Android: NumberPicker - calling setWrapSelectorWheel(false) does nothing!!

In case you're using a NumberPicker instance, you have a good range of min-max values and you're calling NumberPicker.setWrapSelectorWheel(false) but it isn't disabling wrapping around the min/max values, it could be a simple issue of re-ordering your method calls. So, this won't work...

numberPicker.setWrapSelectorWheel(false);
numberPicker.setMinValue(0);
numberPicker.setMaxValue(10);
numberPicker.setValue(5);

... but this will...

numberPicker.setMinValue(0);
numberPicker.setMaxValue(10);
numberPicker.setValue(5);
numberPicker.setWrapSelectorWheel(false);

The key is to call NumberPicker.setWrapSelectorWheel(false) after you've set your NumberPicker's min and max values.

Java/Android - Method for getting a url's domain name

Below is a method which extracts a url's domain name and which uses simple String matching. What it actually does is extract the bit between the first "://" (or index 0 if there's no "://" contained) and the first subsequent "/" (or index String.length() if there's no subsequent "/"). The remaining, preceding "www(_)*." bit is chopped off. I'm sure there'll be cases where this won't be good enough but it should be good enough in most cases!

I read on forums that the java.net.URI class could do this (and was preferred to the java.net.URL class) but I encountered problems with the URI class. Notably, URI.getHost() gives a null value if the url does not include the scheme, i.e. the "http(s)" bit.

/**
* Extracts the domain name from {@code url}
* by means of String manipulation
* rather than using the {@link URI} or {@link URL} class.
*
* @param url is non-null.
* @return the domain name within {@code url}.
*/
public String getUrlDomainName(String url) {
  String domainName = new String(url);

  int index = domainName.indexOf("://");

  if (index != -1) {
    // keep everything after the "://"
    domainName = domainName.substring(index + 3);
  }

  index = domainName.indexOf('/');

  if (index != -1) {
    // keep everything before the '/'
    domainName = domainName.substring(0, index);
  }

  // check for and remove a preceding 'www'
  // followed by any sequence of characters (non-greedy)
  // followed by a '.'
  // from the beginning of the string
  domainName = domainName.replaceFirst("^www.*?\\.", "");

  return domainName;
}

Facebook Android SDK 3.0 - getting a user's profile picture

Here's another Facebook operation which you'd think should not only be easy to do but also be easy to find in the documentation. It certainly was easy to do, but once again wasn't so easy to find in the documentation. Oh and, strictly speaking, you don't need the Facebook SDK for this. You just need to make a HTTP GET call to the Facebook user's picture connection. (You'll need the Facebook SDK to get the user's Facebook id beforehand.)

final String userFacebookId = ...

new AsyncTask<Void, Void, Bitmap>()
{
  @Override
  protected Bitmap doInBackground(Void... params)
  {
    // safety check
    if (userFacebookId == null)
      return null;

    String url = String.format(
        "https://graph.facebook.com/%s/picture",
        userFacebookId);

    // you'll need to wrap the two method calls
    // which follow in try-catch-finally blocks
    // and remember to close your input stream

    InputStream inputStream = new URL(url).openStream();
    Bitmap bitmap = BitmapFactory.decodeStream(inputStream);

    return bitmap;
  }

  @Override
  protected void onPostExecute(Bitmap bitmap)
  {
    // safety check
    if (bitmap != null
        && !isChangingConfigurations()
        && !isFinishing())
      // do what you need to do with the bitmap :)
  }
}.execute();

When methods and functions do too much

It's like asking a robot to get you some milk and it comes back to you with flavoured milk. You might want flavoured milk, but you might not! Your methods should only do as much as they are contracted to do. No more.

Here's another example: you create an Android AlertDialog with the AlertDialog.Builder class. Now every time you click one of the buttons of your AlertDialog, the AlertDialog is automically dismissed, as well as notifying you that a button was clicked. But you don't want the AlertDialog to be dismissed, you only want to be notified that a button was clicked!

Sometimes doing more is less helpful.

Android - load and show html from a file into a TextView

There's a known bug in the Android WebView such that a WebView set with a transparent background colour does not appear with a transparent background on all devices. None of the workarounds are definitive and work for all devices. An alternative to loading html in a WebView is to load it in a TextView. There are limitations as to what HTML tags can be used (see here) but if you're only doing basic HTML tagging, this will work:

try
{
  InputStream inputStream = getResources().getAssets().open("myFile.html");

  String html = IOUtils.toString(inputStream);

  myTextView.setText(Html.fromHtml(html));
}
catch (IOException exception)
{
  myTextView.setText("Failed loading html.");
}

Facebook Android SDK 3.0 - how to log out and close a session

In the previous two Blog posts (here and here), I showed how to connect a user to their Facebook account (i.e. open a Facebook session) and how to make a Facebook API request (requesting additional Facebook permissions en route if necessary). In this final Blog post, I'll show to close the Facebook session, as follows:

public void disconnectFacebookAccount()
{
  showProgressDialog("Disconnecting Facebook account...");

  new AsyncTask<Void, Void, Boolean>()
  {
    @Override
    protected Boolean doInBackground(Void... params)
    {
      if (Session.getActiveSession() != null)
        Session.getActiveSession().closeAndClearTokenInformation();

      clearFacebookInfoFromSharedPreferences();

      // perform any other operations you need to do perform here
      // such as clearing local database tables and so forth

      return true;
    }

    @Override
    protected void onPostExecute(Boolean result)
    {
      // safety check
      if (isFinishing())
        return;

      if (result == null
          || result == false)
        onFailedFacebookDisconnect();
      else
        onSucceededFacebookDisconnect();
    }
  }.execute();
}

That's it! That's the end of my Facebook Android 3.0 series. You should have enough know-how now for all kinds of Facebook API requests! :)

Facebook Android SDK 3.0 - requesting additional permissions and making an API request

At the end of the previous Blog post, I defined a connectFacebookAccount(...) method which connects to a user's Facebook account and opens a Facebook session for subsequent Facebook API requests. In this Blog post, I'll show how to use this method and the opened Facebook session to post to the user's feed. You'll notice in reading through the postFacebookMessage(...) method below that it is sometimes necessary to request additional Facebook permissions before making a Facebook API request. (It's no longer possible to request all required Facebook permissions at the point of first connecting to Facebook.) Without further ado, here's the postFacebookMessage(...) method:

/** Posts the provided message to Facebook,
 * connecting to Facebook
 * and requesting required permissions en route if necessary.*/
public void postFacebookMessage(final String message)
{
  connectFacebookAccount(new FacebookConnectHandler()
  {
    @Override
    public void onSuccess()
    {
      // safety check
      if (isFinishing())
        return;

      showProgressDialog("Posting message to Facebook...");

      // check for publish permissions

      final List permissions_required = Arrays.asList(
          new String[] { Constants.Facebook_Permission_PublishStream });

      if (Session.getActiveSession().getPermissions() == null
          || !Session.getActiveSession().getPermissions().containsAll(
              permissions_required))
      {
        // need to make a Session.openActiveSessionFromCache(...) call
        // because of a bug in the Facebook sdk
        // where a second call to get permissions
        // won't result in a session callback when the token is updated

        if (Session.openActiveSessionFromCache(BaseFacebookActivity.this) == null)
        {
          onFailedPostingFacebookMessage();
          return;
        }

        Session.getActiveSession().addCallback(new Session.StatusCallback()
        {
          @Override
          public void call(
              Session session,
              SessionState state,
              Exception exception)
          {
            if (exception != null
                || state.equals(SessionState.CLOSED)
                || state.equals(SessionState.CLOSED_LOGIN_FAILED))
            {
              // didn't get required permissions

              session.removeCallback(this);

              // safety check
              if (!isFinishing())
                onFailedPostingFacebookMessage();
            }
            else if (state.equals(SessionState.OPENED_TOKEN_UPDATED)
                && session.getPermissions().containsAll(permissions_required))
            {
              // got required permissions

              session.removeCallback(this);

              // safety check
              if (!isFinishing())
                postFacebookMessage(message);
            }
          }
        });

        Session.getActiveSession().requestNewPublishPermissions(
            new Session.NewPermissionsRequest(
                BaseFacebookActivity.this,
                permissions_required));

        return;
      }

      // got sufficient permissions, so publish message

      Bundle bundle_params = new Bundle();

      bundle_params.putString("caption", "Enter your caption here"));
      bundle_params.putString("description", "Enter your description here");
      bundle_params.putString("link", "http://www.your-app-url.com");
      bundle_params.putString("message", message);
      bundle_params.putString("name", "My App for Android");
      bundle_params.putString("picture", "http://www.your-app-icon-url.com");

      new Request(
          Session.getActiveSession(),
          "me/feed",
          bundle_params,
          HttpMethod.POST,
          new Request.Callback()
          {
            @Override
            public void onCompleted(Response response)
            {
              // safety check
              if (isFinishing())
                return;

              if (response.getError() != null
                  || response.getGraphObject() == null)
              {
                onFailedPostingFacebookMessage();
                return;
              }

              Object id = response.getGraphObject().getProperty("id");

              if (id == null
                  || !(id instanceof String)
                  || TextUtils.isEmpty((String)id))
                onFailedPostingFacebookMessage();
              else
                onSucceedPostingFacebookMessage((String)id);
            }
          }).executeAsync();
    }

    @Override
    public void onFailure()
    {
      cancelProgressDialog();
      showToast("Failed connecting to Facebook.");
    }
  });
}

You'll notice two methods above onSucceedPostingFacebookMessage(...) and onFailedPostingFacebookMessage() which you'll need to define to cancel the shown progress dialog, show a toast alerting the user to success or failure, and to perform any additional operations you require. That's it! Just one last Blog post to follow...