Develop Reference

Constantly retrieve data from database in a infinite loop

I created a database with a table named flagTable, this table only has two fields, which are id(auto increment) and an integer field. Next, in my program, I have a button that will trigger a thread to start. When the thread is starting, it constantly retrieve data from database, and check for the for the value, if the value is equal to one then it will trigger another new Thread, something like this:
private class statusOfStrummingInAnotherDevice extends Thread {
int value;
public void run() {
try{
while(true){
try{
if(flagCursor == null){
flagCursor = cdb1.getFlagAll();
}
}catch(Exception e){break;}
try{
Log.i("MAIN3ACTIVITY","getting status");
int size = cdb1.getSize(flagCursor);
Log.i("MAIN3ACTIVITY","SIZE is" + String.valueOf(xyz));
for(int i = 0 ; i < size ; i++){
flagCursor.moveToPosition(i);
Log.i("MAIN3ACTIVITY","getting status jkasdfasdf");
value = cdb1.getFlag();
if(value == 1){
Log.i("FLAGCURSOR=====>>>>","Succesful");
releasingNotes = new ReleasingNotes(IntendedChord);
releasingNotes.start();
//break;
}
cdb1.updateFlag(0);
Log.i("FLAGCURSOR=====>>>>",String.valueOf(value));
}
flagCursor = null;
}catch(Exception e){break;}
Log.i("MAIN3ACTIVITY","thread is sleeping");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
break;
}
}
}catch(Exception e){
}
}
}
In the meantime, the data that were retrieved from the database is using this function:
public Cursor getFlagAll(){
return getReadableDatabase().rawQuery(
"SELECT _ID, flag from flagTable", null);
}
And, the data that were updated to the database through this method:
public int updateFlag(int i) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("flag",i);
return db.update("flagTable" , contentValues , "_ID" + "= ?",new String[]{String.valueOf(1)});
}
Now, above codes will give no error, however, the data that were retrieved from the database is always 1, it keeps trigger a new function. In my above codes, I stated if the value is equal to 1, then the current thread will trigger a new thread to start, When its finished, the program will update the current data to 0. So that, the next round of the infinite loop can stop triggering new thread until a the conditon is met. What is problem overhere? did my codes really updated the new value? or I need to referesh the database every time I updated a new value.

Use Listeners to your database.
use SQLiteTransactionListener and do your things in onCommit()
Some guide in details here :
https://developer.android.com/reference/android/database/sqlite/SQLiteTransactionListener.html and
http://www.programcreek.com/java-api-examples/index.php?api=android.database.sqlite.SQLiteTransactionListener

How to know when SQLite query is finished

Ok, I've got this Retrofit Call that receives a list of objects and insert the into a local SQLite database. I want to display a message saying that the operation was successful with a Ok button that when pressed opens a new activity.
How do I check if my Query has finished so I can show the message?
final ContactApi contactApi = retrofit.create(ContactApi.class);
Call<List<Contact>> callContact = contactApi.getContact(token);
callContact.enqueue(new Callback<List<Contact>>() {
#Override
public void onResponse(Response<List<Contact>> response, Retrofit retrofit) {
List<Contact> contactList = response.body();
if (contactList != null) {
try {
DBHelper dbHelper = new DBHelper(TokenActivity.this, token);
SQLiteDatabase conn = dbHelper.getWritableDatabase();
RepoContact repocontact = new RepoContact(conn);
// Inserts each contact into the database
for (Contatc c : contactList) {
repositorioCadastro.inserirCadastro(c);
Log.i("ACTTOKEN", "Contact insert ID: " + c.getId());
}
} catch (SQLiteException e) {
Log.i("ACTTOKEN", "Faillure on insert: " + e.getMessage());
}
}

wrap your code in try{...}finally{...} blocks with a listener ( beginTransactionWithListener(SQLiteTransactionListener transactionListener)), and use the transactionListner to check whether everything went well within the transaction, in addition to everything within the try/finally.
what you have is good, just try adding finally block..
something like this..
db.beginTransaction();
try {
...
db.setTransactionSuccessful();
} finally {
db.endTransaction();
}

You can try a different loop, something like this:
for(int i = 0; i < contactList.size(); i++) {
Contact c = contactList.get(i);
repositorioCadastro.inserirCadastro(c);
Log.i("ACTTOKEN", "Contact insert ID: " + c.getId());
if(i == (contactList.size() - 1)) {
// DO SOMETHING HERE
}
}

You may check insert statement return a long when query successfully executed then long value.
db.insert()
returns the row ID of the newly inserted row, or -1 if an error occurred

displaying toast in conditional statements in android

i have created an app which insert data to sql server. i made column NAME as unique key.
i want that if i enter same name by edittext to insert...it should give a toast message.
but it's not happening. i cann't understand where i have made error.
in connection to server there is no problem. the only thing is i have to display Toast msg if i entered same name again.
my code is.......
public void onClick(View v) {
// TODO Auto-generated method stub
String myloc=loc.getText().toString();
String myname=name.getText().toString();
String myphone=phone.getText().toString();
initilize();
ResultSet rs;
try{
Statement statement=connect.createStatement();
rs=statement.executeQuery("SELECT * FROM FORM1");
List<Map<String,String>>data=null;
data=new ArrayList<Map<String,String>>();
while(rs.next()){
Map<String,String>datanum=new HashMap<String,String>();
datanum.put("a", rs.getString("NAME"));
data.add(datanum);
}
if(data.contains(myname)){
Toast.makeText(c, myname+" Already stored: please choose different one", Toast.LENGTH_LONG).show();
}
else{
insert(myname,myphone,myloc);
}
}catch(Exception e){
Log.e("ERROR", e.getMessage());
}
}
plzz guys...help me someone...

With data.contains(myname) you are trying to check if there is myname of type String in your data varible, but, in fact, your data have type List<Map<String,String>>, so when you are invoking contains(Object object) method passing a String, you are performing equals operation between Map<String,String> and String, which clearly would always result false. So I would suggest you either write something like this
List<String> data = new ArrayList<String>();
while(rs.next()) {
data.add(rs.getString("NAME"));
}
if(data.contains(myname)){
Toast.makeText(c, myname+" Already stored: please choose different one", Toast.LENGTH_LONG).show();
}
or there is a better way, just change your query to SELECT * FROM FORM1 WHERE NAME = myname and check if your result set is empty.

app not showing data when opend it for the second time

i am looking to make game of questions and answers.i had taken a textview and 4 radio group buttons.and i am fetching data from the external data file from the assets folder.when i installs the app into the emulater it works fine.when i reopens the app in the emulater it is just showing question not showing any text in the radio buttons.here is my code in the data base file
public String makeatext(String My_database_table,int i) {
SQLiteDatabase myDB = getDatabase();
String results = new String();
try {
String firstColumn = "questions";
// final String KEY_ROWID = "id";
// Cursor c = myDB.rawQuery("SELECT questions FROM " +
// My_database_table+ ";",null);
Cursor c = myDB.query(true, My_database_table,
new String[] { firstColumn },null, null, null, null, null,
null);
int iquestion = c.getColumnIndex(firstColumn);
if(c.moveToPosition(i)){
results = c.getString(iquestion)+"\n";
}
//while (c.moveToPosition(1)) {
//String firstName = c.getString(iquestion);
//results =(" "+ firstName + " ");
//}
return results;
} catch (Exception e) {
Log.e("ERROR","ERROR in Make test file :"+e.toString());
e.printStackTrace();
// TODO: handle exception
}
return results;
}
and in the Activity file i am just calling it as
String shoow = myDb.makeatext("question", Qno);
showQuestion.setText(shoow);
and on the top of the oncreate methode i initilized the data base asprivate final DataBaseHelper myDb = new DataBaseHelper(this);
can any one say me why this is happenig.do i need to write the for loop in the activity file also or shall i take a cursor in the activity class .
plz help me out
thanks in advance
for radio buttons the code in the database file is as follows as i have 4 buttons the code for 4 buttons will be as same as this
public String makeExtra1(String My_database_table ,int positions) {
String results = new String();
try {
String secondColumn = "Extra1";
Cursor c = myDataBase.query(true, My_database_table,
new String[] { secondColumn }, null, null, null, null, null,
null);
int iExtra1 = c.getColumnIndex(secondColumn);
if(c.moveToPosition(positions)){
results = results+c.getString(iExtra1)+"\n";
}
return results;
} catch (Exception e) {
Log.e("ERROR","ERROR in Make test file :"+e.toString());
e.printStackTrace();
// TODO: handle exception
}
return results;}
and in the Activity file
String showextra1 = myDb.makeExtra1("question", Qno);
r0.setText(showextra1);
i repeted this thing for 4 times as changing the makeExtra2,3,4 and in the assinged to r1,r2,r3 as above.

You should call Cursor.close() after reading data from it. Better to do it finally{} block.
If you want to raise only one answer per query - fill where param of myDataBase.query().

The unreachable code error is because you are writing finally{} block after return results;
Move this line after the finally{} block, eclipse will not give you any error.
Also do use myDB.close(); in this finally block.

Database values are some times updated but sometimes not?

I have written a simple code for Database updatation, but it is sometime updating and sometimes not... i have written LOG for conformation but the log is giving correct output. Here is what i am trying :=
public void updateDownloadedAssetNumberOfStartingBytesEncrypted(int id, int startingBytesEncrypted)
{
SQLiteDatabase database = null;
int numOfRowsUpdated = 0;
try
{
database = getWritableDatabase();
ContentValues values = new ContentValues();
values.put("StartingBytesEncrypted", startingBytesEncrypted);
if(database.isOpen())
{
Log.v("updating in db","doc id - "+id + " encrypted bytes - "+startingBytesEncrypted);
numOfRowsUpdated = database.update("_assets", values, "Id = "+id, null);
}
else
{
Log.v("Database","the database is not open thus starting encrypted bytes were not updated");
}
Log.v("muber of rows updated - ",""+numOfRowsUpdated);
}
catch(Exception ex)
{
}
finally
{
if(database != null)
{
database.close();
}
}
}
What is the problem?? Any help would be Appreciable.

Ya i got ur code...
Finally i resolved the issue.... actually it is beacuse of threading....
the thread creating the row was executed later and that updating the row was executed first
i have resolved it.Have fun :)

This happened due to connection of database is not open. Pls keep ex.printstacktrace(); in catch statement.