I need to ensure that the visible item of a list is the last. I was thinking about using ScrollTo from the LongListSelector (MessagesList.ScrollTo(VM.Messages.Last())) in the constructor of my view but the ViewModel property is not yet set. Is there another place( event) in the view cycle i can use to ensure that the item viewed is the last one ?
You can create your own ViewModel at any time in your code behind.
Inside MvvmCross, if you haven't already created one, then the framework itself will try to create one when MvxPhonePage.OnNavigatedTo is fired https://github.com/MvvmCross/MvvmCross/blob/v3.1/Cirrious/Cirrious.MvvmCross.WindowsPhone/Views/MvxPhonePage.cs#L43
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I have an array from ajax and i need to create jQuery Mobile Listview. I don't found a method for this, so is it possible?
Here's a working example: http://jsfiddle.net/Gajotres/SS7vJ/
And another example with an array: http://jsfiddle.net/Gajotres/yHHWQ/
$(document).on('pagebeforeshow', '#index', function(){
$('<ul>').attr({'id':'test-listview','data-role':'listview', 'data-filter':'true','data-filter-placeholder':'Search...'}).appendTo('#index [data-role="content"]');
$('<li>').append('Audi').appendTo('#test-listview');
$('<li>').append('Mercedes').appendTo('#test-listview');
$('<li>').append('Opel').appendTo('#test-listview');
$('#test-listview').listview().listview('refresh');
});
Also don't forget to call .listview( twice, first without refresh parameter, and second time with a refresh parameter. Without it you will receive this error:
cannot call methods on listview prior to initialization
If you want to find out more about how jQuery mobile handles dynamically added content and its markup take a look at this ARTICLE, to be transparent it is my personal blog, or find it HERE.
I'm using a custom item renderer in my datagrid, and need to make a button visible or invisible based on if there has been a negative value on any of the values in the renderer. So I'd like to set a flag to false when the first renderer is set off, turn it to true if there's any negative values, and at the end check for the value of the flag. I know I can dispatch a dataChange event for every time the data is changed in the renderer instances, but I was wondering if there is anyway I can know when all of them are done?
Thanks!
There is no such event.
Like any other Flex component, a renderer will dispatch a CREATION_COMPLETE after it's been created. ItemRenderers are generally recycled (the same object gets assigned new data to render), thus listening for CREATION_COMPLETE is not sufficient, unless you disable the recycling.
For a Spark List component, you can disable recycling by setting useVirtualLayout=false on the layout class. I'm not sure if the Spark DataGrid class support this or not. The MX DataGrid may have some other way to do this.
Disabling the recycling, however, can have performance implications. I think your idea w/the DATA_CHANGE event is the best solution:
determine the initial state of the data (ie: are there any negative values)
in the renderer, use the DATA_CHANGE event (or just override the setter for the renderer's data property) to know when the data has changed
When the data changes, dispatch a custom event class that will bubble. This event has a property that tells you if the value is negative or not.
Since your custom event from the renderers will bubble up to the grid, you can add one listener on the grid to handle changes from all the renderers.
You should have a look into RendererExistenceEvents. You should be able to tell when they are all created based on how many items you have in your list or at least how many should be in view at once.
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/spark/events/RendererExistenceEvent.html
I need to create a flex popup which would be a single instance but we can make it visible and invisible whenver we want to display it. I am not sure we can implement this kind of functionality using createPopup or addpopup method. Instance must be one and need to update it every time some event happen and make it visible or invisible.
thanks
createPopUp requires a class name. All the internals of creating the popup are in that method. You won't be able to use createPopUp with an existing instance of a window. However, when you call createPopUp, the results you get will be the instance of the new popup you just created.
However, addPopUp does accept an instance of an already creating component. You'll want to proceed in one of a few ways:
1) if the popup instance exists; use addPopUp; otherwise use createPopUp:
if(myPopUp){
PopUpManager.addPopUp(myPopUp, etc...)
} else {
myPopUp = PopUpManager.createPopUp(this, myPopUpClassName, etc..);
}
2) Create the popup yourself and always use addPopUp
if(!myPopUp){
myPopUp = new myPopUpClass();
}
PopUpManager.addPopUp(myPopUp, etc...);
Whenever you want to hide the pop up, do so using the removePopUp() method. This method will not destroy the pop up instance, just remove it from view.
PopUpManager.removePopUp(myPopUp);
You're going to have to figure out how to store the reference to your popup outside of the PopUpManager.
And I warn you that all the code I wrote here is psuedo code.
Since flex memory management is poor, objects once instantiated dont die very easily (even when they go out of scope), one would need to check on various properties of components. I am using one such thing to know if the screen (which is a display object) is in current view. For this I am turning on a boolean property (currently visible), and I am setting it true on show event of the display object.
What I need to know is, which event (something opposite of show, e.g left?) could be used when the screen is replaced by another display object?
Something like focusIn and focusOut from dotnet.
Or if there is some property which could directly tell me if the display object is currently in view (hasFocus doesnt seem to be giving me expected results).
Thanks.
You can Use PropertyChageEvent check the documentation and base of the newValue and kind property you can do some action :
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/mx/events/PropertyChangeEvent.html
hope this help
Name of the event is: removedFromStage.
I have two Spark Lists with custom Item Renderers. I'm working on an application that enables users to drag these Item Renderers from one List to the other. When one of these IRs is dropped in a new position or in another List, I'm updating the dataproviders: I remove the object from one list's dataprovider and add it to the other's dataprovider. This is working ok.
The problem is that sometimes the IR is cached and it doesn't show the correct information, based on its data.
How can I force the Lists to never cache IRs, so that every time I modify the dataprovider all Item Renders re-create all IRs. Performance won't be an issue since I have few items on each list.
A few things..
1) ItemRenderers should always be cached [and reused]. This is one of the benefits of using a Flex list in the first place. I suspect your itemRenderer is implemented inorrectly as to not change when it's data changes. If you share some code for this it would be helpful. But, basically, your itemRenderer should listen to the dataChange event and when the data changes you should update the component's visual display with new data.
2) In Flex 3, I'd have sworn that dragging an item from one list to another automatically updated the relevant dataProviders. Are you sure you need to write manual code to make those changes? You will, though, need code to update your backend as relevant.
Flextras has some good points, but to answer your specific question, you can set useVirtualLayout to false on Spark Lists. This will ensure there is a renderer for every item in your list and thus avoiding the recycling issues. You should really only do this when you have a relatively short list of items though, otherwise you will have performance issues, which as Flextras noted, is the reason Flex recycles renderers.
I put a reset method in my set data to assure renderer variables are reinitialized
override public function set data(object:Object):void
{
if (object == null)
{
return;
}
reset(); // reset locals to their base. ie. x=0, y=0, counter=0
// set up renderer using data
}