when I add a ViewFlipper, the UI thread seems to wait for the onCreate() method in the activity to be finished. Then it shows the second view. Why does it happen?
My current code is:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_menu);
viewFlipper = (ViewFlipper) findViewById(R.id.ScreenSwitch);
viewFlipper.setInAnimation(AnimationUtils.makeInAnimation(this, true));
viewFlipper.setOutAnimation(AnimationUtils.makeOutAnimation(this, true));
//do the necessary loading, when the splash screen persists
doSomeLoading();
viewFlipper.showNext();
}
Actually, the doSomeLoading consists of a for loop counting to ten millions and doing nothing. Now it just waits for loop to be done and shows the second view.
I would really appreciate a solution without having to create a separate Thread, because it seems to be pointless, invalidate() doesn't help there.
Maybe with viewFlipper.showPrevious();?
EDIT
I don't have your full code but here is the idea :
When you do long loading or slow actions, most of the time, you can think AsynTask or background thread.
So you need to create a new inner class. Lets say AsyncLoader. You will implement the method doInBackground() of this class and put your doSomeLoading() in it.
Now, implement onPostExecute() and put your viewFlipper.showNext(); in it.
Then, in your onCreate() method, replace the doSomeLoading() by new AsyncLoader.execute();
This should be nice. I might have forgotten some stuff as it's not real code. Check this for more explanations.
Related
I have use the v4 support lib for FragmentTabHost
The requirement is that when I am switching tab one to another & another one, that is calling
onCreateView() & onActivityCreated() every time.
That's why my code performance is slow.
So, any other solutions? how to increase performance in fragment tab?
Sounds like a design smell.
Redesign your code so that heavy work is done asynchronously. Fragments should be able to be built quickly. If there is any large processing that needs to be done to in order for a Fragment to display useful information, that work should be done beforehand or asynchronously after the Fragment is created and the Fragment should be notified to update its content when the work is complete.
First thing which you should take care of is to watch about calculations / loading a big set of data should be places on a different worker thread than main UI thread. The best option to do that (in my opinion) is to use AsyncTask. You can use something like this in your Fragment :
private class LoadData extends AsyncTask<Void, Void, Void>{
#Override
protected void onPreExecute(){
super.onPreExecute();
// this is the place where you can show
// progressbar for example to indicate the user
// that there is something which is happening/loading in the background
}
#Override
protected void doInBackground(Void... params){
// that's the place where you should do
// 'the heavy' process which should run on background thread
}
#Override
protected void onPostExecute(Void result){
super.onPostExecute();
// you should update your UI here.
// For example set your listview's adapter
// changes button states, set text to textview and etc.
}
}
This is the way you can make your tabs work faster.Hope this will help you! : )
I found a solution for that. I inserted all websevices & database transaction code in on create. because oncreate in not calling every time untill the ondestroy not call. & the other one solution is also available we can use
fragment.show();
& fragment.hide(); method
As an addition to Android-Developer: if you already are using AsyncTask, remember that even when you use multiple AsyncTask's, they are executed in the background, but all sequentially! If you want more threads to handle your tasks, check out this post, which perfectly explains how to achieve that! Running multiple AsyncTasks at the same time -- not possible?
I'm developing an Android 3.1 application.
I want to execute an AsyncTask after activity is shown. I want to show something to user before execute AsyncTask.
I've read that it is not recommend to execute AsyncTask on onCreate().
Where I have to execute AsyncTask on onStart() or onResume()?
I want to left enough time to show activity before execute it.
onCreate(), onStart() and onResume() are lifecycle methods called by the operating system and shouldn't be called directly. You can however override them to have your code executed at these stages of the activities lifecycle:
However, if you want your AsyncTask to start after all of your Views have been inflated and drawn to the screen then you need to put the code in this:
toReturn.getViewTreeObserver().addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
public void onGlobalLayout() {
toReturn.getViewTreeObserver().removeGlobalOnLayoutListener(this);
// asyncTask.execute();
}
});
In the above example toReturn is a view in your onCreate() method. It can be any view you like.
This pulls a ViewTreeObserver from the View and add's a listener to it which will be called when the view has finished being drawn to the screen. It's important you keep the "removeGlobalOnLayoutListener()` line in as this will stop the code firing every time the View is drawn.
Answer is in onResume()
I hade same requirement in my activity where i need to show some list with other buttons and images..
List were getting data from server so used AsyncTask for that..
But before that required to show empty listview and other part of the screen..
so first when it goes to onCreate() I set empty arraylist to listview's adapter then in onResume() call the Asynctask and in that task fill the ArrayList and call adapter.notifyDataSetChanged()
Then another problem occure..when i go to next activity and come back it always call the asynctask even if i dont require..
So had put some condition like if(arrayList.size()==0) then call asynctask else dont.
You can put yur code in the onWindowsFocusChanged method. You can use a thread inside it to manage the timer to start your specific asynctask.
Be aware that this would be performed each time your activity have the focus, not only the first time you launch your activity (I don't know if this could be a problem for you).
implement a View object and override the onDraw().
that way you'll know exactly when the first screen is visible to the user
In my main activity, I would like to have it set up, so that I first get met by a contentView just showing a background and some text. After X seconds, I want to change to my other view (GLSurfaceView).
This is obviously something I am doing completely wrong.
This is how I've imagined it could've been done (it's all in the onCreate method):
setContentView(R.layout.main);
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
}
viewer = new Viewer(this);
setContentView(viewer);
Where layout Main is what I want to show at the beginning and Viewer is my GLSurfaceView class.
What happens is that it just goes black for 10 seconds and then it starts loading the objects I've got that is shown through OpenGLES.
There's nothing wrong with the layout Main, since it works if I just erase the lines under where the Thread.sleep takes action. Though, nothing happens before the Thread.sleep is over...
With that said, my questions are following:
Why is the contentView not changing until after Thread.sleep is done?
What would be an appropiate solution to what I want to achieve?
I'm assuming this in your onCreate() and thats why you are seeing nothing.
The way I would implement this is to start a thread using AsyncTask sleep in the doInBackground and in the onPostExecute set up the new view.
Don't make sleep the main thread(UI thread).Use a threads,AsynkTask or TimerTask for that type of works instead.
You're not sleeping the UI thread in the way you think you are.
The simplest thing for what you're looking to achieve is to separate the views into separate activities and let Android handle the transition between the views. It adds another file to your codebase, but it's fairly straightforward. Let's say your initial, plain view (R.layout.main) is for a SplashActivity activity, and your post-splash view goes into PostSplashActivity. Then you could do something like this:
public class SplashActivity extends Activity {
private static long DELAY = 10000; //milliseconds;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
new Handler().postDelayed(
new Runnable() {
#Override
public void run() {
Intent postSplash = new Intent(SplashActivity.this, PostSplashActivity.class);
SplashActivity.this.startActivity(postSplash);
SplashActivity.this.finish();
}
}, DELAY);
}
}
This will draw your R.layout.main layout, and then puts a startActivity call for your PostSplashActivity on the message queue and tells the queue to wait DELAY milliseconds to execute it.
It seems like you are making the main thread sleep. This may be why the code is running tell after.
It sounds like you want something like a splash screen. I like to think of these as separate to the following screen, so always use a separate activity rather than calling setContentView twice. You'd still need to sleep in a thread.
Just personal preference though...
How can I make loading page in android? I want it when my application starts.
Like the loading pages in games?
Could You help me with that?
There are loads of examples in the internet, search by "splash screen"
http://www.anddev.org/viewtopic.php?t=815
One way of doing it would be to set your contentview in onCreate() then do all the loading in an async task and when that finishes load the 'real' layout in the onPostExecute. Check out http://developer.android.com/reference/android/os/AsyncTask.html
That way you load your "real" layout when it actually finishes loading rather than picking a generic time to switch views. This is of course assuming that you want a loading page and not a splash screen. If you want that, checkout the other answers.
Here's a quick example... Say you have a file called Hello.java .. You'd set your content view to your loading layout in OnCreate() then call this class with something like.. new DownloadFilesTask().execute(); put this private class in it...
private class DownloadFilesTask extends AsyncTask<String, String, String> {
protected Long doInBackground(String... params) {
//grab stuff from the server, compute pi to 100000 places etc.
}
public void onPostExecute(String result) {
//this will now switch us to our real layout, you can now do all your fancy UI stuff! :)
setContentView(R.layout.reallayout);
}
}
Basically this is multithreading the easy way. onPostExecute runs back on the UI thread (your main one) while doInBackground does everything on a separate thread so no black screens! I'd really urge you not to use Runnable in this situation.
You mean a splash screen right? a simple google search would reveal a lot :)
This piece of work helped me to make a splash screen.
Rather than copy and pasting the code, try to understand how he uses Threading with a time limit to achieve this target.
I just tried a stupid approach and it crashed my app... Basically I have an activity that has three tabs (containing three activities). Each of the tabs gets its input from an xml file downloaded off the net. Everything is fine but when I start my app, it has download the xml file and there's a "wait" time for this.
I managed to get around this by adding a splash screen. It looks beautiful but the problem is when I click on the second tab, it still has to get the list off the net, so it looks ugly now... It waits before displaying the list. So what I did was design an AsyncTask that just downloads the xml file. In my main activity, I spawn two tasks initially and send the URL and Intent as parameters. And inside the acitivities that start inside the tabs, I use a wait(). Inside the AsyncTask, after it is done with the download, I notify the Intent using notify(). This crashed! Of course, I didn't expect it to work but just wanted to try :) Writing it so that I can either get a feedback as to why this failed or to prevent others from wasting their time on this...
Now, I am sure many face the problem of a "wait" time inside the tabs. How do I solve this? I am thinking of either dimming the screen and then displaying a series of toasts or display a progress indicator inside the tabs or pre-fetching the xml files... I don't have a clue on how these can be achieved... Any thoughts?
Credit: To Mark. Thanks!
Problem: Display a Progress Indicator when your application is busy doing some work
Approach:
public class Approach extends ListActivity {
ProgressDialog myProgressDialog = null;
ListView myList = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
myList = getListView();
myProgressDialog = ProgressDialog.show(getParent(),
"Please wait...", "Doing extreme calculations...", true);
//Do some calculations
myProgressDialog.dismiss();
}
}
There are a few challenges (like updating some UI elements). You might want to spawn a different thread to do your calculations if needed.
Also, if you are interested in this, you might be interested in Matt's approach too: android-showing-indeterminate-progress-bar-in-tabhost-activity
ProgressDialog.
Or, make the tabs have android:visibility="gone" until such time as the data is ready, then make them visible. In the interim, show some sort of loading graphic (perhaps with a RotateAnimation applied).