CanvasAPI is an Android library that will help you integrate your own third party app with Canvas by Instructure. CanvasAPI adds support for Android 2.3 (Gingerbread) and up.

CanvasAPI is built on the Canvas API. CanvasAPI is designed to allow for great flexibility while providing an easy to use interface. You can use CanvasAPI to build apps for open source versions of Canvas as well as instances hosted by Instructure.

• Download CanvasAPI
• Become familiar with Retrofit by Square
• Download and explore the project found in the example directory.
• Take a look at the Canvas API for a complete list of endpoints

##Usage

In order to use CanvasAPI with Instructure managed instances of Canvas LMS you must obtain a Client ID and Shared Secret. CanvasAPI uses OAuth 2 for authentication. Request your Client ID and Shared Secret by sending an email to mike@instructure.com. Make sure to give us your name, email, and what you are hoping to do with the CanvasAPI.

Download latest .aar from Maven:

    <dependency>
        <groupId>com.instructure</groupId>
        <artifactId>CanvasAPI</artifactId>
        <version>(insert latest version)</version>
    </dependency>

Or include using gradle:

compile 'com.instructure:CanvasAPI:LATEST_VERSION@aar'

You must also include Retrofit by Square

<dependency>
    <groupId>com.squareup.retrofit</groupId>
    <artifactId>retrofit</artifactId>
    <version>(insert latest version)</version>
</dependency>

###Initializing CanvasAPI Now that you have your Client ID and Shared Secret you can start using CanvasAPI. You then can begin the OAuth native flow outlined here. Once you've received the OAuth Request String, you can begin by calling OAuth.getToken(String clientId, String clientSecret, String oAuthRequest, CanvasCallback<OAuthToken> callback)). This will return the OAuth token for the user. You then need to initialization the CanvasRestAdapter by calling CanvasRestAdapter.setupInstance(Context context, String token, String domain)

###Using the API CanvasAPI is mainly structured around the notion of CanvasContexts. We currently support courses, groups, and users as CanvasContexts. For the most part, when you make an API call, you'll provide the API with a CanvasContext object. Course.java and Group.java both extend from CanvasContext.java so those can be used in these cases. You can also call CanvasContext.getGenericContext(Type type, long id, String name) to generate one on the fly.

###Tips and Tricks

• APIHelpers.java provides a lot of useful methods for CanvasAPI. These include getters/setters for the current OAuth Token, user-agent, protocol, domain, signed-in user, etc.

• CanvasCallback.java is our extension of Retrofit's Callback class. It provides automatic caching and pagination support.

• The cache callback occurs on whichever thread you launched the API call from.

• We only cache the FIRST page of all API calls.

###Error Handling First and foremost, all logging that our library does uses the tag canvas-api, which can be found in APIHelpers.java

We also provided an interface entitled ErrorDelegate that gives you callbacks when an error occurs during an API call. We specify which type of error occurred, so you can handle each of the cases however it makes the most sense for your project. You can set up a default ErrorDelegate inside of CanvasCallback.java which will be used whenever one isn't provided as a constructor argument when creating a new CanvasCallback. If the server returns an HTTP200 or a HTTP401, we also return a CanvasError object that contains the exact error the server returned.

You can also handle errors manually by overriding public boolean onFailure(RetrofitError RetrofitError). This callback allows you to handle errors in API calls before the error delegate methods are called. Returning true from this method means you have successfully handled the error and the error delegate will NOT be called; return false otherwise.

###Using Kaltura

Kaltura has its own flow and half of the calls use a KalturaRestAdapter. To set up the KalturaRestAdapter you first need to make a call to KalturaAPI.getKalturaConfiguration(kalturaConfigurationCallback) From the callback check that Kaltura is enabled.

kalturaConfigCallback = new CanvasCallback<KalturaConfig>(this) {
            @Override
            public void cache(KalturaConfig kalturaConfig) {
                return;
            }

            @Override
            public void firstPage(KalturaConfig kalturaConfig, LinkHeaders linkHeaders, Response response) {

                if (kalturaConfig.isEnabled()) {
                  //If Kaltura is Enabled we want to save the domain, then request an session token
                    kalturaDomain = kalturaConfig.getDomain();
                    KalturaAPI.startKalturaSession(kalturaSessionCallback);
                } else {
                    uploadError();
                }

            }
        };

startKalturaSession(kalturaSessionCallback) will return a KalturaSession object.

kalturaSessionCallback = new CanvasCallback<KalturaSession>(this) {
            @Override
            public void cache(KalturaSession kalturaSession) {
                return;
            }

            @Override
            public void firstPage(KalturaSession kalturaSession, LinkHeaders linkHeaders, Response response) {
                //Using the Kaltura domain from the previuse call and then the Kaltura Session (ks)
                //create a KalturaRestAdapter
                if (!KalturaRestAdapter.setupInstance(getContext(), kalturaSession.getKs(), kalturaDomain)) {
                  //KalturaRestAdapter.setupInstance() returns false if there is an error Handles this
                    uploadError();
                } else {
                  //Request a uploadToken from the Kaltura server
                KalturaAPI.getKalturaUploadToken(kalturaUploadTokenCanvasCallback);
                }
            }
        };

After you have setup the KaltruaRestAdapter you then will need to make a call to KalturaAPI.getKalturaUploadToken(kalturaUploadTokenCallback). Once you have the a KalturaUploadtoken you are ready to upload the file.

 kalturaUploadTokenCanvasCallback = new CanvasCallback<xml>(this) {
            @Override
            public void cache(xml xml) {
                return;
            }

            @Override
            public void firstPage(final xml xml, LinkHeaders linkHeaders, Response response) {
              //Kaltura returns a generic xml object for all responces, this is annoying but we can get around it like so
                if (xml.getResult() != null && xml.getResult().getKalturaError() == null) {


                  kalturaUploadToken = xml.getResult().getId();
                  //Upload the file.
                  xml newReturnXml = KalturaAPI.uploadFileAtPathSynchronous(kalturaUploadToken, mediaUri, getContext());

                  if (newReturnXml != null && newReturnXml.getResult() != null){
                  //After the upload has finished we need to pass data back to canvas.
                  CanvasContext course = CanvasContext.getGenericContext(CanvasContext.Type.COURSE, assignment.getCourseId(), Const.COURSE);
                  //The mediaId is what Canvas uses to find the media on the Kaltura server
                  String mediaId = xml.getResult().getId;
                  long assignmentId = assignment.getId;
                  long userId = APIHelpers.getCacheUser(this).getId;
                  String mediaType = FileUtilities.mediaTypeFromKalturaCode(xml.getResult().getMediaType());

                  SubmissionAPI.postMediaSubmissionComment(course, assignmentId, userId, mediaId, mediaType, submissionCanvasCallback);
                 } else {
                  uploadError()
                }
            }

        };