Hi guys, I am having some trouble today with my app, I am very new to android and java and am having some trouble. When ever I try to run my app I get a nullPointerException. I have read up on them online but having a little trouble finding it in my code. I would be very great full if someone code help!
This is my main activity code where i am getting the error
package com.example.rory.dbtest;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.os.Handler;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
import com.pinchtapzoom.R;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
public class MyActivity extends Activity {
private CustomCursorAdapter customAdapter;
private com.example.rory.dbtest.DBAdapter databaseHelper;
public ListView list1;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
list1 = (ListView)findViewById(R.id.data_list);
Button addBtn = (Button)findViewById(R.id.add);
addBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent(MyActivity.this, addassignment.class);
startActivity(i);
}
});
Button deleteBtn = (Button)findViewById(R.id.delete);
deleteBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent(MyActivity.this, Delete.class);
startActivity(i);
}
});
Button updateBtn = (Button)findViewById(R.id.update);
updateBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent(MyActivity.this, Update.class);
startActivity(i);
}
});
try {
String destPath = "/data/data/" + getPackageName() + "/databases/AssignmentDB";
File f = new File(destPath);
if (!f.exists()) {
CopyDB( getBaseContext().getAssets().open("mydb"),
new FileOutputStream(destPath));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
new Handler().post(new Runnable() {
@Override
public void run() {
databaseHelper.open();
customAdapter = new CustomCursorAdapter(MyActivity.this, databaseHelper.getAllRecords());
list1.setAdapter(customAdapter);
}
});
/*
new android.os.Handler().post(new Runnable() {
@Override
public void run() {
customAdapter = new CustomCursorAdapter(MyActivity.this, db.getAllRecords());
list1.setAdapter(customAdapter);
}
});
*/
/*
ArrayList<String> data_list=new ArrayList<String>();
ListView lv=(ListView)findViewById(R.id.listView1);
Cursor c = db.getAllRecords();
if (c.moveToFirst())
{
do {
data_list.add(c.getString(2));
//data_list.add(c.getString(1));
//DisplayRecord(c);
} while (c.moveToNext());
}
ArrayAdapter<String> aa=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, data_list);
lv.setAdapter(aa);
*/
}
private class DBAdapter extends BaseAdapter {
private LayoutInflater mInflater;
//private ArrayList<>
@Override
public int getCount() {
return 0;
}
@Override
public Object getItem(int arg0) {
return null;
}
@Override
public long getItemId(int arg0) {
return 0;
}
@Override
public View getView(int arg0, View arg1, ViewGroup arg2) {
return null;
}
}
public void CopyDB(InputStream inputStream, OutputStream outputStream)
throws IOException {
//---copy 1K bytes at a time---
byte[] buffer = new byte[1024];
int length;
while ((length = inputStream.read(buffer)) > 0) {
outputStream.write(buffer, 0, length);
}
inputStream.close();
outputStream.close();
}
public void DisplayRecord(Cursor c)
{
Toast.makeText(this,
"id: " + c.getString(0) + "\n" +
"Item: " + c.getString(1) + "\n" +
"Litres: " + c.getString(2),
Toast.LENGTH_SHORT).show();
}
}
This is the Database class that i am using
package com.example.rory.dbtest;
/**
* Created by Rory on 02/11/2014.
*/
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_ITEM = "item";
public static final String KEY_LITRES = "litres";
private static final String TAG = "DBAdapter";
private static final String DATABASE_NAME = "DripDrop";
private static final String DATABASE_TABLE = "assignments";
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_CREATE =
"create table if not exists assignments (id integer primary key autoincrement, "
+ "item VARCHAR not null, litres 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)
{
try {
db.execSQL(DATABASE_CREATE);
} catch (SQLException e) {
e.printStackTrace();
}
}
@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");
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 item, String litres)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_ITEM, item);
initialValues.put(KEY_LITRES, litres);
return db.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---
public Cursor getAllRecords()
{
return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_ITEM,
KEY_LITRES}, null, null, null, null, null);
}
//---retrieves a particular record---
public Cursor getRecord(long rowId) throws SQLException
{
Cursor mCursor =
db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
KEY_ITEM, KEY_LITRES},
KEY_ROWID + "=" + rowId, null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//---updates a record---
public boolean updateRecord(String item, String litres)
{
db.execSQL("UPDATE "+DATABASE_TABLE+" SET "+KEY_LITRES+"='"+litres+"' WHERE "+KEY_ITEM+"='"+item+"'");
return true;
}
/*
public boolean updateRecord(String item, String litres)
{
ContentValues args = new ContentValues();
args.put(KEY_ITEM, item);
args.put(KEY_LITRES, litres);
return db.update(DATABASE_TABLE, args, KEY_ITEM+ "=" + item, null) > 0;
}
*/
}