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Kommander

Kommander is a Java asynchronous Command Pattern implementation, specially recommended to solve Android UI Thread Issue.

Usage

Kommander is designed to be really simple to use. First of all, you need to create a Kommander instance.

Kommander kommander = Kommander.getInstance();

That was easy, right? Now, let's launch an asynchronous execution.

Kommands

kommander.makeKommand(() -> interactor.searchMovie("Titanic"))
    .setOnCompleted(this::paintMovies)
    .kommand();

This example is executing an asynchronous search of a movie and releases the result on paintMovies() when all has worked fine.

• Let's see each step in detail:

  • Making a Kommand

  Kommand<List<Movie>> kommand = kommander.makeKommand(new Action<List<Movie>>() {
      @Override
      public List<Movie> action() throws Throwable {
          return interactor.searchMovie("Titanic");
      }
  });	
  

  A Kommand is an asynchronous context builder of an Action, where it can be defined like a piece of code to be executed in the future that returns a value or throws an exception.

  • Setting up the callback Response

  kommand = kommand.setOnCompleted(new Response.OnCompleted<List<Movie>>() {
      @Override
      public void onCompleted(List<Movie> response) {
          paintMovies(response);
      }    
  });
  
  // ... 
  
  private void paintMovies(List<Movie> movies) {
  // do something
  }
  

  In this step a Response.OnCompleted is being set up, that is who is going to handle the Action result. Also, in a similar way, is possible setting up the Response.OnError when something is not going fine in the Action execution.

  kommand = kommand.setOnError(new Response.OnError() {
      @Override
      public void onError(Throwable error) {
          showMessage("Something failed!");
      }
  });
  

  • Launch the Kommand

  KommandToken token = kommand.kommand();
  

  When a Kommand is fully defined, it can be launched to an asynchronous execution with kommand().
  A KommandToken is returned, you can use it to cancel the Kommand execution. A canceled Kommand, will never be executed if the execution has not started yet, try to stop the execution if that is running, or at least, the response is not delivered when the execution finish.

• Delay You can define a delay time, in milliseconds, to kommand execution.

  long millisecondDelay = 60_000L;
  kommand = kommand.delay(millisecondDelay); 
  

• A Deliverer is just a way to define how and when Kommander will deliver the result of an asynchronous execution.

  kommand = kommand.setDelivered(new Deliverer() {
      @Override
      public void deliver(Runnable runnable) {
          // How do you want to deliver the response? Your code here! 
      }
  });
  

  For instance, using Kommander on Android, you could use the next Deliverer to release the results on the Android's UI Thread.

  @Provides(singleton = true)
  Deliverer provideAndroidDeliverer() {
      Handler handler = new Handler(Looper.getMainLooper());
      return handler::post;
  }
  

KommandTokenBox

When you make Kommand.kommand() you receive a KommandToken instance to take control of the kommand cancellation with KommandToken.cancel(), but often managing these tokens is a few unpleasant. So you can take advance of KommandTokenBox to easy the cancel control.

• Add tokens to box

  KommandTokenBox box = new KommandTokenBox();    // TokenBox
  Kommand<Integer> kommand = kommander.makeKommand(() -> 1);
  
  // Explicit appendToken
  KommandToken token = kommand.kommand();
  box.append(token);                             // AppendToken to the box
  box.append(token, "VIEW_SCOPE_TAG");           // AppendToken to the box with tag
  
  // Implicit appendToken
  kommand.kommand(box);                          // AppendToken to the box
  kommand.kommand(box, "VIEW_SCOPE_TAG");        // AppendToken to the box with tag
  

• Cancelling tokens

  box.cancel("VIEW_SCOPE_TAG");                  // Cancel previously appended tokens with this tag 
  box.cancelAll();                               // Cancel all tokens appended tokens
  

Download

Kommander is available on jcenter. Please ensure that you are using the latest version checking <a href="https://bintray.com/wokdsem/maven/kommander/view">here</a>.

Maven:

<dependency>
  <groupId>com.wokdsem.kommander</groupId>
  <artifactId>kommander</artifactId>
  <version>1.3.0</version>
</dependency>

Gradle:

compile 'com.wokdsem.kommander:kommander:1.3.0'

License

Copyright 2017 Wokdsem

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.