Windows Phone 8

How to load a list of a user’s twitter friends/followers in your Windows Phone app

TwitterFriendsList_WP_Blog During the last days, I was adding a new function to UniShare that suggests users the Twitter handles while typing in some text. The base of this new function is a list of the user’s twitter friends. In this post, I am going to show you how to generate this list and save it for further use. First thing I need to talk about: you can only load a maximum of 3000 friends at once due to the rate limit on Twitter’s part. At the end of the post, I’ll give you also an idea how to continue this after the first 3000 users were loaded. For the most scenarios, 3000 should be enough to cover the major part of your users. To be able to load all friends we first create a Task that fetches 200 entries of our user’s friends list. To be able to perform paging through all entries, Twitter uses so called cursors, which are 64-bit signed integers (long). You can read more about that here on Twitter’s API documentation. Let’s have a look on this Task:

        private async Task<string> TwitterFriendsListString(long twitterCursor)
        {
            ShowProgressIndicator("generating mention suggestion base...");

            //needed for generating the Signature
            string twitterRequestUrl = "https://api.twitter.com/1.1/friends/list.json";

            //used for sending the request to the API
            //for usage of the url parameters, go to https://dev.twitter.com/docs/api/1.1/get/friends/list
            string twitterUrl = string.Format("https://api.twitter.com/1.1/friends/list.json?cursor={0}&screen_name={1}&count=200&skip_status=true&include_user_entities=false", twitterCursor, App.SettingsStore.twitterName);

            string timeStamp = GetTimeStamp();
            string nonce = GetNonce();

            string response = string.Empty;

            //we need to include all url parameters in the signature
            //IMPORTANT: Twitter's API demands them to be sorted alphabetically, otherwise the Signature will not be accepted
            string sigBaseStringParams = "count=200";
            sigBaseStringParams += "&" + "cursor=" + twitterCursor;
            sigBaseStringParams += "&" + "include_user_entities=false";
            igBaseStringParams += "&" + "oauth_consumer_key=" + twitterConsumerKey;
            sigBaseStringParams += "&" + "oauth_nonce=" + nonce;
            sigBaseStringParams += "&" + "oauth_signature_method=HMAC-SHA1";
            sigBaseStringParams += "&" + "oauth_timestamp=" + timeStamp;
            sigBaseStringParams += "&" + "oauth_token=" + App.SettingsStore.twitteroAuthToken;
            sigBaseStringParams += "&" + "oauth_version=1.0";
            sigBaseStringParams += "&" + "screen_name=" + App.SettingsStore.twitterName;
            sigBaseStringParams += "&" + "skip_status=true";
            string sigBaseString = "GET&";
            sigBaseString += Uri.EscapeDataString(twitterRequestUrl) + "&" + Uri.EscapeDataString(sigBaseStringParams);

            string signature = GetSignature(sigBaseString, twitterConsumerSecret, App.SettingsStore.twitteroAuthTokenSecret);

            string authorizationHeaderParams =
                "oauth_consumer_key=\"" + twitterConsumerKey +
                "\", oauth_nonce=\"" + nonce +
                "\", oauth_signature=\"" + Uri.EscapeDataString(signature) +
                "\", oauth_signature_method=\"HMAC-SHA1\", oauth_timestamp=\"" + timeStamp +
                "\", oauth_token=\"" + Uri.EscapeDataString(App.SettingsStore.twitteroAuthToken) +
                "\", oauth_version=\"1.0\"";

            HttpClient httpClient = new HttpClient();

            httpClient.DefaultRequestHeaders.Authorization = new HttpCredentialsHeaderValue("OAuth", authorizationHeaderParams);
            var httpResponseMessage = await httpClient.GetAsync(new Uri(twitterUrl));

            response = await httpResponseMessage.Content.ReadAsStringAsync();

            return response;
        }

As you can see, we need to create our signature based on the url parameters we are requesting. Twitter demands them to be sorted alphabetically. If you would not sort them this way, the Signature is wrong and your request gets denied by Twitter. We are overloading this Task with the above mentioned cursor to get the next page of our user’s friends list. If you need the GetNonce() and GetSignature() methods, take a look at this post, I am using them for all requests to Twitter. Now that we have this Task ready to make our requests, lets load the complete list. First, declare these objects in your page/model:

        public List<TwitterMentionSuggestionBase> twitterMentionSuggestionsList;
        public long nextfriendlistCursor = -1;
        public string friendsResponseString = string.Empty;
        public string friendsJsonFileName = "twitterFriends.json";

Then we need to create a loop to go through all pages Twitter allows us until we are reaching the rate limit of 15 requests per 15 minutes. I using a do while loop, as this is the most convenient way for this request:

            //to avoid double entries, make sure the list is we are using is empty
            if (twitterMentionSuggestionsList.Count != 0)
            {
                twitterMentionSuggestionsList.Clear();
            }
            //starting the do while loop
            do
            {
                //fetching the Json response
                //to get the first page of the list from Twitter, the cursor needs to be -1
                friendsResponseString = await TwitterFriendsListString(nextfriendlistCursor);

                //using Json.net to deserialize the string
                var friendslist = JsonConvert.DeserializeObject<TwitterFriendsClass.TwitterFriends>(friendsResponseString);
                //setting the cursor for the next request
                nextfriendlistCursor = friendslist.next_cursor;

                //adding 200 users to our list
                foreach (var user in friendslist.users)
                {
                    //using the screen name ToLower() to make the further usage easier
                    TwitterMentionSuggestionsList.Add(new TwitterMentionSuggestionBase() { name = "@" + user.screen_name.ToLower() });
                }

                //once the last page is reached, the cursor will be 0
                if (nextfriendlistCursor == 0)
                {
                    //break will continue the code after the do while loop
                    break;
                }
            }
            //the while condition needs to return true if you would set up a Boolean for it!
            while (nextfriendlistCursor != 0);

As long as the cursor is not 0, the loop will load the json string with 200 entries. The class you’ll need for deserializing can be easily generated. Just set a breakpoint after the call of our Task, copy the whole response string and go to http://json2csharp.com to get your class. The TwitterMentionSuggestionBase class only contains a string property for the name and can be extended for you needs:

    public class TwitterMentionSuggestionBase
    {
        public string name { get; set; }
    }

Of course we need to save the list for further use. The code I use is pretty much the same you’ll find when you search for “saving json string to file” with your favorite search engine and works with Windows Phone 8 and 8.1:

            //saving the file to Isolated Storage
            var JsonListOfFriends = JsonConvert.SerializeObject(twitterMentionSuggestionsList);
            try
            {
                //getting the localFolder our app has access to
                StorageFolder localFolder = ApplicationData.Current.LocalFolder;
                //create/overwrite a file
                StorageFile friendsJsonFile = await localFolder.CreateFileAsync(friendsJsonFileName, CreationCollisionOption.ReplaceExisting);
                //write the json string to the file
                using (IRandomAccessStream writeFileStream = await FriendsJsonFile.OpenAsync(FileAccessMode.ReadWrite))
                {
                    using (DataWriter streamWriter = new DataWriter(writeFileStream))
                    {
                        streamWriter.WriteString(JsonListOfFriends);
                        await streamWriter.StoreAsync();
                    }
                }
            }
            catch
            {

            }

This way, we can easily generate a friends list for our users, based on their Twitter friends. Some points that might be helpful:

  • users with more than 3000 friends will receive an error after reaching this point on our task. Catch this error, but continue to save the already loaded list. Save the latest cursor for the next page and prompt the user to continue loading after 15 minutes to continue loading.
  • if you want to have a list with more details about a user’s friends, extend the TwitterMentionSuggestionBase class with the matching properties.
  • this code can also be used to determine the followers of a user, you just need to change the url parameters as well as the signature parameters according to the matching Twitter endpoint

As always, I hope this is helpful for some of you. Until the next post, happy coding!

Posted by msicc in Dev Stories, windev, 3 comments

How to use Text to Speech to read text aloud on Windows Phone 8

tts

Today I started to update my very first app I ever wrote to Windows Phone 8. The app has a read aloud feature that uses the Bing translation service (as TTS was not available on Windows Phone 7).

Of course I am now using the new Windows Phone 8 API, but I had some trouble figuring out how to handle text to speech with different languages and if no language speech pack is installed on a device. I finally found a solution and want to share it with you.

First, we need to declare a new SpeechSynthesizer and an  IEnumerable for VoiceInformation:

SpeechSynthesizer speechSynth = new SpeechSynthesizer();
IEnumerable<VoiceInformation> voices = InstalledVoices.All;

Next, I declared a simple helper method to get the currently used language:

         public string GetCurrentCulture()
         {
             return CultureInfo.CurrentCulture.TwoLetterISOLanguageName.ToString();
         }

I am using the TwoLetterISOLanguageName property because there are different versions of some languages like German or English. This makes it easier to handle throughout other methods.

Now that we are able to read the installed voices and to read the currently used language, we can use a simple Linq query to get the speech language we want to use:

var engVoice = from voice in voices where voice.Language.StartsWith("en") select voice;

The engVoice object contains now all English speech packages – if they are installed. To determine if we have items we can use, we just need to check the Count(). As long as the count is bigger than 0, we can start to let our app reading aloud our text. If not, we should inform the user that there is no matching language pack installed.

                 if (engVoice.Count() > 0)
                 {
                     speechSynth.SetVoice(engVoice.ElementAt(0));
                     await speechSynth.SpeakTextAsync(text);
                 }
                 else
                 {
                     MessageBox.Show("Language package missing");
                 }

My app supports three languages. Because of this, I am using if/else if statements to match the languages. If the user uses another language than the supported ones, I am cancelling all speech attempts and display a message to the user which languages are supported.

Here is my complete method:

         private async void StartReadAloud(string text)
         {
             IEnumerable<VoiceInformation> voices = InstalledVoices.All;

             if (GetCurrentCulture() == "en")
             {
                 var engVoice = from voice in voices where voice.Language.StartsWith("en") select voice;
                 if (engVoice.Count() > 0)
                 {
                     speechSynth.SetVoice(engVoice.ElementAt(0));
                     await speechSynth.SpeakTextAsync(text);
                 }
                 else
                 {
                     MessageBox.Show("Language package missing");
                 }
             }
             else if (GetCurrentCulture() == "it")
             {
                 var itVoice = from voice in voices where voice.Language.StartsWith("it") select voice;
                 if (itVoice.Count() > 0)
                 {
                     speechSynth.SetVoice(itVoice.ElementAt(0));
                     await speechSynth.SpeakTextAsync(text);
                 }                                  
                 else
                 {
                     //msgbox Italian
                 }
             }
             else if (GetCurrentCulture() == "de")
             {
                 var deVoice = from voice in voices where voice.Language.StartsWith("de") select voice;
                 if (deVoice.Count() > 0)
                 {
                     speechSynth.SetVoice(deVoice.ElementAt(0));
                     await speechSynth.SpeakTextAsync(text);
                 }
                 else
                 {
                     //msgbox German
                 }
             }
             else
             {
                 speechSynth.CancelAll();
                 //msgbox notSupported language               
             }
         }

I hope this is helpful for some of you and saves you some trouble.If you have anything to add/correct on my method, feel free to leave a comment below.

Happy coding, everyone!

Posted by msicc in Dev Stories, windev, 1 comment

A simple approach to remove QueryStrings from NavigationContext on Windows Phone

QuerystringsRemove

Like most of you know, I am currently adding a lot of new features to my NFC Toolkit for Windows Phone.

Today, my coding session is all about uri schemes again. I successfully added some new uri schemes that you will be able to use soon.

However, if you start an app via an uri scheme, you will have  QueryStrings in your NavigationContext on the desired ApplicationPage. If a user continues to use your app, navigates away from the launched page and back to it, the code based on your QueryStrings will be called again.

As I am a daily Windows Phone user by myself, I know this is somewhat annoying. So I searched for a solution. I first thought about removing entries in the BackStack, but that would need a lot of code if you are running an application that has more than two pages – you’ll need to add methods to check if you are coming from an uri scheme, clear the BackStack, pass the parameters to the next page, get back to your MainPage, check the parameters again. Totally unusable in my opinion.

The NavigationContext.QueryString property has a Remove() method as I found out while researching a bit more – that’s what I am using now to get the result I want – make the app running like it was launched normally without uri scheme after the action has taken place.

I found some examples that are using the method in the  OnNavigatedTo() event. I don’t think that’s the right way, as I often happen to have some more code in this event, and it will probably break other functionality. I am using the OnNavigatedFrom() event.

Add this lines of code for every QueryString you want to remove (depending on your method structure, it is ok to remove only the QueryString you rely on in your further code, additional parameters can be still there ):

protected override void OnNavigatedFrom(NavigationEventArgs e)
{
   if (NavigationContext.QueryString.ContainsKey("key1"))
   {
      NavigationContext.QueryString.Remove("key1");                                
   }
   if (NavigationContext.QueryString.ContainsKey("key2"))
   {
       NavigationContext.QueryString.Remove("key2");
   }            
   base.OnNavigatedFrom(e);
}

This way, if you are navigating to another page in your app or even if the user uses the Windows Button, the corresponding QueryString will be removed – and your users are able to use the app as they would have launch it without an uri scheme.

However, that’s not all. When your app get’s Tombstoned, the UriMapper will map the uri scheme again on Activation – not what you might want. To get around this, I use a simple Boolean, set it to true when I am coming back from Tombstoning:

private void Application_Activated(object sender, ActivatedEventArgs e)
{
    if (!e.IsApplicationInstancePreserved)
    {
        wasTombstoned = true;  
    }
}

Now the only thing you will need to to is to add

&& App.wasTombstoned == false

as second argument to your QueryString clause – that’s it!

I am not sure if this is a good approach or not, but it works. It allows you to launch your uri scheme, and enables the user to use your app after that as it would have been launched normally. If you have other ways to get the same result, feel free to leave a comment below.

Otherwise, I hope this post is helpful for some of you.

Happy coding!

Posted by msicc in Dev Stories, windev, 5 comments

Application ID’s of built in Windows Phone 8 apps

 

As you may have noticed, I am currently working on an NFC app. Development goes pretty well at the moment, thanks to the absolutely awesome and easy to use NDEF library by Andreas Jakl.

If you want to open apps from your app or from an NFC tag, you will need to use the AppId of the desired app. If you have an installed app from the Windows Phone Store, this is pretty easy. You can go to the application list on your phone, long tap and hit “send”. If you now choose mail or SMS, you can obtain the AppId very easy, as it is the last part behind “appId=” on the web address.

With the built in apps, it is a bit more difficult. Luckily, the app NFC interactor for Windows Phone 8, which is aimed at developers, has a solution. The app is written also by Andreas Jakl, who provides a huge tool with this app to support you on developing your own app and it is worth every cent.

I made it through all records for built in apps and extracted the following list, which might come handy for some of you:

  • Alarms AppId 5B04B775-356B-4AA0-AAF8-6491FFEA560A
  • Bing Scan AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5682
  • Calculator AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5603
  • Calendar AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5612
  • Camera AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5631
  • Data Sense AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5646
  • Games AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5634
  • Help+Tips AppId E05410F1-753B-47BC-B101-226E5802B9E1
  • IE AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5660
  • Maps AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5661
  • Messaging AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5610
  • Music+Videos AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5630
  • Office AppId 5B04B775-356B-4AA0-AAF8-6491FFEA561E
  • OneNote AppId 5B04B775-356B-4AA0-AAF8-6491FFEA561B
  • People AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5615
  • Phone AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5611
  • Photos AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5632
  • Rooms AppId 5B04B775-356B-4AA0-AAF8-6491FFEA562D
  • SIM Applications AppId 5B04B775-356B-4AA0-AAF8-6491FFEA562C
  • Start (Home Screen) AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5602
  • Store AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5633
  • Wallet AppId 5B04B775-356B-4AA0-AAF8-6491FFEA5683

All credits for this App IDs goes to Andreas Jakl, I only put them together as a list to find them more easily.

Posted by msicc in Dev Stories, windev, 4 comments