The onPostExecute method synchronizes itself again with the user interface thread and allows it to be updated. This method is called by the framework once the doInBackground method finishes. By default, AsyncTask tasks are executed sequence for Android versions higher than Android 3.
The following code demonstrates how to use the AsyncTask to download something from the Internet. The code requires the android. One challenge in using threads is to consider the lifecycle of the application.
The Android system may kill your activity or trigger a configuration change which will also restart your activity. You also need to handle open dialogs, as dialogs are always connected to the activity which created them. In case the activity gets restarted and you access an existing dialog you receive a View not attached to window manager exception.
To use your application class assign the classname to the android:name attribute of your application. The application class is automatically created by the Android runtime and is available unless the whole application process is terminated.
This class can be used to access objects which should be cross activities or available for the whole application lifecycle. In the onCreate method you can create objects and make them available via public fields or getter methods. The onTerminate method in the application class is only used for testing. If Android terminates the process in which your application is running all allocated resources are automatically released.
Fragments which do return null in the onCreateView methods are called headless fragments , as the provide no views. Headless fragments can retain there fields between configuration changes via the setRetainInstance true method call.
For example, if you define an AsyncTask as field in a headless fragment, it can continue to run during configuration changs. Networking with Android. Google blog about multithreating.
Introduction to Android Development. Tutorial about the usage of fragments. Tutorial about Android services. Free use of the software examples is granted under the terms of the Eclipse Public License 2. Sponsor our Open Source development activities and our free content to help us make development easier for everyone. This tutorial introduces the concept of asynchronous processing in Android applications. Background processing in Android 1. Why using concurrency? Android enforces a worst case reaction time of applications.
If an activity does not react within 5 seconds to user input, the Android system displays an Application not responding ANR dialog. Fortega When you have no issue in running task parellel, for the same thing i. For asyncTask when you need something to be returned from a background work, or want to wait for some process to finish before executing some other process or update some view etc. Similar question answered: stackoverflow.
My requirement is to hit a service and then retrieve some data and keep list of object in list and also update ui for its progress the retrieval may take time — user Add a comment.
Active Oldest Votes. Basically Use AsyncTask for: Simple network operations which do not require downloading a lot of data Disk-bound tasks that might take more than a few milliseconds And Use Java threads for: Network operations which involve moderate to large amounts of data either uploading or downloading High-CPU tasks which need to be run in the background Any task where you want to control the CPU usage relative to the GUI thread For more information refer Mohit's answer Click Here Edit: Service is like an Activity but has no interface.
Improve this answer. Rissmon Suresh 9, 5 5 gold badges 27 27 silver badges 35 35 bronze badges. Bhavin Nattar Bhavin Nattar 3, 2 2 gold badges 19 19 silver badges 30 30 bronze badges. Tomasz Gawel Tomasz Gawel 8, 4 4 gold badges 33 33 silver badges 59 59 bronze badges. By default AsyncTask is run in serial in a single thread, but you can run it in parallel on multiple threads too. I don't understand the question Do you mean creating threads and running a asynctask in each threads?
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Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta. If you use Java threads then you need to handle the following requirements in your own code: Synchronization with the main thread if you post back results to the user interface No default for canceling the thread No default thread pooling No default for handling configuration changes in Android AsyncTask AsyncTask enables proper and easy use of the UI thread.
An asynchronous task is defined by a computation that runs on a background thread and whose result is published on the UI thread. Invoked on the background thread immediately after onPreExecute finishes executing. Invoked on the UI thread after a call to publishProgress Progress Why should you use AsyncTask? Easy to use for a UI Thread. So, use it when the caller thread is a UI thread. No need to manipulate Handlers. URL urldisplay. So you can do UI changes in the same class implementation without using Handler and message passing.
To use this class, you need to write the following line: new DownloadImageTask Activity. Which is better for which condition. It's now clear when to use Thread and when to use AsyncTask.
View All. Chintan Rathod Updated date Mar 31,
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