I added exception handling for the pages, now I want to do it for the panels.
I found http://apache-wicket.1842946.n4.nabble.com/ExceptionHandling-in-Panels-td3311271.html and http://apache-wicket.1842946.n4.nabble.com/newbie-best-practice-for-not-rendering-component-td1871632.html, but the answers are not satisfying as I realized that there is no built-in support in Wicket for exception handling for panels as there is for pages. And choosing between a fragment with the panel markup and an error fragment is not the robust support I'm looking for.
Since most of the exceptions in my web app can rise in the section of the logic where the components are added and models are used, I thought of placing that part of the logic in the constructor, so when an error occurs, I could catch it and then show the error panel I want. Something like:
try{
add(new MyPanel(panelId, model));
}catch (Exception e){
add(new ErrorPanel(panelId, e));
...
}
But I get warnings when resolving properties in the constructor by using the getString() method.
So, my questions are:
- Is there any online example where this has been solved? Or any idea about that?
- If using the getString() in the constructor throws that type of warnings, what would the best practice then?
- I I can't place that logic in the constructor, because you are not supposed to resolve properties there, what options are there besides the one I mentioned?
As with most logic in panels, the constructor isn't the best place. During construction-time, the panel (or any other component) isn't yet attaced to a page. That leaves the component in a fragile state where some components don't even have any markup.
More complex logic should be placed outside of the constructor. Wicket 1.5 offers an onInitialRender method that can be overridden where one can safely put any logic. In Wicket 1.4.x there is an easy way to simulate that hook by implementing onBeforeRender as
#Override
protected void onBeforeRender() {
if (!hasBeenRendered()) {
onInitialRender();
}
super.onBeforeRender();
}
thus creating an onInitialRender-hook that's only executed once and IMO the best place to put any logic that's not dependent on other hooks.
Edit: In your case the warning indicated that the intended chain of Resource-Lookups can't be used since the is no hierarchy of components that can be used as fallbacks if the resource isn't found at the current component or final application level.
Note: Wicket 1.5 does not offer an onInitialRender method (it was probably added and removed during some pre-releases). Instead, the onInitialize method should be used for adding child components to the panel (or any other component).
see https://cwiki.apache.org/WICKET/migration-to-wicket-15.html#MigrationtoWicket1.5-ComponentInitializationComponent%2523onInitialize for details.
Related
Is there a way to execute a method exactly after the component has its properties available but before the first render?
I mean something between the class contructor() and firstUpdated().
It sounds trivial, maybe in fact I'm missing something trivial..
The element's constructor is called when the element is created, either through the HTML parser, or for example through document.createElement
The next callback is connectedCallback which is called when the DOM node is connected to the document. At this point, you have access to the element's light DOM. Make sure to call super.connectedCallback() before doing your own work, as the LitElement instance has some work to do here.
The next callback is shouldUpdate, which is an optional predicate that informs whether or not LitElement should run its render cycle. Useful if for example, you have a single observed data property and destructure deep properties of it in render. I've found that it's best to treat this one as a predicate, and not to add all sorts of lifecycle logic inside.
After that, update and render are called, then updated and firstUpdated. It's generally considered bad practice to perform side effects in render, and the occasions that you really need to override update are rare.
In your case, it sounds very much like you should do your work in connectedCallback, unless you are relying on LitElement's rendered shadow DOM, in which case, you might consider running your code in firstUpdated, then calling this.requestUpdate() to force a second update (or changing some observed property in firstUpdated)
More info: https://lit-element.polymer-project.org/guide/lifecycle
I have one swing code written by other person. For swing tabbed pane, he has added both change and container listener and both calls the same method:
addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent theEvent ) {
someMethod();
}
} );
addContainerListener(new ContainerAdapter() {
public void componentAdded(ContainerEvent theEvent) {
someMethod();
}
public void componentRemoved(ContainerEvent theEvent) {
someMethod();
}
} );
Whenever tab is removed from this tabbed pane, it internally calls JTabbedPane.removeTabAt(int index), which in turn calls fireStateChanged() causing new change event listened by change listener.
Now as new component (tab) is removed from tabbed pane, it also calls componentRemoved(ContainerEvent theEvent) method of container listener.
Both change even and container events, then calls same method someMethod(), which does set background and foreground colors.
I would like to know, if this kind code might cause some issues. Recently we are facing random IndexOutOfBoundException exeptions. I am just wondering, if this is causing this issue.
Also as per my understanding in swing, once event is listened, logic inside it should be executed using worker thread (e.g. SwingWorker). Please let me know if this is correct.
I am new to swing, thus any hint would be appreciated.
Thanks.
Whenever tab is removed from this tabbed pane, it internally calls
JTabbedPane.removeTabAt(int index), which in turn calls
fireStateChanged() causing new change event listened by change
listener.
This is true if the removed tab is also the selected tab. In the other cases, you won't be notified.
You need to choose what event you want to listen to:
Addition/Removal of components?--> go for ContainerListener
Selected tab? --> go for ChangeListener
I would like to know, if this kind code might cause some issues.
Recently we are facing random IndexOutOfBoundException exeptions. I am
just wondering, if this is causing this issue.
Since there is no line in your sample code that could throw that Exception, it is impossible to answer your question. Post an SSCCE that shows your issue.
Also as per my understanding in swing, once event is listened, logic
inside it should be executed using worker thread (e.g. SwingWorker).
Please let me know if this is correct.
It depends:
If you need to modify anything in the UI, anything related to Swing, it needs to be executed on the EDT (Event Dispatching Thread) and thus, SwingWorker is not an option.
If you need to perform business logic operations, and especially if they can be lengthy, then you should indeed use a SwingWorker or any other mechanism to execute that code in another thread than the EDT. Consider visiting the Swing tag wiki on "Concurrency"
I'm currently working on a project that involve a re-implementation of the Array class.
This object needs to be an Array for compatibility reasons, while I also need to keep control of what is written in.
I cannot seem to find any way to check property creation inside of a dynamic object in AS3. Something that would work like the Event.ADDED_TO_STAGE but, like, ClassEvent.PROPERTY_ADDED.
I override methods like push, splice etc, but I cannot control direct assignation : MyArray[i] = ...
Is such a thing even possible ?
Of course, I could make some kind of validations elsewhere, but this would involve accessing a part of the code I cannot modify.
Thanks for your time !
I'm not sure I follow you entirely but you may be looking for the Proxy class:
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/utils/Proxy.html
An example at the bottom shows you how you can override direct assignment:
override flash_proxy function setProperty(name:*, value:*):void {
_item[name] = value;
}
Using this you would be able to dispatch a custom event that would be fired any time an item was added to your ProxyArray
Having read many tutorials, articles and questions, I am still have confusions about updating the GUI. Plus there are numerous related questions here on this website and still no luck - even though I think my problem is very simple.
Basically, I have a JFrame that has a JLayeredPane as its root container. And I have some layers of JPanels inside it.
The main issue is with updating a particular JPanel in this JLayeredPane. And for this particular Panel, I have implemented an update method that changes the contents inside it.
updatePanel(int para)
//doesn't remove this panel
//removes some existing labels and replaces it with new ones
Once I create the whole Frame, obviously just calling this method won't show any change displayed the frame.
private void static main (String[] args){
WindowFrame frame = new WindowFrame()//WindowFrame extends JFrame
frame.updatePanel(2);
.....
.....
}
And that's where I am stuck. I want to update the contents as the frame is displayed.
I saw these methods mentioned by people but due to nature of problems, I couldn't fully grasped the concepts. Plus the documentation on these methods isn't really helping - at least to me.
revalidate()
validate()
repaint()
How/when should these methods should be called? Or is this not the right way of what I should be doing, given these methods and the problem I am trying to solve?
Thank you for your time.
Basically you need two methods:
revalidate()
This method does the same as invalidate() but in AWT event dispatching thread (i will just call it Swing thread later on)). It updates container and all of its ancestors (parent containers in which this one is placed) layouting.
Basically if you either move something inside this container or place/remove components inside of it you should call this method (or invalidate in case you are performing it in Swing thread, for example inside any Mouse/Action listener body or just inside).
repaint()
This method forces component, all its sub-components (if it has them) and parent container (basically if this component is NOT opaque) to update what they are "painting".
Usually you don't need this method since all standard Swing components know when to repaint themselves and they do it on their own (that ofcourse depends on components UIs and some other things). This method might be useful in case you have your own specific components with some unique painting-way (for e.g. some custom selection over the components) and in some rare problematic cases with standard components.
Also the way this method acts depends on the components placement (due to some Swing painting optimizations) - if you have some massive repaints rolling you'd better optimize them to repaint only those parts (rects) that you actually need to repaint. For example if you change the component bounds inside any container the best choice is either to repaint its old bounds rect and new bounds rect OR repaint rect that contains both of those bounds, but not the whole container to avoid repainting uninvolved in the action components.
So, basically in your case after some changes with panels you should call revalidate on their container (or invalidate) followed by repaint (in case revalidate leaves some visual artefacts) again for the container.
Guess i didn't miss anything and i hope that now you know the basic meaning of those methods.
revalidate at the end of your update method like so .
updatePanel(int para){
.....
.....
this.revalidate(); //of course this refer to the panel
parent.revalidate(); // parent refer to the window
}
I'm try to put together a bare bones robotlegs-signals project but all the samples I've seen are flex ie
Index.mxml
<context:SignalCafeContext contextView="{this}"/>
SignalCafeContext.as
public class SignalCafeContext extends SignalContext
{
override public function startup():void
{
injector.mapSingleton.... etc etc
}
}
Is this possible to replace the mxml with another .as file - normally I would pass from the main class
context = new MyContext(this); // where this is DisplayObjectContainer
however super() takes no parameters in SignalContext so I might be missing something.
More Info:
libs:
as3-signals-v0.5.swc
robotlegs-framework-v1.03.swc
signals-extensions-SignalsCommandMap.swc
What you're trying would work in the current RobotLegs v.1 release (v.1.5.2). Context and its subclass SignalContext take optional params. The first param is your context view:
contextView:DisplayObjectContainer = null
Here's the SignalContext class extending Context.
Note, Context in Robotlegs 2 does not take parameters (source).
I imagine you need to start with a actionscript project instead of a flex project in FlashBuilder first.
Yes, your right, you just extend the Context class, as you can see in the basic HelloFlash robotlegs demo
mxml tags are just shorthand for actionscript classes. So I'd imagine you could start by taking a look at the auto-generated actionscript code. There is a flash builder compiler option that will let you see this. Using that as a template, you probably can't go too far wrong.