I am building a windows 8 metro app using javascript and html5. I want to know following things.
How can I cancel the current instance of any running background task.
What are the possible conditions when system automatically cancels background task.
JavaScript background tasks are executed in web workers, so just use close() within running background task to end it when ever you want. If you want to do this from your app code, check out following MSDN sample: http://msdn.microsoft.com/en-us/library/windows/apps/jj160500.aspx.
There are many conditions when system may cancel your task, but that depends how you registered it (is it lock screen task etc). In normal conditions each background tasks has 1s CPU quota and 7.5 MB daily data quota. You can read more about it here: http://msdn.microsoft.com/en-us/library/windows/apps/hh977046.aspx
Related
Currently I'm using a viewModelScope to launch a coroutine which in turns retrieves data from a remote server and caches the results in a local ROOM database.
My question is if I should use instead a GlobalScope to launch the coroutine to get such remote data, as the retrieval/caching can be interrupted if the app is sent to the background when using the viewModelScope.
Android discourages to perform continuous running tasks in the background since it uses battery and memory in the main thread. However, if you specifically need code to run in the background, consider using Background Services or Work Manager which is also responsible for starting background tasks.
I ran into a very weird problem. I have a VB.NET program which calls another program which runs in the background. We're using a special software here to deliver this software over web. What this software basically does is, that i creates a new remote desktop connection, grabs the screen and opens up a web server.
While running the sub programm / sub process the screen does not react smooth anymore, it gets very low and then freezes. We figured out, that we're triggering too many screen updates at once so that we simply flood our connection which causes the crash in the browser.
Is there any simple way to determine how many screen updates were sent and which causes these updates? Best would be that we can identify the process so that we can investigate further.
The whole process is ran as a backgroundWorker which then creates another process.
Edit:
Could it have something to do with the CPU load (which is very high)? Although the subprocess is executed in the background - and is visible in the process list - is there any chance that this causes the UI Update?
Finally solved it. It was a Timer updating the View every microsecond becuase the Interval was not correctly set.
I'm developing Windows Metro App and in my App I need to download some information(about 60Mb, every time) from server in background. Download should occur regularly, for example every 8 hours. So I tried to use Background Task, but there are some CPU and network quotas(https://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh977051.aspx), and I can't do this. Could somebody help me with advice in this problem?
Instead of attempting to do the entire transfer in the background task itself, have the background task start a background transfer, which runs independent of the task and independent of the app as well. See the topic, Transferring Data in the Background, https://msdn.microsoft.com/en-us/library/windows/apps/hh452979.aspx. You can run the background task periodically according to the schedule you need, and it will easily stay under CPU and networking quotas because the background transfer doesn't count against that.
There is an app in Windows Store called "The Time" which shows current time (every minute) on its Tile. The app can do this without registering any Background Task.
How can it do this?
UPDATE: it seems that it schedules lots and lots of tiles!
Because if you draw back the computer time, it will stop working.
However, I don't know how many tiles it schedules and how many tiles it is possible to schedule?
From the author himself:
Live tile updates may be scheduled
Applications may be given slices of time via the background task infrastructure
So, simply, when The Time’s background tasks are executed by the OS they queue up a number of live tile updates.
As far as I know this is not possible in Windows 8 - the background task for updating tiles can run every 15 minutes, but not more frequently.
Being productive in the background – background tasks
I have a VB.NET desktop application that I'm using to monitor events in another windows application running on my system. I need to respond to certain events in a matter of seconds. One of the events I'm monitoring instantly changes the window title of a child window within the main process (I'm not changing it, the application I'm monitoring causes the change in it's own child window title). I have a function that uses windows API's to iterate through the title text of all the process's child windows, and I'm checking for certain values in the titles.
Is it a bad idea to be running this timer/title check once every second? Are there performance issues associated with running a timer in windows every second 24/7? Is it also bad for performance to be calling the API's which retrieve the titles of all the application's child windows? Could I eventually cause that application to crash by sending requests to it so often?
Thanks!
You will have to benchmark it to see, but if I recall correctly, iterating through every window has significant overhead.
Can't you simply monitor a single window? If you do that, you should be fine.