Some useful Xamarin Android snippets
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Request class: A useful HttpClient that works with a Builder Object pattern.
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Installation: Just copy the Request and MockRequest classes into your project and change the namespace to your project.
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Usage:
The T parameter is the json response object.
await new Request<T>() .SetHttpMethod(HttpMethod.[Post|Put|Get|Delete].Method) //Obligatory .SetEndpoint("http://www.yourserver.com/profilepic/") //Obligatory .SetJsonPayload(someJsonObject) //Optional if you're using Get or Delete, Obligatory if you're using Put or Post .OnSuccess((serverResponse) => { //Optional action triggered when you have a succesful 200 response from the server //serverResponse is of type T }) .OnNoInternetConnection(() => { // Optional action triggered when you try to make a request without internet connetion }) .OnRequestStarted(() => { // Optional action triggered always as soon as we start making the request i.e. very useful when // We want to start an UI related action such as showing a ProgressBar or a Spinner. }) .OnRequestCompleted(() => { // Optional action triggered always when a request finishes, no matter if it finished successufully or // It failed. It's useful for when you need to finish some UI related action such as hiding a ProgressBar or // a Spinner. }) .OnError((exception) => { // Optional action triggered always when something went wrong it can be caused by a server-side error, for // example a internal server error or for something in the callbacks, for example a NullPointerException. }) .OnHttpError((httpErrorStatus) => { // Optional action triggered when something when sending a request, for example, the server returned a internal // server error, a bad request error, an unauthorize error, etc. The httpErrorStatus variable is the error code. }) .OnBadRequest(() => { // Optional action triggered when the server returned a bad request error. }) .OnUnauthorize(() => { // Optional action triggered when the server returned an unauthorize error. }) .OnInternalServerError(() => { // Optional action triggered when the server returned an internal server error. }) //AND THERE'S A LOT MORE OF CALLBACKS THAT YOU CAN HOOK OF, CHECK THE REQUEST CLASS TO MORE INFO. .Start(); -
Examples:
GET Request : A GET request to http://www.yourserver.com/user/ will return a collection of User json objects.
await Request<List<User>>()
.SetHttpMethod(HttpMethod.Get.Method)
.SetEndpoint("http://www.yourserver.com/user/")
.OnNoInternetConnection(() =>
{
UserDialogs.Instance.Alert(AppResources.no_internet_message,
AppResources.error_title,
AppResources.accept_button_text);
})
.OnSuccess((serverResponse) => {
//serverResponse is a List<User>
})
.Start();
POST Request : A POST request to http://www.yourserver.com/user/ sending the json object { "name" : "Simon", "last_name" : "Smith"} will create a new User and it will return that created user as result.
var jsonPayload = JsonConvert.SerializeObject(new { name = "Agustin", last_name = "Larghi" });
await new Request<User>()
.SetHttpMethod(HttpMethod.Post.Method)
.SetEndpoint("http://www.yourserver.com/user/")
.SetJsonPayloadBody(jsonPayload) //The jsonPayload will be set as the raw body in the request
.OnSuccess((serverResponse) => {
//serverResponse is the created User
})
.OnNoInternetConnection(() =>
{
App.Current.MainPage.DisplayAlert(AppResources.error_title,
AppResources.no_internet_message,
AppResources.accept_button_text);
})
.Start();
DELETE Request: Sending a DELETE request to the http://www.yourserver.com/user/{id} URL will delete an User from the server side, and it returns the deleted user.
await Request<User>()
.SetHttpMethod(HttpMethod.Delete.Method)
.SetEndpoint("http://www.yourserver.com/user/13")
.OnSuccess((serverResponse) => {
//serverResponse is the deleted User
})
.OnNoInternetConnection(() =>
{
App.Current.MainPage.DisplayAlert(AppResources.error_title,
AppResources.no_internet_message,
AppResources.accept_button_text);
})
.Start();
PUT Request: Sending a PUT request to http://www.yourserver.com/user/ with the json object { "name" : "Simon", "last_name" : "Smith", "id" : 13} as payload will update that User record.
var jsonPayload = JsonConvert.SerializeObject(new { name = "Agustin", last_name = "Larghi", id = 13 });
await new Request<User>()
.SetHttpMethod(HttpMethod.Put.Method)
.SetEndpoint("http://www.yourserver.com/user/")
.SetJsonPayloadBody(jsonPayload) //The jsonPayload will be set as the raw body in the request
.OnSuccess((serverResponse) => {
//serverResponse is the updated User
})
.OnNoInternetConnection(() =>
{
App.Current.MainPage.DisplayAlert(AppResources.error_title,
AppResources.no_internet_message,
AppResources.accept_button_text);
})
.Start();
Multipart Request: Sending a Multipart POST request to http://www.yourserver.com/profilepic/ will upload a file to the server.
await new Request<Picture>()
.SetHttpMethod(HttpMethod.Post.Method)
.SetEndpoint("http://www.yourserver.com/profilepic/")
.SetFile(mf, "file")
.OnSuccess((serverResponse) => {
//serverResponse is a Picture file
})
.OnNoInternetConnection(() =>
{
App.Current.MainPage.DisplayAlert(AppResources.error_title,
AppResources.no_internet_message,
AppResources.accept_button_text);
})
.Start();
Mock Request: Class created to mock a Request. For example, this way we can mock a Request, result is a List<User> you can use mock libraries such as NBuilder to build the mock response objects.
await MockRequest<List<User>>().SetResult(result).Start();
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Architecture: The idea of this Http Client is having your app network layer split in two, the real Http Client and a Mock Http Cliend. For example let's continue with the /user webservice example. We have an interface were we have all the server side methods:
public interface IRestService { Request<List<User>> GetUsersDataAsync(); }
Then we have two concrete implementations of this interface, the mock implementation:
class RestMockService : IRestService
{
public Request<List<User>> GetUsersDataAsync()
{
var result = new List<User>();
result.add(new User("Agustin", "Larghi"));
result.add(new User("Sam", "Simon"));
result.add(new User("Brad", "Bradley"));
return MockRequest<List<User>>().SetResult(result);
}
}
And the real rest client:
class RestMockService : IRestService
{
public Request<List<User>> GetUsersDataAsync()
{
return Request<List<User>>()
.SetHttpMethod(HttpMethod.Get.Method)
.SetEndpoint("http://www.yourserver.com/user/")
//See! We can handle globally some events directly in the network layer!
.OnNoInternetConnection(() =>
{
DisplayAlert(AppResources.no_internet_message,
AppResources.error_title,
AppResources.accept_button_text);
});
}
}
So in our PCL project we'll call GetUsersDataAsync() regardless of which implementation it uses. We can easly switch from the real http layer to the mocked one.
//...
await restService.GetUsersDataAsync()
.OnSuccess((listOfUsers) => {
//And we have the list of users no matter if its the mocked one or the real one.
})
.Start();
//...