Develop Reference

How to get a single SQLite row data with its id?

I have successfully retrieved SQLite data to ListView. Now I am trying to implement OnItemClickListener to show the data in Dialog but I am getting this error
2019-04-08 18:42:53.020 20591-20591/com.app E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.app, PID: 20591
java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.File android.content.Context.getDatabasePath(java.lang.String)' on a null object reference
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:292)
at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:262)
at com.app.SQLiteAdaptor.GetUserByUserId(SQLiteAdaptor.java:99)
at com.app.OrderHistory$1.onItemClick(OrderHistory.java:64)
at android.widget.AdapterView.performItemClick(AdapterView.java:318)
at android.widget.AbsListView.performItemClick(AbsListView.java:1181)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3165)
at android.widget.AbsListView$3.run(AbsListView.java:4147)
at android.os.Handler.handleCallback(Handler.java:794)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:173)
at android.app.ActivityThread.main(ActivityThread.java:6634)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:822)
This is where I need to retrieve row
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
final Dialog fullscreenDialog = new Dialog(getApplicationContext(), R.style.Dialog);
fullscreenDialog.setContentView(R.layout.dialog_oh);
SQLiteAdaptor db = new SQLiteAdaptor(c);
ArrayList<HashMap<String, String>> userList = db.GetUserByUserId(i); //Line 64
HashMap<String, String> hashDetails = userList.get(0);
//Use this index accordingly
tvit.setText(hashDetails.get("item"));
tvpr.setText(hashDetails.get("price"));
tvqu.setText(hashDetails.get("quantity"));
tvad.setText(hashDetails.get("address"));
tvna.setText(hashDetails.get("name"));
tvem.setText(hashDetails.get("email"));
tvtim.setText(hashDetails.get("time"));
fullscreenDialog.show();
}
});
Here is the SQLiteAdaptor get row data by id method snippet
public ArrayList<HashMap<String, String>> GetUserByUserId(int userid ){
SQLiteDatabase db = this.getReadableDatabase(); \\Line 99
ArrayList<HashMap<String, String>> userList = new ArrayList<>();
String query = "SELECT item, price, quantity, name, address, email, orderid FROM "+ Table_Name;
Cursor cursor = db.query(Table_Name, new String[]{COL_2, COL_3, COL_4, COL_5, COL_6, COL_7, COL_8, COL_9}, COL_1+ "=?",new String[]{String.valueOf(userid)},null, null, null, null);
if (cursor.moveToNext()){
HashMap<String,String> user = new HashMap<>();
user.put("item",cursor.getString(cursor.getColumnIndex(COL_2)));
user.put("price",cursor.getString(cursor.getColumnIndex(COL_3)));
user.put("quantity",cursor.getString(cursor.getColumnIndex(COL_4)));
user.put("name",cursor.getString(cursor.getColumnIndex(COL_5)));
user.put("address",cursor.getString(cursor.getColumnIndex(COL_6)));
user.put("email",cursor.getString(cursor.getColumnIndex(COL_7)));
user.put("orderid",cursor.getString(cursor.getColumnIndex(COL_8)));
user.put("time",cursor.getString(cursor.getColumnIndex(COL_9)));
userList.add(user);
}
return userList;
}
And it is not null pointer exception because I am nit getting any error while retrieving data in Listview
Or any other way to how to retrieve row with its id
Any help and solutions are appreciated
Thanks in advance

Try this
SQLiteAdaptor db = new SQLiteAdaptor(view.getContext());

Getting data from sqlite to recycler view

I have used this code with json object. Now I'm with sqlite, and it has NPE error.
Cursor newRes = myDb.getAllData();
while (newRes.moveToNext()) {
Product product = new Product(Integer.parseInt(newRes.getString(0).toString()), Integer.parseInt(newRes.getString(1).toString()), newRes.getString(2).toString(),
newRes.getString(3).toString(), newRes.getString(4).toString(), newRes.getString(5).toString(), Double.parseDouble(newRes.getString(6).toString()), newRes.getString(7).toString());
productTransList.add(product);
}
adapter = new ProductAdapter(mCtx, productTransList);
transRecyclerView.setAdapter(adapter);
EDIT
07-13 09:05:29.763 13314-13351/com.example.arlene.capsmobile E/libdataflow_monitor: open error=Operation not permitted
07-13 09:05:31.542 13314-13314/com.example.arlene.capsmobile E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.arlene.capsmobile, PID: 13314
java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference
at com.example.arlene.capsmobile.translistTab.loadTransList(translistTab.java:135)
at com.example.arlene.capsmobile.translistTab.onCreate(translistTab.java:72)
Error at the line of productTransList.add(product);

Initialize the productTransList first and then add objects to the list.
productTransList = new ArrayList<>();
This will fix the issue.

In your SQLiteHelper Class you need to initialize the List:
public List<Product> getAllProducts() {
try {
List<Product > listProducts = new ArrayList<>();
String selectQuery = "SELECT * FROM " + dbSchema.table_name;
SQLiteDatabase mDb = this.getWritableDatabase();
Cursor cursor = mDb.rawQuery(selectQuery, null);
if (cursor.moveToFirst()) {
do {
Product product = new
Product(Integer.parseInt(cursor.getString(0).toString()),
Integer.parseInt(cursor.getString(1).toString()),
cursor.getString(2).toString(),
cursor.getString(3).toString(),
cursor.getString(4).toString(),
cursor.getString(5).toString(),
Double.parseDouble(cursor.getString(6).toString()),
cursor.getString(7).toString());
listProducts.add(mRecord);
} while (cursor.moveToNext());
}
return listProducts;
} catch (Exception ex) {
return null;
}
}
Here is a reference for SQLite:
SQLite Demo
From your activity, use the helper method getAllProducts asynchronously and pass an empty list to it as an input param.

First Initialize a ArrayList
productTransList = new ArrayList<>();
Cursor newRes = myDb.getAllData();
while (newRes.moveToNext()) {
Product product = new Product(Integer.parseInt(newRes.getString(0).toString()), Integer.parseInt(newRes.getString(1).toString()), newRes.getString(2).toString(),
newRes.getString(3).toString(), newRes.getString(4).toString(), newRes.getString(5).toString(), Double.parseDouble(newRes.getString(6).toString()), newRes.getString(7).toString());
productTransList.add(product);
}
adapter = new ProductAdapter(mCtx, productTransList);
transRecyclerView.setAdapter(adapter);
Hope this may help you

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

Returns zero for all values retrieved from the parse database

I'm using parse backend to store and retrieve the datas for my android app, the storing gets done properly but i have problem in retrieving it. I just went through the parse documentation to retrieve the result but what i get is just 0 for all the retrieved values..im suret that the class exists in the parse cloud with valid values but still i get 0 for all the queries.. this is my code to save:
Toast.makeText(getApplicationContext(),"writing to parse",Toast.LENGTH_SHORT).show();
ParseObject dataObject = new ParseObject("Score");
dataObject.put("correct",correctAnswers);
dataObject.put("wrong",wrongAnswers);
dataObject.put("percent", percentage);
dataObject.saveInBackground();
this is how i get back the saved data
ParseQuery<Score> query = ParseQuery.getQuery("Score");
try {
List<Score> scoreList = query.find();
} catch (ParseException e) {
e.printStackTrace();
}
query = ParseQuery.getQuery("Score");
final Activity ctx = this;
query.findInBackground( new FindCallback<Score>() {
#Override public void done(List<Score> scoreList, ParseException e) {
if ( e == null ) {
ParseObject dataObject = ParseObject.create("Score");
int p = dataObject.getInt("correct");
int q = dataObject.getInt("wrong");
int r = dataObject.getInt("percent");
Toast.makeText(ExamRecordActivity.this,String.valueOf(p),Toast.LENGTH_SHORT).show();
Toast.makeText(ExamRecordActivity.this,String.valueOf(q),Toast.LENGTH_SHORT).show();
Toast.makeText(ExamRecordActivity.this,String.valueOf(r),Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(ctx,
"Error updating questions - please make sure you have internet connection",
Toast.LENGTH_LONG).show();
}
}
});

Inside the done method you are creating a new by calling ParseObject dataObject = ParseObject.create("Score"); and then trying to read values from it without putting any in.
I don't know what the structure of your class is but you need to be iterating through List<Score> scoreList in order to get the queried data.

Saving ArrayLists in SQLite databases

So I want to save an ordered set of double values, and I want to be able to insert, retrieve or delete any value from this easily. As of such, I'm using a an ArrayList, where I define a class called Doubles to store the double values.
How do I store this arraylist in a record in an SQLite database? I mean...what should the columns type be? Can it be done?

You cannot insert ArrayList directly into Sqlite. Instead, you could use JSONObject (org.json.JSONObject) to insert the ArrayList. Please check below snippet, you can try something like below....
To insert,
JSONObject json = new JSONObject();
json.put("uniqueArrays", new JSONArray(items));
String arrayList = json.toString();
Insert the string into db.
To Read,
Read the string from db as String,
JSONObject json = new JSONObject(stringreadfromsqlite);
ArrayList items = json.optJSONArray("uniqueArrays");

To Insert :
ArrayList<String> inputArray=new ArrayList<String>();
Add Values to inputArray
Gson gson = new Gson();
String inputString= gson.toJson(inputArray);
System.out.println("inputString= " + inputString);
Use "inputString" to save the value of ArrayList<String> in SQLite Database
To retreive:
Get the String from the SQLiteDatabse what you saved and changed into ArrayList type like below:
outputarray is a String which is get from SQLiteDatabase for this example.
Type type = new TypeToken<ArrayList<String>>() {}.getType();
ArrayList<String> finalOutputString = gson.fromJson(outputarray, type);

In my case it was ArrayList of POJO classes Note
private String mNoteTitle;
private int mFingerIndex;
private Point mNoteCoordinates;
public Note(String noteTitle, int fingerIndex, Point noteCoordinates) {
this.mNoteTitle = noteTitle;
this.mFingerIndex = fingerIndex;
this.mNoteCoordinates = noteCoordinates;
}
As manual says JSONObject supports only following types: Object: a JSONObject, JSONArray, String, Boolean, Integer, Long, Double, NULL, or null. May not be NaNs or infinities. So, I should break my Note class into supported objects.
JSONObject json = new JSONObject();
JSONArray jsonArray = new JSONArray();
for(Note note: chordShape.getNotes()){
JSONObject singleNoteJsonObject = new JSONObject();
try {
singleNoteJsonObject.put(SHAPE_NOTE_TITLE, note.getNoteTitle());
singleNoteJsonObject.put(SHAPE_NOTE_FINGER_INDEX, note.getFingerIndex());
singleNoteJsonObject.put(SHAPE_NOTE_X, note.getNoteCoordinates().x);
singleNoteJsonObject.put(SHAPE_NOTE_Y, note.getNoteCoordinates().y);
} catch (JSONException e){
e.printStackTrace();
}
jsonArray.put(singleNoteJsonObject);
}
Pack created array into JSONObject.
try {
json.put(SHAPE_NOTES, jsonArray);
Log.i(TAG, json.toString());
} catch (JSONException e){
e.printStackTrace();
}
Create String.
String notesList = json.toString();
Put created String in ContentValues, cause in my case it's Android app
if(notesList.length() > 0){
contentValues.put(DatabaseHelper.SHAPE_NOTES_LIST, notesList);
}
And when i should read values from SQLite database.
ArrayList<Note> notes = new ArrayList<>();
while(cursor.moveToNext()){
JSONObject jsonNotes = null;
try {
jsonNotes = new JSONObject(cursor.getString(cursor.getColumnIndex(DatabaseHelper.SHAPE_NOTES_LIST)));
} catch (JSONException e){
e.printStackTrace();
}
if(jsonNotes != null){
Log.i(TAG, jsonNotes.toString());
JSONArray jsonArray = jsonNotes.optJSONArray(SHAPE_NOTES);
for(int i = 0; i < jsonArray.length(); i++){
Note note = null;
JSONObject arrayObject = null;
try {
arrayObject = jsonArray.getJSONObject(i);
} catch (JSONException e){
e.printStackTrace();
}
if(arrayObject != null){
try {
note = new Note(
arrayObject.getString(SHAPE_NOTE_TITLE),
arrayObject.getInt(SHAPE_NOTE_FINGER_INDEX),
new Point(
arrayObject.getInt(SHAPE_NOTE_X),
arrayObject.getInt(SHAPE_NOTE_Y)
)
);
} catch (JSONException e){
e.printStackTrace();
}
}
if(note != null){
notes.add(note);
}
}
}
}
cursor.close();

I suggest going through all 3 Notepad tutorials you want to store the values your storing to a database table. you don't store the actual array directly into the database just the data. but you shouldn't actually need to use an array at all instead of adding a new item to the array instead call your db insert method

I've needed to do something similar in my application, where I have a custom class (Foo, Bar, etc.) and I have an ArrayList of foo, bar, etc. that I persist to SQL. My knowledge of SQL isn't strong, but I'll explain my approach here in case it helps.
My understanding is that to store any kind of object, you need to define a particular table for that object type, where the table has separate columns representing the primitive types within that object. Furthermore, to persist and retrieve an ArrayList of those objects, you'll use one table row per ArrayList entry, and iterate over in a loop to store and retrieve.
There are ArrayLists of several custom classes in my application that I wanted to persist to DB. So, to make things tidy (well, to me at least -- I'm still a relatively new Java / Android programmer, so take this with a pinch of salt) I decided to implement a kind of "SQL Serializable Interface" that my DB-persistable objects must implement. Each object (Foo, Bar, etc.) that can be persisted to DB must implement:
A public static final TABLE_NAME string, the name of the SQL DB table used for this object type.
A public static final TABLE_CREATE_STRING, a complete SQL instruction to create the table for this object.
A constructor method to populate its member variables from a ContentValues object.
A 'get' method to populate a ContentValues from its member variables.
So, say I have ArrayLists of objects Foo and Bar. When the DB is first created, within my DB helper class I call Foo.TABLE_CREATE_STRING, Bar.TABLE_CREATE_STRING, etc. to create the tables for those objects.
To populate my ArrayList, I use something like:
cursor = dbh.retrieve(Foo.TABLE_NAME);
if(!cursor.moveToFirst()){
return false
}
do{
DatabaseUtils.cursorRowToContentValues(cursor, vales);
FooArrayList.add( new Foo(values) );
} while( cursor.moveToNext() );

Create a dbHelper class which has an inner class and pretty much whatever the notepad tutorial says. The class must be having an insertion method somthing like this :-
public long insertRows(ContentValues values, String tableName) {
long val = myDatabase.insert(tableName, null, values);
return val;
}
This method will then add values into the table row.
After that you can call this method from your main activity and since you are using cursor i believe you will call the method in a for loop
for(i=0;list.length();i++) // or may be its list.size :P
{
// Call the method here
}
and keep adding value in the database by calling the method in for loop