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You are here: Home / Android syllabus Topics Course details / AsyncTask

AsyncTask

 

 

AsyncTask:
In Android, we have 2 types of threads.
1) UI/Main Thread
2) Worker/Background Thread

UI/Main Thread – This thread is responsible for all the UI related operations. All the View Hierarchy and its operations only on Main Thread. No other threads can touch View Hierarchy other than the UI/Main Thread.

Worker/Background Thread – This is a background thread, which is used for network-based operations, database related huge data operations to ensure the UI Thread is not blocked with lot of operations. We can create any number of background threads and do some operations. We use this thread to achieve parallel computing/processing. This thread cannot perform any UI operations. This can be started from the Main thread, finish its task and reports the result back to Main Thread.

 

To create a worker thread and get some task done and report back to the main thread,
we need to do a lot manual checks. It requires of lot of coding. To overcome this problem, we have AsyncTask in Android.

AsyncTask:

AsyncTask performs following operations.
1) Accepts task from Main thread.
2) Creates worker thread
3) Finishes the task in worker thread
4) Reports result back to Main Thread

 

AsyncTask is a generic class, which accepts 3 types of parameters while it is creating

Params – The type of parameters we pass from main thread to asynctask while we are creating asynctask

Progress – The type of data we want asynctask to update as progress

Result – The type of result data passed after the task is completed from worker thread to main thread

 

Methods in AsyncTask:

1) onPreExecute() – Which is called immediately when the AsyncTask is called, used to perform the operations when the task is created. Runs on Main thread

2) doInBackground(Params) – Called in the background thread after the onPreExecute is called. All the task related code is written here only. This method must be overriden in asynctask

3) onProgressUpdate(Progress) – This will be called when there is a need to update progress on Main thread. This would be called if we call publishProgress() method. It runs on Main thread

4) onPostExecute(Result) – This is the final method to execute. In this method, asynctask delivers result to main thread. Runs on Main Thread

Create AsyncTask:

1) Create a subclass of AsyncTask<Params, Progress, Result>
2) Override doInBackground method – mandatory
3) Override other required methods – optional

Start AsyncTask:

1) Create object of the subclass of AsyncTask
2) Create array of parameters – optional
3) Call execute(params) method – If we have parameters
(or)
Call execute() method – If we don’t have parameters

 

 

 

 

 

 

 

 

 

 

 

 

 

 






Android syllabus Topics Course details

  • Options Menu
  • JSON parsing
  • Handling Views
  • RelativeLayout
  • ActionBar
  • ListView
  • Custom List View
  • Dialogs
  • AlarmManager
  • Notifications
  • Vibration
  • WebView
  • Fragments Runtime
  • SQLiteDatabase
  • Bluetooth
  • WiFi
  • Google Maps
  • Handling Activity Back Button
  • AsyncTask
  • Runtime Permissions
  • Logging
  • Activity Lifecycle
  • Toast
  • Service
  • Database with Cursor Adapter
  • SharedPreferences
  • Location
  • Libraries
  • Webservices
  • Creating Activity class
  • Creating XML
  • Registering Activity in AndroidManifest.xml:
  • Steps for creating an Android application:
  • Handling button clicks
  • Identifying Views
  • Getting Text from Views
  • intent with Data
  • Intent
  • Resources Handling in Android
  • Intent with Result Data
  • Broad cast Receiver
  • Fragment
  • Handling Button click by using On Click Listener:
  • Material Design
  • RecyclerView
  • JSON
  • Rename Android Package [with images 2018]

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