById(R.id.buttonDownload);
buttonDownload.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View view) {
try {
//this is the file you want to download from the remote server
String path ="http://www.manilafame.com/website-assets/downloads/exhibitor-application-kit/local/201704/1-Summary-of-Participation-Details-April-2017_MN_002.pdfp";
//this is the name of the local file you will create
String targetFileName = null;
boolean eof = false;
URL u = new URL(path);
HttpURLConnection c = (HttpURLConnection) u.openConnection();
c.setRequestMethod("GET");
c.setDoOutput(true);
c.connect();
FileOutputStream f = new FileOutputStream(new File("c:\\junk\\"+targetFileName));
InputStream in = c.getInputStream();
byte[] buffer = new byte[1024];
int len1 = 0;
while ( (len1 = in.read(buffer)) > 0 ) {
f.write(buffer,0, len1);
}
f.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
}
I also got the source code from here and here.

if you want resumable, speed of download ...
follow this steps
create a class DownloadManager.java
public class DownloadManager extends AsyncTask<String,String,String>{
String downloadlink,fileDestination;
public static final int ON_INIT=100,ON_ERROR=102,ON_PROGRASS=103,ON_COMPLETED=104,STATUS_DOWNLOADED=1500,STATUS_NOT_YET=1501;
private onUpdateListener onUpdateListener;
private String downloadedPath="";
private long downloaded=0;
private File file;
private String returnData=null;
private File cacheDownloadFile;
public DownloadManager(String downloadlink,String fileDestinationPath){
this.downloadlink=downloadlink;
this.fileDestination=fileDestinationPath;
file=new File(fileDestination, Tools.getFileName(downloadlink));
cacheDownloadFile=new File(AppCostants.CHACHE_PATH+Tools.getFileName(downloadlink));
try {
if(cacheDownloadFile.isFile())
downloaded=Tools.getFileSize(cacheDownloadFile);
else
downloaded=0;
Log.d("FILE_DOWNLOAD_TAG_p",downloaded+" <- "+cacheDownloadFile.getAbsolutePath());
} catch (IOException e) {
e.printStackTrace();
}
fireOnUpdate(ON_INIT,"init ...");
}
#Override
protected String doInBackground(String... params) {
try {
File dir=new File(fileDestination);
File chacheDir=new File(AppCostants.CHACHE_PATH);
if(!chacheDir.isDirectory())
chacheDir.mkdirs();
if(!dir.isDirectory()){
dir.mkdirs();
}
if(file.exists()) {
Log.d("FILE_DOWNLOAD_TAG","File exist return complete");
return "COMPLETED";//file exist
}
if(!cacheDownloadFile.exists()){
cacheDownloadFile.createNewFile();
}
Log.d("FILE_DOWNLOAD_TAG","LINK "+downloadlink);
URL url=new URL(downloadlink);
HttpURLConnection urlConnection= (HttpURLConnection) url.openConnection();
if(downloaded>0)
urlConnection.setRequestProperty("Range","byte="+downloaded);
urlConnection.connect();
int status = urlConnection.getResponseCode();
InputStream inputStream=urlConnection.getInputStream();
int totalSize=urlConnection.getContentLength();
if(totalSize<=downloaded){
returnData= "COMPLETED";
publishProgress("File checked "+Tools.getFileName(file.getAbsolutePath()));
return returnData;
}
this.downloadedPath=cacheDownloadFile.getAbsolutePath();
byte[] buffer=new byte[1024];
int bufferLength=0;
FileOutputStream fileOutput=new FileOutputStream(cacheDownloadFile);
long d=0;
long starttime=System.currentTimeMillis();
while ((bufferLength=inputStream.read(buffer))>0){
fileOutput.write(buffer,0,bufferLength);
downloaded+=bufferLength;
d+=bufferLength;
//String l=" "+Tools.getFileName(file.getAbsolutePath())+" ( "+Tools.convertMemory(downloaded)+" / "+Tools.convertMemory(totalSize)+" )";
String l=" "+Tools.convertMemory(downloaded)+" / "+Tools.convertMemory(totalSize)+" ( "+getDownloadSpeed(starttime,d)+" )";
publishProgress(l);
if(downloaded>=totalSize){
break;
}
}
Log.d("FILE_DOWNLOAD_TAG","DWONLOADED TO "+downloadedPath+" ("+cacheDownloadFile.length()+")");
fileOutput.close();
if(Tools.fileCopy(file,cacheDownloadFile)){
Log.d("FILE_DOWNLOAD_TAG","file Copied, delete cache");
cacheDownloadFile.delete();
}
returnData="COMPLETED";
} catch (MalformedURLException e) {
returnData=null;
e.printStackTrace();
publishProgress(e.toString());
Log.d("###################",e+"");
} catch (IOException e) {
returnData=null;
e.printStackTrace();
publishProgress(e.toString());
}
return returnData;
}
#Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
fireOnUpdate(ON_PROGRASS,values[0]);
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
if(s!=null){
fireOnUpdate(ON_COMPLETED,downloadedPath);
}else{
fireOnUpdate(ON_ERROR,"Download failed");
}
}
public interface onUpdateListener{
void onUpdate(int code,String message);
}
public void setOnUpdateListener(onUpdateListener onUpdateListener){
this.onUpdateListener=onUpdateListener;
}
private void fireOnUpdate(int code,String message){
if(onUpdateListener!=null)
onUpdateListener.onUpdate(code,message);
}
private String getDownloadSpeed(long starttime,float totalDownloaded) {
long elapsedTime = System.currentTimeMillis() - starttime;
//byte :
float speed=1000f * totalDownloaded / elapsedTime;
return convert(speed);
}
private String convert(float value){
long kb=1024
,mb=kb*1024
,gb=mb*1024;
if(value<kb){
String speed=(value+"");
speed=speed.substring(0,speed.indexOf('.')+2);
return speed+" B/s";
}else if(value<mb){
value=value/kb;
String speed=(value+"");
speed=speed.substring(0,speed.indexOf('.'));
return (speed)+" KB/s";
}else if(value<gb){
value=(value/mb);
String speed=(value+"");
speed=speed.substring(0,speed.indexOf('.'));
return speed+" MB/s";
}
return "";
}
}
use this code in onClick()
DownloadManager downloadManager = new DownloadManager(url,filepath);
set event
downloadManager.setOnUpdateListener(new DownloadManager.onUpdateListener() {
#Override
public void onUpdate(int code, String message) {
if (code == DownloadManager.ON_COMPLETED) {
}
if(DownloadManager.ON_PROGRASS==code){}
}
});
start download by
downloadManager.execute();
lib setup
compile "commons-io:commons-io:+"
Tools.java
public static long getFileSize(File file) throws IOException {
FileOutputStream fileOutputStream=new FileOutputStream(file);
fileOutputStream.close();
return file.length();
}
public static boolean fileCopy(File dest,File source){
try {
FileUtils.copyFile(source,dest);
return true;
} catch (IOException e) {
e.printStackTrace();
return false;
}
}

It is really bad idea to download file in main thread.
Use separate Thread for this
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
//your downloading here
}
});
thread.start();
it`s better, but still not so good. There are some problems with it:
1) User know nothing about downloading
So better to show additional layout which overlays screen with progress bar, probably indeterminate if you want to write less code. Then after downloading is finished you just hide your layout.
You can use runOnUiThread inside run method in thread for it.
runOnUiThread(new Runnable() {
#Override
public void run() {
//just hide some popup
//or do what you want after downloading is finished
popupLayout.serVisibility(View.GONE);
}
});
2) If user will do action which re-creates activity/fragment (like changing screen orientaion) with running thread you will get memory leak and probably activity will not know about end of download.
There are few ways to solve this problem:
You can block screen orientation at this screen, at least while downloading. Probably easiest way in your case.
You can use downloading in foreground service. Its really good
practice, but you will have to learn about services.
You can try to interrupt downloading by calling thread.interrupt()
method in onDestroy of your Activity/Fragment
You can use something like rxJava/rxAndroid (so you don not use threads at all, but you need some time for learn rxJava)
UPD
About threads
Not so bad tutorial about threads in android
You can use AsyncTask instead of Thread, but I highly recommend to use threads especially for long operations.

Android File IO: Not saving/not loading the data

Background:
I am using three fragments and one activity in my application. Two fragments use recyclerViews and the other uses an expandableListView.
Problem:
I am trying to properly program the onPause(), onResume(), onStop(), and onRestart() methods to save the state of my application when the home, back, or switch views buttons are pressed.
To save the state of the program and load it when it comes back I have created the save() and load() methods in my one and only activity.
//from the end of onCreate
load();
}
#Override
protected void onStart() {
super.onStart();
mRef = new Firebase("https://sure-7856d.firebaseio.com/");
}
#Override
protected void onStop(){
super.onStop();
save();
}
#Override
protected void onPause(){
super.onPause();
save();
}
#Override
protected void onResume(){
super.onResume();
load();
}
#Override
protected void onRestart(){
super.onRestart();
load();
}
In the save method I get the adapters from my 2 recyclerViews and my expandableListView`s ArrayList that keeps track of which checkboxes are checked.
After that I put them each into a temporary Arraylist then I add each of those ArrayLists to a single arraylist that will be saved to the file.
private void save(){
//saved_data = new File("saved_data");
/*try {
if(saved_data.exists()==false){
//saved_data.createNewFile();
saved_data.setWritable(true);
}
} catch (IOException e) {
e.printStackTrace();
}*/
File myFile;
try{
myFile = new File(getFilesDir().getAbsolutePath(), "dir/save_data.bin");
myFile.mkdirs();
myFile.createNewFile();
FILENAME = myFile.getName();
}catch (IOException e){
e.printStackTrace();
}
OneFragment f20 = (OneFragment) frags.get(0);
TwoFragment f21 = (TwoFragment) frags.get(1);
ThreeFragment f22 = (ThreeFragment) frags.get(2);
ArrayList saveTasks = f20.adapter.getList();
ArrayList saveReqs = f21.adapter.getList();
ArrayList saveMap = new ArrayList<String>();
if(f22.listAdapter!=null) {
if (f22.listAdapter.getExport() != null) {
saveMap = f22.listAdapter.getExport();
}
}
ArrayList results = new ArrayList();
results.add(saveTasks);
results.add(saveReqs);
results.add(saveMap);
ObjectOutputStream oos1 = null;
FileOutputStream fos1 = null;
try {
fos1 = openFileOutput(FILENAME, Context.MODE_PRIVATE);
oos1 = new ObjectOutputStream(fos1);
oos1.writeObject(results);
oos1.close();
fos1.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
if(oos1 != null){
try {
oos1.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
In the load code I get the object from the file and update the adapters to their previous state.
private void load(){
//saved_data = new File("saved_data");
ArrayList results = new ArrayList();
FileInputStream fis = null;
ObjectInputStream ois = null;
if(FILENAME==null){
return;
}
try {
fis = new FileInputStream(FILENAME);
ois = new ObjectInputStream(fis);
}catch (FileNotFoundException e) {
e.printStackTrace();
return;
}catch (IOException e) {
e.printStackTrace();
}
try {
while (true) {
results = (ArrayList)(ois.readObject());
}
} catch (OptionalDataException e) {
if (!e.eof) try {
throw e;
} catch (OptionalDataException e1) {
e1.printStackTrace();
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
ois.close();
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
for(int i = 0; i < results.size();i++){
if(i == 0){
frags.set(0,results.get(i));
}
else if(i == 1){
frags.set(1,results.get(i));
}
else if(i == 2){
frags.set(2,results.get(i));
}
else{
}
}
}
When I press the square button at the bottom of the emulator and go back to it one of a few things happen
It crashes saying the file could not be found
W/System.err: Caused by: android.system.ErrnoException: open failed: ENOENT (No such file or directory)
And this error points to the load method as the point of failure specifically
FileInputStream fis = null;
When I hit the triangle button nothing happens in logcat, everything is gone upon returning, and the app loses its functions of adding strings to lists on both recyclerViews and displaying both lists in the expandableListView.
Hitting the center circle button and going back to the app is fine nothing breaks.
Since Im getting a file not found error I think that the file isnt getting written
I have searched Stack for a solution and I am new to File IO and fragments, so I have no idea where to go from here.

Playing music from Parse.com android

so I'm implementing like music playlist app, my audios are uploaded to Parse.com as mp3 , I want to retrieve those audios ..
final Button btn = (Button) v.findViewById(R.id.button);
final ParseFile fileObject = object.getParseFile("music");
if (fileObject != null) {
fileObject.getDataInBackground(new GetDataCallback() {
#Override
public void done(byte[] bytes, com.parse.ParseException e) {
final String audioFileURL = fileObject.getUrl();
mediaPlayer = new MediaPlayer();
mediaPlayer.reset();
mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
btn.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
try {
mediaPlayer.setDataSource(audioFileURL);
mediaPlayer.prepare();
mediaPlayer.start();
} catch (IllegalArgumentException e1) {
e1.printStackTrace();
}//end catch
catch (IOException e1) {
e1.printStackTrace();
}
}//end on click
}//end listener
);
}//end done
});//end get data
}//end if
this is how I retrieve music from Parse.com but this is taking so much time specially that I have a list of audios .. I want a way to download group of the audios in the background .. so when I click the button, the music play so fast .. any help would be greatly appreciated.

I have no time right now to understand why your code doesn't work, but you can take my sample app on github (committed just now), you should solve your problem...if not, let me know. Please, take note of the README.md
https://github.com/fullwipe/ParseAudioFileExample
Hope it helps...
Edit This is the essential part of my repository. Record and save:
String outputFile = Environment.getExternalStorageDirectory().
getAbsolutePath() + "/rumor.mp3";
myRecorder = new MediaRecorder();
myRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
myRecorder.setOutputFormat(MediaRecorder.OutputFormat.DEFAULT);
myRecorder.setAudioEncoder(MediaRecorder.OutputFormat.AMR_NB);
myRecorder.setOutputFile(outputFile);
Then, start recording...
try {
myRecorder.prepare();
myRecorder.start();
} catch (IllegalStateException e) {
// start:it is called before prepare()
// prepare: it is called after start() or before setOutputFormat()
e.printStackTrace();
} catch (IOException e) {
// prepare() fails
e.printStackTrace();
}
When you stop recording, save it on Parse.com in this way:
FileInputStream fileInputStream = null;
File fileObj = new File(outputFile);
byte[] data = new byte[(int) fileObj.length()];
try {
//convert file into array of bytes
fileInputStream = new FileInputStream(fileObj);
fileInputStream.read(data);
fileInputStream.close();
} catch (Exception e) {
e.printStackTrace();
}
ParseFile parseAudioFile = new ParseFile("audiofile.mp3", data);
parseAudioFile.saveInBackground();
ParseObject parseObject = new ParseObject("AudioFileClass");
parseObject.put("audiofile", parseAudioFile);
parseObject.saveInBackground(new SaveCallback() {
public void done(ParseException e) {
if (e == null) {
Toast.makeText(getApplicationContext(),"Audio file saved successfully", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(getApplicationContext(),"Error: audio file not saved", Toast.LENGTH_SHORT).show();
}
}
});
Retrieve and play from Parse.com is very simple, I have used a ParseQueryAdapter. This is the part where you get the mp3 file and play it:
ParseFile descr = object.getParseFile("audiofile");
if (descr != null) {
String audioFileURL = descr.getUrl();
MediaPlayer mediaPlayer = new MediaPlayer();
mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
try {
mediaPlayer.setDataSource(audioFileURL);
mediaPlayer.prepare();
mediaPlayer.start();
}
...
...