When my quiz app starts for the first time it needs to add questions to a database and a few other things and this takes a few seconds. I want to display a indeterminate progressbar whilst this occurs. Once the questions are added, the class calls finish() and moves on to the main screen. The problem is that the layout isn't drawn unless finish isn't called. I assume it doesn't draw the XML layout until after the oncreate and onstart are called. So how do I get around this?
The reason, the UI isn't shown while you're filling your DB is probably that you're doing that in the UI-Thread - the main thread of your application. As the thread is busy filling your DB, there is no time to show the UI, animate the progress indicator or react to user actions.
Thus you should always run time-consuming tasks in a separate thread. See this excellent entry in the android devloper's blog about painless threading for more information and to do it right:
http://android-developers.blogspot.co.at/2009/05/painless-threading.html
Use AsyncTask, display progress dialog in its onPreExecute and dismiss in onPostExecute prepare your db in doInBackground.
You would have to handle device rotation unless you are using DialogFragment to display your dialog.
Related
So I understand that any changes to the UI need to be on the main thread for an Android application. And also, you should use other threads to do work so that the UI doesn't freeze up. But some of the work I want to do is preparing UI elements which will be shown later on. I want to get those things ready on a separate thread and then enable a button once its done - that way the user won't be able to access it until it's ready BUT they'll be able to use the main page quickly.
Exactly what operations count as changing the UI? I want to do as much preparation in the background so that the first part of the app ready can be shown ASAP while other parts are still loading.
For example, it seems like findViewById is fine, but what about creating/modifying Views, setting listeners, setId, setEnabled and so on? If I newly create a Button which hasn't been added to a parent, can I setText on it in a background thread?
This question already has an answer here:
How can I display a Progress at start up application in android
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Closed 5 years ago.
I have a heavy user interface that can delay the application load. I want to show an preloader before the UI of activity loaded. note that my ui is in xml file
EDIT:
If you want to load 10 tabs in a view pager, use a FragmentStatePagerAdapter which only loads neighboring tabs(default behavior).
If the heavy UI you specify is only the UI elements, then the app must freeze while loading it. So you'd better show a non-cancelable dialog(without animation) with loading message and after a few moment (like 200ms) load up your UI and explicitly dismiss the dialog.
But if the heavy stuffs is not just UI, maybe some calculations or image processing, just do it in a background thread while showing a dialog with progress and cancel the dialog when the task is done.
#Hassan according to me if on clicking the launcher icon if it takes sometime for your application to render the first screen(perhaps giving a black screen in between). This needs to be corrected in your application.
On the contrary if your applications main screen requires population/retrieval of certain resources for effectively engaging the users, You can possibly do something like a splash screen(outdated) where you do all "population/retrieval" and then simply pass data to your heavy UI.
Now regarding the progress bar if this fetching of data is small, you can give an indeterminate "custom"(some moving animation that would suite your app) progress bar,else if its something like a download you can easily track its progress and show in a horizontal progressbar
You sure can! You are describing a preloader. Here is a nice example of one https://github.com/rtheunissen/md-preloader
You'll have to add more info to your question to get a specific answer, but there are a few basic principles.
You make your life a lot easier if you use a preloader which doesn't show progress of the load, it just goes round and round, because the speed of some load processes can't be measured.
If its a data-load which is taking the time (such as a call to an API), you might want to set a variable for "loading" to true at the top of your script, then when the data has resolved, set it to "false". In your view, have a state or a conditional element which hides / unhides the preloader.
If lots of images are slowing down the page, you might want to look into "lazy-loading" or using "infinite scroll" to only show content when the UI needs to display it on screen.
Thats all the info I can give without more information on the code you have so far. Hope that helps!
i have created a android app it works fine and I am loading my UI that contains a scroll tab with several fragments, the UI in the main activity takes 4-6 seconds to load and only a blank white screen is seen till then, how can I show a progressbar till that UI has finished loading there s no data to load just the UI so please dont tell about asynctasks
You will have to first display a simple activity with your progress bar and then start to add the parts of your ui in background one by one to the activity by using an async task.
If you are using commands that can only be performed by the ui thread you have to post them to a view or a handler from your async task.
Ensure that the different blocks you are loading are not taking too long to give the ui thread time to update your progress bar in between.
I know you don't want to use an Async task but that would be the best solution. Start an async task loading the UI (Can use existing class) and read a true false (indicating when done) value from onProgressUpdate(), which can be accessed from the UI thread. Display a spinner while false. Hope this helps.
I have a large activity that contains 100 or more buttons. But it's working fine once loaded. Problem however is loading. From clicking its launch icon to getting the first view it takes 10-12 seconds. Until the first view, it shows gray title bar in black background.
At least, I want to show a simple progress bar or dialog while its loading. But it seems like you cannot show anything before setContentView executed. I think I have tried everything I could without any success. If you can give me any hint or idea, I would be thankful.
UPDATE:
I found a dramatic resolution. It takes now a second to load the view. I didn't use splash, thread or async task at all - BTW, don't try to use thread or async on UI because Android UI is not thread-safe. Problem was that those buttons were based on a custom class that requires initialization to load same resource. - so 100 or more file operations were happening on setContentView. Making them a just single loading solved my problem.
You are loading data on same UI thread , so nothing will be desplayed during the time of loading .
Use Async Task for loading in separate thread.
1)Show a progressBar in onPreExecute()
2)load data in doInBackground() . no UI related stuff here
3) Update changes on UI ,hide progressBar in onPostExecute()
Use this code before setContentView() is called. Maybe it helps.
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
requestWindowFeature(Window.FEATURE_PROGRESS);
setProgressBarIndeterminateVisibility(true);
setProgressBarVisibility(true);
I'd like to have a splash screen while loading resources (images and sounds). How do I know everything is loaded?
Are all resources loaded at app startup?
Thanks
For accordingly implementing a splash screen in Android you want to:
Show a foreground screen with some progress indication for the user.
Execute a background thread for doing tasks that take some indefinitive time.
Both threads communicating between them, as you need the foreground to show the progress on the background.
Correctly kill the background thread when it finishes doing it's task. If you are planning to use AsyncTask in Android you have an issue there. (Link)
I've found this tutorial and I strongly suggest it:http://www.41post.com/4588/programming/android-coding-a-loading-screen-part-1
Part 1 accomplish this basic task, part 2 shows you how to correctly kill the AsyncTask. And part 3 puts a customized view in the foreground instead of the ProgressActivity.
You could do all your loading in an asyncTask then your onPostExecute remove the splash screen. This would help ensure that you don't block the UI thread while doing any expensive tasks that could cause an ANR popup.
Here you go, wrote a tutorial on how to create a SplashScreen with a progress bar:
http://blog.blundellapps.com/tut-splashscreen-with-progress-bar/
Basically, instead of your thread it starts an ASyncTask, you pass a reference to your progressSpinner into the ASyncTask and this will update it as the thread is downloading resources (or whatever you want to do).
Here is a complete tutorial on how to get it done. I've used this one myself with great results.
http://www.barebonescoder.com/2010/04/a-simple-android-splash-screen/