Android :: Best Way Of Handling UI Code From Thread?
Feb 7, 2010
I know how to use handlers to update UI elements such as progress bars toasts etc. The problem I am having is when the context goes away such as the user pressing the back button or the Activity finishing for some reason. This causes my application to crash often. I tried using
getApplicationContext()
(Thinking that this would be available throughout my entire application) but this did not work, ever - instead my application crashed! I put try catch blocks around all UI update code, this works but is it necessary? What is the bast way to handle this?
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Sep 16, 2009
OK I'm reading this page:
http://developer.android.com/guide/appendix/faq/commontasks.html#thre...
The code is as in the example (see below). In my application, the worker thread has done loading of large bitmaps, and I need to notify the UI thread the filename of the bitmap that was loaded as they get loaded. How can I notify the UI thread of the filename of the bitmap just loaded? I can see anyway to for updateResultsInUi() to be able to take a parameter from the example below.
public class MyActivity extends Activity {
[ . . . ]
// Need handler for callbacks to the UI thread final Handler mHandler = new Handler();
// Create runnable for posting final Runnable mUpdateResults = new Runnable() { public void run() { updateResultsInUi();
} };
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);
[ . . . ]
} protected void startLongRunningOperation() {
// Fire off a thread to do some work that we shouldn't do directly in the UI thread
Thread t = new Thread() { public void run() {
mResults = doSomethingExpensive();
mHandler.post(mUpdateResults);
} };
t.start();
} private void updateResultsInUi() {
// Back in the UI thread -- update our UI elements based on the data in mResults
[ . . . ]
}
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Jul 14, 2009
I'm a new Android developer. I would like to make a simple game using the SurfaceView (Canvas drawing).the game has a a custom Object name Box. Box can draw itself and need to get an event when it is clicked. when it does, there is an animation sequence coming out of the box like a "jumping clown". I have several Boxes on the screen when each of them can be activated. Several Boxes animation can also be presented simultaneously.Here it gets tricky: Since I have a "complicated" animation sequence, each Box extends SurfaceView. The problem is I haven't figured it out how can I handle several SurfaceView's drawing using only one Thread (in order to present an animation I need to use one) and also how can I get the onClick/ onThouch event from my Activity to each of my Boxes.
The LunarLanding example in the SDK uses only one Thread but also uses only one SurfaceView which manage the animation of the game components (there are no several game components SurfaceViews). Also, there is no need to get onTouch event, so this example doesn't match to my case. I have several questions about what is the right approach do code this:
1. Should I use Box extends SurfaceView?
2. Can SurfaceView gets user events like onTouch/onClick?
3. Is there a way to add to the "main" SurfaceView another SurfaceView (Box)?
4. If none of the above questions is positive, should I use one SurfaceView (and one Thread) and try to map the other Boxes on the screen for user event handling. I mean Box only paints itself but the user event is being handled by me (not by the OS).
5. Should each Box (SurfaceView) should handle it's own Thread in case of animation (it is not good design but it is also an option)?
6. do you have any other proposal?
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Nov 9, 2010
I want to know if it is possible to support multiple profiles within Android? To explain my question better, can we have two or more applications, which uses a Data Call, operating simultaneously in Android? For e.g. is it possible to have one IM, one e-mail application and one SNS(like Facebook) operating simultaneously in Android phones? If yes, I want to know how this is being handled within the Android Stack code. Since the platform code is open source, any suitable reference to any portion of the code handling this behavior would be perfect.
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Jul 10, 2010
I am trying to make APP native code for Android. The Native code is in cplusplus. Whenever I try to make, the following error appears.
H236Plus.cpp:135: error: exception handling disabled, use -fexceptions to enable
How do I use -fexceptions to enable exception handling, and where do I use it?
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Jul 23, 2010
I have an AIDL service that is intended to be used by both out-of- process remote users and in-process local users. As a result, my common interface methods will either be invoked on the UI thread or in a binder background thread. The logic between the two is not the same. How do I distinguish between these two cases?
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Aug 4, 2010
We have a service that seem to get deadlocked very occasionally in the field. It's not possible to hook up to a debugger. We can detect the deadlock situation programmatically. Is it possible to do this from within Java code?
if (ohIamDeadlocked()) { Thread.something.dumpStacksOfAllThreads(); }
If this is not possible, is there an adb command that could do it? I tried "adb dumpsys" but it doesn't print any stack information.
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Sep 7, 2010
How can I implement a run() method of thread if I create a Thread Global?
I mean If I create a Thread Globally then can I implement its run() method {" public void run()"} anywhere in my Application?
In the run() method I have to write the code to perform some action.
IF I can do it then please can anyone show me briefly how to do it particularly.
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May 21, 2009
I am writing an application in which i need to handle messages between the main thread(the deafult UI related thread) and the user created Gamethread.
The requirement is like this.
An activity(say "Activity_X") is setting the view by "setContentView(some "View_Y")". In "Activity_X" i have implemeted "onCreateOptionsMenu()" and "onOptionsItemSelected()" fucntions for creating menus & a switch case for action to be taken on selecting those menus.Menu has items like "resume/pause/zoom/" .
All action to be take on selecting these menus are implemented in "View_Y" in a separate Gamethread by extending "Thread" class.
So whenever a menu is selected in "Activity_X" i need to send a message to "View_Y". And on receiving this ,a particular action/method should be called in View_Y(GameThread).
How can i achieve this using Handlers?Is there any other way of doing this? Please do share with me some code snippets for these.
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May 27, 2010
I have a separate thread running to get data from the internet. After that, I would like to update the ListView in the main thread by calling adapter.notifyDataSetChanged(). But it does not work. Any workaround for that?
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Jul 22, 2009
I want to do the drawing in another thread to speed up the game(it is way to slow right now). I was told to do this but don't quite understand why that would speed things up. Is it GameView that should implement Runnable? Should I make the thread sleep when not drawing? where should I start the thread? package com.android.WWS;
import android.app.Activity; import android.content.Context; import android.graphics.*; import android.os.Bundle; import android.view.SurfaceView; import android.view.KeyEvent; import android.view.View; import android.view.View.OnKeyListener; import java.lang.Runnable; import java.lang.Thread;...................
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Feb 20, 2009
I need to suspend/resume a thread from another thread in the same process. I tried to look into thread apis,but I couldn't figured out a way to achieve this.Can anyone pls point me some references to look or give a tip to do this.
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Dec 28, 2009
Does anyone know how to delete certain texts from a thread in an easy manner instead of having to delete a whole thread??
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Jul 16, 2010
The Android doc says "Like activities and the other components, services run in the main thread of the application process." Is the main thread here the same thing as UI thread?
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Sep 2, 2010
Android device is much slower and have much lower memory compare to PC/server, So what is the best way to handling XML in Android? And I have a set of very complex xml needed to parse. both SAX or DOM will cause too much code. Anybody have good suggestion? I want to make it clean and fast.
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Aug 9, 2010
I read somewhere not to exception handle when developing in Android, is that true?
If one does need to exception handle are there any logging tools for 2.1 and above?
If shouldn't exception handle, why is it not recommended to at least use the below?
try {body-code} catch (exception-classname variable-name) {handler-code}
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Apr 6, 2010
I'm using a PostMethod, and wondering what try/except handling I should use.
The exception handling here seems to work okay in most scenarios, but is there anything I might be missing? In particular, I'm wondering whether this handles the network connection going down midway through the upload.
CODE:...................
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Jan 1, 2010
I've been wondering if Handcent is supposed to move all my pictures to the top of each thread? And is there anyway to save the pictures with Handcent?
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Jun 3, 2010
From the documentation regarding the android:configChanges='orientation' attribute of the activity tag in the manifest:
Using this attribute should be avoided and used only as a last-resort. Please read Handling Runtime Changes for more information about how to properly handle a restart due to a configuration change.
Why does it say this?
In the case of threads and networking requests via a service API library, a request could be made with a reference to the original Activity, and then an orientation change could occur, leaving the thread pointing to the old Activity.
While this can be fixed, it's tedious and ugly compared to just handling the configuration changes yourself.
Why should it be avoided?
I guess I should also ask: would this be an acceptable reason for doing the orientation configuration changes yourself?
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Sep 22, 2010
I'm trying to do is draw circles around two points that are being touched, and as the fingers drag along on the screen, have these circles follow each finger.
However, I'm getting some weird behavior that I can't figure out. So when I place two fingers on the screen I get my circles no problem. When I drag around with the two fingers everything works like I want it. However, if I lift the first finger, everything stops redrawing, and the second finger that is still on the screen stops being tracked. If I place the first finger back on, everything behaves good again. I figure I must be handling the two fingers poorly.
Also, if I have two fingers on the screen, and I lift and touch the second finger, everything behaves well. It's only in the case where I have two fingers and I lift the first one do I see a problem.
CODE:........................
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Jun 16, 2010
I have some required try/catch statements in my application that in my testing never get called. I have sent them up with:
Log.e("messaage", e.toString());
For my debugging and now that I'm ready to release I am not sure if I should take that out or not. I see in android market you can get error/crash reports and while I do not expect my app to catch any errors, I would like to know if that happens and wondering if I need specific syntax for that. My question is what should I do in the catch statement for these errors? I'm already handling the error from a user standpoint...
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Mar 23, 2010
I want to handle key press and long key press for the key code KEYCODE_CALL(dial button). can any one suggest me how this in android 1.5(API level 3).
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Mar 8, 2010
in my app a background service starts and from that service i want to set Status bar notification, that the service has Started following is the Notification is displayed in Status bar But whin i click on that MyClass.class is not fired.And in log cat it shows
"Input Manager Service Window already focused ignoring focusing ...." Code...
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Aug 18, 2009
AsyncTask blocks exceptions? Please see the below code. My "getOffersStatus" function catches certain exceptions and show them in a AlertDialog. But instead of getting my custom exceptions message I get default error dialog "The application ... has stopped unexpectdly. Please try again".
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Nov 24, 2010
I'm developing a media file app that is meant to play sounds stored in my raw folder. There are about 32 sounds in all. And this is what i'm doing on the click of each button:
CODE:.......
I get a runtime exception saying "app stops unexpectedly" with the follow messages in my logcat window:
CODE:................
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Sep 3, 2010
Have a dump_log which points to "Out of Memory exception". How do I fix the issue as we have a number of applications running on the Android target?
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Oct 11, 2010
I'm trying to run this piece of code inside my onCreate method as an initial test into writing private data for my app to use. This code is straight out of the Android SDK development guide located here (http://developer.android.com/guide/topics/data/data-storage.html#filesInternal)
CODE:................
However, this code give me errors for the 3 lines of code at the bottom. The error is an unhanded exception. The suggested quick fix is do to the following:
CODE:..........
But after doing that I get an error for the bottom two lines which states that fos may not be uninitialized. How can I fix this code? It's kind of annoying that the Android SDK gives you an example that doesn't even work.
I can't say I'm an expert at exception handling either.
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May 11, 2010
I would like to build an application that caters for multiple accounts (eg. home, work) and account types (e.g. ISP, VoIP, Mobile). Essentially, I would like to get the user to create the accounts they want and then have all the accounts listed on the start page grouped by type.
For example:
ISP:
- Home
- Work
Mobile:
- Mum
- Dad
When you click on the account, it would take you to another screen where I do a bunch of calcs and display the results.
I currently do this via multiple apps but am looking at consolidating into the one app. I am just not sure where to start or how I go about achieving this? The way the Contacts app works is a good example of what I am wanting to do.
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Apr 18, 2010
We have created an AppWidget that takes user inputted text into an EditText and displays a calculated amount of text inside a TextView on the Home Screen. We calculate the amount of text based on the AppWidgetInfo.minWidth, minHeight attributes. We do this to simulate scrolling; we cut up the user-inputted text into chunks that will fit into the widget and swap them based on button clicks.
When we save the widget with the device in Landscape mode, it calculates the appropriate amount of text for Landscape mode and displays it in the widget. The problem is when the user changes orientation of the device to Portrait mode (without opening the widget and resaving the text), the calculated amount of text for Landscape mode is still displayed. This also happens in the vice versa case (the user is in Portrait and saves, etc.)
How can we tell our AppWidget to recalculate the amount of text displayed on screen orientation change? Is this possible? How would you solve this problem?
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Jul 6, 2010
My project is working fine when i hold my HTC device vertical.But the moment i rotate my screen 90degrees , it throws a force close error.Starts all over again, runs fine until i again change the orientation.How do i handle it ?
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