Well I just want to press a button and a countdown appears in it however when I press the button the program stops and finally shows the number 1 but doesn't show 3 or 2.
btnTurno.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
btnTurno.setText("3");
SystemClock.sleep(1000);
btnTurno.setText("2");
SystemClock.sleep(1000);
btnTurno.setText("1");
}
});
What I'm doing wrong?
First of all, Sleep should be called as Thread.sleep(x);
But on the other hand , sleep is NOT recommended since it will block the user interaction with the application.
If you want to make a countdown ( as it looks like what you are doing ), you should look at this
http://developer.android.com/reference/android/os/CountDownTimer.html
onClick is being executed in single handler message on GUI thread, so each time you change text, it overwrites previous value, so system is not able to redraw view.
Also you should not call sleep() on main gui thread, that will cause ANR - application is notresponding
Setting the text and drawing the text are separate operations that both happen on the same thread. You're setting the text three times before the framework gets the chance to draw anything, so all you see is the last change.
For this to work, you'd need to do your text updates and sleeps on a separate thread. However, you can't make UI calls directly on a different thread, so you need to post your messages.
One approach would be to create an AsyncTask, and use your code above but call publishProgress() where you're currently calling setText(). The publishProgress() call in the async thread results in onProgressUpdate() running in the UI thread; from there, you can call setText() to update the UI.
Edit: the CountDownTimer approach mentioned in a different answer is better.
Related
Context
I need to manage the concurrency of an app. I declared a Object sync to use monitors on that object.
The main goal is that the first button, A, will execute some code, but, when reaching some points, it needs button B to be clicked to be able to continue. Something like this:
Issues
The issue is that the B button can't be clicked, I guess it's because the UI thread is stuck waiting for the code of button A to be fully executed before raising other button events.
If I execute the code in button A in a new Thread, when I try to update the View (called UI in the drawing), I get CalledFromWrongThreadException.
Edit
I solved it adding a Handler for the UI update and the already added Thread for the code in A.
Factor the code that is taking the time into a Runnable that you execute in a separate thread, but once you've started that thread, do the UI update in the original thread.
Is there any callBack to setContentView in Android, since i'm doing a heavy operation right after setContentView line, and it seems to skip that setContentView.
So i was thinking of moving the heavyOperation to the callBack of setContentView.
Thanks
EDIT:
Pseudo Code:
AudioRecord Finishes
SetContentView(1) //To show a "Processing" screen with no buttons
FFT analysis
SetContentView(2) //On FFT analysis DONE.
In my case "SetContentView(1)" NEVER occurs.
EDIT # 2:
I did the heavy operation in another Thread, and used Handler to send a Message after heavy operation finishes to treat it as a callBack.
Thanks for all the help guys
Short answer: No callback for the setContentView.
If you are doing network operation then you can use the AsyncTask for this.
If you are doing any more heavy operation and want to update the UI then you can do that using the Service and BroadCastReceiver.
For this you have to make your own callback using the interface.
heavy work should be done in asynk tasks or as a service or on other threads
Don't do any heavy calculations on the main UI thread where onCreate() and such are run.
What happens that the first setContentView() posts a "layout and draw" message to the UI thread message queue. Then your calculation blocks the UI thread, preventing messages in the queue from being processed. The second setContentView() posts another message to the queue. When the control eventually returns to the message loop, both messages are processed and you'll get the layout set up by the last call to setContentView().
For heavy computations, use a separate thread. For example, an IntentService or an AsyncTask make threading easier.
My hack.
final Handler handler = new Handler();
setContentView(layoutResID); // This posts some messages to message queue.
handler.post(new Runnable() { // Post another message at the end.
#Override
public void run()
{
// Called after layout has changed.
// If you want to skip some more works (like transitions),
// call another handler.post() here.
}
});
To see what happens, set a break point at the line Message msg = queue.next(); in Looper.loop() may help.
I was facing a quite similar problem a day ago, but I figured it out. (I know your problem is solved, just offering a different approach which doesn't require a handler or callback.
Most Suitable for running U.I. functions :
If you need to do something like this :runTask() then
setContentView() (or any other ui function) you can run the task on different thread by using AsyncTask or you can set a timer for when the task is completed (if your task takes a certain time), the User Interface functions will be called.
But since the Timer class, runs the functions on a different thread, you can not run the setContentView() inside it. So you can use a runOnUiThread(Runnable action) method inside the overloaded run() function of Timer class. You just need to define a function that returns a runnable. Define your Ui operations in the runnable action.
Hope it helps someone.
I know it sounds crazy that someone is using runOnUiThread inside AsyncTask. Somehow, it is working for me but I wanna know if it is an acceptable and robust approach or not. Here is the scenario:
I have an app in which after successful login, user is rendered to next screen. In this new screen, 3 different methods are loading different types of data from a web server. These methods are:
getMembersForList() : It loads the list of community members and shows it in a listview.
getProfileData() : It loads the profile of logged in user and shows his name , image etc on the screen.
getNotificationCounts : It loads the count of new notifications for the user.
I applied 3 different approaches for it :
(1) Calling all 3 methods simply in onCreate i.e. no exclusive thread is being used for any of the methods . In this case , the transition from login screen to this screen becomes very slow and black screen shows up for some time before this activity shows up.
(2) Calling getMembersForList() on UI thread and the other 2 methods on exclusive threads. In this case transition becomes fast and list shows up quickly but Notification counts and username etc. don't show up because WrongThreadException occurs saying that this thread can't touch other thread's views (TextViews for username, notification count etc. which are declared globally) . The same thing happens when I start these threads from an AsyncTask as well.
(3) Calling getMembersForList() on UI thread and then starting an AsyncTask in which the other 2 methods are being called in "runOnUiThread" inside doInBackground() method. This solves both the above issues. Now the screen transition is faster and the WrongThread exception is also not occuring.
So far the approach-(3) is working good for me but I am not sure if this is the right way to do it because runOnUiThread and AsyncTask are 2 completely opposite things. Can anyone please clear my doubts about this scenario. Thanx in advance.
Yes, use-cases like this are a big reason why the runOnUiThread() method exists in the first place. The idea is you allow your background thread(s)/AsyncTask instance(s) to run your lengthy operations in the background, and then provide a simple hook that they can use to update the interface when they have the result (or at arbitrary intervals, as different pieces of the result become available).
As long as that's what you're doing, then your usage is fine. What you want to avoid doing is performing a lengthy operation on the main thread, either directly or indirectly by passing in some lengthy operation from a background thread.
Of course you don't have to do it that way if you don't want to. You could use postExecute() instead. Or you could store the result somewhere and then use any sort of message-passing API to notify the main thread that the result is ready, and so on.
I would advice to run all the 3 calls in the asyncTask, and update the UI in the postExecute() of the AsyncTask after the background taks is complete, postExecute runs on UIthread so you need not call anything explicit to run them on UIthread.
I have some worker thread that gets an address using the geocoder, and when its done, i want to show the result on the application thread's TextView, using setText() from the worker thread leads to an exception, so what is the best practice to do that?
Android UI Views must not be touched from external threads, Any code that calls Methods on Views must run in UI thread only. You Should use AsyncTask . It provides useful callback methods to update UI from task running in a separate thread.
It's hard to say without seeing your code or knowing what exception:
but check if:
your textView object is linked with the one in your layout (findViewById(R.id.textView1))
is it visible in you layout?(sometimes when dimensions of elements dont't add up, views get pushed off screen)
Is it really a String you're trying to set? (not an int or so?)
Try this inside your thread where you want to set text:
// you should finalize your text before using it in another thread,
// else the IDE would show an error
final String text = yourTextToBeSet;
runOnUiThread(new Runnable() {
#Override
public void run() {
textView.setText(text);
}
});
The exception you get when you call setText() on non-UI thread is because you can't call anything related to UI when you are on a non-UI thread. You can, as above, easily call runOnUiThread(Runnable) to divert code execution on UI thread.
Keep in mind that this solution is not good enough if your code is not as simple as that, which in such situations, using AsyncTask is recommended.
I'm trying to implements a game AI, and I got the following problem :
I'm calling a method from another class my UI Activity class, this method call itself some methods of the UI Activity class (to simulate click on screen among other things), and the things is, at the end of this method, I need to "pause" the game a few seconds to let the user see what did the AI.
So I tried running the method in another thread, but I got the error message providing from editing a widget from another thread. I tried to sleep the UI thread, but by doing that, the user can't use the scrollview anymore, and the changes aren't display before the sleep but after.
So I'd like to know how can I do this ?
(I've read some topics about AsyncTask, Handler, but can't make it work the way I need)
Thank's
You need runOnUiThread.
http://developer.android.com/reference/android/app/Activity.html#runOnUiThread(java.lang.Runnable)
http://steve.odyfamily.com/?p=12