What is the difference when a class extend from Handler and Thread?
As described in developer.android.com
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Each Handler instance is associated with a single thread and that thread's message queue.
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Does the thread has no message queue ?
Any benefit for a class extend from Handler?
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I need to update my ui for an android app and I'm trying to use the Handler class to do it, using http://developer.android.com/resources/articles/timed-ui-updates.html and the android developer resources "Common Task" for using Handlers as guides.
Basically, I need something between the two - a timed update of the user interface, but without a button. So here is the relevent code that I am working on.
CODE:...............
I want to have a class "Utils", that will have several methods used all over my code. For example, I have a top bar with a textview and two ImageButtons that must display different texts and icons on different activities.I created the class Util, but it doesn't extend Activity. The problem is that if it doesn't, findViewById isn't there, can't find stuff etc.
View 1 Replies View RelatedIn Handler, we can pass some data from a background thread to the UI thread like this:
private void someBackgroundThreadOperation() {
final String data = "hello";
handler.post(new Runnable() {
public void run() {
Log.d(TAG, "Message from bg thread: " + data);
}
}
}
If we use the above, we cannot then use Handler.removeCallbacks(Runnable r), because we won't have references to any of the anonymous runnables we created above. We could create a single Runnable instance, and post that to the handler, but it won't allow us to pass any data through:.............
My program threw a NullPointerException the other day when it tried to use a Handler created on another thread to send that thread a message. The Handler created by the other thread was not yet created, or not yet visible to the calling thread, despite the calling thread having already called start on the other thread. This only happens very rarely. Almost every test run does not get the exception. I was wondering what the best way is to avoid this problem for sure with minimal complication and performance penalty. The program is a game and very performance sensitive, especially once it is running. Therefore I try to avoid using synchronization after setup, for example, and would prefer to avoid spinning on a variable at any time.
View 2 Replies View RelatedI have a class that uses a Handler for a timed, asynchronous activity.
Something like this:
CODE:.................
I try to make several connection in a class and update the multiple progressbar in the main screen. But I've got the following error trying to use thread in android : Code: 05-06 13:13:11.092: ERROR/ConnectionManager(22854): ERROR:Can't create handler inside thread that has not called Looper.prepare() Here is a small part of my code in the main Activity.
public class Act_Main extends ListActivity
{ private ConnectionManager cm;
public void onCreate(Bundle savedInstanceState)
{ super.onCreate(savedInstanceState);
// Set up the window layout
requestWindowFeature(Window.FEATURE_CUSTOM_TITLE);
setContentView(R.layout.main);
getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE, R.layout.custom_title); }
public void startConnection() { ......
Instead of finding the button (as per the id specified in xml) i.e
CODE:.....
Is it possible to set the Listener class name directly in the xml definition. Most of the time dealing with id's for attaching listeners is affecting our productivity.
I go back and forth about how to name activity classes.Activity seems to imply a verb, like EditContact, for example.But that seems more like what one would call the Intent that triggers EditContact.Should the activity be named ContactEditor instead?
View 2 Replies View RelatedI have an app with a two threads - main and data loader. When data loader finishes it posts a Runnable object to the main thread (as described in the DevGuide), but it never gets delivered and run. Here's the basic code:
class MyApp extends Application{
public void onCreate()
{LoaderThread t = new LoaderThread();
t.start(); }
private class LoaderThread extends Thread {
public void run()
{ SystemClock.sleep(2000);
boolean res = m_handler.post(m_runnable);
if(res)
Log.d(TAG, "Posted Runnable"); } ............
I was curious about the nature of the handleMessage() and sendMessage() behavior of the Handler class. I want to be able to send message to another thread in such a way that the destination thread can process the message queue when it wants to. It seems, however, that the message is processed by handleMessage() practically as soon as it's sent.
I'm trying to design a game loop thread that does something like this:
CODE:.....
However, I as soon as sendMessage() is called (from the parent/calling thread), the Handler.handleMessage() is processed (in the child/receiving thread), even if the child/receiving thread is blocking in a while loop.
I've seen this problem solved in other games by using a thread-safe list (ConcurrentLinkedQueue). The UI thread just posts events to this queue, and the game loop can remove the events as it seems fit. I just assumed the Handler class was designed for this purpose. It seems it's more intended for asynchronous callbacks to the parent thread.
Ok. I know there are a few other (older) threads about this. I haven't even got my Eris yet, but will be getting it Saturday. I've read through the the how to extend battery life thread. I have yet to look at the tips and tricks thread though.
Anyways, what I would like to know is what are the "Must have" apps. What should I do with it right out of the box? Anything particular I should know/expect?
I hope this will be a pleasant experience, it's my first Android phone (first smartphone actually) although I do have an iPod Touch, so I hope that will shorten the learning curve.
What does the following exception mean? And how can I fix it?
This is the code:Toast toast = Toast.makeText(mContext, 'Somthing', Toast.LENGTH_SHORT);
This is the exception:
D/VVM ( 684): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
D/VVM ( 684): at android.os.Handler.(Handler.java:121)
D/VVM ( 684): at android.widget.Toast.(Toast.java:68)
D/VVM ( 684): at android.widget.Toast.makeText(Toast.java:231)
I am using an Executor [fixed thread pool] with my own ThreadFactory that adds a Looper:
CODE:...............
I am running a thread that makes network requests but if the network fails I would like a dialog message to be displayed to the user. This process is rather involving since it requires making AND displaying the request in the UI thread. I can wait for the user's response to the dialog by simply adding a Loop to the network thread and wait for a message to be send from the UI thread. This allows me to encapsulate the network requests in a while(tryAgain) thread. All works well except when the Looper.loop() method is called the second time (after a second network error dialog is displayed) and a message is sent by the dialog (in the UI thread) to the network thread's handler:
CODE:.............
In the AlertDialog instance is an OnClickListener:
CODE:...............
I've checked that the thread is still active with handler.getLooper().getThread().isAlive() which always returns true but it still gives me "sending message to a Handler on a dead thread". How is it that the Message/Handler has decided that the thread is dead? Shouldn't it rely on the .isAlive() method? In the end I am trying to avoid replicating the thread management build into the Android OS .
I want to download some data from internet.It should not block main UI thread. I know both thread and service can handle the work. What is the difference between them?
View 4 Replies View RelatedI am getting reports of 'Can't create handler inside thread that has not called Looper.prepare()' once I added ScoreNinja to my Android app, and released it to the market. It seems that it isn't happening all the time as the ScoreNinja highscore has lots of entries from users. I have looked on the web for help but there are no clear directions on what to do. I have used the ScoreNinja code exactly as shown on the scoreninja website. BTW If anyone is having problems with ScoreNinja only displaying one score, check to see if the launchmode is not set to 'singleinstance' in your manifest. This fixed it for me!
View 6 Replies View RelatedI am trying to figure out what is the best way to go about creating dialogs. I can either create my own Dialog class (which, to me, is more clean and organized), or I can use AlertDialog.Builder (which would be done inline, and funky looking)... What are the positivies and negatives of either implementation?
View 1 Replies View RelatedWhat's the difference between file, class and activity in android?
View 3 Replies View RelatedWhat is the difference between Service, Async Task & Thread. If i am not wrong all of them are used to do some stuff in background. So, how to decide which to use and when?
View 2 Replies View RelatedI have some questions about android ui api.
Give a example, that I want to implement.
Main_UI_Thread.java. code...
I know the message passing can be do that;
But I want the ui program is be implemented in DisplayClass.java. Is it possible?
I have a class 2 16gb sandisk card, would I notice a difference with a class 6? And would a class 6 card snap photos faster. And with that I mean no lag after the photo is taken.
View 1 Replies View RelatedI need to update my ui for an android app and I'm trying to use the Handler class to do it, using http://developer.android.com/resources/articles/timed-ui-updates.html and the android developer resources "Common Task" for using Handlers as guides.
Basically, I need something between the two - a timed update of the user interface, but without a button. So here is the relevent code that I am working on.
CODE:...................
When I put the setContentView in thread as below, it crashes while running in emulator. code...
View 2 Replies View RelatedIs there a reason why the Thread class in the SDK LunarLander and JetBoy examples are not each in a separate java file, rather than being inside the View file?
It would make things a bit clearer, IMHO. Am I missing something?
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.
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.
I'm creating a new class, using eclipse "New Java Class" dialog box. I can write the superclass I want (I can't find using "browse" button), but I can't write or select an interface to implement. I click "add" but ther is nothing to select. What I'm doing wrong?
View 4 Replies View RelatedI 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?
View 1 Replies View RelatedI 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;...................
I'm just getting into Android development, and I have a question about communicating between a receiver class and an activity class. I'm very new to JAVA and Android so I hope I don't sound too stupid. I'm developing an application where I intercept an SMS message and then based on various elements of that SMS I might delete it once it's been saved to the inbox. I have a receiver class that intercepts the txt message, and I am also able to delete messages from my inbox with code in the activity class using a button at the moment. The problem I have is communicating between the receiver class and the activity class where the code to delete a message resides. I tried putting that code directly into the receiver class but as I'm sure most of you already know the BroadcastReceiver class doesn't seem to support what I need to delete messages. I've been searching for an answer to this for a while, but haven't been able to find anything. Honestly I'm not sure I know enough about JAVA and Android to even recognize a solution if I saw it.
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