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I can't send data to sqlite to database [duplicate]

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What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 2 years ago.
I am trying to add data to the SQLite database but when I add the data it gives me null pointer exception.
This is the error in the logcat
java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.File android.content.Context.getDatabasePath(java.lang.String)' on a null object reference
enter code here
package com.llmago.autism;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import java.util.Objects;
public class StartFragment extends Fragment {
private EditText edtName, edtAge, edtScore;
private Button save, load;
Db db = new Db(getActivity());
public StartFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_start, container, false);
initUI(view);
// Inflate the layout for this fragment
return view;
}
public void initUI(View view) {
edtName = view.findViewById(R.id.name);
edtAge = view.findViewById(R.id.age);
edtScore = view.findViewById(R.id.result);
save = view.findViewById(R.id.save);
save.setOnClickListener(v -> btnSaveAction(view));
}
public void btnSaveAction(View view) {
String name = edtName.getText().toString();
String age = edtAge.getText().toString();
String score = edtScore.getText().toString();
boolean result = db.insertData(name, age, score);
if (result == true) {
Toast.makeText(getActivity(), "Done", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getActivity(), "Error", Toast.LENGTH_LONG).show();
}
}
}
package com.llmago.autism;
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import androidx.annotation.Nullable;
public class Db extends SQLiteOpenHelper {
public static final String databaseName = "autism.db";
public Db(#Nullable Context context) {
super(context, databaseName, null, 1);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table autism(id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, age TEXT, score TEXT)");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS autiusm");
onCreate(db);
}
public boolean insertData(String name, String age, String score){
SQLiteDatabase sqLiteDatabase = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("name", name);
contentValues.put("age", age);
contentValues.put("score", score);
long result = sqLiteDatabase.insert("autism", null, contentValues);
if (result == -1)
return false;
else
return true;
}
}

Declare the mContext inside FragmentClass
Context mContext;
Change constructor from
public StartFragment(Context context) {
mContext = context;
db = new Db(mContext);
}
Also replace the db() constructor
public Db(#Nullable Context context) {
super(context, databaseName, null, 1);
this.getWritableDatabase();
}
Note: When you creating fragment instance you have to pass Activity Reference

I cant call my constructor method SQLite

I'm new at the android studio. I tried creating SQLite Database but when I try inserting data android studio cannot resolve it. i also tried MainActivity.this and getApplicationContext instead of db=new DatabaseHelper(this); on this line. and on device monitor, it isn't creating a database file
MainActivity.java
package com.example.lenovo.sqlite_2_deneme;
import android.content.Context;
import android.media.midi.MidiDevice;
import android.provider.ContactsContract;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends AppCompatActivity {
DatabaseHelper db;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
db=new DatabaseHelper(this);
EditText et_name,et_surname,et_number;
Button btn_data;
et_name= (EditText) findViewById(R.id.et_isim);
et_surname= (EditText) findViewById(R.id.et_soyisim);
et_number= (EditText) findViewById(R.id.et_numara);
btn_data= (Button) findViewById(R.id.btn_veri);
btn_data.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
db.insertData();
}
});
}
}
and my DatabaseHelper class
package com.example.lenovo.sqlite_2_deneme;
import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.provider.ContactsContract;
import android.widget.TableLayout;
public class DatabaseHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME= "student_info.db";
public static final String TABLE_NAME="student_table";
public static final String COL_1="ID";
public static final String COL_2="NAME";
public static final String COL_3="SURNAME";
public static final String COL_4="NUMBER";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, 1);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE"+ TABLE_NAME+"(ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT, SURNAME TEXT, NUMBER INTEGER)");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS"+ TABLE_NAME);
this.onCreate(db);
}
public Boolean DataInsert(String name, String surname, String number)
{
SQLiteDatabase db=this.getWritableDatabase();
ContentValues contentValues=new ContentValues();
contentValues.put(COL_2,name);
contentValues.put(COL_3,surname);
contentValues.put(COL_4,number);
long sonuc= db.insert(TABLE_NAME,null,contentValues);
if(sonuc==-1)
return false;
else
return true;
}
}

Your database will be created at the instance when you call
SQLiteDatabase db=this.getWritableDatabase();
At the moment I dont see you have called this anywhere in your code. You have written a DataInsert method but it is not getting called in the code you have shared so far.

your'e sql query is wrong give the space in table (insert data),and also in onupgrade and there is no method insertData()
db.execSQL("CREATE TABLE "+ TABLE_NAME+"(ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT, SURNAME TEXT, NUMBER INTEGER)");

There is no method insertData() . You should use
DataInsert() method .
db=new DatabaseHelper(MainActivity.this);
EditText et_name,et_surname,et_number;
Button btn_data;
et_name= (EditText) findViewById(R.id.et_isim);
et_surname= (EditText) findViewById(R.id.et_soyisim);
et_number= (EditText) findViewById(R.id.et_numara);
btn_data= (Button) findViewById(R.id.btn_veri);
btn_data.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
db.DataInsert(et_name.getText().toString(),et_surname.getText().toString(),et_number.getText().toString());
}
});
FYI
void onCreate (SQLiteDatabase db)
Called when the database is created for the first time.

Please tell me what is wrong in the piece of code written below

I have written a piece of code, which populates a database. However, when i execute that code in my android device or emulator, it gives an error "sorry app1 has stopped working" Please help me out to find out what's wrong.
the MainActivity.java file
package cu_coders.app1;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.common.api.GoogleApiClient;
public class MainActivity extends AppCompatActivity {
public final EditText e=(EditText)findViewById((R.id.text1));
public final file1 f=new file1();
TextView t=(TextView)findViewById(R.id.textView1);
final myDB x=new myDB(this, null, null, 1);
/**
* ATTENTION: This was auto-generated to implement the App Indexing API.
* See https://g.co/AppIndexing/AndroidStudio for more information.
*/
private GoogleApiClient client;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
Button enter=(Button)findViewById(R.id.button1);
Button delete=(Button)findViewById(R.id.button2);
enter.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String s = e.getText().toString();
f.set_name(s);
x.addItem(f);
t.setText(x.printTable());
}
});
}
}
A CLASS NAMED FILE1.JAVA
package cu_coders.app1;
/**
* Created by user pc on 03-10-2016.
*/
public class file1 {
private int _roll;
private String _name;
public file1() {
}
public file1(String _name) {
this._name = _name;
}
public int get_roll() {
return _roll;
}
public String get_name() {
return _name;
}
public void set_roll(int _roll) {
this._roll = _roll;
}
public void set_name(String _name) {
this._name = _name;
}
}
THE CLASS FOR DATABASE MANAGEMENT-- myDB.java
package cu_coders.app1;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
/**
* Created by user pc on 03-10-2016.
*/
public class myDB extends SQLiteOpenHelper {
private static int DATABASE_VERSION=1;
private static String DATABASE_NAME="file.db";
private static String TABLE_FILE1="class_cse";
public static String COLUMN_KEY="_key";
public static String COLUMN_NAME="_name";
public myDB(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_FILE1 + "(" +
COLUMN_KEY + " INTEGER PRIMARY KEY "+
COLUMN_NAME+" TEXT "+
");";
db.execSQL(query);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_FILE1+";");
onCreate(db);
}
public void addItem(file1 f){
ContentValues cv=new ContentValues();
cv.put(COLUMN_NAME,f.get_name());
SQLiteDatabase db=getWritableDatabase();
db.insert(TABLE_FILE1,null,cv);
db.close();
}
/*public void deletItem(String item){
SQLiteDatabase db=getWritableDatabase();
db.execSQL("DELETE FROM "+TABLE_FILE1+" WHERE "+COLUMN_NAME+" =\" "+ item +"\";");
db.close();
} */
public String printTable(){
String dbstring="";
SQLiteDatabase db=getWritableDatabase();
String query="SELECT * FROM "+TABLE_FILE1+" WHERE 1;";
Cursor c=db.rawQuery(query,null);
c.moveToFirst();
while(!c.moveToLast()){
if(c.getString(c.getColumnIndex(COLUMN_NAME))!=null) {
dbstring += c.getString(c.getColumnIndex(COLUMN_NAME));
dbstring += '\n';
}
}
db.close();
return dbstring;
}
}
please help me out to find out what is wrong. thank you in advance.

you should change several items i guess...
change myDB Constructor to this :
public myDB(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
and in mainActivity class change all global variable like this :
private EditText e ;
private file1 f ;
private TextView t;
and in oncreate() initial them :
e=(EditText)findViewById((R.id.text1));
f=new file1();
t=(TextView)findViewById(R.id.textView1);

sqLite Android..Unfortunately, applicaton has stopped

I am new to Android Programming.. I am trying to create sqLite Database in android Here is my code
sqLitee.java
package com.example.sqlite;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class sqLitee extends SQLiteOpenHelper
{
public static final String DB_NAME="student.db";
public static final String TABLE_NAME="student";
public static final String COL_1="ID";
public static final String COL_2="FIRST_NAME";
public static final String COL_3="LAST_NAME";
public static final String COL_4="MARKS";
public sqLitee(Context context)
{
super(context, DB_NAME,null, 1);
// TODO Auto-generated constructor stub
SQLiteDatabase db=this.getWritableDatabase();
}
#Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("CREATE TABLE " + TABLE_NAME + "(ID INTEGER PRIMARY KEY AUTO INCREMENT, FIRST_NAME TEXT, LAST_NAME TEXT, MARKS INTEGER)");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXIST " + TABLE_NAME);
onCreate(db);
}
}
MainActivity.java
package com.example.sqlite;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends Activity {
sqLitee myDB;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myDB = new sqLitee(this);
setContentView(R.layout.activity_main);
}
}
When I am trying to run it on Android virtual Device , It says unfortunately , sqLite has stopped..
Thanks

remove this line in your sqllite constructor:
SQLiteDatabase db=this.getWritableDatabase();
you try to get the db, which is currently initializing.

There's a syntax error in your CREATE TABLE SQL. AUTO INCREMENT should be AUTOINCREMENT.
As always, first see the logcat for exception stacktrace and to learn what is failing and where.

How can I operate SQLite when I use IntentService?

It seems that SQLiteOpenHelper need pass Context parameter when I create a object, so I pass PublicPar.myContext=getApplicationContext() in Main (extends Activity).
But in IntentService, there isn't UI, and there isn't Activity, maybe I can't use getApplicationContext(). How can I operate SQLite when I use IntentService?
public class Main extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
...
PublicPar.myContext=getApplicationContext();
RuleMain dBMainHelper=new RuleMain(PublicPar.myContext);
return dBMainHelper.ListAllRuleMain();
...
}
}
Helper:
package dal;
import java.util.ArrayList;
import java.util.List;
import model.MPublicPar.IncomingType;
import model.MRule;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class RuleMain extends SQLiteOpenHelper {
private final static String DBName="smsforwardrulemain.db";
private final static String TableRuleMain="rulemain";
public RuleMain(Context context) {
super(context, DBName, null, DBPublicPar.DBVersion);
}
#Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
String sql = "Create table "
+ TableRuleMain
+ " (ruleID INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,"
+ "enabled INTEGER NOT NULL,"
+ "incomingType INTEGER NOT NULL,"
+ "name TEXT NOT NULL"
+ ");";
db.execSQL(sql);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
String sql=" DROP TABLE IF EXISTS "+TableRuleMain;
db.execSQL(sql);
onCreate(db);
}
public List<MRule> ListAllRuleMain(){
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM "+TableRuleMain, null);
List<MRule> myRuleMainList=GetMRuleListFromCursor(cursor);
cursor.close();
db.close();
return myRuleMainList;
}
}