I am using a custom component at the top of my application that includes an image and a buttonBar. I have the namespace declared in main.mxml as comps and the package is components. When I assign the dataProvider to the buttonBar and run the application, all I get is a blank page. If I remove the dataProvider everything loads fine. the dataProvider is supposed to be the ViewStack component I have in the main.mxml. The buttonBar and image custom component is TopNav.mxml
The problem is that my TopNav component does not know the dataProvider I am asking it to change; MyViewStack. Do I need to create a public viewstack variable and pass it to the component?
Your application is probably throwing a runtime error. Do you have Flash Player debug installed? You can see it here: http://kb2.adobe.com/cps/155/tn_15507.html
If your application has a runtime error, it won't continue executing code. You probably have a null pointer somewhere.
Related
I have a flex 3 datagrid that is in a completely separate container from the object that I am trying to reference it from - i.e. the datagrid is in a vbox, and I am trying to set a property in the datagrid from a popup.
How do I access the datagrid from the popup?
I'd like to do something like:
myView.myDatagrid.resizableColumns = false;
Using cairngorm as a framework if that is of any help.
You'll have to explain your architecture better to get a specific answer. This answer may help as everything I said about running methods on another component, also applies to accessing properties.
One solution for you is to pass the DataGrid instance into the popup as an instance variable; then the PopUp will be able to change the DataGrid's properties easy.
When you add your popup, you need to listen for an event. Then your PopUp needs to dispatch an event that the parent can handle.
myPopup.addEventListener(SomeEvent.DISABLE_COLUMNS,disableResize);
and then in the parent component
public function disableResize(event:SomeEvent):void{
myDatagrid.resizableColumns = false;
}
This assumes a custom event called SomeEvent... you can actually just create a default Flash event and give it a name like
dispatchEvent(new Event("MyDisableResizeEvent"));
Assuming you've got a button in your popup:
<mx:Button click="{dispatchEvent(new Event('MyDisableResizeEvent'));}" label="Disable Resizing"/>
I am new to flex framework.
I have created an application using flex framework 4.1 which is having various components that are shown to the end user in the form of a popup window using <mx:TitleWindow>.
This titlewindow is closed either on the click of the close button (displayed in it's titlebar) or by pressing the "escape key" on the keyboard.
I coded a functionality wherein I close the current TitleWindow whenever an 'escape' button is pressed.
Here is what I did.
On the keydown event of TitleWindow I called this function
private function detectescapekeypress(event:KeyboardEvent):void
{
if(event.charCode == Keyboard.ESCAPE)
PopUpManager.removePopUp(this);
}
But this function does not work when I define it in the main home screen of my application and call it using parentApplication.detectescapekeypress(event) on the keydown event of TitleWindow
I had to repeat this code for every TitleWindow that I have used in the project.
How can I write the above functionality only once and reuse it amongst various TitleWindow and other components so that the code for the same is not repeated across various components?
Note: Every TitleWindow that I am using has different code, scripts and layout in it.
Thanks
Why don't u just extend the TitleWindow component and add that functionality to your new custom component? Then use it everywhere instead of the original TitleWindow.
I assume u're using at least SDK 4.1
Create a new mxml file called for example CustomTitleWindow.mxml and paste the following
http://www.copypastecode.com/68211/
Then change all your title windows to CustomTitleWindow.
P.S. Note that in order for the key event to be dispatched, the component must have focus.
blz
In short:
I need an event listener in a custom component so all its instances (without editing them) react at the same time, fired by a dispatched event in its parent container.
In detail:
I have a custom component with Tab navigator. (The tabs are intended to show different preferences for different Languages.)
I have a button bar with buttons for all the languages.
There are a lot of instances of the custom component.
I want to click in a button of the languages bar and get ALL the instances switched to the same tab (the custom component contains the logic to change the tab).
I can do it by adding the event listener for EACH INSTANCE of the custom component, so it calls an internal function that changes the tab. But it seems to be very coupled, isn't it?
I wonder if it can be done in the master CLASS of the component, so it listen for events in its parent container, whichever it is.
In my mind this code shoud work, but it doesn´t (obviously ill'use a custom event to pass the new language value):
this.parent.addEventListener("lang_change", this.change_tab);
This way I can just drop an instance of the component, and see it working for itself.
Thank you in advance
I need an event listener in a custom
component so all its instances
(without editing them) react at the
same time, fired by a dispatched event
in its parent container.
The very thing you want to do, by definition, breaks encapsulation. In an ideal world, a component should know nothing of it's parent. If the component needs to communicate with it's parent, it should dispatch an event. IF a parent needs to communicate to children it should call a public method on that child (or change a public property). From an encapsulation stand point, I cannot recommend that the child listen for events on the parent.
I want to click in a button of the
languages bar and get ALL the
instances switched to the same tab
(the custom component contains the
logic to change the tab).
So, then put a click handler for the button and do something like this:
public function onClick():void{
myCustomTabNavigator1.selectedIndex = 1
myCustomTabNavigator2.selectedIndex = 1
myCustomTabNavigator2.selectedIndex = 1
}
You can also set the selectedItem if you a reference to it. , If you have your custom TabNavigators in an Array, you can loop over them. IF the custom TabNavigators are child of your custom component you can create a method in that custom component to set the defaults and call that method on each component instead of setting selectedIndex directly.
I think you should to use some MVC model like:
Cairngorm
http://code.google.com/p/swizframework/
http://www.robotlegs.org/
http://puremvc.org/
Is it possible to destroy/close open item editor or item renderer of a datagrid in different mxml page?
I heard about the functions editedItemRenderer and destroyItemEditor on Datagrid. Can I use these functions in different mxml page?
Your question is a bit confusing.
Flex Applications do not have the concept of a page in the same way that HTML does. You probably mean different views, or MXML Components.
All itemEditors are created and destroyed as needed. If you are not viewing the itemEditor on screen, then likely something else has focus and the itemEditor was destroyed automatically.
In most cases, two components should not talk to each other using anything other than their defined API. so, you can have one component dispatch an event, then it's parent listen for the event and have that parent call methods on another component [such as a DataGrid].
I have two mxml files. one is main that is application tag mxml file and another is my mxml component file.
I have a viewstack in my main mxml whose id is, say, "mainViewStack".
Now I want to set selectedChild property of "mainViewStack" from my mxml component file.
But I m getting error:
Error #1009: Cannot access a property or method of a null object reference.
on accessing mainObj.mainViewStack.selectedChild.id where mainObj is the object of main mxml file.
Please help me out.
Thank u.
My guess is that you're trying to access the child before it's created. But that's hard to tell without the code.
Try waiting until the FlexEvent.CREATION_COMPLETE event on the application to access the selected child.
This issue is referred to as "deferred instantiation" and is a product of the Flex Component Lifecycle. If you want an extremely thorough explanation of this concept, this white paper is probably the best I have read.
Essentially Flex creates components as they are needed. Each component has a lifecycle that takes it through stages:
Construction
Addition
Initialization
Invalidation
Validation
Update
Removal
A sub-component isn't going to be accessible until it has passed through the initialization phase. This is the point at which a Flex component will dispatch its CREATION_COMPLETE event, letting you (and the framework) know that it is ready for interaction. Prior to this event, you are going to receive null reference errors when attempting to access the component or its children.
ViewStacks compound this by default by not initializing sub-components until they are called for display. The creationPolicy property of a ViewStack, by default, is set to auto. There are several options for this property, including all. Be aware, however, that this can potentially present severe performance issues, as all of the components inside the stack are going to be initialized immediately regardless of whether or not the user actually even looks at the component.
In your specific case this isn't the problem. The component that contains the view stack hasn't been completely initialized. You need to set the child of the ViewStack in a CREATION_COMPLETE event handler.
or you can give "creationPolicy=all" because Flex only creates the first visible child from the viewstack
You can use this code in your MXML component to change application's ViewStack selected child from other MXML component. However it is not a good practice.
FlexGlobals.topLevelApplication.mainViewStack.selectedChild = FlexGlobals.topLevelApplication.childId
You can use static event dispatcher to dispatch an event from one view and listen that event in an other view.