I'm using Javascript to dynamically create a QML component via:
var component = Qt.createComponent(qmlURL)
var item = component.createObject(parentLayout, properties)
In this case, the parentLayout is a ColumnLayout and it always creates the object at the end of the children list (which means it is displayed at the bottom of the column).
How can I specify the index position within the children of where the object is placed, or how can I move it in the children list post instantiation?
(I tried assigning parentLayout.children[i] to no avail)
Use case: I have a large existing multi-level (nested) Menu system that is static, but I'd like insert and remove custom submenu items in the hierarchy in response to external plugins registering/unregistering via a service API. While we could completely re-implement the menu system as a dynamic treeview, that seems overkill just to insert a couple menu subitems dynamically.
Related
Why in JavaFX some controls and layout has "children" property, when other has "items" property for essentailly same purpose? Is there any philosophy behind or may be some technical difference?
The getChildren() method is defined in Parent, and consequently inherited by all subclasses of Parent, including Pane, and Control. The implementation of this method in Parent returns an unmodifiable list of child nodes (so it can be used for navigation through the scene graph, but cannot be used to manipulate what is contained in the parent).
The Pane class, and its subclasses, are designed to allow you to lay out other nodes in the scene graph. So Pane overrides getChildren() to return a modifiable list of these nodes: essentially the functionality of a Pane is to allow you to add nodes to it and remove them later if you need. The Pane subclasses position these nodes in various ways.
The Control class is a subclass of Parent, as controls contain other nodes. (E.g. a ComboBox contains a label or text field (if it's editable), and a button for displaying the drop down list.) Control inherits its getChildren() method from Parent, so it returns an unmodifiable list of the child nodes, but doesn't allow you to change that list (because if you removed nodes from a control, it would no longer behave in the way that control was designed to behave).
Some controls are designed to display other content. Trivially, a Label or Button can have a graphic, which is any node. The API for these classes allows you to change that node (via setGraphic()).
More complex controls allow you to add and remove a collection of nodes, as part of their intended functionality. So for example a SplitPane allows you to add as many nodes as you like, and remove them if you need. However, these are not the only nodes contained in the SplitPane. So the getChildren() method still has its implementation from the superclass: it returns an unmodifiable list of all the child nodes of the split pane: that includes the items you add, and the dividers (and potentially other things too). On the other hand, the getItems() method returns the list of nodes that you are allowed to change: so you can remove an item by calling splitPane.getItems().remove(...) (and the split pane will remove the corresponding divider from its child list as well).
Other complex controls have getItems() methods that might return specific types: e.g. Menu.getItems() returns an ObservableList<MenuItem> (so you can't put a TableView in a menu, you can only put menu items in there). Similarly TabPane.getItems() returns an ObservableList<Tab>.
So in short, the two things have completely different functionality. getChildren() returns the list of child nodes for the parent: it allows you to inspect and navigate the scene graph. Parent subclasses that specifically choose to do so may return a modifiable list, allowing you to use them as general containers.
The getItems() methods that some Control classes define are there to define specific functionality of that particular control. They still have getChildren() methods, which will return a different list.
Hy!
I'm building a top view 2D map, that it's objects are stored on the server.
The kind of objects are 10 and might be a photo, label, button, lists, mix of them or labels with tooltips.
The component must request the "areas" that are missing on screen.
An area is 1000x1000 px and is cached in flex.
To move in the map, will be like in google maps (drag-and-drop)
I should be able to have another list and move objects from one to another using drag-an-drop on objects. Ex.: I grab an objects from a list and I move it on this map, I release the mouse button and the item is placed there.
Now the problem is: I build a custom component for this trying to emulate the item renderer for performance and recyclage, implement drag-and-drop on objects and request the areas that are missing?
or
I extend the List component from spark and I add some features as multiple kind of itemrenderers and use recycle on them. Of course it must be able to request the missing areas on the screen and cache it's data.
Maybe create a custom layout is needed too.
What I need is something that must be really fluid, so the lighter this component is, the better!
Thanks for your help! (:
UPDATE:
*There will be not any object over another.
*I will not use hitTest on bitmaps because all bitmaps are wrapped in another component,as they,for now are itemrenderers.
Anyway I already begin to do this using a class that extends the SkinnableDataContainer and a custom layout. As the layout is not like a grid, is sparse, random items at diferent points(x, y).
Now I have this problem: https://stackoverflow.com/questions/4192934/how-to-get-the-localx-and-localy-relative-to-item-renderer-and-not-to-the-spark
Maybe you could use a combination of some of the following:
A canvas background (for layered components), looks fluid if using hitTest. Split up the canvas using constraintColumn/constraintRow for a grid layout.
Use hitTest (on items bitmapdata) for collision detection, and move the items to a new position (if items are dropped on top of one another).
Use a combo of mouseDown, mouseMove, mouseUP (example here) for drag n drop.
Use a 2D/3D indexed array to track the position of items (example here)
I have created a custom item renderer for the tree, i have added some children in create children function, my problem is that sometimes i need to show these children and sometimes i don't, depending on clicking on a button which also i have added at create children, the problem is that i had to create the item even if i don't want it to be visible, and removed it by making visible false, and this costs a lot of memory, i have tried to create it at buttons click listener but when scrolling the child disappears, and it may appear again if i keep scrolling up and down..
i am trying to add the child just when i need it to be visible, is this possible or i have to create it on child creation method?
Typically you do something like this with states. This way the components within the container (in this case your item renderer) are only created when the container enters the given state. The nice thing about taking this approach is that you can remain oblivious to when components need to be created/removed and let the states model handle that for you. Hope that helps.
I am using a ContextMenu for an AdvancedDataGrid in my application. I could implement the normal context menu for the grid. Now, I am planning to make the context menu dynamic.
For example, if I click on a particular cell, I need to see only the items related to that cell in the Context Menu. Is there any way we can do that?
ContextMenu class contains a customItems property which is (quoting from Adobe livedocs):
An array of ContextMenuItem objects. Each object in the array represents a context menu item that you have defined. Use this property to add, remove, or modify these custom menu items.
To add new menu items, you create a ContextMenuItem object and then add it to the customItems array (for example, by using Array.push()). For more information about creating menu items, see the ContextMenuItem class entry.
I found the solution for this. Quite simple:
http://www.pubbs.net/flex/200905/73331/
I have a flex application that has three tabs. Each of these tabs has a component that loads a ‘form’ that has a dropdown combo box. These combo boxes depend on external data in order to populate correctly. Currently the first tab is being created and the data that should be populated in the combo box is not in there. The combo box for the second tab is populated with the required data.
What I’d like to do is create an event that is dispatched after the data is loaded. When this event happens I’d like to then create these tabs, or the components of the tabs. Is there a way to wait for the data to be loaded before the application creates the components?
You could create the components in actionscript.
this code will create a ComboBox:
var newBox = new ComboBox();
newBox.dataProvider = aDataProvider;
// You could alternativley use (v/h)box.addChild(newBox)
// to add it as a child of a specific element
Application.application.addChild(newBox);
You can use that sort of technique to create the components in actionscript, you will still need to set all the properties that are usually set in mxml, but they all have the same names.