Subject sounds mutually exclusive, and this is probably a terrible hack, but I'll ask anyway.
I have an single-threaded VB.NET application which is setting status bar label to "Loading..." and then synchronously loading data from database which in some cases can take up to 1-2 minutes. Is there any way to show user an AJAX-type animation while data is being loaded? Of course, the correct way is to use separate thread/BackgroundWorker for data access and manage UI separately, but I can't currently change data access model and have been asked for a "temporary fix".
Here are some of my ideas at the moment:
Update label (and only that single label) from another thread, force it's redraw, somehow circumventing windows forms message pump (probably not possible)
Keep another process in background and send "show" message to it from main application. It shows up in front of application, shows animation until "hide" message from main application is received. (problems with user switching away from main application but "animation" form still visible)
I'll probably get down voted for suggesting it (and quite frankly I don't blame people) but this sounds like a job for DoEvents.
I wouldn't normally suggest it, but you are looking for a hack.
Related
I have a timer that talks to java objects through LS2J. It has only to call some getters of the java objects and to update the GUI with new values. This causes the GUI in iNotes Client to show the "Busy" cursor very shortly when the timer ticks. I is really annoying because it occurs even when another window is open and even in the designer.
I actually have to expect that the functionality in the timer event will get more complicated in the future, so I don't want to solve the problem by making my handler lighter.
Is there a way to tell iNotes client not to show this cursor or even an alternative way to make this regular check without timers?
The NotesTimer class in Notes client (not iNotes) does take over the foreground when it triggers, so there will be a bit of a delay if you do something that takes time to execute. It's possible to set up the Notes client to execute background scheduled agents in local database replicas, so that might be an option. You can to the heavy lifting in background and deposit the results somewhere -- say, in a profile document -- that can be accessed quickly by the UI code.
Alternately, you could try a XPages in the client application. I believe it can do partial refreshes while other stuff is going on.
For the record, I simplified the functionality of the Java call by preparing the data so that the timer only has to read the results. I also made the timer run every 3 seconds instead of 1.
Now I don't see any flicker!
According to J. Likness on page 166 of "Building Windows 8 Apps with C# and XAML," in speaking of the OnResuming event: "The main reason [for this event ] is for applications that provide timely data to refresh their information."
I have one page in my app that has such data; so, if the user has resumed the app, and he explicitly
returns or is implicitly/automatically returned to that page (assuming he was on that page when the app was suspended), I want to refresh the data. But how do I know that my app was suspended/resumed?
My idea is to set a bool that the data-rich page can interrogate in its OnNavigatedTo() event; if it is true, I will refresh the data. Is there a better way to do this, and perhaps more importantly: is the OnNavigatedTo() event fired if the user was on that page, the app was suspended, and then resumed? Or does the app view the page as never having been left, and thus it is not being navigated back to? Perhaps another page-level event would be more appropriate?
I'd say you need to determine what the threshold is for when the page of interest needs to be refreshed; I don't think it's as simple as a Boolean. A user could suspend and pretty much immediately resume (say within 15 seconds) and that may not merit a refresh, but that same user could also linger on secondary page, never suspend, and come back to a page 30 minutes later, in which case the page data could be quite stale. Your Boolean may need to be more of a timestamp.
That said, the Resuming event does not fire OnNavigatedTo. If you need to know what page you're coming back to, you'd need to save that info when you suspend, perhaps in LocalSettings. But now consider that if you're using SuspensionManager in C#/XAML, that is already happening on your behalf, and if you think about it, the behavior you want is not too different (if at all) from what should occur when the application comes back from a terminated state.
So in a similar fashion, you could add a call
await SuspensionManager.RestoreAsync()
as your implementation of the Resuming event. That would, in turn, cause an OnNavigatedTo and you'd run through the normal logic of bringing up that page.
It's technically not resuming anymore, you're just using the resuming event to trigger the reload of the entire page. That could be overkill depending on the nature of the page (e.g., maybe there's a lot of semi-static data and only a tiny bit of volatile data - resuming doesn't need to restore the static data). You may want to dial back how much is refreshed on a 'resume' versus a 'terminate,' but since SuspensionManager is code you can see and change, so you can control that level of granularity. And maybe it's here that you introduce you're idea of the Boolean to differentiate what needs to be done in LoadStateAsync when it's invoked by Resuming versus by other means.
In my application in VB.NET, I have started an application and introduced a wait delay of 20 seconds. But for loading the second application, the time is varying. Is it possible to have a do while loop, similar to the structure as shown below:
Start the application1
do {
sleep(2seconds)
}until(Application1 Window is loaded
Did you look at Process.WaitForInputIdle()? It's waiting until the application has entered a message loop for it's user interface (created a window).
Edit: See the MSDN description on the topic here
The biggest obstacle you're going to face is how the child process communicates that it's ready. Determining if another process's window is loaded is shaky at best. It's much cleaner if you decide on something more definitive
Creating a particular registry key
Writing a value to a predetermined file
Windows Messages
Once you decide on that then it's fairly straight forward loop
Dim span = TimeSpan.FromSeconds(20)
Thread.Sleep(span)
Do While Not IsProcessReady()
Thread.Sleep(span)
Loop
As said before you'll need to pick a mechanism to communicate "loaded" and that becomes your IsProcessReady function
I have created a web-service app and i want to populate my view controllers according to the response i fetch(via GET) in main thread. But i want to create a scheduled timer which will go and control my server, if there becomes any difference(let's say if the count of an array has changed) i will create a local notification. As far as i read from here and some google results, i cant run my app in background more then ten minutes expect from some special situations(Audio, Vo-IP, GPS).. But i need to control the server at least one per minute.. Can anyone offer some idea-or link please?
EDIT
I will not sell the app in store, just for a local area network. Let's say, from the server i will send some text messages to the users and if a new message comes, the count of messages array will increment, in this situation i will create a notification. I need to keep this 'controlling' routing alive forever, whether in foreground or background. Does GCD give such a solution do anyone have any idea?
Just simply play a mute audio file in loop in the background, OR, ping the user's location in the background. Yes, that will drain the battery a bit, but it's a simple hack for in-home applications. Just remember to enable the background types in your Info.plist!
Note: "[...] I fetch (via GET) in main thread." This is not a good approach. You should never fetch any network resources on the main thread. Why? Because your GUI, which is maintained by the main thread, will become unresponsive whenever a fetch isn't instantaneous. Any lag spike on the network results in a less than desirable user experience.
Answer: Aside from the listed special situations, you can't run background apps. The way I see it:
Don't put the app in the background. (crappy solution)
Try putting another "entity" between the app and the "server". I don't know why you "need to control the server at least one per minute" but perhaps you can delegate this "control" to another process outside the device?
.
iOS app -> some form of proxy server -> server which requires
"babysitting" every minute.
In an iOS app, I'm writing a class that will be messaged, go do a background request (via performSelectorInBackground:withObject:), and then return the result through a delegate method (that will then be displayed on a map). Everything seems to work right when one request is happening at a time, but I'm trying to figure out how to handle multiple overlapping requests. For example, if a user enters something in a search box that starts a background thread, and then enters something else before the initial background thread completes, how should this be handled?
There are a few options (don't let the second request start while the first is in progress, stop the first as soon as the second is requested, let both run simultaneously and return independent results, etc.), but is there a common/recommended way to deal with this?
I don't think there's universal answer to this. My suggestion is to separate tasks (in form of NSOperations and/or blocks) by their function and relationships between them.
Example: you don't want add image resizing operation to the same queue with fetching some unrelated feed from web, especially if no relationship between them exists. Or maybe you do because both require great amount of memory and because of that can't run in parallel.
But you'd probably want to add web image search operations to same queue while canceling operations of the same type added to this queue before. Each of those image search operations might init image resize operation and place it into some other queue. Now you have an relationship and have to cancel resizing in addition to image search operation. What if image search operation takes longer than associated resize operation? How do you keep a reference to it or know when it's done?
Yeah, it gets complicated easily and sorry if I didn't give you any concrete answers because of uniqueness of each situation but making it run like a Swiss clock in the end is very satisfying :)