Passing string to Asyntask

Question

I am trying to pass the password value entered to a dialog box and pass it to the asyntask so that it could be sent to the database to compare. I am getting nullpointerexception at the password field. It seems like the value wasn't passed. How do I fix this problem?

Dialog box which require password to continue:

public void onClick(View view) {
            LayoutInflater layoutInflater = LayoutInflater.from(context);
            View promptView = layoutInflater.inflate(
                    R.layout.prompt_password, null);
            AlertDialog.Builder alert = new AlertDialog.Builder(context);

            alert.setView(promptView);

            // Set an EditText view to get user input
            final EditText input = (EditText) promptView
                    .findViewById(R.id.passwordInput);

            alert.setPositiveButton("OK",
                    new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            String pass = (input.getText()).toString();
                            // Do something with value!
                            Log.d("Value", pass);
                            ProgressDialog progressDialog = new ProgressDialog(DisplayReqItemInfo.this);
                            progressDialog.setMessage("Cheking password...");

                            ItemEdit itemEdit = new ItemEdit(DisplayReqItemInfo.this, progressDialog);
                            itemEdit.execute();
                        }
                    });

            alert.setNegativeButton("Cancel",
                    new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            // Canceled.
                            dialog.cancel();
                        }
                    });

            AlertDialog dialog = alert.create();
            dialog.show();

        }
    });

}

The class which is suppose to retrieve the value:

public class ItemEdit extends AsyncTask<String, Void, Integer> {

private ProgressDialog progressDialog;
private DisplayReqItemInfo activity;

private int responseCode = 0;

public ItemEdit(DisplayReqItemInfo activity, ProgressDialog progressDialog)
{
    this.activity = activity;
    this.progressDialog = progressDialog;
}

@Override
protected void onPreExecute()
{
    progressDialog.show();
}

protected Integer doInBackground(String... arg0) {
    TextView PID = (TextView)activity.findViewById(R.id.req_pid);
    EditText passwordEdit = (EditText)activity.findViewById(R.id.passwordInput);
    String pid = PID.getText().toString();  
    String password = passwordEdit.getText().toString();
    ItemFunction itemFunction = new ItemFunction();
    JSONObject json = itemFunction.requestItem(pid, password);

    // check for response
    try {
        if (json.getString(KEY_SUCCESS) != null) {
            String res = json.getString(KEY_SUCCESS);

            if(Integer.parseInt(res) == 1){

                responseCode = 1;

            }else{
                responseCode = 0;
            }
        }

    } catch (NullPointerException e) {
        e.printStackTrace();

    }
    catch (JSONException e) {
        e.printStackTrace();
    }

    return responseCode;
}

@Override
protected void onPostExecute(Integer responseCode)
{   
    if (responseCode == 1) {
        progressDialog.dismiss();
        Intent i = new Intent();
        i.setClass(activity.getApplicationContext(), MainMenu.class);
        activity.startActivity(i);
    }
    else {
        progressDialog.dismiss();

    }

}
}

Answer 1

There can be no screen I/O from inside the AsyncTask.doInBackground function. You can do the screen I/O in the onPreExecute or onPostExecute functions, which have access to the UI thread. So you can get the value from the EditText field in onPreExecute and put it into a variable that is global to AsyncTask's methods and read by doInBackground.

(Using your example)

public class ItemEdit extends AsyncTask<String, Void, Integer> {
String password;
String pid;

  @Override
  protected void onPreExecute()
  {
    TextView PID = (TextView)activity.findViewById(R.id.req_pid);
    EditText passwordEdit = (EditText)activity.findViewById(R.id.passwordInput);

    pid = PID.getText().toString();  
    password = passwordEdit.getText().toString();
  }

  protected Integer doInBackground(String... arg0) {
    ItemFunction itemFunction = new ItemFunction();
    JSONObject json = itemFunction.requestItem(pid, password);

    . . . 
  }
}

You can also pass parameters into the AsyncTask initializer and pass via the class global:

TextView PID = (TextView)activity.findViewById(R.id.req_pid);
EditText passwordEdit = (EditText)activity.findViewById(R.id.passwordInput);

String pid = PID.getText().toString();  
String password = passwordEdit.getText().toString();

// start background task
mAuthTask = new UserLoginTask(pid, password);
mAuthTask.execute();


public class UserLoginTask extends AsyncTask<Void, Void, Boolean> {
  private String userLoginId;
  private String userPassword;

  private UserLoginTask(String loginId, String password) {
    userLoginId = loginId;
    userPassword = password;
  }

  @Override
  protected Boolean doInBackground(Void... params) {

        . . .

        // Do something with userLoginId, userPassword 

        . . . 
  }
}

Answer 2

You can pass parameter in your execute

  ItemEdit itemEdit = new ItemEdit(DisplayReqItemInfo.this, progressDialog);
  itemEdit.execute(new String[] { "yourstring" });

In your Async there is doInBackground

protected Integer doInBackground(String... arg0) {
 String response = args0[0];
TextView PID = (TextView)activity.findViewById(R.id.req_pid);