Issue with setting sqlite database
Question
I am new to android and tried to use open source project. The projects database is sqlite database. When I run project and checked, I saw there is no data in my android device monitor. Please someone check my codes if there are mistakes?
package com.andisofttechnology.myapplication;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.widget.Toast;
public class databaseHandler {
SQLiteDatabase database;
Activity activity;
public databaseHandler(Activity activity) {
this.activity = activity;
database = activity.openOrCreateDatabase("ASSIST", activity.MODE_PRIVATE, null);
createTable();
}
public void createTable()
{
try {
String qu = "CREATE TABLE IF NOT EXISTS STUDENT(name varchar(1000)," +
"cl varchar(100), " +
"regno varchar(100) primary key, contact varchar(100),roll integer);";
database.execSQL(qu);
}catch (Exception e)
{
Toast.makeText(activity,"Error Occured for create table",Toast.LENGTH_LONG).show();
}
try {
String qu = "CREATE TABLE IF NOT EXISTS ATTENDANCE(datex date," +
"hour int, " +
"register varchar(100) ,isPresent boolean);";
database.execSQL(qu);
}catch (Exception e)
{
Toast.makeText(activity,"Error Occured for create table",Toast.LENGTH_LONG).show();
}
try {
String qu = "CREATE TABLE IF NOT EXISTS NOTES(title varchar(100) not null," +
"body varchar(10000), cls varchar(1000), sub varchar(1000) ,datex TIMESTAMP default CURRENT_TIMESTAMP);";
database.execSQL(qu);
}catch (Exception e)
{
Toast.makeText(activity,"Error Occured for create table",Toast.LENGTH_LONG).show();
}
try {
String qu = "CREATE TABLE IF NOT EXISTS SCHEDULE(cl varchar(100),subject varchar(1000)," +
"timex time, day_week varchar(100));";
database.execSQL(qu);
}catch (Exception e)
{
Toast.makeText(activity,"Error Occured for create table",Toast.LENGTH_LONG).show();
}
}
public boolean execAction(String qu)
{
Log.i("databaseHandler", qu);
try {
database.execSQL(qu);
}catch (Exception e)
{
Log.e("databaseHandler", qu);
Toast.makeText(activity,"Error Occured for execAction",Toast.LENGTH_LONG).show();
return false;
}
return true;
}
Cursor execQuery(String qu)
{
try {
return database.rawQuery(qu,null);
}catch (Exception e)
{
Log.e("databaseHandler", qu);
// Toast.makeText(activity,"Error Occured for execAction",Toast.LENGTH_LONG).show();
}
return null;
}
}
Student_registration.class
package com.andisofttechnology.myapplication;
import android.app.Activity;
import android.app.AlertDialog;
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.ImageView;
import android.widget.Spinner;
import android.widget.Toast;
/*import java.util.ArrayList;*/
public class Student_Registartion extends AppCompatActivity {
private EditText name,register,contact;
Activity activity = this;
Spinner spinner;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_student__registartion);
spinner = (Spinner) findViewById(R.id.spinner);
/* ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, AppBase.divisions);
spinner.setAdapter(adapter);*/
Button btn = (Button) findViewById(R.id.btnSave);
assert btn != null;
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
saveToDatabase(v);
}
});
}
public void saveToDatabase(View view) {
EditText name = (EditText)findViewById(R.id.name);
EditText roll = (EditText)findViewById(R.id.roll);
EditText register = (EditText)findViewById(R.id.register);
EditText contact = (EditText)findViewById(R.id.contact);
String classSelected = spinner.getSelectedItem().toString();
if(name.getText().length()<2||roll.getText().length()==0||register.getText().length()<2||
contact.getText().length()<2||classSelected.length()<2)
{
AlertDialog.Builder alert = new AlertDialog.Builder(activity);
alert.setTitle("Invalid");
alert.setMessage("Insufficient Data");
alert.setPositiveButton("OK", null);
alert.show();
return;
}
String qu = "INSERT INTO STUDENT VALUES('" +name.getText().toString()+ "'," +
"'" + classSelected +"',"+
"'" + register.getText().toString().toUpperCase() +"',"+
"'" + contact.getText().toString() +"',"+
"" + Integer.parseInt(roll.getText().toString()) +");";
Log.d("Student Reg" , qu);
AppBase.handler.execAction(qu);
qu = "SELECT * FROM STUDENT WHERE regno = '" + register.getText().toString() + "';";
Log.d("Student Reg" , qu);
if(AppBase.handler.execQuery(qu)!=null)
{
Toast.makeText(getBaseContext(),"Student Added", Toast.LENGTH_LONG).show();
this.finish();
}
}
}
......................................................................
Log Cat
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.andisofttechnology.myapplication, PID: 32163
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at com.andisofttechnology.myapplication.Student_Registartion.saveToDatabase(Student_Registartion.java:48)
at com.andisofttechnology.myapplication.Student_Registartion$1.onClick(Student_Registartion.java:37)
at android.view.View.performClick(View.java:6294)
at android.view.View$PerformClick.run(View.java:24770)
at android.os.Handler.handleCallback(Handler.java:790)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
2 answers
solution1
0 2018-09-18 12:21:47
Do FindViewById in OnCreate Method thats what it creating a NullPointException
See the snippet below hope will resolve that issue
public class Student_Registartion extends AppCompatActivity { private EditText name,roll,register,contact; Activity activity = this; Spinner spinner; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_student__registartion); name = (EditText)findViewById(R.id.name); roll = (EditText)findViewById(R.id.roll); register = (EditText)findViewById(R.id.register); contact = (EditText)findViewById(R.id.contact); spinner = (Spinner) findViewById(R.id.spinner); /* ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, AppBase.divisions); spinner.setAdapter(adapter);*/ Button btn = (Button) findViewById(R.id.btnSave); assert btn != null; btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { saveToDatabase(v); } }); } public void saveToDatabase(View view) { String classSelected = spinner.getSelectedItem().toString(); if(name.getText().length()<2||roll.getText().length()==0||register.getText().length()<2|| contact.getText().length()<2||classSelected.length()<2) { AlertDialog.Builder alert = new AlertDialog.Builder(activity); alert.setTitle("Invalid"); alert.setMessage("Insufficient Data"); alert.setPositiveButton("OK", null); alert.show(); return; } String qu = "INSERT INTO STUDENT VALUES('" +name.getText().toString()+ "'," + "'" + classSelected +"',"+ "'" + register.getText().toString().toUpperCase() +"',"+ "'" + contact.getText().toString() +"',"+ "" + Integer.parseInt(roll.getText().toString()) +");"; Log.d("Student Reg" , qu); AppBase.handler.execAction(qu); qu = "SELECT * FROM STUDENT WHERE regno = '" + register.getText().toString() + "';"; Log.d("Student Reg" , qu); if(AppBase.handler.execQuery(qu)!=null) { Toast.makeText(getBaseContext(),"Student Added", Toast.LENGTH_LONG).show(); this.finish(); } } }
solution2
0 2018-09-18 20:55:07
You have a number of issues, all basically the same, that is incorrect/no instantiation of objects.
The following code works and has been checked. The corrections are commented with //<<<<<<<<<< .
Note that for testing an additional line has been added to provide a value for the spinner and that the line that attempts to get the value from the spinner has been commented out.
No changes have been made to databaseHandler.java
Student_Registartion.java :-
public class Student_Registartion extends AppCompatActivity {
private EditText name,roll,register,contact; //<<<<<<<<<< ADDED roll
databaseHandler handler; //<<<<<<<<<< ADDED (used instead of AppBase.handler)
Activity activity = this;
Spinner spinner;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_student__registartion);
//<<<<<<<<<< ADDED BLOCK
name = this.findViewById(R.id.name);
roll = this.findViewById(R.id.roll);
register = this.findViewById(R.id.register);
contact = this.findViewById(R.id.contact);
//<<<<<<<<<< END OF ADDED BLOCK
handler = new databaseHandler(this); //<<<<<<<<<< ADDED
spinner = (Spinner) findViewById(R.id.spinner);
/* ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, AppBase.divisions);
spinner.setAdapter(adapter);*/
Button btn = (Button) findViewById(R.id.btnSave);
assert btn != null;
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
saveToDatabase(v);
}
});
}
public void saveToDatabase(View view) {
//<<<<<<<<<<< REMOVED BLOCK
EditText name = (EditText)findViewById(R.id.name);
EditText roll = (EditText)findViewById(R.id.roll);
EditText register = (EditText)findViewById(R.id.register);
EditText contact = (EditText)findViewById(R.id.contact);
//<<<<<<<<<<< END OF REMOVED BLOCK
//String classSelected = spinner.getSelectedItem().toString(); //<<<<<<<<<< commeneted out
String classSelected = "MyCLass"; //<<<<<<<<<< Temporary get around for no spinner data
if(name.getText().length()<2||roll.getText().length()==0||register.getText().length()<2||
contact.getText().length()<2||classSelected.length()<2)
{
AlertDialog.Builder alert = new AlertDialog.Builder(activity);
alert.setTitle("Invalid");
alert.setMessage("Insufficient Data");
alert.setPositiveButton("OK", null);
alert.show();
return;
}
String qu = "INSERT INTO STUDENT VALUES('" +name.getText().toString()+ "'," +
"'" + classSelected +"',"+
"'" + register.getText().toString().toUpperCase() +"',"+
"'" + contact.getText().toString() +"',"+
"" + Integer.parseInt(roll.getText().toString()) +");";
Log.d("Student Reg" , qu);
handler.execAction(qu); //<<<<<<<<<< changed
qu = "SELECT * FROM STUDENT WHERE regno = '" + register.getText().toString() + "';";
Log.d("Student Reg" , qu);
if(handler.execQuery(qu)!=null) //<<<<<<<<< changed
{
Toast.makeText(getBaseContext(),"Student Added", Toast.LENGTH_LONG).show();
this.finish();
}
}
}
Testing Results
Here's the log from a run that successfully adds data (Toasts Error Occured for execAction for a duplicate, Toasts Student Added and displays dialog when no data is input) :-
09-18 20:45:23.160 1379-1379/so52386209.so52386209 D/Student Reg: INSERT INTO STUDENT VALUES('harold','MyCLass','BLAH','blah',54321);
09-18 20:45:23.160 1379-1379/so52386209.so52386209 I/databaseHandler: INSERT INTO STUDENT VALUES('harold','MyCLass','BLAH','blah',54321);
09-18 20:45:23.160 1379-1379/so52386209.so52386209 E/databaseHandler: INSERT INTO STUDENT VALUES('harold','MyCLass','BLAH','blah',54321);
09-18 20:45:23.164 1379-1379/so52386209.so52386209 D/Student Reg: SELECT * FROM STUDENT WHERE regno = 'blah';
09-18 20:45:23.212 1379-1379/so52386209.so52386209 W/IInputConnectionWrapper: showStatusIcon on inactive InputConnection
09-18 20:45:23.680 1379-1379/so52386209.so52386209 D/OpenGLRenderer: TextureCache::flush: target size: 2284
TextureCache::callback: name, removed size, mSize = 57, 1728, 2080
09-18 20:49:49.900 1379-1379/so52386209.so52386209 W/EGL_genymotion: eglSurfaceAttrib not implemented
09-18 20:49:49.916 1379-1379/so52386209.so52386209 D/OpenGLRenderer: TextureCache::get: create texture(0xb8f77208): name, size, mSize = 158, 1728, 3808
09-18 20:49:58.896 1379-1382/so52386209.so52386209 D/dalvikvm: GC_CONCURRENT freed 223K, 9% free 6603K/7239K, paused 10ms+0ms, total 14ms
09-18 20:50:24.516 1379-1379/so52386209.so52386209 D/Student Reg: INSERT INTO STUDENT VALUES('ian','MyCLass','77889900','something',12345);
09-18 20:50:24.516 1379-1379/so52386209.so52386209 I/databaseHandler: INSERT INTO STUDENT VALUES('ian','MyCLass','77889900','something',12345);
09-18 20:50:24.520 1379-1379/so52386209.so52386209 D/Student Reg: SELECT * FROM STUDENT WHERE regno = '77889900';
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.
Related Question
Setting up sqlite database
Database issue with SQLite
SQLite database connection issue
SQLite Database issue in TextView
Android SQLite database query issue
SQLite Database issue not inserting data in the database
Setting initial column value in SQLite database to 0
Data Retrieval issue from sqlite database in Android
Sqlite Database locked issue using threading : Android
Android - SQLite issue with adding more tables to database
Related Tags