Preeyah Preeyah - 29 days ago 4
Android Question

Issues with opening activity due to database

I'm having problems with my application.It seem that I can't open my

Activity
as well as I can't insert data from a
ListView
into database.

But, I can open
Activity
and insert data into database before I've created 5 tables into one
DBAdapter
class.

But after I've created the tables in one
DBAdapter
, I'm having problems with making my application work. I've followed examples which made my application work.

This is my LogCat:

08-21 13:36:27.421: D/AndroidRuntime(543): Shutting down VM
08-21 13:36:27.421: W/dalvikvm(543): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
08-21 13:36:27.441: E/AndroidRuntime(543): FATAL EXCEPTION: main
08-21 13:36:27.441: E/AndroidRuntime(543): java.lang.RuntimeException: Unable to start activity ComponentInfo{main.page/main.page.PersonalInformation}: java.lang.NullPointerException
08-21 13:36:27.441: E/AndroidRuntime(543): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
08-21 13:36:27.441: E/AndroidRuntime(543): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
08-21 13:36:27.441: E/AndroidRuntime(543): at android.app.ActivityThread.access$600(ActivityThread.java:123)
08-21 13:36:27.441: E/AndroidRuntime(543): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
08-21 13:36:27.441: E/AndroidRuntime(543): at android.os.Handler.dispatchMessage(Handler.java:99)
08-21 13:36:27.441: E/AndroidRuntime(543): at android.os.Looper.loop(Looper.java:137)
08-21 13:36:27.441: E/AndroidRuntime(543): at android.app.ActivityThread.main(ActivityThread.java:4424)
08-21 13:36:27.441: E/AndroidRuntime(543): at java.lang.reflect.Method.invokeNative(Native Method)
08-21 13:36:27.441: E/AndroidRuntime(543): at java.lang.reflect.Method.invoke(Method.java:511)
08-21 13:36:27.441: E/AndroidRuntime(543): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
08-21 13:36:27.441: E/AndroidRuntime(543): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
08-21 13:36:27.441: E/AndroidRuntime(543): at dalvik.system.NativeStart.main(Native Method)
08-21 13:36:27.441: E/AndroidRuntime(543): Caused by: java.lang.NullPointerException
08-21 13:36:27.441: E/AndroidRuntime(543): at main.page.BuddyDBAdapter.getAllNames(BuddyDBAdapter.java:37)
08-21 13:36:27.441: E/AndroidRuntime(543): at main.page.PersonalInformation.onCreate(PersonalInformation.java:41)
08-21 13:36:27.441: E/AndroidRuntime(543): at android.app.Activity.performCreate(Activity.java:4465)
08-21 13:36:27.441: E/AndroidRuntime(543): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
08-21 13:36:27.441: E/AndroidRuntime(543): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
08-21 13:36:27.441: E/AndroidRuntime(543): ... 11 more
08-21 13:36:27.711: I/dalvikvm(543): threadid=3: reacting to signal 3
08-21 13:36:27.751: I/dalvikvm(543): Wrote stack traces to '/data/anr/traces.txt'
08-21 13:36:28.061: I/dalvikvm(543): threadid=3: reacting to signal 3
08-21 13:36:28.061: I/dalvikvm(543): Wrote stack traces to '/data/anr/traces.txt'


This is the code where I've created the 5 tables within one
DBAdapter
:

package main.page;


import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class AnniversaryDBAdapter
{

private static final String DATABASE_NAME = "AllTables";
private static final int DATABASE_VERSION = 2;

private static final String CREATE_TABLE_TITLE = "create table titles(title_id integer primary key autoincrement, name text not null, image text not null);";
private static final String CREATE_TABLE_BUDDIESLIST = "create table buddiesList(name_id integer primary key autoincrement, name text not null);";
private static final String CREATE_TABLE_LIKES = "create table likes(likes_id integer primary key autoincrement,like text not null, name text not null, FOREIGN KEY(name)REFERENCES "+CREATE_TABLE_BUDDIESLIST+" (name));";
private static final String CREATE_TABLE_DISLIKES = "create table dislike(dlike_id integer primary key autoincrement, dislike text not null, name text not null, FOREIGN KEY(name)REFERENCES "+CREATE_TABLE_BUDDIESLIST+" (name));";
private static final String CREATE_TABLE_EVENTS = "create table events(date_id integer primary key autoincrement, date text not null, starttime text not null, endtime text not null, name text not null,title_id integer, desc text not null, alarm text not null, location text not null, FOREIGN KEY(name)REFERENCES "+CREATE_TABLE_BUDDIESLIST+" (name), FOREIGN KEY(title_id)REFERENCES "+CREATE_TABLE_TITLE+" (title_id));";

private final Context context;
private static final String TAG = "DBAdapter";

private DatabaseHelper DBHelper;
private SQLiteDatabase db;

public AnniversaryDBAdapter(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(CREATE_TABLE_BUDDIESLIST);
db.execSQL(CREATE_TABLE_LIKES);
db.execSQL(CREATE_TABLE_EVENTS);
db.execSQL(CREATE_TABLE_TITLE);
db.execSQL(CREATE_TABLE_DISLIKES);

}

@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");

onCreate(db);

}

}


public AnniversaryDBAdapter open() throws SQLException
{
this.db = this.DBHelper.getWritableDatabase();
return this;
}

public void close()
{
this.DBHelper.close();
}

}


I've followed from these 2 examples


1. http://www.devdaily.com/android/sqlite-foreign-keys-example


2. http://androidforbeginners.blogspot.sg/2010/01/creating-multiple-sqlite-database.html

This is my code which I can't open in my application:

package main.page;

import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.SimpleCursorAdapter;
import android.widget.Spinner;
import android.widget.Toast;

public class PersonalInformation extends Activity
{
Button btnSave, btnBack, btnView;
EditText txtDate, txtType, txtLikes, txtDislikes;

final Context context = this;
private int mSpinnerNamesId;

LikesDBAdapter likeDB = new LikesDBAdapter(this);
DislikesDBAdapter dislikeDB = new DislikesDBAdapter(this);


@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.info);


BuddyDBAdapter buddyDB = new BuddyDBAdapter(this);

buddyDB.open();

Spinner namesSpinner = (Spinner) findViewById(R.id.nameSpinner);
Cursor namesCursor = buddyDB.getAllNames();
startManagingCursor(namesCursor);

String[] from = new String[] {BuddyDBAdapter.KEY_NAME};
int[] to = new int[] {android.R.id.text1};

SimpleCursorAdapter namesSpinnerAdapter = new SimpleCursorAdapter(this, android.R.layout.simple_spinner_item, namesCursor, from, to);
namesSpinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
namesSpinner.setAdapter(namesSpinnerAdapter);
buddyDB.close();

namesSpinner.setOnItemSelectedListener(new OnItemSelectedListener()
{
@Override
public void onItemSelected(AdapterView<?> parent, View view, int pos, long id)
{
Cursor c = (Cursor)parent.getItemAtPosition(pos);
mSpinnerNamesId = c.getInt(c.getColumnIndexOrThrow(BuddyDBAdapter.KEY_ROWID));
}

@Override
public void onNothingSelected(AdapterView<?> parent)
{
}
});


btnSave = (Button) findViewById(R.id.btnSave);
btnSave.setOnClickListener(new View.OnClickListener()
{

@Override
public void onClick(View v)
{
likeDB.open();
long likes_id;
Spinner nameSpinner = (Spinner) findViewById(R.id.nameSpinner);
String NameValue = nameSpinner.getSelectedItem().toString();

EditText txtLikes = (EditText) findViewById(R.id.txtLikes);
String LikesValue = txtLikes.getText().toString();

likes_id = likeDB.insertLikes(NameValue, LikesValue);
likeDB.close();

dislikeDB.open();
long dislikes_id;
Spinner names = (Spinner) findViewById(R.id.nameSpinner);
String NamesValue = names.getSelectedItem().toString();

EditText txtDislikes = (EditText) findViewById(R.id.txtDislikes);
String DislikesValue = txtDislikes.getText().toString();

dislikes_id = dislikeDB.insertDislikes(NamesValue, DislikesValue);

Toast.makeText(getBaseContext(),
"Your information is saved successfully!", Toast.LENGTH_SHORT).show();
dislikeDB.close();
}
});

btnBack = (Button) findViewById(R.id.btnMain);
btnBack.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
finish();
}
});

}
}


This is BuddyDBAdapter.java which connects to PersonalInformation.java

package main.page;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;

public class BuddyDBAdapter extends AnniversaryDBAdapter
{
public static final String KEY_ROWID = "name_id";
public static final String KEY_NAME = "name";
private static final String TAG = "DBAdapter";
private static final String CREATE_TABLE_BUDDIESLIST = "buddiesList";

private SQLiteDatabase db;

public BuddyDBAdapter(Context ctx)
{
super(ctx);
}

public long insertNames(String name)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_NAME, name);
return db.insert(CREATE_TABLE_BUDDIESLIST, null, initialValues);
}

public boolean deleteName(long rowId)
{
return db.delete(CREATE_TABLE_BUDDIESLIST, KEY_ROWID + "=" + rowId, null) > 0;
}

public Cursor getAllNames()
{
return db.query(CREATE_TABLE_BUDDIESLIST, new String[] { KEY_ROWID, KEY_NAME }, null, null, null, null, null);
}

public Cursor getName(long rowId) throws SQLException
{
Cursor c = db.query(true, CREATE_TABLE_BUDDIESLIST, new String[] { KEY_ROWID, KEY_NAME }, KEY_ROWID + "=" + rowId, null, null, null, null, null);
if(c != null)
{
c.moveToFirst();
}
return c;
}
}


Any help will be appreciated.

Answer

Your BuddyDBAdapter class is not using the DatabaseHelper class like your base class. In that DatabaseHelper class, you are actually creating and opening the database.

In BuddyDBAdapter, db has not been initialized and is throwing the exception. Modify this class to use the functionality written in the base class.

Hope this helps...