I have a Parent / Child relation as follows and I use C# and db4o for persistence.
class Parent{
List<Child> children = new List<Child>();
}
class Child{
Parent parent;
}
It takes long time to retrieve objects of type Child.
Is there something I missed?
I don't know the graph your data encode. But it look like your are loading the complet / large portion of the graph for each object.
Without special configuration Db4o load all the objects that have a relation with the object that is load.
If you want lazy loading you should look at the transparent activation. It require a litte more of configuration.
Related
Right now , my development of app is in the optimizing stage. I have a problem when adding one of my components: PlayerInfo, which is extended from Group and has some Labels and Images in it,I have to create 60 of this component and put'm all into a HGroup. But in the process of adding them into the hgroup, my app just stops responding for a few seconds,which is not tolerable. Can I achieve this with less memory usage?
I have read this page and thought if I can do it with any of my components,not only bitmaps.does anyone know how to do that?
here is how I did it:
class PlayerInfo extends Group{
private var name:Label;
private var age:Label;
private var photo:Image;
}
and in my list class:
public function addPlayers(arrPlayer:Array):void{
for(;;){
var player:PlayerInfo=new PlayerInfo();
HGroup.addElement(player);
}
}
Can I achieve this with less memory usage?
Yes! With your current approach; if you have 60 instances of your component, then the app creates 60 instances of the component, renders them all and puts them on the screen; even if they are not currently a view area.
You should make use of a class, such as a List or DataGroup, as #RiaStar suggests. Your custom component, PlayerInfo, should be used as the itemRenderer and the 'list' you are creating these components from should become the List's dataProvider.
Once you do this, then your app will make use of the List's renderer recycling. So, only the visual elements displayed on screen will be displayed to the user. So, if you have 10 items shown on screen from your list of 60; the app will generate 50 less an items. This will make better use of processing power and better use of device memory.
To change your class to a renderer, you will have to implement a dataChange() event handler so that the component updates whenever the list changes the data that the renderer should display.
I don't think we enough information to get a more detailed explanation. What is your dataProvider? What propeties need to be set on your custom component?
I currently use: Flexglobals.toplevelapplication.component1.compnent2.currentState = 'something';
is there a better way of doing do? Can I bind the state of a components to variable in my model?
Ideally, components should be self contained little pieces of your application. One component shouldn't have any effect (including changing the state) on any component, except possibly it's children.
The "Encapsulation proper" approach to change the state of an unrelated component is to dispatch an event from the component. The component's parent (or some component higher up in the hierarchy chain) is going to execute an event listener and change that state of the appropriate component, by either calling a method on the component that needs a state change or changing a property on the component that needs a state change.
If you have a complicated hierarchy, this approach can lead to a lot of tedium, creating events up the chain, and creating properties / methods down the chain in order to preserve encapsulation. Some frameworks, such as Cairngorm introduce a global singleton to avoid this tedium. In Cairngorm that singleton is the ModelLocator.
The ModeLlocator is, basically, a global dependency in your application. You can give any component access to it, and through the use of binding if a property is changed in one place, it an be automatically updated elsewhere. To change the state using binding, use an approach like this:
In the ModelLocator, create a variable to hold the state for the view in question:
[Bindable]
public var comp1State : String = 'defaultState';
In comp1 do something like this:
<mx:Container currentState="{model.comp1State}" otherComponentProperties>
<!-- other component code including defining the states -->
</mx:Container>
Then in the component where you want to change the state, do something like this:
model.comp1State = 'nextState'
Binding will take it from here. I wouldn't use his approach lightly though. It depends on the component you're trying to create and how much you car about reuse. The most common way I've seen this implemented is not with states, but with the selectedIndex in a ViewStack. But, the approach would be the same.
Yes. I usually bind the sate of my component to a property in my model.
As long as you are making the properties on your model bindable you should be able to bind
directly to you model in your view. You sitl have to set the state in you model. Id look into using a framework like [swiz][http://swizframework.org/] or or mate.
I am trying to create an application that dumps all processes and their children controls to a text file. I used EnumChildWindow but it visits all children including children's childdren. I can't create hierarchy using this method.
Is there another way of doing this?
Thanks
You should instead use FindWindowEx() and specify NULL for the hwndChildAfter parameter.
This will enumerate all direct descendant child windows.
I am adding DisplayObjects to a Canvas using
ContentContainer.addChild(c);
Where ContentContainer is my Canvas object and c is the DisplayObject I have created at run-time
Some of these DisplayObjects also have children of there own which are added at run-time prior to the DisplayObject being added to the Canvas
I then need to iterate over all the children of ContentContainer but the first time I do this, it says that ContentContainer has no children (ie, ContentContainer.numChildren = 0). If I do it again tho then it is fine and returns the correct number of children.
Is there something I need to call to get ContentContainer to recalculate how many children it has?
As Michael noted it would be helpful to see the code but you might want to look into the Event overview and About the creation policy sections in the docs - http://livedocs.adobe.com/flex/3/html/help.html?content=containers_intro_3.html
Specifically the childAdd event might be what you want to listen for before you iterate over it:
add Dispatched by a component after the component has been added to its container and the parent and the child are in a consistent state. This event is dispatched after the container has dispatched the childAdd event and all changes that need to be made as result of the addition have happened.
=Ryan
ryan#adobe.com
I did a similar task with a callLater in order to wait till after a dragdrop completed before recalculating some tasks. This might work for you.
public function myFunct():void{
//do your adding
callLater(
function():void{
//do your loop
}
)
}
I have a TitleWindow mxml class wich has several components, and listeners.
On its creationComplete and init state i add some listeners which listen for events on its gui.
This TitleWindow is only shown when the user click on a "button", i made TitleWindow a singleton with the following code:
public static function getInstance():MyWindow
{
if ( MyWindow.singleton )
{
return MyWindow.singleton;
}
else{
MyWindow.singleton = new MyWindow();
return MyWindow.singleton;
}
}
I needed a singleton because the user will call this window several times as much as he wants and i only need one.
The problem is the following on some special external events i need to "modify" some listeners (remove listeners and add new ones) on a button from MyWindow, before it was even shown once.
I still have MyWindow.getInstance() in memory when my application starts up.
However adding /removing listeners does not seem to have any effect if he actual rendering of the components did not happen, event when using the following code on app startup.
myWindow= MyWindow.getInstance();
myWindow.initialize();
Not suprisingly if i "show" ('render') the myWindow at least once then the events modifications on the myWindow instance works perfectly.
How can i fake the complete initialisation of this component without showing it on startup ?
Thanks !
Which sort of a container holds your button? If you are using a Multiple View Container you can try setting the creationPolicy to all. Single View Containers create all their children in one go and you shouldn't face this problem.
From Flex 3.0 docs I could retrieve this:
The default creation policy for all containers, except the Application container, is the policy of the parent container. The default policy for the Application container is auto.
This looks like the cause for all your troubles.
Update: I did not mention this earlier, since I thought this was to be expected :) Setting the creationPolicy to all makes your application load more slowly. So, read up on Ordered Creation -- this technique helps you to choose if the controls are displayed all in one go (which is the default behavior, after all of the controls have been created) or step-by-step, as and when they are created.