I've run across an issue using Caliburn.Micro when sharing a Screen between multiple parent Screens. In this example I have 2 tabs inside a shell. Each tab shares a single instance of SharedViewModel (essentially a singleton).
var shared = new SharedViewModel();
Items.AddRange(new []
{
new TabViewModel { Shared = shared },
new TabViewModel { Shared = shared },
});
And each tab's view has a ContentControl bound to the Shared property which is SharedViewModel:
<ContentControl cal:View.Model="{Binding Shared}"/>
Here's the order of events:
Start the app. See the shared view.
Switch to second tab. See the shared view.
Switch back to first tab. Shared view is gone.
Switch to second tab again. The shared view is there.
Proceed to pull hair out.
You can see the example application on my github.
The Screen class is based on ViewAware which caches and reuses its view once it has been loaded. As one and the same instance of a visual can't be attached to the visual tree multiple times, this leads to the behavior you're observing.
Try overriding this in your screen:
public override object GetView(object context = null)
{
return null;
}
Related
I am building an app that makes use of some App links. In below example, I want to open a ResetPasswordPage when the user activates a link from an e-mail.
protected override async void OnInitialized()
{
InitializeComponent();
await NavigationService.NavigateAsync("/NavigationPage/LoginPage");
}
protected override void OnAppLinkRequestReceived(Uri uri)
{
if (uri.Host.EndsWith("site.nl", StringComparison.OrdinalIgnoreCase))
{
if (uri.AbsolutePath.StartsWith(#"/appname/resetpassword/"))
{
if (uri.Segments.Length == 4)
{
string resetCode = uri.Segments[3];
NavigationParameters param = new();
param.Add(NavConst.PasswordResetCode, resetCode);
await NavigationService.NavigateAsync("ResetPasswordPage", param);
}
}
}
}
This code works, but not what I would expect (for both iOS and Android). I would expect that ResetPasswordPage would be added to the navigation stack that was set in OnInitialized, so that it would contain a back button in the navigation bar, bringing the user back to the login page in this case.
But instead, it looks like the navigation stack gets replaced. When ResetPasswordPage is shown, and the user clicks the hardware back button, the app is closed. However, i want it to go back to where the user was before.
Am I not understanding some navigation concepts well or might this be a bug?
The NavigationService is a rather unique service within Prism for Xamarin.Forms. It is constructed new for each page as navigation and the navigation stack is dependent on where you are navigating from.
For instance when you Navigate from the context of a MasterDetailPage / FlyoutPage, it understands that you aren't trying to push a modal on top of that page but instead you are starting from the context of Detail/Flyout. If the NavigationService continually updated the Page context then the navigation service injected into that MasterDetailPage/FlyoutPage's ViewModel would have no idea that it needed that page as the context to navigate from.
Your issue here ultimately is that you are Navigating from the context of the Application which has a NavigationService with no Page set. As a result even a relative Navigation will still have the effect of an absolute Navigation thus resetting the Application.MainPage since that NavigationService does not have the contextual understanding of another page.
Depending on your business requirements you have a few different options. One is to do an absolute Navigation that gives you navigation stack that you're looking for.
Optionally you may want to get the currently displayed page and update the NavigationService to understand it. In the App class you might add something like:
protected override void OnAppLinkRequestReceived(Uri uri)
{
if (NavigationService is IPageAware pa)
{
page.Page = PageUtilities.GetCurrentPage(MainPage);
}
if (someCondition)
{
// This will now navigate from relatively from the page
// returned by GetCurrentPage.
NavigationService.NavigateAsync("SomeRelativeUrl")
.OnNavigationError(HandleNavigationError);
}
}
I have a window editor that holds nodes. I would like to open a custom inspector when one of these nodes is selected. The node class is a custom serializable class. Is this possible?.
It seems that custom inspectors can be created manually through the Editor.CreateEditor method but can't see how to let it appear docked like an usual inspector in the unity inspector window.
I would like to achieve the same behaviour that we have when we select a gameobject in sceneview that inmediately show properties for the object (Components, etc...) in the unity inspector.
Cheers
As I'm not sure what you're asking, here are multiple different solutions;
Selection
If you just want your nodes to become the focus of the hierarchy, then in your custom window's OnGUI method, use the code below;
[CustomEditor(typeof(NodeManager))]
public class NodeManager : EditorWindow
{
private static NodeManager window;
private Node[] m_nodes;
[MenuItem("Custom Windows/Node Inspector")]
public static void Init()
{
if(window == null)
window = GetWindow<NodeManager>("Node Manager", true, typeof(SceneView));
}
public void OnGUI()
{
m_nodes = GameObject.FindObjectsOfType<Node>();
foreach(Node node in m_nodes)
{
GUILayout.BeginHorizontal();
{
GUILayout.Label(node.name);
if (GUILayout.Button("Select"))
Selection.objects = new Object[] { node.gameObject };
}
GUILayout.EndHorizontal();
}
}
}
This adds a Button for each object in your custom window view, that will then select that object in the hierarchy.
Auto-Docking
I originally found the second response to this question, which goes into the details of parameters of the GetWindow method, and with this you can clearly see how to dock the window (I've converted it from JS to C# below).
(I looked fairly extensively in UnityEditor and UnityEditorInternal namespaces but couldn't find the Hierarchy or the Inspector).
GetWindow<T>(string title, bool focus, params System.Type[] desiredDockNextTo)
Which we can write for this example as;
EditorWindow.GetWindow<NodeInspector>("Node Test", true, typeof(SceneView));
This example docks the windows next to the SceneView window. This functionality can be combined with a custom inspector's OnInspectorGUI method, to automatically launch the custom node window, if it's not already open.
[CustomEditor(typeof(Node))]
public class NodeInspector : Editor
{
public override void OnInspectorGUI()
{
base.OnInspectorGUI();
NodeManager.Init();
}
}
Sorry if this isn't what you are looking for, if it's not then please give more details and I will amend my answer to better suit the question.
Hope this helped.
Has a possibility, you can make a custom ScriptableObject and Custom Editor for It, and when open the node inspector, just find a instance of the scriptable object and use Selection.selectedObject = scriptableObject, and in the custom editor, make a static field called 'editor' to draw inside.
It will work.
So here's my screnario. I have a toolbar at the top (office style), with buttons. This is hosted in a shell. Some of those buttons are applicable only to certain child view models as they get loaded. Ideally what I would like to happen is have the buttons action.target repositioned to child view model as it gets created (I kind of got this working by settings Action.Target="ActiveItem" on them. This doesn't solve the problem fully though:
a) When the child viewmodel is closed and there is no active item, I want them to reposition to Shell as the target so they can be set to "default" state.
b) I noticed that when child viewmodel is closed and the shell being the conductor has it ActiveItem=null, the hooks from the action are still bound to the living instance of the last viewmodel, so doesn't looks like it got disposed of. Memory leak?
Any suggestions how to implement this scenario?
What about adding a property to your ShellViewModel which points to the action target and updating it when stuff gets activated/deactivated:
e.g.
public class ShellViewModel
{
public object ActionTarget
{
get { return _actionTarget; }
set
{
_actionTarget = value;
NotifyOfPropertyChange(() => ActionTarget);
}
}
// Then when the active item changes just update the target:
public override NotifyOfPropertyChange(string propertyName)
{
if(propertyName == "ActiveItem")
{
if(ActiveItem == null) ActionTarget = this;
else ActionTarget = ActiveItem;
}
}
}
Now bind to that:
<SomeMenu cal:Action.Target="{Binding ActionTarget}" />
Not sure if that will work or not but I'm sure I've done something similar in the past. (You may also have to explicitly call NPC on your actions before they will update after you have changed ActiveItem)
I am working with a digital book application. I make use of swf loader to load swf pages created from pdf. I use TextSnapsot to draw inline text highlight on the pages. The highlight is thoroughly retained on the respective pages throughout the session and later it can be updated/deleted without any problem. Everything was working great till I made the following changes in the swf loading approach to enable page caching:
I am now loading swf loader object into application memory and while doing jumping from one page to other page I am just copying the content of the next page to the current swf loader which is on the display to the user. There are two sets of swf loaders - one for displaying the page and other to cache the next/previous page(s). On the caching side, I load the swf into application memory and after getting it loaded I pick all the contents of the loaded swf page (the children of it's movie clip) into an array collection. While changing the page I copy the cached content into the swf loader's movie clip which is displaying the page.
Now when I highlight on the page on display and navigate back/forth from the page and comeback again to the page where I did the highlighting: It shows the highlight I did. But as soon as I try to draw another highlight on that page, the previous highlight is instantly disappears from the page.
I suspect that the Textsnapshot object which draws highlight while navigating (to the target display page) is different from the one which redraws/update the highlight on the same page next time. Although the Textsnapshot object id for both the objects is same.
Here are some code snippet:
For copying the content from the swf loader object cached in application memory:
private function copyPageContent():void
{
var contentCollection:ArrayCollection = new ArrayCollection();
_pageContentVO = new PageContentVO();
_pageContentVO.contentHeight = MovieClip(_swfPageLoader.content).height;
_pageContentVO.contentWidth = MovieClip(_swfPageLoader.content).width;
var count:int = MovieClip(_swfPageLoader.content).numChildren;
for(var i:int=0;i<count;i++)
{
var dispObject:DisplayObject = MovieClip(_swfPageLoader.content).removeChildAt(0);
contentCollection.addItem(dispObject);
}
_pageContentVO.pageContentCollection = contentCollection;
_swfPageLoader = null;
}
For copying the content to the swf loader which is displaying the page:
private function copyContent(pageContentVo:PageContentVO):void
{
for(var i:int = 0;i<pageContentVo.pageContentCollection.length;i++)
{
var dispObject:DisplayObject = pageContentVo.pageContentCollection.getItemAt(i) as DisplayObject;
MovieClip(this.content).addChild(dispObject);
}
this.content.height = this.height;
this.content.width = this.width;
}
after this I dispatch swf loader's complete manually and in the handler of that event I take the text snap shot object.(highlightManager.as)
Code I use to draw highlight manually(using mouse drag on the page).
public function setHighlight():void
{
removeAll();
if(_textSnapShot!=null && _textSnapShot.getText(0,_textSnapShot.charCount)!="")
{
if(_isCoveredTextSelectedAtAnyInstance)
{
_textSnapShot.setSelected(_beginIndex,_endIndex+1,false); //this is the global variable to the class
}
else
{
_textSnapShot.setSelectColor(0xfff100);
_textSnapShot.setSelected(_beginIndex,_endIndex+1,true);
}
if(saveHighlight)
{
countHighlightedSegments();
}
}
}
Code I use to redraw previously drawn highlight when I return to the page:
public function showHighlights(textSnapShot:TextSnapshot,currentPageNum:int):void
{
if(currentPageNum >= 0)
{
textSnapShot.setSelected(0,textSnapShot.charCount,false);
var pageVO:PageVO = _model.eBookVO.eBookPagesVO.getItemAt(currentPageNum) as PageVO;
var objColl:ArrayCollection = new ArrayCollection();
objColl.source = pageVO.highLightSelection;
for(var i:int=0;i<objColl.length;i++)
{
var highlightVO:HighlightVO = new HighlightVO();
highlightVO.beginIndex = objColl.getItemAt(i).beginIndex;
highlightVO.endIndex = objColl.getItemAt(i).endIndex;
setHighlightedSegment(textSnapShot,highlightVO.beginIndex,highlightVO.endIndex);
}
}
}
private function setHighlightedSegment(textSnapShot:TextSnapshot,beginIndex:int,endIndex:int):void
{
textSnapShot.setSelectColor(0xfff100);
textSnapShot.setSelected(beginIndex,endIndex,true);
}
Looking forward to your support to resolve this issue.
Regards,
JS
What you're doing is not 'caching', it's preloading previous/next pages. Also, what you're doing is really bad practice. I'm not even sure why you're casting these things into MovieClips unless the SWFs are that; if they're Flex SWFs, they'll be UIComponents. I would recommend you rethink your approach. I wouldn't even bother copying the children or anything over. Once the browser loads a SWF, it is now part of the browser cache, meaning the next time it's requested, it won't actually download it.
If you want to 'cache' your SWFs for a quicker next/previous page flipping, I would recommend you use something like SWFLoader to just load the other SWFs without actually adding it to the display, then removing it from memory. That will cache the SWFs for you in the browser. Then when the user click previous/next, just change the url of the main swfloader of the currently displayed page and it will load it up really quickly. No downloading since it's already cached, it will just need to instantiate.
I am building a complex Flex app, and now I am at the point where navigation becomes a problem. I make use of Viewstacks with a Menu Bar, but I am not sure how to clearly structure this.
Depending on the logged in User and chosen Company by the user, he can see different pages. For now I restricted this hiding the appropriate buttons in the Menu Bar. However, not just the menu bar, but also buttons/links from within the app should be able to navigate to each existing page.
When I am loading up an existing page, it needs some initialization (depending on the context it is loaded from). In addition, when a company is chosen, I need to load the status from the backend, and depending on this status a specific page might be visible.
Are there any guidelines how to tackle more complex navigation/site hierarchies in Flex?
Now I am having all my views in a viewstack in the Application, and refer to it with Application.application.appViews.selectedChild -> but that's obviously not best practice, since it violates encapsulation.
Was thinking of implementing some sort of State Machine, which takes care of all this, but not quite sure it this would make sense, or if there is any better way.
Thanks guys,
Martin
If it's really complex, you might want to consider breaking your application up into modules.
Also, Mate is a great Flex framework for handling complex communication and navigation. Mate's EventMaps help you centralize the communication and logic between components, modules, etc. And, it keeps you away from the dreaded Application.application references.
Even if you don't use a framework like Mate, you can avoid the Application.application references by having components dispatch custom events that bubble up to the top-level of your application. The top level of the application can listen and catch these events and act on them. I've found this to be a much more flexible approach. I avoid Application.application as much as possible!
If you have a complex menu bar that needs to enable / disable a lot of buttons or options based on many different logic conditions, the State pattern is a decent way to handle it. I built an enterprise-level app that had a "Word-like" button bar at the top...and there were so many different conditions that affected the states of the buttons that I had to centralize the logic in one place. At first I didn't use the State pattern and maintaining the code was a difficult chore. One day, I bit the bullet and re-factored all the conditional logic into a StateManager class. It definitely made life easier from there on out.
Again, you might want to consider using Custom Events to broadcast important events to your application. You can make these events bubble up to the Application level. Then, by adding event listeners at the Application level, you can capture and respond to these events and target components or modules from the Application level. This gives you a central location for handling events and "directing traffic". It also prevents the tight-coupling of the Application.application approach. (Which quickly becomes a nightmare as your application grows and scales!)
For example, your StateManager can contain the case statements for deciding which state your application needs to be in. Once the decision about the current state is determined, you would dispatch a custom StateEvent. (Which might have properties like StateEvent.STATE_CHANGED and StateEvent.CURRRENT_STATE) This event can bubble up to the Application level and be caught by a listener. The listener then calls a method to load / change the state.
Does that clarify it for you? If not, perhaps I can spend an hour or two putting together a little sample.
Let me know,
=Bryan=
I can give you the approach I used for some of your sub-questions, the problem of initializing a page at runtime and how to encapsulate navigation.
For page initialization, the issue I came across is that it's not always known once you navigate to a page whether certain elements should be shown, since it not-only depends on overall user permissions, but also permissions against the currently-selected data. And if the information needed to determine this must be loaded from the server, you cannot show the page as-is while loading the information. So we created a control called LoadingPanel, which is a container that can cover content with a loading indicator until additional information has been received. Here's a shortened version of the ActionScript:
[DefaultProperty("children")]
public class LoadingPanel extends ViewStack
{
public function LoadingPanel()
{
this.resizeToContent = false;
super();
}
public function get children():Array { return _children }
public function set children(value:Array):void { _children = value; }
public function get loadingImageStyle():String {
return _loadingImgStyle; }
public function set loadingImageStyle(value:String):void {
_loadingImgStyle = value;
if (_loadingIndic)
_loadingIndic.loadingImageStyle = value;
}
public function showLoadingIndicator():void
{
if (_loadingIndic)
{
super.selectedChild = _loadingIndic;
}
else
{
_pendingLoadingIndic = true;
var me:LoadingPanel = this;
var listener:Function = function(event:Event):void
{
if (me._pendingLoadingIndic)
me.showLoadingIndicator();
}
addEventListener(FlexEvent.CREATION_COMPLETE, listener);
}
}
public function hideLoadingIndicator():void
{
_pendingLoadingIndic = false;
if (_content)
{
super.selectedChild = _content;
}
else
{
var me:LoadingPanel = this;
var listener:Function = function(event:Event):void
{
me.hideLoadingIndicator();
}
addEventListener(FlexEvent.CREATION_COMPLETE, listener);
}
}
public function waitForEvent(target:EventDispatcher, event:String):void
{
_eventCount++;
showLoadingIndicator();
var me:LoadingPanel = this;
target.addEventListener(
event,
function(evt:Event):void
{
me._eventCount--;
if (!me._eventCount)
{
me.hideLoadingIndicator();
}
}
);
}
override public function addChild(child:DisplayObject):DisplayObject
{
var result:DisplayObject = child;
if (_content)
{
result = _content.addChild(child);
invalidateDisplayList();
}
else
{
if (!_children)
{
_children = [];
}
_children.push(child);
}
return result;
}
override protected function createChildren():void
{
super.createChildren();
if (!_content)
{
_content = new Box();
_content.percentWidth = 1.0;
_content.percentHeight = 1.0;
super.addChild(_content);
}
if (!_loadingIndic)
{
_loadingIndic = new LoadingIndicator();
_loadingIndic.percentWidth = 1.0;
_loadingIndic.percentHeight = 1.0;
_loadingIndic.loadingImageStyle = _loadingImgStyle;
super.addChild(_loadingIndic);
}
if (_children)
{
for each (var child:DisplayObject in _children)
{
_content.addChild(child);
}
}
}
private var _loadingImgStyle:String = "loadingIndicatorDark";
private var _loadingIndic:LoadingIndicator = null;
private var _content:Box = null;
private var _children:Array = null;
private var _pendingLoadingIndic:Boolean = false;
private var _eventCount:int = 0;
}
We typically used these by wrapping a LoadingPanel around content then calling the panel's waitForEvent method. Typically, the event we'd wait for is for a web service response to come in. The class also lets you wait on multiple events before it will show its children.
Another recommendation I would make for your project is that you look into deep linking in Flex. Our users appreciated being able to bookmark a resource/location in our complex Flex application as well as being able to hit refresh in their browser and return to the same "page" they were on. But implementing deep linking also helped me out for one of the problems you mentioned; how do you send the UI to a specific page in an encapsulated manner? The way we did it is by raising a bubbling navigation event containing a destination "URL." A top-level navigation "manager" then handled interpreting the URL and "sending" the user to the appropriate area.
Hopefully this will give you some ideas for some of the challenges you face.