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Android immediately run on ui thread

I have read a lot of other answers on StackOverflow, cant seem to find my answer.
I have a listener in my class, i perform a long running task in an async block:
AsyncTask.execute(() -> {
// long running task here
// ...
listener.updateTitle(newTitle);
});
Once I have the data I pass it back to the relevant class:
#Override
public void updateTitle(String newTitle) {
getActivity().runOnUiThread(() -> title.setText(newTitle));
}
Now from what I researched online calling runOnUiThread(..) adds the runnable to a queue of tasks that need to be run on ui. My problem is this updating the title is more important than any of the other ui tasks running.
Is it possible to add this task to the front of the queue, or execute currently executing task, then execute this new task and continue executing the tasks as they were in the previous order?

Sure:
new Handler(Looper.getMainLooper()).postAtFrontOfQueue(() -> title.setText(newTitle));
It may not be sufficient for your needs though as this action will be executed with some delay anyway. If you need to update the title for the next frame, you may want to consider subclassing TextView and providing a synchronized method for setting text from any thread.

Few things:
If your UI thread is busy that you need to wait for the title to be updated, you need to re-think you app design not find a way to get ahead of the Q.
From the AsynTask, to get something to be run in UI thread, use publishProgress
HTH

Android - What should I use to continually check a boolean until it is true?

I am developing an Android app that has a page that requires a connection to be active AND requires a certain piece of information to be collected from the device before allowing users to move to the next step.
I was using an AsyncTask to check both of these booleans. If either of them were 'false', it would display a Toast. It would then Thread.sleep for 1 second, check again and toast again until both booleans are true or they have left the page.
The problem, we learned yesterday, is that Thread.sleep sleeps all Async tasks in the threadpool. So it was also sleeping the Connection AsyncTask and preventing us from ever being able to successfully connect.
My alternate plan was to switch my current Task to a scheduled Timer, until I read that it "is discouraged in Android" (but the link to the article is broken): Android Asynctask vs Runnable vs timertask vs Service
I feel that spawning a thread to check the status of two booleans is not a good idea in the first place, but I'm not sure how else to handle it. Thank you for your suggestions!
EDIT:
I have reworded the question to be more clear.

The other two guys provides you with the clean solution that you probably should use. I however think there is a quick and dirty fix if you don't want to re-write your code.
The problem is the default behaviour of AsyncTask; They run sequentally. So when your thread sleeps, the other tasks are just waiting in line for it to finish. To change this behaviour you can do your AsyncTask with .executeOnExecutor(); rather than .execute();
This will make other AsyncTasks run without interference, allowing multiple threads at a time.

Regarding your bluetooth devices from your original question, you should use a BroadcastReceiver and listen for specific system actions like BluetoothDevice.ACTION_ACL_CONNECTED, BluetoothDevice.ACTION_ACL_DISCONNECTED and BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED.
This way, you keep your app updated about the status of connected devices.
Now for your recent edit, you should use a Handler and a Runnable for this. Declare both as members of your Activity and start the Runnable like so on your activity's onResume():
myHandler.postDelayed(myRunnable, 1000);
Your Runnable should look like:
private Runnable myRunnable = new Runnable() {
#Override
public void run() {
//Check your logic here
if (logic not present) {
myHandler.postDelayed(myRunnable, 1000);
}
}
};
Inside the Runnable you check if your variables match what you want. If they don't, you use your Handler to run the Runnable again. One last thing, on your Activity onPause() you should stop the Runnable from running:
myHandler.removeCallbacks(myRunnable);
Hope that helps.

better to listen for Bluetooth Connection state change Intent, and if the connection goes from DISCONNECTED to CONNECTED, you will know in via Intent(broadcast receiver).
You do not need to check state every second or so.
See below answer to understand how you can register for events.
How to register intent for Connection States
Also see Android Documentation

If I start an AsyncTask during onCreate, when will it begin execution?

I want to ensure that I don't slow down my app's startup time and need to start a background task that's unrelated to user input--for instance, filling a cache.
If I start an AsyncTask from my onCreate method, when will the doInBackground method actually begin to execute? (Assume a single core device)
Is it possible that Android could schedule it before onCreate/onResume has completed, or is it smart enough to recognize that the background thread shouldn't run until the UI thread is completely finished?

If you look at AsyncTask source code you will see that it is just using ThreadPoolExecutor or serial executor for running tasks. Default internal behavior depends on Android version (from AsyncTask docs):
When first introduced, AsyncTasks were executed serially on a single background thread. Starting with DONUT, this was changed to a pool of threads allowing multiple tasks to operate in parallel. Starting with HONEYCOMB, tasks are executed on a single thread to avoid common application errors caused by parallel execution.
But anyway doInBackground execution is not connected with Activity lifecycle so AsyncTask may be executed at almost any time. This depends only on how many tasks you have already started, on default Executor which is used by AsyncTask and on thread scheduler.

I usually use AsyncTasks in onCreate() like this:
private MySuperSpecialTask mySuperSpecialTask;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// setContentView(...);
// [...]
mySuperSpecialTask = new MySuperSpecialTask();
mySuperSpecialTask.execute();
}
#Override
protected void onDestroy() {
super.onDestroy();
if (mySuperSpecialTask != null) {
mySuperSpecialTask.cancel(true);
}
}
This makes sure that everything is initialized before the task gets started.

actually strictly speaking there is no execution order of your UI code and starting the asynctask I found out. Normally one does not experience this, however, if your UI thread takes longer for some reason, eg waiting for external input etc, the asynctask might have gotten started BEFORE UI code has finished.
Writing UI code is just a request to the Android system and this waits in the execution loop. So if asynctask starts before that because there are enough ressources (or as mentioned UI thread is delayed for whatever reason) there is no execution order guarantee.
One easy way to enforce this is - in case you don't mind and you can be sure that it is suffiencient - delay the starting of the asynctask with ScheduledExecutorService or a "cleaner" way would be to implement some kind of gate keeper that waits for a flag to be set to true and then start the asynctask. Or you may even have a while-loop at the beginning of your asynctask that waits for the flag to be set to true, like in many communication situations with external devices.
The flag would be set to true AFTER you can be (normally) sure that your UI has finished.

How to make a new instance of a Thread? [duplicate]

I am having a real hard time finding a way to start, stop, and restart a thread in Java.
Specifically, I have a class Task (currently implements Runnable) in a file Task.java. My main application needs to be able to START this task on a thread, STOP (kill) the thread when it needs to, and sometimes KILL & RESTART the thread...
My first attempt was with ExecutorService but I can't seem to find a way for it restart a task. When I use .shutdownnow() any future call to .execute() fails because the ExecutorService is "shutdown"...
So, how could I accomplish this?

Once a thread stops you cannot restart it. However, there is nothing stopping you from creating and starting a new thread.
Option 1: Create a new thread rather than trying to restart.
Option 2: Instead of letting the thread stop, have it wait and then when it receives notification you can allow it to do work again. This way the thread never stops and will never need to be restarted.
Edit based on comment:
To "kill" the thread you can do something like the following.
yourThread.setIsTerminating(true); // tell the thread to stop
yourThread.join(); // wait for the thread to stop

Review java.lang.Thread.
To start or restart (once a thread is stopped, you can't restart that same thread, but it doesn't matter; just create a new Thread instance):
// Create your Runnable instance
Task task = new Task(...);
// Start a thread and run your Runnable
Thread t = new Thread(task);
To stop it, have a method on your Task instance that sets a flag to tell the run method to exit; returning from run exits the thread. If your calling code needs to know the thread really has stopped before it returns, you can use join:
// Tell Task to stop
task.setStopFlag(true);
// Wait for it to do so
t.join();
Regarding restarting: Even though a Thread can't be restarted, you can reuse your Runnable instance with a new thread if it has state and such you want to keep; that comes to the same thing. Just make sure your Runnable is designed to allow multiple calls to run.

It is impossible to terminate a thread unless the code running in that thread checks for and allows termination.
You said: "Sadly I must kill/restart it ... I don't have complete control over the contents of the thread and for my situation it requires a restart"
If the contents of the thread does not allow for termination of its exectuion then you can not terminate that thread.
In your post you said: "My first attempt was with ExecutorService but I can't seem to find a way for it restart a task. When I use .shutdownnow()..."
If you look at the source of "shutdownnow" it just runs through and interrupts the currently running threads. This will not stop their execution unless the code in those threads checks to see if it has been ineterrupted and, if so, stops execution itself. So shutdownnow is probably not doing what you think.
Let me illustrate what I mean when I say that the contents of the thread must allow for that thread to be terminated:
myExecutor.execute(new Runnable() {
public void run() {
while (true) {
System.out.println("running");
}
}
});
myExecutor.shutdownnow();
That thread will continue to run forever, even though shutdownnow was called, because it never checks to see if it has been terminated or not. This thread, however, will shut down:
myExecutor.execute(new Runnable() {
public void run() {
while (!Thread.interrupted()) {
System.out.println("running");
}
}
});
myExecutor.shutdownnow();
Since this thread checks to see whether or not it has been interrupted / shut down / terminated.
So if you want a thread that you can shut down, you need to make sure it checks to see if it has been interrupted. If you want a thread that you can "shut down" and "restart" you can make a runnable that can take new tasks as was mentioned before.
Why can you not shut down a running thread? Well I actually lied, you can call "yourThread.stop()" but why is this a bad idea? The thread could be in a synchronized (or other critical section, but we will limit ourselves to setions guarded by the syncrhonized key word here) section of code when you stop it. synch blocks are supposed to be executed in their entirity and only by one thread before being accessed by some other thread. If you stop a thread in the middle of a synch block, the protection put into place by the synch block is invalidated and your program will get into an unknown state. Developers make put stuff in synch blocks to keep things in synch, if you use threadInstance.stop() you destroy the meaning of synchronize, what the developer of that code was trying to accomplish and how the developer of that code expected his synchronized blocks to behave.

You can't restart a thread so your best option is to save the current state of the object at the time the thread was stopped and when operations need to continue on that object you can recreate that object using the saved and then start the new thread.
These two articles Swing Worker and Concurrency may help you determine the best solution for your problem.

As stated by Taylor L, you can't just "stop" a thread (by calling a simple method) due to the fact that it could leave your system in an unstable state as the external calling thread may not know what is going on inside your thread.
With this said, the best way to "stop" a thread is to have the thread keep an eye on itself and to have it know and understand when it should stop.

If your task is performing some kind of action in a loop there is a way to pause/restart processing, but I think it would have to be outside what the Thread API currently offers. If its a single shot process I am not aware of any way to suspend/restart without running into API that has been deprecated or is no longer allowed.
As for looped processes, the easiest way I could think of is that the code that spawns the Task instantiates a ReentrantLock and passes it to the task, as well as keeping a reference itself. Every time the Task enters its loop it attempts a lock on the ReentrantLock instance and when the loop completes it should unlock. You may want to encapsulate all this try/finally, making sure you let go of the lock at the end of the loop, even if an exception is thrown.
If you want to pause the task simply attempt a lock from the main code (since you kept a reference handy). What this will do is wait for the loop to complete and not let it start another iteration (since the main thread is holding a lock). To restart the thread simply unlock from the main code, this will allow the task to resume its loops.
To permanently stop the thread I would use the normal API or leave a flag in the Task and a setter for the flag (something like stopImmediately). When the loop encountered a true value for this flag it stops processing and completes the run method.

Sometimes if a Thread was started and it loaded a downside dynamic class which is processing with lots of Thread/currentThread sleep while ignoring interrupted Exception catch(es), one interrupt might not be enough to completely exit execution.
In that case, we can supply these loop-based interrupts:
while(th.isAlive()){
log.trace("Still processing Internally; Sending Interrupt;");
th.interrupt();
try {
Thread.currentThread().sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}

There's a difference between pausing a thread and stopping/killing it. If stopping for you mean killing the thread, then a restart simply means creating a new thread and launching.
There are methods for killing threads from a different thread (e.g., your spawner), but they are unsafe in general. It might be safer if your thread constantly checks some flag to see if it should continue (I assume there is some loop in your thread), and have the external "controller" change the state of that flag.
You can see a little more in:
http://java.sun.com/j2se/1.4.2/docs/guide/misc/threadPrimitiveDeprecation.html
May I ask why you want to kill the thread and restart it? Why not just have it wait until its services are needed again? Java has synchronization mechanisms exactly for that purpose. The thread will be sleeping until the controller notifies it to continue executing.

You can start a thread like:
Thread thread=new Thread(new Runnable() {
#Override
public void run() {
try {
//Do you task
}catch (Exception ex){
ex.printStackTrace();}
}
});
thread.start();
To stop a Thread:
thread.join();//it will kill you thread
//if you want to know whether your thread is alive or dead you can use
System.out.println("Thread is "+thread.isAlive());
Its advisable to create a new thread rather than restarting it.

How to cancel Service/IntentService/AsyncTask/Looper

I'm going nuts here.
I want a simple thing - I have a long task (fetching several data objects from the web) and I want the ability to cancel it.
I tried a lot of things (a lot) and nothing works
The flow goes like this:
the user click on a button
I start the work (I tried with AsyncTask, Service, IntentService and Looper)
the task takes care of everything including adding ongoing notification for progress updates
the intent in the notification has a call for a new activity that her only purpose is to cancel the ongoing task
in the cancelActivity I tried to call stopService() for Service/IntentService or do
Looper.quit() for the Looper (I don't remember what I tried for AsyncTask, not sure if there is such api for canceling it)
In my point of view the best option will be using IntentService (I could have several task lining up and IntetService will do it in order like I want) but
I'm open to suggestions for any type of implementation - I don't care what the code will be, just that I will have the option to cancel the task
Thank you in advance for your help
Dror
(I'm off to bed - 8 hours on the same issue is just too much)

It does not matter what specific operation you use to stop the task if you don't recognize the stop condition in your background logic. The only way to cleanly accomplish it is if background worker stops and exits in good faith.
There are few possible scenarios and solutions that you can use for canceling background work.
Background thread executes many short steps (for example computation with some loops). In this case, check some flag (could be isInterrupted()) between operations and exit if this flag indicates that operation must stop.
Background thread is waiting on monitor. Call interrupt() on background thread, catch exception in in exception handler make appropriate steps to finish this task cleanly and exit.
Background thread is waiting on IO. This use case is very hard to solve in general case. If you use some socket, you can try closing this socket externally and catch the exception. In worst case scenario, you can just abandon the thread in the state that if it ever returns from IO it knows that it is canceled and IO results must be discarded. If you do it often - you will run out of memory, so I would not really recommend it.
In any case, there is no way (except killing the thread which is really bad) to stop your task if it does not know about possibility of being stopped.

Ok, i manged to do something close to what I want.
I'm using IntentService that will queue my task. each new task is AsyncTask. the AsyncTask starts with sending notification with pendingIntent for cancelActivity.
When clicking on the notification the user gets a warning popup about stopping the task. If he clicks yes than I do stopService() on my IntentService.
In the IntentService I added:
#Override
public void onDestroy() {
currentTask.cancel(true);
if (mNotificationHelper != null)
mNotificationHelper.completed();
super.onDestroy();
stopSelf();
}
in the AsyncTask I added:
#Override
protected void onCancelled() {
isCanclled = true;
httpClient.getConnectionManager().shutdown();
mNotificationHelper.completed();
if (mAsyncTaskListener != null)
mAsyncTaskListener.AsyncTaskCanceled();
}
so that will drop all the connection currently in motion. In the actual code that do the work I need to catch the exception for connection shutdown and handle it
so in the end I'm not actually stopping the AsyncTask/Service but rather exposing the httpClient so I will be able to drop the connection in asynchrony why.
I think is a bit ugly but I got no other way
thank you all