How to Return Boolean Values from an Android AsyncTask?

Returning Boolean Values from AsyncTask

AsyncTasks provide a convenient way to perform background operations in Android applications. However, when you need to communicate the results of an AsyncTask to the main thread, such as returning a boolean value, the standard AsyncTask completion methods may not suffice.

Original Code

Consider the following code, where an AsyncTask is used to establish an FTP connection:

AsyncConnectTask task = new AsyncConnectTask(SiteManager.this,
            _address, _username, _password, _port);
task.execute();

In this code, the AsyncConnectTask will perform the connection operation in the background and return the result as a boolean value. However, there is no mechanism to retrieve this boolean value in the main thread.

Custom Interface Approach

To return a boolean value from an AsyncTask, you can create a custom interface that will be implemented in the activity or fragment that creates the AsyncTask. For example:

public interface MyInterface {
    public void myMethod(boolean result);
}

Modified AsyncTask

The AsyncTask can then be modified to implement this interface and pass the result back to the main thread through the interface:

public class AsyncConnectTask extends AsyncTask<Void, Void, Boolean> {

    private MyInterface mListener;

    public AsyncConnectTask(Context context, String address, String user,
        String pass, int port, MyInterface mListener) {
        // ...
        this.mListener  = mListener;
    }

    @Override
    protected Boolean doInBackground(Void... params) {
        // ...
        return result;
   }

    @Override
    protected void onPostExecute(Boolean result) {
        if (mListener != null) 
            mListener.myMethod(result);
    }
}

Usage

With the custom interface and modified AsyncTask, you can execute the task and receive the boolean result in the main thread:

AsyncConnectTask task = new AsyncConnectTask(SiteManager.this,
            _address, _username, _password, _port,  new MyInterface() {
    @Override
    public void myMethod(boolean result) {
        if (result == true) {
            // Connection successful
        } else {
            // Connection failed
        } 
    }
});

task.execute();

By using this approach, you can return boolean values from AsyncTasks and process the results on the main thread.

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