Let's see the structure of a typical AsyncTask class.
private class myBrightHubTask extends AsyncTask<X, Y, Z>
protected void onPreExecute(){
}
This method is executed before starting the new Thread. There is no input/output values, so just initialize variables or whatever you think you need to do.
protected Z doInBackground(X...x){
}
The most important method in the AsyncTask class. You have to place here all the stuff you want to do in the background, in a different thread from the main one. Here we have as an input value an array of objects from the type “X” (Do you see in the
header? We have “...extends AsyncTask<X,Y,Z>” These are the TYPES of the input parameters) and returns an object from the type “Z”.
protected void onProgressUpdate(Y y){
}
This method is called using the methodpublishProgress(y) and it is usually used when you want to show any progress or information in the main screen,
like a progress bar showing the progress of the operation you are doing in the background.
protected void onPostExecute(Z z){
}
This method is called after the operation in the background is done. As an input parameter you will receive the output parameter of the doInBackground method.
What about the X, Y and Z types?
As you can deduce from the above structure:
X – The type of the input variables value you want to set to the background process. This can be an array of objects.
Y – The type of the objects you are going to enter in the onProgressUpdate method.
Z – The type of the result from the operations you have done in the background process.
How do we call this task from an outside class? Just with the following two lines:
myBrightHubTask
brightHubTask = new
myBrightHubTask();
brightHubTask.execute(x);
Where x is the input parameter of the type X.
Once we have our task running, we can find out its status from “outside”. Using the “getStatus()” method.
brightHubTask.getStatus();
and we can receive the following status:
RUNNING -Indicates that the task is running.
PENDING -Indicates that the task has not been executed yet.
FINISHED -Indicates thatonPostExecute(Z)has finished.