Question

I have a login page that accepts username & password. When the user clicks “Login” a loading screen “Signing in..” is shown with the background thread calling a doLogin() method that calls a web service and load the appropriate page.

The problem I am facing is to “Cancel” signing in from Dialog.cancel() after login has been clicked. It cancels the loading screen but the background thread is still processing and even after clicking “cancel”, the new page is loaded. How can I cancel the background thread?

Thread backgroundWorker = new Thread(new Runnable() {
    public void run() {
        doLogin(uname, pwd);
    }
});
Dialog busyDialog = new Dialog("Signing in...",
                               new String [] { "Cancel" },
                               new int [] { Dialog.CANCEL},
                               Dialog.CANCEL,
                               Bitmap.getPredefinedBitmap(Bitmap.HOURGLASS))
{
    public void fieldChanged(Field field1, int context1)
    {
        //Something to stop the login and close the loading screen
    }
};
busyDialog.setEscapeEnabled(false);
busyDialog.show();
backgroundWorker.start();

And the method which it is calling that pushes the new screen is doLogin():

private String doLogin(String user_id, String password)
{
    SoapObject resultRequestSOAP = null;
    HttpConnection httpConn = null;
    HttpTransport httpt;
    SoapPrimitive response = null;
    SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME);
    request.addProperty("username", user_id);
    request.addProperty("password", password);
    System.out.println("The request is=======" + request.toString());
    SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
    envelope.dotNet = true;
    envelope.setOutputSoapObject(request);
    httpt = new HttpTransport(URL+C0NNECTION_EXTENSION);
    httpt.debug = true;
    try
    {
        httpt.call(SOAP_ACTION, envelope);
        response = (SoapPrimitive) envelope.getResponse();
        String result = response.toString();
        resultRequestSOAP = (SoapObject) envelope.bodyIn;
        String[] listResult = split(result, sep);
        strResult = listResult[0].toString();
        if(strResult.equals("credentialdenied"))
        {
            Dialog.alert("Invalid login details.");
        }
        else
        {
            strsessionFirstName = listResult[1].toString();
            strsessionLastName = listResult[2].toString();
            strsessionPictureUrl = MAINURL + listResult[3].substring(2);
            strsessionStatusId = listResult[4].toString();
            strsessionStatusMessage = listResult[5].toString();
            strsessionLastUpdateTst = listResult[6].toString();
        }
        if(strResult.equals("credentialaccepted"))
        {
            if(checkBox1.getChecked() == true)
            {
                persistentHashtable.put("username", user_id);
                persistentHashtable.put("password", password);
            }
            Bitmap bitmap = getLiveImage(strsessionPictureUrl, 140, 140);
            nextScreen.getUsername(user_id);
            nextScreen.getPassword(password);
            nextScreen.setPictureUrl(bitmap);
            nextScreen.setImage(strsessionPictureUrl);
            nextScreen.setFirstName(strsessionFirstName, strsessionLastName, strsessionLastUpdateTst, strsessionStatusMessage);
            UiApplication.getUiApplication().invokeLater( new Runnable()
            {
                public void run ()
                {
                    UiApplication.getUiApplication().pushScreen(nextScreen);
                }
            } );
        }
    } catch (IOException e) {
        System.out.println("The exception is IO==" + e.getMessage());
    } catch (XmlPullParserException e) {
        System.out.println("The exception xml parser example==="
           + e.getMessage());
    }
    System.out.println( resultRequestSOAP);
    return response + "";
} 

Answer 1

You might need to add a boolean member variable to your class, that you check at multiple steps, within your doLogin() method:

private boolean stopRequested = false;

private synchronized void requestStop() {
    stopRequested = true;
}

private synchronized boolean isStopRequested() {
    return stopRequested;
}

private String doLogin(String user_id, String password)          
{          
    SoapObject resultRequestSOAP = null;          
    HttpConnection httpConn = null;          
    HttpTransport httpt;          
    SoapPrimitive response = null;          
    SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME);          
    request.addProperty("username", user_id);          
    request.addProperty("password", password);          
    System.out.println("The request is=======" + request.toString());          
    SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);          
    envelope.dotNet = true;          
    envelope.setOutputSoapObject(request);          
    httpt = new HttpTransport(URL+C0NNECTION_EXTENSION);          
    httpt.debug = true;

    if (isStopRequested()) return null;          

    try          
    {          
        httpt.call(SOAP_ACTION, envelope);          
        response = (SoapPrimitive) envelope.getResponse();          
        String result = response.toString();          
        resultRequestSOAP = (SoapObject) envelope.bodyIn;          
        String[] listResult = split(result, sep);          
        strResult = listResult[0].toString();          
        if(strResult.equals("credentialdenied"))          
        {          
            Dialog.alert("Invalid login details.");          
        }          
        else          
        {          
            strsessionFirstName = listResult[1].toString();          
            strsessionLastName = listResult[2].toString();          
            strsessionPictureUrl = MAINURL + listResult[3].substring(2);          
            strsessionStatusId = listResult[4].toString();          
            strsessionStatusMessage = listResult[5].toString();          
            strsessionLastUpdateTst = listResult[6].toString();          
        }    

        if (isStopRequested()) return null;          

        if(strResult.equals("credentialaccepted"))          
        {          
            if(checkBox1.getChecked() == true)          
            {          
                persistentHashtable.put("username", user_id);          
                persistentHashtable.put("password", password);          
            }          
            Bitmap bitmap = getLiveImage(strsessionPictureUrl, 140, 140);          
            nextScreen.getUsername(user_id);          
            nextScreen.getPassword(password);          
            nextScreen.setPictureUrl(bitmap);          
            nextScreen.setImage(strsessionPictureUrl);          
            nextScreen.setFirstName(strsessionFirstName, strsessionLastName, strsessionLastUpdateTst, strsessionStatusMessage);

            if (isStopRequested()) return null;          

            UiApplication.getUiApplication().invokeLater( new Runnable()          
            {          
                public void run ()          
                {          
                    UiApplication.getUiApplication().pushScreen(nextScreen);          
                }          
            } );          
        }          
    } catch (IOException e) {          
        System.out.println("The exception is IO==" + e.getMessage());          
    } catch (XmlPullParserException e) {          
        System.out.println("The exception xml parser example==="          
           + e.getMessage());          
    }          
    System.out.println( resultRequestSOAP);          
    return response + "";          
}           

Then, stop the thread like this:

Dialog busyDialog = new Dialog("Signing in...",               
                               new String [] { "Cancel" },               
                               new int [] { Dialog.CANCEL},               
                               Dialog.CANCEL,               
                               Bitmap.getPredefinedBitmap(Bitmap.HOURGLASS))               
{               
    public void fieldChanged(Field field1, int context1)               
    {               
        requestStop();               
    }               
};