Android :: Pass Messages Between Threads?

Jan 9, 2010

Currently I have two threads, other than the UI thread, which need to communicate with each other. Thread one needs to be able to send messages directly to thread two, and vice versa. What is the best way to implement this?

At the minute, my code looks like this...

Android :: Pass messages between threads?


Android :: Volatile Reference A Safe Way To Pass MotionEvents Between Threads?

Jun 29, 2010

I am curious about the safety of this method I have considered using for passing touch events in my Android application (and testing my understanding of concurrency in Java). Here's the basics:

I have a SurfaceView hooked up to SurfaceHolder.Callback to get user input events, mainly the onTouchEvent callback. After the onTouchEvent method is invoked, I see if event.getAction() == MotionEvent.ACTION_UP and, if so, call a method I have named postTouchEvent which is a member method of my app thread that updates the application's state and draws to the canvas. Code...

Now I understand that it is certainly not atomic, but since I treat it as immutable after receiving it from framework, won't this work? (Instead of synchronizing the post method and the if statement, which I have no problem doing, but I'm asking to learn.)

Here are my thoughts. I know I will have a valid reference to the object but I am unsure in what state I will actually see the object. While testing everything is working out just fine but I am aware of how uncommon threading exceptions can be, even if something is broken.

Also, I can see one problem with this: If another MotionEvent comes though, it's possible that inputEvent in the run() method will be set to a different event than the one that was referenced when this.mInputEvent != null was checked, but this really isn't an issue.

So, is there anything I am missing or, for my purposes, should this be ok?

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HTC Desire :: Merge Message Threads In Messages

Jun 2, 2010

I imported text messages from my old phone, but they didn't merge with the contacts who had texted me on my new phone.

For example: if I had 5 texts already on my HTC Desire from John and then I imported 40 texts from my old phone from the same number (John), then they have two separate threads of "John" rather than merging into one thread with 45 messages. Anyone know how to merge these threads?

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Motorola Droid :: Lost Messages In Gmail Threads?

Feb 11, 2010

I just noticed something that is quite annoying in the native gmail app. If you "reply" to an email, but change the address you are replying to, you lose the ability to see the original message of the thread on your Droid. Here is an example. A friend of mine, Jane, was organizing a ski trip and sent out and email to the 20 people that were going with the details (dates, addresses, prices, contact info, etc). I replied to the email, but changed the address to John's email, because he was going to be driving me and I didn't want to reply to all. John and I continued the thread with multiple messages back and forth to setup details of when we were leaving. In all versions of g mail (on both my desktop and my Droid), I see "Jane, Me, John (8) >> ski trip details..." for this thread. When I am in the browser version of g mail (either desktop or the Droid browser) I can click on the thread and see all 8 messages. However, in the native g mail app on the Droid, I click on the thread, see the last message, and behind that it only says "6 read messages" (there should be 7 more) and when I expand them, Jane's original message is the one missing. The thread comes up though when I search for Jane's email address or any of the text within Jane's original email. But I can't read it.

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Sprint HTC Hero :: Messages Force Close - All Threads Wiped Clean

Nov 22, 2009

Just tried to delete a messages thread in the stock sms app that was 480 messages long. It was one thread of about 15 that were saved in my phone from people I communicate with on a regular basis. The phone froze up for about a minute, then message force closed. Opening up the messages app again reveals All of my threads have been wiped clean.

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Android :: Application Threads Vs Service Threads

Apr 13, 2010

What are the advantages/disadvantages in placing a lengthy network access code in a thread in an activity or a thread in a service? How would it affect the application? I am writing a streaming audio player and from what I've read so far putting the code in a service will still end up blocking the application so a new thread is needed, does anyone know if it makes more sense to put this piece of code in a service.

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HTC Incredible :: Can't Sign Into Application Store Pass Invalid Go To Recover Pass?

Jul 13, 2010

I was just on there yesterday i go into browse tonight and now all of a sudden it says pass world invalid from last night till this morning i tried typing in the little letters they had and I cant read it so I go to the google site. I put the info in and it says sorry account has been terminated for terms and conditions I didnt even do any thing to violate them?

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Android :: IntentService And Threads

Oct 22, 2010

We are in the process of refitting some of our recievers and services with IntentServices (mostly to address rare ANR issues - and because IntentService is pretty cool...). In one case we are converting a traditional service to an IntentService. The original service fired off a few methods whose job was to download data from our servers. Each of these requests would spawn a thread of their own to do the work (apparently not fast enough to avoid the occasional ANR). So now we have a question concerning the life cycle of these processes.

For example, the following situation demonstrates what is happening:

- Start Intent Service - Trigger Download1 - Download 1 thread starts - End Intent Service

- Download 1 thread continues..... - Download 1 thread ends

Our question concerns our exposure to the OS shutting down the Download 1 thread because the Intent Service has terminated before it finishes up. Not sure if it is becomes more or less likely that the OS will view it as something that can be flushed.

If the Download 1 thread is more likely to be flushed by OS we will need to take a different approach.

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Android :: Threads Or ASyncTask

Apr 6, 2010

I am working on a simple application (studying purposes) which list all the files from a selected folder. On top of that I would like to have a search feature where the user can search for files (the code for that is already in place). Now, I was thinking about having the search running in the background somehow, whilst the user can still navigate, create folders, copy, sort and do other stuffs normally. When the search finishes the user would get a notification and then could click on it and go to that activity (It ideally should be the same ListView I already use for browsing the files, I would just need to update the Adapter there with the latest processed data after clicking in the notification). What's the best answer for that? Threading or AsyncTask?

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Android :: Services X Threads

Feb 22, 2010

I'm trying to understand the idea behind the Services. If it runs in the program's thread, why not create just a separate thread (or AsyncTask) to do the job? Can a service keep running in the background? For example, i want to create a task that will continuously be polling data from a server, even if the main application is not running. Can this be achieved with a Service?

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Android :: Asynctask Threads Never End

Mar 13, 2010

while debugging and app that uses AsyncTask to record audio and update UI I noticed that everytime that an AsyncTask object ends running (finishes doInBackground and onPostExecute or on Cancelled its thread stays alive (running status).At least for me that should not be the behavior of the class since the doInBackground task may not stay running forever (as an example the android manual says that a status bar should be updated by an asynctask, and it wont last for the whole app running time).Is there anything Im missing, as a method to destroy it, or should I just ignore and keep creating threads as I need and the VM will handle them as it needs resources?

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Android : Way To Save Threads?

Jun 5, 2010

how do i save certain threads?

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Android : Do Threads Add A Lot Of Overhead To An App

Aug 3, 2010

As my app matures, I find myself finding more and more uses for threads. By now I must have about 25 threads, all doing important things and working together in symphony.

I notice however that my app is sitting around 15.5MB resident. Compared to the browser (+/-35MB) I feel pretty safe, but I do notice the resident size of my app ever increasing.

The question is, how much overhead is involved with adding a thread?

I'm also wondering if the synchronized keyword encounters more and more latency with each new thread that is present?

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Android :: Timer - Threads - Reliability

Mar 4, 2010

I have an activity that uses a Timer (java.util.Timer) to control the display. I set it off to repeat its run() method every second or so. When it runs, it updates some View elements.

As Timer runs in its own thread, I assumed this would be reliable. But I notice that sometimes there is a stutter, or delay, in the views updating. It's like they occasionally get stacked up, and all happen together. Studying the output from logcat, I notice that this happens when the device is doing something else - some system functions, or sometimes a garbage collection.

How can I avoid this? I'm not aware I can run the main activity in a thread of its own, can I? If the timer has its own thread, why is it affected?

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Android :: Suspending And Resuming Threads

Nov 17, 2009

We are developing an application that needs to suspend and resume threads like a debugger (meaning in a non-safe way like Object.wait() and Object.notify()).In the Java SDK the methods Thread.suspend() and Thread.resume() are deprecated but we can still use them. Also there is the Java debugger API which allows one to do that if you connect to the VM as a debugger. Is there some API for android we can use? Is there a published Java Debugger API we can apply for Android?

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Oct 30, 2009

I have a question about the background thread handling change that went into SDK 1.6. I read here that BG threads get placed in a scheduling class that can't use more than 5-10% of the CPU in order to keep the foreground responsive. Do system services get into that scheduling class?

My app uses repeating alarms. It was great with 1.5, very reliable. Since the upgrade to 1.6, the phone seems to be dropping some of my repeating broadcasts, especially if I am doing something fun in the foreground like with WIFI when the Alarm is supposed to fire. I do not have any of the task killer programs that have been a hot topic lately. To be clear, the dropped alarm broadcast behavior is intermittent. I am not 100% sure if I really am doing something when it has failed. If the timer is a one shot, it seems to work better but there is no real empirical evidence here. My phone is usually in my pocket when I fire one of the one shot alarms. If my theory about system services in the background scheduling class is correct, then I probably cannot find a workaround or defensively code a solution. Will it be the same in 2.0?

Have others seen issues with alarms and with the setRepeating method? I am looking for suggestions to troubleshoot this problem. How can I determine if the problem is the broadcast, if it is the repeating alarm creation, or if there is some other issue like low memory coming in to play.

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Android :: Memory Error With Threads

Mar 4, 2010

I have a couple of worker threads in my app which I stop and restart during onPause() and onResume(). I use a method that clears all the reference to and from the threads when stopping. However ThreadGroup is still retaining a reference to my threads and causing a small memory leak. After pausing and resuming my app about 40 to 50 times I will then get OutOfMemory Errors when loading bitmaps. Allthough this doesn't effect most of my users I do get occasional reports of crashes. How can I remove the references to my threads from ThreadGroup so that GC can do it's job.

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Android :: Delete Threads In Handcent?

Sep 24, 2010

When i try to delete a threads, handcent crashes. the reason i want to delete threads is because i believe my conversations of upwards 2000 messages are slowing down the handcent performance and therefore my phone >
anyone else have this problem or know a way to delete all that garbage?

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Android : Is Way Of Doing Threads In Phone Correct

May 17, 2010

I'm writing a live wallpaper, and I'm forking off two separate threads in my main wallpaper service. One updates, and the other draws. I was under the impression that once you call thread.start(), it took care of everything for you, but after some trial and error, it seems that if I want my update and draw threads to keep running, I have to manually keep calling their run() methods? In other words, instead of calling start() on both threads and forgetting, I have to manually set up a delayed handler event that calls thread.run() on both the update and draw threads every 16 milliseconds. Is this the correct way of having a long running thread?

Also, to kill threads, I'm just setting them to be daemons, then nulling them out. Is this method ok? Most examples I see use some sort of join() / interrupt() in a while loop. I don't understand that one...

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Android :: Sensor Listeners - Threads And Responsiveness

Jun 24, 2010

I have two questions about sensor listeners

1. from which thread are sensor values updated and should this be synchronized? can sensor's listener callback be a good place to call custom's view onDraw method? as this should be done from different thread. I cant find anything about it. In another words my problem is that I want to listen to sensors change and draw something on view surface but I dont know which thread (the main thread of the application?) is updating sensor's state

2. If I register sensor listener with SENSOR_DELAY_FASTEST my application is not responsive at all! Raw application with TextView only is not reacting to go back or home button! How should I deal with this or am I doing something wrong?

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Android :: Keep Threads And Views Alive Between Activities

Sep 13, 2010

Trying to understand the Android framework model. I have an application that needs to have several threads running. On thread gets GPS fixes, another picks up GPS fixes and pushes them to server, and yet another occasionally polls a server for dispatched orders. Some of these threads update status Views as well.

Since I am new to Android, the application framework model hasn't clicked for me. Where are these threads started? Right now I start the threads in the initial Activity, but if I understand it right, once that Activity goes invisible it is stopped. Furthermore, I have to track GPS and network statistics so that I can have a View which may (or may not) be the active View.

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Android :: Threads And Screen Orientation Change

Aug 30, 2009

In the following sequence of events:

1. Start a new thread (as a result of a button click - or similar).

2. User changes the screen orientation (causing the Activity that started the thread to be destroyed).

3. Thread finishes, and wants to do some dialog (or any UI) work. However, doing a showDialog, dismissDialog, ... will crash, as the thread it still referring to the old Activity.

This can be solved by updating the data in the thread to refer to the new Activity upon a screen orientation change.

However, couldn't the Android framework just forward any requests from a destroyed activity, to the newly created Activity, saving us developers of handling it ourselves?

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Android :: Google Team - Pin Favorite Threads

Mar 18, 2009

I was wondering, why there is no functionality to pin threads a user is interested in. As there is such a high traffic on these groups, it takes time to find the threads I answered to or some I am interested to see how the problem is solved. Sometimes you don't remember the naming of the subject or the user that wrote it and then searching becomes annoying. An easy way would be to pin some threads! I mean the right side is nearly empty an everybody is authenticated when she uses the group, not to just read.

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Android :: How Emulator Schedules Application Threads?

Sep 22, 2010

Are there any limits on the number of threads or any constraints on how the emulator (under Eclipse) schedules the application threads? I get suspended threads that don't really wait on anything but rather get bumped out from execution time. I will try using the Debug class to get some statistics on the thread alloc etc. even though the DDMS does that already. One example is, I have a simple class that simply prints a '.' every 3 seconds - well, the LogCat shows the emulator collecting garbage objects but the thread is suspended and does not print the '.'

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Android :: Running Listeners In Separate Threads

Aug 25, 2009

I would like to know how to run a listener on an isolated thread. Because I would like to use a LocationListener and make some calculations in the main thread. So the LocationListener would be "slow down", because of those calculations. Is it possible to have it run in a different thread? Or is it by default in a separate thread?

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Android :: Way To Create Methods / Threads In Java?

Sep 7, 2010

I want to create one method and call the created Thread inside that method in my Android Application, I am new to Java as I had told before. Can anybody giive me an example of how should I create a method and call a Thread inside that method!

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Android :: Threads Cache Instance Variables?

Jul 3, 2010

I am starting to develop an Android App and have noticed the following behaviour in my test code (not yet designed the real app):

A thread that loops around doing Bluetooth IO accesses an instance variable that is declared in the enclosing class. That instance variable gets set to null by the GUI thread in the onBackPressed() method which also closes the Bluetooth socket which causes an exception in the IO thread (which is what I want).

The odd thing is that if I set the instance variable to null before I close the socket, the IO thread sees the null value, but if I close the socket first and then set the variable to null, the IO thread doesn't see the null value.

The instance variable is being used in a loop in the IO thread and it appears as if that variable is being cached while within the loop. So any changes to that variable by another thread are not visible. Is that possible? If so, is there a workaround to guarantee that the VM will read the value of the instance variable?

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Android :: CursorAdapters - ListViews And Background Threads

Aug 26, 2009

This application I've been working on has databases with multiple megabytes of data to sift through. A lot of the activities are just ListViews descending through various levels of data within the databases until we reach "documents", which is just HTML to be pulled from the DB(s) and displayed on the phone. The issue I am having is that some of these activities need to have the ability to search through the databases by capturing keystrokes and re-running the query with a "like %blah%" in it. This works reasonably quickly except when the user is first loading the data and when the user first enters a keystroke. I am using a ResourceCursorAdapter and I am generating the cursor in a background thread, but in order to do a listAdapter.changeCursor(), I have to use a Handler to post it to the main UI thread. This particular call is then freezing the UI thread just long enough to bring up the dreaded ANR dialog. I'm curious how I can offload this to a background thread totally so the user interface remains responsive and we don't have ANR dialogs popping up.

Just for full disclosure, I was originally returning an ArrayList of custom model objects and using an ArrayAdapter, but (understandably) the customer pointed out it was bad memory-manangement and I wasn't happy with the performance anyways. I'd really like to avoid a solution where I'm generating huge lists of objects and then doing a listAdapter.notifyDataSetChanged/Invalidated()

Here is the code in question:

CODE:.....................

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Android :: Stop Threads With Long Operations?

Aug 28, 2009

Android experts, I have a tricky question that I would like some advice on. code...

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Android :: Closing Down Service That Has Active Threads

Feb 10, 2010

When I load my application I also load and Android Service that helps me download files from the internet.The user may have 1 or more downloads at any given time, all in their own Thread which is managed by the service. If the user presses the home button I do not destroy the service but instead let it run, however, if the user presses the back button I do stop() the service as I felt this was the right thing to do (the user would not want stray services running).

This works OK unless there are stray Threads that have not completed yet (this could happen if the internet connection is not active etc.).How could I manage this? How could I stop all Threads as I have no reference to them...or somehow command android to stop my service once all Threads are complete and my app has closed?

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