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Cant get a database connection as I cant pass context to DBManager

I have a Dummy Data manager that will populate an ArrayList with the content of a SQLite database. When I try to create a DB object I get an error stating Says 'com.example.listview.manager.ActivityDummyDataManager.this' cannot be referenced from a static context.
package com.example.listview.manager;
import android.database.Cursor;
import com.example.listview.DBManager;
import com.example.listview.model.ActivityItem;
import java.util.ArrayList;
public class ActivityDummyDataManager {
public static ArrayList<ActivityItem> getActivityItemList() {
DBManager db = new DBManager(this);
Cursor cursor = db.fetch();
ArrayList<com.example.listview.model.ActivityItem> list = new ArrayList<>();
while (cursor.moveToNext()) {
int index;
index = cursor.getColumnIndexOrThrow("id");
Long id = cursor.getLong(index);
index = cursor.getColumnIndexOrThrow("activity");
String activity = cursor.getString(index);
index = cursor.getColumnIndexOrThrow("description");
String description = cursor.getString(index);
index = cursor.getColumnIndexOrThrow("description");
String date = cursor.getString(index);
ActivityItem item = new ActivityItem();
item.setId(id);
item.setActivity(activity);
item.setDescription(description);
item.setDate(date);
list.add(item);
}
return list;
}
}
I have a DBManager class I would normally access using DBManager db = new DBManager(this) but for some reason, this will not work from this class.
package com.example.listview;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
public class DBManager {
private DatabaseHelper dbHelper;
private Context context;
private SQLiteDatabase database;
public DBManager(Context c) {
context = c;
}
public DBManager open() throws SQLException {
dbHelper = new DatabaseHelper(context);
database = dbHelper.getWritableDatabase();
return this;
}
public void close() {
dbHelper.close();
}
public void insert(String activity, String description, String date) {
ContentValues contentValue = new ContentValues();
contentValue.put(DatabaseHelper.ACTIVITY, activity);
contentValue.put(DatabaseHelper.DESCRIPTION, description);
contentValue.put(DatabaseHelper.DATE, date);
database.insert(DatabaseHelper.TABLE_NAME, null, contentValue);
}
public Cursor fetch() {
String[] columns = new String[] {
DatabaseHelper._ID,
DatabaseHelper.ACTIVITY,
DatabaseHelper.DESCRIPTION,
DatabaseHelper.DATE
};
Cursor cursor = database.query(DatabaseHelper.TABLE_NAME, columns, null,
null, null, null, "DATE DESC");
if (cursor != null) {
cursor.moveToFirst();
}
return cursor;
}
public Cursor fetchForEdit(String id) {
String[] columns = new String[] {
DatabaseHelper._ID,
DatabaseHelper.ACTIVITY,
DatabaseHelper.DESCRIPTION,
DatabaseHelper.DATE
};
String [] args = new String [] {id};
Cursor cursor = database.query(DatabaseHelper.TABLE_NAME, columns, "_ID=?",
args, null, null, null);
if (cursor != null) {
cursor.moveToFirst();
}
Log.d("DATABASE", "cursor= "+cursor.getColumnName(1));
return cursor;
}
public int update(long _id, String activity, String description, String date) {
ContentValues contentValues = new ContentValues();
contentValues.put(DatabaseHelper.ACTIVITY, activity);
contentValues.put(DatabaseHelper.DESCRIPTION, description);
contentValues.put(DatabaseHelper.DATE, date);
int i = database.update(
DatabaseHelper.TABLE_NAME, contentValues,
DatabaseHelper._ID + " = " + _id,
null);
return i;
}
public void delete(long _id) {
database.delete(DatabaseHelper.TABLE_NAME,
DatabaseHelper._ID + "=" + _id,
null);
}
}
Why can't I set the DBManager db = new DBManager(this); to get a DB connection.
Says 'com.example.listview.manager.ActivityDummyDataManager.this'
cannot be referenced from a static context.
Could someone also explain the context argument as I don't really understand it.

Your Constructor DBManager(Context c) expects a context as parameter, If you call this constructor from Activity or Service class it will work as both Activity and Service are sub-classes of Context, So passing this should suffice. As ActivityDummyDataManager does not handle context you need to pass Context either from activity or you can pass application context getApplicationContext().
Change your method as below
public static ArrayList<ActivityItem> getActivityItemList() {
DBManager db = new DBManager(mContext);
//rest of your code.
}
and while calling it use activity or application context whichever is suitable.

Unable to delete data from SQLite

I am having issues when trying to clear the entries from a Arraylist in Android studio, not matter what code I try the app either does nothing or as with the code below crashes. I'm pulling my hair out with this as in my mind it should work.
I have also tried (not included in the code):
odb.rawquery(" delete from DATABASE_TABLE") //from memory so may not be 100%
This crashed the app and it would not reload, I'm assuming that it was successful in removing the table and not re-creating it?
It will be running on KitKat
Have I missed anything?
This is the last thing I need to make it work so any help or suggestions would be great!
TIA
Main
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleAdapter;
public class MainActivity extends Activity {
private ListView list_lv;
private EditText col2_ed;
private Button sub_btn;
Button del_btn;
private DBclass db;
private ArrayList<String> collist_2;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
collist_2 = new ArrayList<String>();
items();
getData();
DeleteData();
}
private void items() {
sub_btn = (Button) findViewById(R.id.submit_btn);
del_btn = (Button) findViewById(R.id.delete_btn);
col2_ed = (EditText) findViewById(R.id.ed2);
list_lv = (ListView) findViewById(R.id.dblist);
sub_btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
submitData();
}
});
}
public void DeleteData(){
del_btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
db.deleteData();
}
});
}
protected void submitData() {
String b = col2_ed.getText().toString();
db = new DBclass(this);
long num;
db.open();
num = db.insertmaster(b);
db.close();
getData();
}
public void getData() {
collist_2.clear();
db = new DBclass(this);
try {
db.open();
Cursor cur = db.getAllTitles();
while (cur.moveToNext()) {
String valueofcol2 = cur.getString(2);
collist_2.add(valueofcol2);
}
}
finally {
db.close();
}
printList();
setDataIntoList();
}
private void printList() {
for (int i = 0; i < collist_2.size(); i++) {
}
}
private void setDataIntoList() {
// create the list item mapping
String[] from = new String[] { "col_2" };
int[] to = new int[] { R.id.col2tv };
// prepare the list of all records
List<HashMap<String, String>> fillMaps = new ArrayList<HashMap<String, String>>();
for (int i = 0; i < collist_2.size(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
map.put("col_2", collist_2.get(i));
fillMaps.add(map);
}
// fill in the grid_item layout
SimpleAdapter adapter = new SimpleAdapter(this, fillMaps,
R.layout.custom, from, to);
list_lv.setAdapter(adapter);
}
}
DBclass
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DBclass {
public String KEY_ROWID = "_id";
public String KEY_COL2 = "col2";
private String DATABASE_NAME = "mydb";
private String DATABASE_TABLE = "mytable";
private int DATABASE_VERSION = 1;
private Context ourContext;
private DbHelper dbh;
private SQLiteDatabase odb;
private String USER_MASTER_CREATE =
"CREATE TABLE IF NOT EXISTS " + DATABASE_TABLE+ "("
+ KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_COL2 + " VARCHAR(15) )";
private class DbHelper extends SQLiteOpenHelper {
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(USER_MASTER_CREATE);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// if DATABASE VERSION changes
// Drop old tables and call super.onCreate()999
}
}
public DBclass(Context c) {
ourContext = c;
dbh = new DbHelper(ourContext);
}
public DBclass open() throws SQLException {
odb = dbh.getWritableDatabase();
return this;
}
public void close() {
dbh.close();
}
public long insertmaster(String col2) throws SQLException{
ContentValues IV = new ContentValues();
IV.put(KEY_COL2, col2);
return odb.insert(DATABASE_TABLE, null, IV);
// returns a number >0 if inserting data is successful
}
public void updateRow(long rowID, String col2) {
ContentValues values = new ContentValues();
values.put(KEY_COL2, col2);
odb.update(DATABASE_TABLE, values, KEY_ROWID + "=" + rowID, null);
}
public void deleteData(){
odb.delete(DATABASE_TABLE, null,null);
}
public Cursor getAllTitles() {
// using simple SQL query
return odb.rawQuery("select * from " + DATABASE_TABLE, null);
}
public Cursor getallCols(String id) throws SQLException {
Cursor mCursor = odb.query(DATABASE_TABLE, new String[] { KEY_COL2 }, null, null, null, null, null);
Log.e("getallcols zmv", "opening successfull");
return mCursor;
}
public Cursor getColsById(String id) throws SQLException {
Cursor mCursor = odb.query(DATABASE_TABLE, new String[] { KEY_COL2 }, KEY_ROWID + " = " + id, null, null, null, null);
Log.e("getallcols zmv", "opening successfull");
return mCursor;
}
}

I think you're not opening the database before trying to delete.
public void DeleteData(){
del_btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
//Try adding these lines
try {
db = new DBclass(this);
db.open();
db.deleteData();
}catch(Exception e){
e.print
}finally{
db.close();
}
}
});
}

Add this in DBclass will delete all data from the particular table
public void deleteAll(){
SQLiteDatabase db = this.getWritableDatabase();
String deleteStmt="DELETE FROM "+TABLE_NAME;
db.execSQL(deleteStmt);
db.close();
}
Deleting a single row or single item (where item is the model class or you can pass the keyId/primarykey )
// Deleting single Item
public void deleteItem(Item item) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_NAME, KEY_ID + " = ?",
new String[] { String.valueOf(item.getKeyId()) });
db.close();
}
Also please refer the below link :
https://www.androidhive.info/2013/09/android-sqlite-database-with-multiple-tables/

How to Retrieve Multiple data when clicked on listview?

I want all edit text content that I have saved in SQL to be displayed on the edit bills activity when I click on the list item, but I am only able to retrieve the name and display it again in the intent. Rather than saving another data it should update the record with the new data if I save the existing record another time in the editbills_activity.
Here is my DBAdapter.java
package com.example.dhruv.bills;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DBAdapter {
public static final String KEY_ROWID = "id";
public static final String KEY_NAME = "name";
public static final String KEY_AMOUNT = "amount";
public static final String KEY_DUEDATE = "duedate";
private static final String TAG = "DBAdapter";
private static final String DATABASE_NAME = "billsdb";
private static final String DATABASE_TABLE = "bills";
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_CREATE =
"create table if not exists assignments (id integer primary key autoincrement, "
+ "name VARCHAR not null, amount VARCHAR, duedate date );";
// Replaces DATABASE_CREATE using the one source definition
private static final String TABLE_CREATE =
"CREATE TABLE IF NOT EXISTS " + DATABASE_TABLE + "(" +
KEY_ROWID + " INTEGER PRIMARY KEY, " + // AUTOINCREMENT NOT REQD
KEY_NAME + " DATE NOT NULL, " +
KEY_AMOUNT + " VARCHAR ," +
KEY_DUEDATE + " DATE " +
")";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(TABLE_CREATE); // NO need to encapsulate in try clause
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS contacts"); //????????
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
}
//---opens the database---
public DBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
//---closes the database---
public void close()
{
DBHelper.close();
}
//---insert a record into the database---
public long insertRecord(String name, String amount, String duedate)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_NAME, name);
initialValues.put(KEY_AMOUNT, amount);
initialValues.put(KEY_DUEDATE, duedate);
//return db.insert(DATABASE_TABLE, null, initialValues);
// Will return NULL POINTER EXCEPTION as db isn't set
// Replaces commented out line
return DBHelper.getWritableDatabase().insert(DATABASE_TABLE,
null,
initialValues
);
}
//---deletes a particular record---
public boolean deleteContact(long rowId)
{
return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
//---retrieves all the records--- SEE FOLLOWING METHOD
public Cursor getAllRecords()
{SQLiteDatabase db = DBHelper.getWritableDatabase();
String query ="SELECT * FROM " + DATABASE_TABLE;
Cursor data = db.rawQuery(query,null);
return data;
}
//As per getAllRecords but using query convenience method
public Cursor getAllAsCursor() {
return DBHelper.getWritableDatabase().query(
DATABASE_TABLE,
null,null,null,null,null,null
);
}
public Cursor getItemID(String name) {
SQLiteDatabase db = DBHelper.getWritableDatabase();
String query = "SELECT " + KEY_ROWID + " FROM " + DATABASE_TABLE +
" WHERE " + KEY_NAME + " = '" + name + "'";
Cursor data = db.rawQuery(query, null);
return data;
}
//---retrieves a particular record--- THIS WILL NOT WORK - NO SUCH TABLE
/* public Cursor getRecord()
{String query1 ="SELECT * FROM" + KEY_TITLE;
Cursor mCursor = db.rawQuery(query1,null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}*/
// Retrieve a row (single) according to id
public Cursor getRecordById(long id) {
return DBHelper.getWritableDatabase().query(
DATABASE_TABLE,
null,
KEY_ROWID + "=?",
new String[]{String.valueOf(id)},
null,null,null
);
}
//---updates a record---
/* public boolean updateRecord(long rowId, String name, String amount, String duedate)
{
ContentValues args = new ContentValues();
args.put(KEY_NAME, name);
args.put(KEY_AMOUNT, amount);
args.put(KEY_DUEDATE, duedate);
String whereclause = KEY_ROWID + "=?";
String[] whereargs = new String[]{String.valueOf(rowId)};
// Will return NULL POINTER EXCEPTION as db isn't set
//return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
// Replaces commented out line
return DBHelper.getWritableDatabase().update(DATABASE_TABLE,
args,
whereclause,
whereargs
) > 0;
}*/
}
Here is my Bills.java
(MainActivity)
Problem: Bills.java has the list view that shows the intent whenever the item in list view is clicked, but it does not put the amount and date or update the record. Instead it saves another record.
Solution: I want to retrieve it and display all (name ,amount,duedate) and instead of saving another record it should update it.
package com.example.dhruv.bills;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
public class bills extends AppCompatActivity {
DBAdapter dbAdapter;
ListView mrecycleview;
private static final String TAG ="assignments";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bills);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mrecycleview =(ListView) findViewById(R.id.mRecycleView);
dbAdapter = new DBAdapter(this);
// mlistview();
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent i = new Intent(getApplicationContext(),Editbills.class);
startActivity(i);
}
});
mlistview();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_bills, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private void mlistview(){
Log.d(TAG,"mlistview:Display data in listview");
Cursor mCursor = dbAdapter.getAllRecords();
ArrayList<String> listData = new ArrayList<>();
while (mCursor.moveToNext()){
listData.add(mCursor.getString(1));
}
ListAdapter adapter = new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,listData);
mrecycleview.setAdapter(adapter);
mrecycleview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
String name = adapterView.getItemAtPosition(i).toString();
Log.d(TAG, "onItemClick: You Clicked on " + name);
Cursor data = dbAdapter.getItemID(name); //get the id associated with that name
int itemID = -1;
while(data.moveToNext()){
itemID = data.getInt(0);
}
if(itemID > -1){
Log.d(TAG, "onItemClick: The ID is: " + itemID);
Intent editScreenIntent = new Intent(bills.this, Editbills.class);
editScreenIntent.putExtra("id",itemID);
editScreenIntent.putExtra("name",name);
startActivity(editScreenIntent);
}
else{
}
}
});
}
}
here is my editbills.java code
package com.example.dhruv.bills;
import android.content.ContentValues;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
public class Editbills extends AppCompatActivity {
Button button;
private static final String Tag= "assignments";
DBAdapter db = new DBAdapter(this);
private String selectedName;
private int selectedID;
DBAdapter dbAdapter;
private EditText editText,editText2,editText3;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_editbills);
button=(Button)findViewById(R.id.button);
editText =(EditText)findViewById(R.id.editText);
editText2=(EditText)findViewById(R.id.editText2);
editText3 =(EditText)findViewById(R.id.editText3);
//get the intent extra from the ListDataActivity
Intent receivedIntent = getIntent();
//now get the itemID we passed as an extra
selectedID = receivedIntent.getIntExtra("id",-1); //NOTE: -1 is just the default value
//now get the name we passed as an extra
selectedName = receivedIntent.getStringExtra("name");
//set the text to show the current selected name
editText.setText(selectedName);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Log.d("test", "adding");
db.open();
long id = db.insertRecord(editText.getText().toString(), editText2.getText().toString(), editText3.getText().toString());
db.close();
Toast.makeText(Editbills.this," Added", Toast.LENGTH_LONG).show();
Intent q = new Intent(getApplicationContext(),bills.class);
startActivity(q);
}
});
}
}

There are two parts/questions.
First to retrieve the data, so that it can be displayed in the editbills activity, you can utilise the row's id that is passed to the activity in conjunction with the getRecordById method.
I'd suggest that adding a method to the editbills class will simplyfy matters.
private void populateDisplay(int id) {
Cursor csr = dbAdapter.getRecordById(id);
if (csr.moveToFirst()) {
editText.setText(csr.getString(csr.getColumnIndex(DBAdapter.KEY_NAME)));
editText2.setText(csr.getString(csr.getColumnIndex(DBAdapter.KEY_AMOUNT)));
editText3.setText(csr.getString(csr.getColumnIndex(DBAdapter.KEY_DUEDATE)));
}
csr.close();
}
You could invoke the above method after retrieving the id from the Intent using :-
populateDisplay(selectedID);
To update based upon the content's of the EditTexts un-comment the updateRecord method in DBAdapter.java and the change :-
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Log.d("test", "adding");
db.open();
long id = db.insertRecord(editText.getText().toString(), editText2.getText().toString(), editText3.getText().toString());
db.close();
Toast.makeText(Editbills.this," Added", Toast.LENGTH_LONG).show();
Intent q = new Intent(getApplicationContext(),bills.class);
startActivity(q);
}
});
to :-
mButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (dbAdapter.updateRecord(
selectedId,
editText.getText().toString(),
editText2.getText().toString(),
editText3.getText().toString())
) {
Log.d("TEST","Row successfully updated.");
Toast.makeText(getApplicationContext(),"Row Updated.",Toast.LENGTH_LONG).show();
populateDisplay(selectedId);
} else {
Toast.makeText(getApplicationContext(),"Row not Updated",Toast.LENGTH_LONG).show();
}
Intent q = new Intent(getApplicationContext(),bills.class);
startActivity(q);
}
});
You will additionally have to add a line initialise the dbAdapter i.e. dbAdapter = new DBAdapter(this); i.d suggest adding this line immediately after the line setContentView(R.layout.activity_editbills);
Note the above code is in-principle and has not been thoroughly tested so it may contains errors.
Edit complete working example :-
The following code is basically an implementation of the above, except modified to utilise a Bill class. Rather than an ArrayList<String> as the source for the Adapter it has ArrayList<Bill>.
Thus all the data (id, name, amount and duedate) is available.
You should notice that I've overridden the toString method to return a String that combines the name, amount and duedate. The ArrayAdapter uses the object's toString method to populate the view.
Saying that the critical value is the rowid or an alias of rowid as this can be used to identify a row even if the other data is identical (as would happen when running this example more than once due to the addSomeData method). Hence, only the id is extracted and passed to the Editbills activity when an item in the list is long clicked (changed from just clicked to reduce the potential for accidental use).
Bill.java
public class Bill {
private long id;
private String name;
private String amount;
private String duedate;
public Bill(long id, String name, String amount, String duedate) {
this.id = id;
this.name = name;
this.amount = amount;
this.duedate = duedate;
}
/*
Note if this Constructor used then setId should be used
*/
public Bill(String name, String amount, String duedate) {
new Bill(0,name,amount,duedate);
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAmount() {
return amount;
}
public void setAmount(String amount) {
this.amount = amount;
}
public String getDuedate() {
return duedate;
}
public void setDuedate(String duedate) {
this.duedate = duedate;
}
/*
As ArrayAdapter uses toString method change this
to return all items
*/
#Override
public String toString() {
return name + " " + amount + " " + duedate;
}
}
MainActivity.java
This is the equivalent to your Bills.java without a lot of the bloat such as FAB. :-
public class MainActivity extends AppCompatActivity {
public static final String ID_INTENTEXTRA = DBAdapter.KEY_ROWID + "_INTENTEXTRA"; //<<<< ADDED
DBAdapter mDBAdapter;
Cursor mCsr;
ListView mrecycleview;
ArrayAdapter adapter; //<<<< NOT ListAdapter
Context context; // ADDED
private static final String TAG ="assignments";
ArrayList<Bill> mBillList = new ArrayList<>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context = this;
mrecycleview = this.findViewById(R.id.mRecycleView);
mDBAdapter = new DBAdapter(this);
addSomeData();
adapter = new ArrayAdapter<Bill>(
this,
android.R.layout.simple_list_item_1,
mBillList
);
mrecycleview.setAdapter(adapter);
mrecycleview.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
#Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
Bill b = (Bill) adapter.getItem(position);
Intent i = new Intent(context,Editbills.class);
i.putExtra(ID_INTENTEXTRA,b.getId()); //Get ID
startActivity(i);
return true;
}
});
rebuildBillList();
}
//<<<< ADDED Method to refresh the ListView resumed
#Override
protected void onResume() {
super.onResume();
rebuildBillList();
}
// Add some data (note will add 2 rows each time it is run)
private void addSomeData() {
mDBAdapter.insertRecord("Bill1","2018-10-02","English");
mDBAdapter.insertRecord("Bill2","2018-09-03","Mathematics");
mDBAdapter.insertRecord("Bill3","2018-11-04", "Geography");
}
public void rebuildBillList() {
mBillList.clear();
mCsr = mDBAdapter.getAllAsCursor();
while (mCsr.moveToNext()) {
mBillList.add(new Bill(
mCsr.getLong(mCsr.getColumnIndex(DBAdapter.KEY_ROWID)),
mCsr.getString(mCsr.getColumnIndex(DBAdapter.KEY_NAME)),
mCsr.getString(mCsr.getColumnIndex(DBAdapter.KEY_AMOUNT)),
mCsr.getString(mCsr.getColumnIndex(DBAdapter.KEY_DUEDATE))
)
);
}
adapter.notifyDataSetChanged();
}
}
Note the above adds 3 rows each time it is run.
Editbills.java
public class Editbills extends AppCompatActivity {
Button button;
private static final String Tag = "assignments";
DBAdapter db = new DBAdapter(this);
private String selectedName;
private long selectedID;
DBAdapter dbAdapter;
private EditText editText,editText2,editText3;
Context context;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_editbills);
context = this;
dbAdapter = new DBAdapter(this); //<<<< ADDED
button=(Button)findViewById(R.id.button);
editText =(EditText)findViewById(R.id.edittext);
editText2=(EditText)findViewById(R.id.edittext2);
editText3 =(EditText)findViewById(R.id.edittext3);
//get the intent extra from the ListDataActivity
Intent receivedIntent = getIntent();
//now get the itemID we passed as an extra
selectedID = receivedIntent.getLongExtra(MainActivity.ID_INTENTEXTRA,-1L); //NOTE: -1 is just the default value
populateDisplay(selectedID);
//now get the name we passed as an extra
//selectedName = receivedIntent.getStringExtra("name");
//set the text to show the current selected name
//editText.setText(selectedName); <<<< commented out
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
/*
Log.d("test", "adding");
db.open();
long id = db.insertRecord(editText.getText().toString(), editText2.getText().toString(), editText3.getText().toString());
db.close();
Toast.makeText(Editbills.this," Added", Toast.LENGTH_LONG).show();
*/
/*
* <<<< Not the way as it ends/closes the existing activity
Intent q = new Intent(getApplicationContext(),MainActivity.class);
startActivity(q);
*/
String toast = "Updated.";
if (dbAdapter.updateRecord(selectedID,
editText.getText().toString(),
editText2.getText().toString(),
editText3.getText().toString())) {
} else {
toast = "Not Updated.";
}
Toast.makeText(context,toast,Toast.LENGTH_LONG).show();
finish(); //<<<< ends/closes this activity and returns to calling activity
}
});
}
private void populateDisplay(long id) {
Cursor csr = dbAdapter.getRecordById(id);
if (csr.moveToFirst()) {
editText.setText(csr.getString(csr.getColumnIndex(DBAdapter.KEY_NAME)));
editText2.setText(csr.getString(csr.getColumnIndex(DBAdapter.KEY_AMOUNT)));
editText3.setText(csr.getString(csr.getColumnIndex(DBAdapter.KEY_DUEDATE)));
}
csr.close();
}
}
Basically as per the original answer.
DBAdapter.java
public class DBAdapter {
public static final String KEY_ROWID = "id";
public static final String KEY_NAME = "name";
public static final String KEY_AMOUNT = "amount";
public static final String KEY_DUEDATE = "duedate";
private static final String TAG = "DBAdapter";
private static final String DATABASE_NAME = "billsdb";
private static final String DATABASE_TABLE = "bills";
private static final int DATABASE_VERSION = 2;
// Replaces DATABASE_CREATE using the one source definition
private static final String TABLE_CREATE =
"CREATE TABLE IF NOT EXISTS " + DATABASE_TABLE + "(" +
KEY_ROWID + " INTEGER PRIMARY KEY, " + // AUTOINCREMENT NOT REQD
KEY_NAME + " DATE NOT NULL, " +
KEY_AMOUNT + " VARCHAR ," +
KEY_DUEDATE + " DATE " +
")";
private Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(TABLE_CREATE); // NO need to encapsulate in try clause
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS contacts"); //????????
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
}
//---opens the database--- NOT NEEDED
public DBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
//---closes the database--- NOT NEEDED
public void close()
{
DBHelper.close();
}
//---insert a record into the database---
public long insertRecord(String name, String amount, String duedate)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_NAME, name);
initialValues.put(KEY_AMOUNT, amount);
initialValues.put(KEY_DUEDATE, duedate);
return DBHelper.getWritableDatabase().insert(DATABASE_TABLE,
null,
initialValues
);
}
//---deletes a particular record---
public boolean deleteContact(long rowId)
{
return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
//---retrieves all the records--- SEE FOLLOWING METHOD
public Cursor getAllRecords()
{SQLiteDatabase db = DBHelper.getWritableDatabase();
String query ="SELECT * FROM " + DATABASE_TABLE;
Cursor data = db.rawQuery(query,null);
return data;
}
//As per getAllRecords but using query convenience method
public Cursor getAllAsCursor() {
return DBHelper.getWritableDatabase().query(
DATABASE_TABLE,
null,null,null,null,null,null
);
}
public Cursor getItemID(String name) {
SQLiteDatabase db = DBHelper.getWritableDatabase();
String query = "SELECT " + KEY_ROWID + " FROM " + DATABASE_TABLE +
" WHERE " + KEY_NAME + " = '" + name + "'";
Cursor data = db.rawQuery(query, null);
return data;
}
// Retrieve a row (single) according to id
public Cursor getRecordById(long id) {
return DBHelper.getWritableDatabase().query(
DATABASE_TABLE,
null,
KEY_ROWID + "=?",
new String[]{String.valueOf(id)},
null,null,null
);
}
//---updates a record---
public boolean updateRecord(long rowId, String name, String amount, String duedate) {
ContentValues args = new ContentValues();
args.put(KEY_NAME, name);
args.put(KEY_AMOUNT, amount);
args.put(KEY_DUEDATE, duedate);
String whereclause = KEY_ROWID + "=?";
String[] whereargs = new String[]{String.valueOf(rowId)};
return DBHelper.getWritableDatabase().update(DATABASE_TABLE,
args,
whereclause,
whereargs
) > 0;
}
}
Basically as was except that upDateRecord has been un-commented, again as per the original answer.
Results
1st Run - MainActivity (Bills) :-
Long Click Bill2 (note changed from Click as Long Click is less prone to accidental use)
Change data (Update button not clicked)
Update Button Clicked (Toast was Updated.)
Note use of finish() to return to the invoking activity and then the use of onResume to refresh the list according to the updated data (possibly your next question).
using startActivity will simply result in issues.
Note Values are date and course rather then amount and duedate because I didn't change the values in the addSomeData method (easily done).
the actual data itself is irrelevant to the process.

Android app stalls when implementing SQLite database

At first the app would just crash when I started it with an emulator, Not sure what I changed to get it to run but now it will run the onCreate method however, when I implement the addButtonClicked method the app just stalls and the Android Monitor displays "Suspending all threads" every few seconds and I'm not sure where to even begin debugging. Any pointers in the right direction would be greatly appreciated as I'm fairly new to Android development.
MainActivity.java
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
EditText testInput;
TextView testText;
MyDBHandler dbHandler;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
testInput = (EditText) findViewById(R.id.testInput);
testText = (TextView) findViewById(R.id.testText);
dbHandler = new MyDBHandler(this, null, null, 1);
printDatabase();
}
//Add product to database
public void addButtonClicked(View view){
Products product = new Products((testInput.getText().toString()));
dbHandler.addProduct(product);
printDatabase();
}
// Delete Items
public void deleteButtonClicked(View view){
String inputText = testText.getText().toString();
dbHandler.deleteProduct(inputText);
printDatabase();
}
public void printDatabase(){
String dbString = dbHandler.databaseToString();
testText.setText(dbString);
testInput.setText("");
}
}
Products.java
public class Products {
private int _id;
private String _productname;
public Products(){
}
public Products(String productname) {
this._productname = productname;
}
public void set_id(int _id) {
this._id = _id;
}
public void set_productname(String _productname) {
this._productname = _productname;
}
public int get_id() {
return _id;
}
public String get_productname() {
return _productname;
}
}
MyDBHandler.java
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.Cursor;
import android.content.Context;
import android.content.ContentValues;
public class MyDBHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 15;
private static final String DATABASE_NAME = "products.db";
public static final String TABLE_PRODUCTS = "products";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_PRODUCTNAME = "productname";
public MyDBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
String query = "CREATE TABLE " + TABLE_PRODUCTS +"(" +
COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT ," +
COLUMN_PRODUCTNAME +" TEXT " +
");";
db.execSQL(query);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_PRODUCTS);
onCreate(db);
}
//Add new row to the database
public void addProduct(Products product){
ContentValues values = new ContentValues();
values.put(COLUMN_PRODUCTNAME, product.get_productname());
SQLiteDatabase db = getWritableDatabase();
db.insert(TABLE_PRODUCTS, null, values);
db.close();
}
//Delete product from database
public void deleteProduct(String productName){
SQLiteDatabase db = getWritableDatabase();
db.execSQL("DELETE FROM " + TABLE_PRODUCTS + " WHERE " + COLUMN_PRODUCTNAME + "=\"" + productName + "\";" );
}
//Print of DB as sting
public String databaseToString(){
String dbString = "";
SQLiteDatabase db = getWritableDatabase();
String query = "SELECT * FROM " + TABLE_PRODUCTS + " WHERE 1";
//Cursor point to a location in your results
Cursor c = db.rawQuery(query, null);
//Move to the first row in your results
c.moveToFirst();
while (!c.isAfterLast()){
if(c.getString(c.getColumnIndex("productname"))!= null){
dbString += c.getString(c.getColumnIndex("productname"));
dbString += "\n";
}
}
db.close();
return dbString;
}
}

for your databaseToString method you are performing a retrieve operation. You should be doing a read operation in a thread other than UI thread. Try fetching in AsyncTask. It should work. Implementation for your databaseToString should be handled by AsyncTask.
Happy Coding..

ListView duplicates items everytime I restart the activity

I feel like this is a really simple fix but I am new the android and sqlite in general. I have a array that takes data from a database and then shows them in a list. However every time I restart the app the list adds the items once again into the list. How can I make it not do this?
package com.example.assignmenttracker;
import java.util.ArrayList;
import java.util.List;
import android.content.Intent;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import com.example.assignmenttracker.MySQLiteHelper;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.app.Activity;
public class MainActivity extends Activity {
private ListView ListView;
private Button addbutton;
public final static String ID_EXTRA="com.example.assignmenttracker._ID";
public static ArrayList<String> ArrayofName = new ArrayList<String>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.addbutton = (Button)this.findViewById(R.id.button1);
this.addbutton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent intent=new Intent(MainActivity.this, AddAssign.class);
startActivity(intent);
}
});
}
private void populateListView() {
MySQLiteHelper db = new MySQLiteHelper(this);
List<tasklist> contacts = db.getSometasklist();
for (tasklist cn : contacts) {
Log.d("Reading: ", "Reading all contacts..");
String log = "Id: "+cn.getID()+" ,Task: " + cn.getTask() + " ,Date: " + cn.getDate() + " ,Status: " + cn.getStatus();
Log.d("Name: ", log);
}
ListView = (ListView) findViewById(R.id.listView1);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, ArrayofName);
ListView.setAdapter(adapter);
ListView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v,
int position, long id) {
Intent i = new Intent(MainActivity.this, ViewAssign.class);
i.putExtra(ID_EXTRA, String.valueOf(id));
startActivity(i);}
});
}
#Override
public void onResume() {
super.onResume();
populateListView();
}
}
here is the code of mysqlitehelper
package com.example.assignmenttracker;
import java.util.ArrayList;
import java.util.List;
import android.database.Cursor;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase;
import android.content.ContentValues;
import android.content.Context;
public class MySQLiteHelper extends SQLiteOpenHelper {
// Contacts Table Columns names
private static final String TABLE_CONTACTS = "tasklist1";
private static final String KEY_ID = "id";
private static final String KEY_TASK = "task";
private static final String KEY_DESC = "desc";
private static final String KEY_MOD = "module";
private static final String KEY_DATE = "date";
private static final String KEY_TYPE = "type";
private static final String KEY_STATUS = "status";
private static final int DATABASE_VERSION = 3;
private static final String DATABASE_NAME = "tasklist1";
public MySQLiteHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public void onCreate(SQLiteDatabase db) {
String CREATE_TASKLIST_TABLE = "CREATE TABLE tasklist1 ( " +
"id INTEGER PRIMARY KEY AUTOINCREMENT, " +
"task TEXT, "+
"desc TEXT, "+
"module TEXT, "+
"date TEXT, "+
"type TEXT, "+
"status INTEGER )";
db.execSQL(CREATE_TASKLIST_TABLE);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older task list table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
// create fresh task list table
this.onCreate(db);
}
public void insertTask(tasklist tasklist){
// 1. get reference to writable DB
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_TASK, tasklist.getTask());
values.put(KEY_DESC, tasklist.getDesc());
values.put(KEY_MOD, tasklist.getModule());
values.put(KEY_DATE, tasklist.getDate());
values.put(KEY_TYPE, tasklist.getType());
values.put(KEY_STATUS, tasklist.getStatus());
// Inserting Row
db.insert(TABLE_CONTACTS, null, values);
db.close(); // Closing database connection
}
public List<tasklist> getAlltasklist(int passedid) {
List<tasklist> tasklistList = new ArrayList<tasklist>();
// Select All Query
String selectQuery = "SELECT * FROM " + TABLE_CONTACTS +
" where id = " + passedid;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
tasklist contact = new tasklist();
contact.setTask(cursor.getString(1));
contact.setDesc(cursor.getString(2));
contact.setModule(cursor.getString(3));
contact.setDate(cursor.getString(4));
contact.setType(cursor.getString(5));
contact.setStatus(cursor.getInt(6));
String name = cursor.getString(1);
String desc =cursor.getString(2);
String module =cursor.getString(3);
String date = cursor.getString(4);
String type = cursor.getString(5);
int status = cursor.getInt(6);
ViewAssign.task= name;
ViewAssign.desc=desc;
ViewAssign.module=module;
ViewAssign.date=date;
ViewAssign.type=type;
ViewAssign.status=status;
// Adding contact to list
tasklistList.add(contact);
db.close();
} while (cursor.moveToNext());
}
return tasklistList;
}
public List<tasklist> getSometasklist() {
List<tasklist> tasklistList = new ArrayList<tasklist>();
// Select All Query
String selectQuery = "SELECT * FROM " + TABLE_CONTACTS;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
tasklist contact = new tasklist();
contact.setTask(cursor.getString(1));
contact.setDate(cursor.getString(4));
String name = cursor.getString(1) +"\n"+ cursor.getString(4);
MainActivity.ArrayofName.add(name);
// Adding contact to list
tasklistList.add(contact);
db.close();
} while (cursor.moveToNext());
}
return tasklistList;
}
public void deleteTask(long row) {
// Deletes a row given its rowId, but I want to be able to pass
// in the name of the KEY_NAME and have it delete that row.
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_CONTACTS, KEY_ID + "=" + row, null);
db.close();
}
}

I suspect the culprint is this:
public static ArrayList<String> ArrayofName = new ArrayList<String>();
It is a static variable, meaning that in some circumstances, it will STILL have the objects you added on app first run when you run it second time.
Possible solutions:
remove "static" keyword, or
clear ArrayOfName before populating it, eg. ArrayOfName.clear()

I know I am late but maybe it will help someone else.
You need to split ArrayList into two parts
Place the following code in MainActivity
public static ArrayList<String> ArrayofName;
And place the following in onCreate() OR onResume() method
ArrayofName = new ArrayList<String>();