Introduction:Sometime back I visited a website that had the drag and drop shopping cart feature. Users can simply drag and drop the items they wish to buy in the basket and the basket is updated with the new results. I was extremely impressed with this feature and decided to create a small application that does the same. In this article I will implement a page which enables the users to drag and drop the items they wish to buy into the shopping basket. The shopping basket items and the price will be updated. The code presented in this article is browser compatible. Note: Before reading this article I highly recommend reading the article Drag and Drop Using JavaScript. The Database Design:I used SQL SERVER 2005 Express to create a simple database called "ToyShopDatabase". The database contains a single table "tblToys" which contains four columns.
I have populated the database with some dummy data. Let's see how we can display the data on the page. Displaying Data on the Page:I have used private void BindData()
{
string connectionString = ConfigurationManager.ConnectionStrings _
["ConnectionString"].ConnectionString;
SqlConnection myConnection = new SqlConnection(connectionString);
SqlDataAdapter ad = new SqlDataAdapter("SELECT * FROM tblToys",_
myConnection);
DataSet ds = new DataSet();
ad.Fill(ds);
dlToys.DataSource = ds;
dlToys.DataBind();
}
You can see the items displayed on the page in the screen shot below:
You can also see the shopping cart displayed on the left side of the screen. The shopping cart displays $0.00 since there are no products added to the cart. The interesting thing is the HTML code for the <asp:DataList Height="100%" Width="100%" ID="dlToys" runat="server"
RepeatColumns="3" CellPadding="20" CellSpacing="20">
<ItemTemplate>
<div ID="a" runat = "server" class="dragElement">
<asp:Label ID="lblTitle" runat=
"server" Text='<%# Eval("Title") %>' />
<asp:Label ID="lblPrice" runat="server" Text =
'<%# Eval("Price") %>' />
<asp:Image ID="imgPicture" runat="server" ImageUrl=
'<%# Eval("ImageUrl") %>' />
</div>
</ItemTemplate>
</asp:DataList>
As you can see in the code above I have added a <DIV> element inside the
Making Elements Dragable:At this point we know that our DIV elements will serve as the dragable objects. But there can be several DIV controls on the page which will not be a part of this drag and drop feature. We will use regular expression to filter the correct DIV elements. <script>
var dragElementPattern = ".+_a$";
var divElements = document.getElementsByTagName("div");
for(i=0;i<divElements.length;i++)
{
if(IsMatch(divElements[i].id, dragElementPattern))
{
MakeElementDraggable(divElements[i]);
}
}
</script>
First, I retrieve all the DIV elements on the page and then find the correct ones using the regular expression. The function IsMatch(id, pattern)
{
var regularExpresssion = new RegExp(pattern);
if(id.match(regularExpresssion)) return true;
else return false;
}
Dragging the Cloned Element:Cloning the drag element is necessary to get the correct effect. If you don't clone the element then you will be moving the actual element itself which looks kinda weird. Take a look at the screen-shot where I have moved the actual element without cloning.
And here is the effect when the clone is created.
Here is the code that initiates the drag and creates the clone. function InitiateDrag(e)
{
mouseState = 'down';
var evt = e || window.event;
startX = parseInt(evt.clientX);
startY = parseInt(evt.clientY);
clone = obj.cloneNode(true);
clone.style.position = 'absolute';
clone.style.top = parseInt(startY) + 'px';
clone.style.left = parseInt(startX) + 'px';
document.body.appendChild(clone);
document.onmousemove = Drag;
document.onmouseup = Drop;
return false;
}
Dropping the Element in the Drop Zone:I had some hard time creating a browser-compatible drop zone event. The Drop is only successful when the product is dropped inside the drop zone. In my article, "Drag and Drop Using JavaScript", I used the parent approach where I found the element based on the mouse position. But unfortunately, that approach was not browser compatible. The approach that is discussed here is browser compatible and it based on the mouse position and the drop zone position on the page. Take a look at the diagram below which explains how to get the drop zone position.
And here is the code for dropping the product in the drop zone: function Drop(e)
{
var evt = e || window.event;
var evtTarget = evt.target || evt.srcElement;
var dZone = document.getElementById("dZone");
if( evt.clientX > dZone.offsetLeft &&
evt.clientX < (dZone.offsetLeft + dZone.offsetWidth) &&
evt.clientY > dZone.offsetTop &&
evt.clientY < (dZone.offsetTop + dZone.offsetHeight))
{
AddPrice();
}
document.onmouseup = null;
document.onmousemove = null;
document.body.removeChild(clone);
mouseState = 'up';
ResetColor();
}
If the product is not inside the drop zone then the product just disappears. However, if the product is inside then it is added to the shopping cart. Adding the Product to the Shopping Cart:The  Collapsefunction AddPrice()
{
var title = GetProductTitle();
var price = GetProductPrice();
var dZone = document.getElementById("dZone");
var textNode = document.createTextNode(title);
var priceNode = document.createTextNode(price);
var spaceNode = document.createTextNode(': $');
var paragraphElement = document.createElement('p');
// create the delete button
var deleteButton = document.createElement('button');
deleteButton.value = 'Delete';
deleteButton.innerHTML = 'Delete';
deleteButton.onclick = DeleteItem;
var item = document.createElement('div');
item.id = 'itemDiv' + uniqueNumber;
item.appendChild(paragraphElement);
item.appendChild(textNode);
item.appendChild(spaceNode);
item.appendChild(priceNode);
item.appendChild(spaceNode);
item.appendChild(deleteButton);
dZone.appendChild(item);
// increment the price
IncrementTotal(price);
uniqueNumber++;
}
Check out the image below which display two products added to the shopping cart.
Deleting the Item from the Shopping Cart:Once the product is added to the shopping cart it is displayed with the delete button. The delete button is used to remove the product from the shopping cart and adjust the total balance. function DeleteItem(e)
{
var evt = e || window.event;
var evtTarget = evt.target || evt.srcElement;
if(IsFireFox())
{
price = evtTarget.parentNode.childNodes[2].nodeValue;
evtTarget.parentNode.parentNode.removeChild(evtTarget.parentNode);
}
else
{
price = evtTarget.parentElement.childNodes[2].nodeValue;
evtTarget.parentElement.parentElement.removeChild(
evtTarget.parentElement);
}
DecrementTotal(price);
}
Since the code to access the child nodes is different for different browsers I have created an Improvements:Several places I have used constant indexes to locate the items inside the container. This should be replaced by dynamic access of items. I have included: a checkout feature, the ability to select multiple items, the ability to view the image of the product inside the shopping cart. Recommended Reading:Conclusion:In this article we learned how to create dragable objects and drop them in the shopping cart. I hope you liked the article, happy coding! About azamsharp |
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来自： thy > 《asp.net1》
