Author: greg

Xpath alternate row colors
This XPath expression will let you alternate row colors
```
Alternate Rows

	ROW A Color

	ROW B Color
```
Example

I will provide complete example soon.
September 15, 2009

Scrolling div on Android in webview

Problem

Simple thing as scrolling a div with overflow:auto is currently not possible on the Android platform.
Due to my application requirement I really needed this functionality so here is what I come up with

Challenges

Currently when we call node.offsetHeight we will not get the full height of the div only the content visible
to fix that I change the positioning to absolute and height 100% to get the true height of the div.

Android project with scrollable div can be download here

Code

Code consist of three parts

CSS
JavaScript
HTML markup

 /**
		 * WebKit Div Scroller class
		 * @author:Greg Bugaj
		 * Initial release
		 */
		 //Namespace
		var GB=GB || {};
		GB.Scroller=
		{
			SCROLL_INREMENT:5,//Amount to scroll per update
			SCROLL_TIME:75,//Time between update Intervals in  MS	
			
			getElementsByClassName:function(classname, node)  {
				if (!node) {
					node = document.getElementsByTagName('BODY')[0];
				}
				var a = [];
				var re = new RegExp('\\b' + classname + '\\b');
				var els = node.getElementsByTagName("*");
				for(var i=0,j=els.length; i=  contentHeight)){
							cancelTimer=true;
						}
						if(cancelTimer){
							clearInterval(iTimer);
							return;
						}						
						t+=GB.Scroller.SCROLL_INREMENT*direction;
						scroller.style.top=t+"px";				
					};
					
					
					//Attach events to navigation 
					var tapUP = GB.Scroller.getElementsByClassName("scroll_up", scroller_container);
					if(tapUP==null){
						alert("There is no DIV with class 'scroll_up'");
					}
					tapUP=tapUP[0];//There should be only 1 element in the array
					
					var tapDOWN = GB.Scroller.getElementsByClassName("scroll_down", scroller_container);
					if(tapDOWN==null){
						alert("There is no DIV with class 'scroll_down'");
					}
					tapDOWN=tapDOWN[0];//There should be only 1 element in the array
					
						
					tapUP.addEventListener('touchstart', function(e){
						iTimer=setInterval(function(){ scrollContent(e, -1);}, GB.Scroller.SCROLL_TIME);
					}, false);
					
					tapUP.addEventListener('touchend', function(e){
						clearInterval(iTimer);
					}, false);
					
					tapDOWN.addEventListener('touchstart', function(e){
							iTimer=setInterval(function(){scrollContent(e, 1);}, GB.Scroller.SCROLL_TIME);
					}, false);
					
					tapDOWN.addEventListener('touchend', function(e){
						clearInterval(iTimer);
					}, false);
					
				}//for
			}//function
		};
		
		//Initialize all the scrollable components on the page
		window.addEventListener('load', function(){ GB.Scroller.init(); }, true);

   
         
            Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Donec dapibus ipsum in nulla rhoncus a blandit enim lobortis. Mauris scelerisque justo eu purus molestie ut sodales diam laoreet. Integer id volutpat urna. Sed lacinia risus id magna pharetra scelerisque. Proin venenatis blandit sapien vitae pulvinar. Nulla et urna in erat venenatis posuere eu id ipsum. Proin magna mi, congue ultrices malesuada id, sollicitudin a urna. Praesent id lorem leo. Phasellus vestibulum dapibus mattis. Fusce et faucibus risus.  
     Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Donec dapibus ipsum in nulla rhoncus a blandit enim lobortis. Mauris scelerisque justo eu purus molestie ut sodales diam laoreet. Integer id volutpat urna. Sed lacinia risus id magna pharetra scelerisque. Proin venenatis blandit sapien vitae pulvinar. Nulla et urna in erat venenatis posuere eu id ipsum. Proin magna mi, congue ultrices malesuada id, sollicitudin a urna. Praesent id lorem leo. Phasellus vestibulum dapibus mattis. Fusce et faucibus risus.

Feature request/updates

I will add features as I need them or upon request.

August 13, 2009

Android ImpulseShopper released
About

ImpulseShopper(pre-beta) is application that lets you monitor your favorite daily deals websites like woot.com, 1saleaday.com, dailysteals.com etc…
Includes both widget and full blown application.
- Engine based
- Filters
- Product thumbnails
- Share via SMS, Email, Twitter
- Notifications
- Deployed on Google AppEngine
Screenshots

[nggallery id=7]
August 12, 2009

HashTable implemented using quadratic probing for collision resolution

Using quadratic probing for collision resolution

#define ERROR_TABLE_FULL       -1
#define ERROR_RECORD_NOT_FOUND -1
#define ERROR_DUPLICATE_RECORD -1

class HashTable{
public:
	HashTable(int table_size);
	int insert(const string &record);
	int retrieve(const string &record);
private:
	int hash(const string &record);
	int hash_size;
	int record_count;
	string* table;
};

/**
 * Constructor accepting table_size
 */
HashTable::HashTable(int table_size){
	hash_size = table_size;
	table = new string[hash_size];
	record_count = 0;
}
/**
 * Hash function calculated using
 * product p of all the characters of the key
 * and then returns the index where index=s%hash_size
 */
int HashTable::hash(const string &key) {
	int value = 1;
	for (int position = 0; position < max_key_length; position++){
		if(key[position] == 0){
			break;
		}
		value *= key[position];
	}
	value %= hash_size;
	if (value < 0){
		value += hash_size;
	}
	return value;
}
/**
 * Insert new record
 * Collision function uses h+i^2
 *
 */
int HashTable::insert(const string &record){
	if(record_count == hash_size){
		return ERROR_TABLE_FULL;
	}

	int hash_key = hash(record);
	int increment = 1;

	int probe_counter=0;
	int hash_mid=(hash_size+1)/2;

	while(1){
		//Check for overflow
		if(probe_counter > hash_mid){
			return ERROR_RECORD_NOT_FOUND;
		}
		string tmp = table[hash_key];
		//Empty slot
		if(tmp.empty()){
			break;
		}//Position already taken, duplicate keys are not allowed
		else if(tmp.compare(record) == 0) {
			return ERROR_DUPLICATE_RECORD;
		}
		else{
			//Handles collision using h+i^2
			hash_key = (hash_key+increment) % hash_size;
			increment+=2;
			probe_counter++;
		}
	}
	table[hash_key] = record;
	record_count++;
	return hash_key;

}
/**
 * Retrieve record index
 */
int HashTable::retrieve(const string &record){
	int hash_key = hash(record);
	int increment = 1;

	int probe_counter=0;
	int hash_mid=(hash_size+1)/2;

	while(1){
		//Overflow encountered if the probe is bigger than hash_size/2
		if(probe_counter > hash_mid){
			return ERROR_RECORD_NOT_FOUND;
		}
		string tmp = table[hash_key];
		//Record empty for the key
		if(tmp.empty()) {
			break;
		}
		else if(tmp.compare(record) == 0){
			return hash_key;
		}
		else{
			hash_key = (hash_key+increment) % hash_size;
			increment+=2;
			probe_counter++;
		}
	}
	return ERROR_RECORD_NOT_FOUND;
}

July 14, 2009

HashTable implemented using linear probing for collision resolution

Using linear probing for collision resolution in hashtable


#define ERROR_TABLE_FULL       -1
#define ERROR_RECORD_NOT_FOUND -1
#define ERROR_DUPLICATE_RECORD -1

class HashTable{
public:
	HashTable(int table_size);
	int insert(const string &record);
	int retrieve(const string &record);

private:
	int hash(const string &record);
	int hash_size;
	int record_count;
	string* table;
};

/**
 * Constructor accepting table_size
 */
HashTable::HashTable(int table_size){
	hash_size = table_size;
	table = new string[hash_size];
	record_count = 0;
}

/**
 * Hash function calculated using
 * product p of all the characters of the key
 * and then returns the index where index=s%hash_size
 */
int HashTable::hash(const string &record) {
	int value = 1;
	for (int position = 0; position < max_key_length; position++){
		if(record[position] == 0){
			break;
		}
		value *= record[position];
	}
	value %= hash_size;
	if (value < 0){
		value += hash_size;
	}
	return value;
}

/**
 * Insert new record into out table, making sure that the table is not full
 */
int HashTable::insert(const string &record){
	//Check if HashTable is full if it is then return overflow
	if(record_count == hash_size){
		return ERROR_TABLE_FULL;
	}
	int hash_key = hash(record);
	while(1){
		string tmp = table[hash_key];
		//Check if table bucket is empty
		if(tmp.empty()) {
			break;
		}//Position already taken, duplicate keys are not allowed 0 = equal
		else if(tmp.compare(record) == 0) {
			return ERROR_DUPLICATE_RECORD;
		}
		//Collision detected multiple records mapped to same location
		//Try next bucket
		else {
			hash_key = (hash_key+1) % hash_size;
		}
	}
	table[hash_key] = record;
	record_count++;

	return hash_key;
}

/**
 * Retrieve record index
 */
int HashTable::retrieve(const string &record){
	int hash_key = hash(record);
	while(1){
		string tmp = table[hash_key];
		//Record empty for the key
		if(tmp.empty()){
			break;
		}//if entry found return index
		else if(tmp.compare(record) == 0) {
			return hash_key;
		}
		else { //Resolving collision using linear probing
			hash_key = (hash_key+1) % hash_size;
		}
	}

	//No record Found
	return ERROR_RECORD_NOT_FOUND;
}

July 14, 2009

Quicksort implementation using Linked List

About QuickSort

Wikipedia QuickSort definition.

General idea revolves around partitioning a list where values less than pivot go into left list while greater than go into right list.
Pivot here is the first item of the passed in list. We apply this recursively to the sublists them merge left+pivot+right.

CPP Code

First of all not a cpp developer so if you can improve this them post a comment with suggestions.


template 
Node * List::quick_sort_recursive(Node* list)
{
	//Base case : list  is NULL
	if(list ==  NULL){
		return NULL;
	}

	//We choose first entry in the list as the pivot node
	Node * pivotNode = new Node();
	pivotNode->entry=list->entry;
	Record pivot = pivotNode->entry;

	Node *tmp=list->next;
	Node *leftHead=NULL;
	Node *rightHead=NULL;

	Node *leftTail=NULL;
	Node *rightTail=NULL;

	//Partition the list into left/right sublists
	while(tmp != NULL){
		Node *entryNode=new Node();
		entryNode->entry = tmp->entry;
		entryNode->next = NULL;
		if(tmp->entry < pivot){
			if(leftTail == NULL){
				leftTail = entryNode;
				leftHead=entryNode;
			}else{
				leftTail->next=entryNode;
				leftTail=leftTail->next;
			}
		}
		else{
			if(rightTail == NULL){
				rightTail = entryNode;
				rightHead=entryNode;
			}else{
				rightTail->next=entryNode;
				rightTail=rightTail->next;
			}
		}
		tmp = tmp->next;
	}

	//Recursively subdivide the left / right list
	leftHead  = quick_sort_recursive(leftHead);
	rightHead = quick_sort_recursive(rightHead);

	//Combine left+pivot+right
	Node * mergedHead=NULL;
	Node * mergedTail=NULL;

	Node *tmpNode=leftHead;
	while(tmpNode){
		Node *new_node=new Node();
		new_node->entry=tmpNode->entry;
		if(mergedTail == NULL){
			mergedTail = new_node;
			mergedHead= new_node;
		}else{
			mergedTail->next= new_node;
			mergedTail=mergedTail->next;
		}
		tmpNode=tmpNode->next;
	}
	//Pivot point
	if(mergedTail == NULL){
		mergedTail = pivotNode;
		mergedHead = pivotNode;
	}else{
		mergedTail->next=pivotNode;
		mergedTail=mergedTail->next;
	}
	//Right sublist
	tmpNode=rightHead;
	while(tmpNode){
		Node *new_node=new Node();
		new_node->entry=tmpNode->entry;
		mergedTail->next=new_node;
		mergedTail=mergedTail->next;
		tmpNode=tmpNode->next;
	}

	return mergedHead;
}



template 
struct Node {
//  data members
   Node_entry entry;
   Node *next;
//  constructors
   Node();
   Node(Node_entry, Node *link = NULL);
};

July 9, 2009

Android Daily Deals Agent – ImpulseShopper
Update : Beta released

First beta have been unlished on the Android Marketplace. So far so good, some one reported that the program crashes(unknown cause)

Overview

This is idea for my Daily deals agent that will monitor certain sites for daily deals.

Current sites to consider
- Woot.com – woot | shirt | wine | sellout
- 1saleaday.com – wireless, watches
Simple yet powerful enough to help me keep tabs on sweet deals.

Screenshots

[nggallery id=7]
July 1, 2009

Level order traversal – Breadth-first

Here is implementation of level order traversal of a binary tree.

Level order traversal is nothing more than traversing each level at a time

           10              Lev 1
          /   \
        9     15          Lev  2
      /      /   \ 
    7      12    17      Lev 3

Output

10 9 15 7 12 17

AVL Tree example

++++++++++++++++++++++
69:  29  77 
29:  15  48 
15:  5  23 
5:  3  11 
11:  -  14 
23:  16  26 
16:  -  18 
48:  33  64 
33:  32  46 
64:  50  68 
77:  72  84 
72:  71  76 
84:  80  89 
80:  79  82 
89:  87  93 
++++++++++++++++++++++

The level order result is:
++++++++++++++++++++++
69 29 77 15 48 72 84 5 23 33 64 71 76 80 89 3 11 16 26 32 46 50 68 79 82 87 93 14 18 
++++++++++++++++++++++

Implementation

/**
 * Implementation of Level order traversal
 * Prints nodes at each level left to right
 */
template 
void AVL_tree::level_order() {
	cout << "++++++++++++++++++++++" << endl;
	if(this->root == NULL){
		cout << "EMPTY TREE" << endl;
	}else{
		cout << endl;
		queue*> nodeQueu;
		nodeQueu.push(this->root);
		while(!nodeQueu.empty()){
			Binary_node* entry=nodeQueu.front();
			cout<data<<" ";
			if(entry->left != NULL){
				nodeQueu.push(entry->left);
			}
			if(entry->right != NULL){
				nodeQueu.push(entry->right);
			}
			nodeQueu.pop();
		}
	}
	cout << "\n++++++++++++++++++++++" << endl;
}

Complexity

Running time complexity of this algorithm is O(n) since every node will have to be explored

June 30, 2009

Display all managed-beans in JSF at runtime

Sometimes we like to see whats going on under the hood of jsf application (Checkout my JSFConsole). One such task is being able to display all the registered managed-beans during runtime.
Here we can see all registered beans, including implicit object(cookie,header,param etc…)

Result

     a4j
     a4jSkin
     ajaxContext
     ajaxHandler
     application
     applicationScope
     beeHive       --- My Managed bean
     cookie
     facesContext
     header
     headerValues
     initParam
     param
     paramValues
     request
     requestScope
     richSkin
     session
     sessionScope
     view

Source

/**
	 * Retrieve all registered beans for given {@link ScopeType}
	 * @param scopeType to search in
	 * @return List of beanNames
	 */
	public static List getRegisteredBeans(ScopeType scopeType){
		FacesContext facesContext=FacesContext.getCurrentInstance();
		ApplicationAssociate application = ApplicationAssociate.getInstance(facesContext.getExternalContext());
		BeanManager  beanManager = application.getBeanManager();
		Map beanMap=beanManager.getRegisteredBeans();
		Set>beanEntries=beanMap.entrySet();
		List registeredBeans=new ArrayList();
		for(Entry bean:beanEntries){
			String beanName=bean.getKey();
			if(!beanManager.isManaged(beanName)){
				continue;
			}			
			BeanBuilder builder=bean.getValue();
			Scope bScope=builder.getScope();
			if(scopeType==ScopeType.ALL || bScope.toString().equals(scopeType.toString())){
				registeredBeans.add(beanName+":"+bScope.toString());
			}
		}

		if(scopeType==ScopeType.ALL || scopeType==ScopeType.IMPLICIT){
			List implicitList=getProperties(new ImplicitObjectELResolver(), null);
			for(String implicitBeanName:implicitList){
				registeredBeans.add(implicitBeanName+":"+ScopeType.IMPLICIT.toString());
			}
		}

		Collections.sort(registeredBeans);
		return registeredBeans;
	}

ScopeType is nothing more than an emun wrapper


/**
 * Scope type with additional properties for all/implicit
 * @author devil
 *
 */
public enum ScopeType {
	//Really not a scope but a marker
	ALL("all"),
	IMPLICIT("implicit"),
	
	REQUEST("request"),
	SESSION("session"),
	APPLICATION("application");

	String scope;
	ScopeType(String scope) {
		this.scope = scope;
	}

	public String toString() {
		return scope;
	}

	
	/**
	 * Get Enum from value
	 * @param name
	 * @return
	 */
	public static ScopeType fromValue(String name) {
		name=name!=null?name.toUpperCase():"";
		for(ScopeType v:values()){
			if(v.name().equals(name)){
				return v;
			}
		}
		//By default return all scoped objects
		return ScopeType.ALL;
	}
}

June 18, 2009

TabWidget demo project

Sorry it took little longer than expected, run in some issues with cupcake (SDK 1.5)
I have attached a Demo project for all interested with some screenshots and modified .project for TabWidget Project(fixes cupcake problem ref http://groups.google.com/group/android-developers/browse_thread/thread/5537ae10e4143240) if you use eclipse.

1. My env:
Eclipse Version: 3.4.2
Android SDK 1.5
Windows

2.After you import the TabWidgedDemo project you will probably need to fix your buildpath.
Make sure to add TabWidet as a reference to TabWidgedDemo.

3.In TabWidged project you will need to update the .project file otherwise you will get Verify error when deploying to the device.

If you have any questions let me know, I hope you enjoy the project, more improvements to come

Download tabwidgetdemo for eclipse

June 18, 2009

Author: greg

Example

I will provide complete example soon.