#4 Adding double click event to v2 list, tree, and datagrid

[Carlos Rovira]

http://www.darronschall.com/weblog/archives/000135.cfm

The v2 list-based components don't have an event for
letting a user double click a row in the list. That's
changed as of today.

Consider the following code snippet:

------------------

// Double-Click Hack for List-based components
// Nov. 15, 2004 - Darron Schall

// create quick reference to ScrollSelectList's prototype
var sslp =
_global.mx.controls.listclasses.ScrollSelectList.prototype;

// only run this code once.., make sure that
$oldOnRowPress is not
// defined to avoid inifinite recursion when onRowPress
is called
if (!sslp.$oldOnRowPress) {
sslp.DOUBLE_CLICK_INTERVAL = 300; // in
milliseconds, how close two clicks must
// be received to register as a double click

// save a reference to the onRowPress function since
we need to overwrite it to add
// functionality, and we don't want to lose the original.
sslp.$oldOnRowPress = sslp.onRowPress;

// add doubleClick event to the ScrollSelectList class
sslp.onRowPress = function(rowIndex) {
// if the user pressed the samw row within the time
limit, fire off
if (getTimer() - this.lastPressedTime <
this.DOUBLE_CLICK_INTERVAL && this.lastPressedRow ==
rowIndex) {

this.dispatchEvent({target:this,type:"doubleClick",row:rowIndex});
} else {
// not a double click - record their click time
and the row selected to prepare
// for double click

// only allow double clicks under the proper
conditions
if (this.enabled && this.selectable) {
this.lastPressedTime = getTimer();
this.lastPressedRow = rowIndex;
} else {
// not really necessary, but just in case..
make sure
// doubleClick doesn't accidentally fire
this.lastPressedTime = 0;
this.lastPressedRow = -1;
}

// invoke the old method that we just overwrote -
using apply to get the scope correct
this.$oldOnRowPress.apply(this, [rowIndex]);
}
};
}
delete sslp;

-------------

The basic premise is that when an item is clicked in a
list-based component, the onRowPress method is called
(see SelectableRow.as). The onRowPress method is
defined in ScrollSelectList and is in charge of
determining if a row can be selected, then firing off
the change event as necessary (which is done in selectRow).

In order to add the double click event, we replace the
onRowPress in ScrollSelectList with one that times
press events. If the same row was pressed 2 times
within a certain interval, we can fire off the double
click event. We also make sure to call the original
onRowPress (that we saved in $oldOnRowPress) in order
to keep current functionality working.

In order for this to work, place the above code snippet
on a frame after the export frame for the classes in
your movie. The code modifes the ScrollSelectList class
at runtime, so ScrollSelectList must be loaded before
this code executes. Typically, you can just drag a list
on the stage and place this code in frame 1 since the
default export for classes is before frame 1.

Then, you can listen for a new event - "doubleClick" -
from List, Tree, and DataGrid components. Anything that
inherits from ScrollSelectList now has a doubleClick
event. Sample usage is as follows:

------------

// drag v2 list component onto stage and name it "list"
// place above code on frame 1 followed by below code:
list.dataProvider =
[{label:"test"},{label:"test2"},{label:"test3"}];
list.addEventListener("doubleClick",
mx.utils.Delegate.create(this, onItemSelected));
function onItemSelected(eventObj) {
// do something with the selected item
trace("double click");
}

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Yup, this is a hack.. As always, your mileage may vary.

Good luck, and enjoy!