How to pass different objects as a parameter to AsycTask?

Question

I am using following code to create an AsyncTask.

public  class SaveFileToExternalStorage extends AsyncTask<File, Void, Boolean>{

    protected Boolean doInBackground(File... file) {

        DalCategories c= new  DalCategories();
        boolean result  = c.saveObject(customlistobject,file[0]);

        return result;    
    }


    protected void onProgressUpdate() {       
        //setProgressPercent(progress[0]); 

    } 

    protected void onPostExecute(boolean result) {     
        //showDialog("Downloaded " + result + " bytes");  

    }

}

Now I want to pass it two parameters customlistobject and File objects with void progress and boolean return type.

I don't know how to pass that customlistobject to my AsyncTask along with the File object.

Answer 1

A not perfect but working solution is to use Object as parameter.

public  class SaveFileToExternalStorage extends AsyncTask<Object, Void, Boolean>{
    protected Boolean doInBackground(Object... param) {
        File file = (File) param[0];
        List list = (CustomList) param[1];
        return result;    
    }

    protected void onProgressUpdate() 
    {       
        //setProgressPercent(progress[0]); 
    } 

    protected void onPostExecute(boolean result) 
    {     
        //showDialog("Downloaded " + result + " bytes");  
    }
}

This code is just a sample, you should ensure that the objects at index 0 and 1 are really a File or your CustomList by using instanceof.

Octavian Damiean has also written a good method...

Answer 2

One option is to have a constructor of your AsyncTask that takes those parameters

public  class SaveFileToExternalStorage extends AsyncTask<File, Void, Boolean>{
    List customlistobject;

    public SaveFileToExternalStorage(List aList) {
        customlistobject = aList;
    }

    protected Boolean doInBackground(File... file) {

        DalCategories c= new  DalCategories();
        boolean result  = c.saveObject(customlistobject,file[0]);

The other option is to pass object as first type parameter of AsyncTask:

public  class SaveFileToExternalStorage extends AsyncTask<Object, Void, Boolean>{

    protected Boolean doInBackground(Object... objs) {

        File file = (File) ibjs[1];
        List customlistobject =  (List) objs[2];
        DalCategories c= new  DalCategories();
        boolean result  = c.saveObject(customlistobject,file[0]);

This works, as the actual parameter to doInBackground() is a varargs list and not a single object.

Answer 3

If you need to pass it two objects as a parameter just create your own holder and send it the holder objects.

You create an object that holds your custom object along with the File object. Depending on the situation you can also make your custom object just hold the File object and pass the AsyncTask the custom object.

Inside of the doInBackground method just extract the objects so you can process them as necessary.