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AndroidForms - MVC Forms for Android

Forms, data validation... They can be annoying sometimes. This library is here to try to help you out. AndroidForms aims to be a simple, Generic form library for android. At it's core, there aren't even any dependencies! You could easily move Source, Drain, and Form into any project you'd like. Because I wanted a good way to handle forms on Android, I'm keeping it as a dependency so I can build out helper Sources and helper Drains, like ViewSource!


Form is a final class. That means you can't override it. And you know what? You shouldn't have to. All a form does is expose 6 methods:

  • public save() -- Saves the form from Source into Drain if Source is valid
  • public save(bundle) -- Saves the form from Source into Drain if Source is valid. If Bundle isn't null, it writes bundle data to Drain first.
  • public forceSave() -- Saves the form from Source into Drain.
  • public forceSave(bundle) -- Saves the form from Source into Drain. If Bundle isn't null, it writes bundle data to Drain first.
  • public display() -- Writes the Drain information if not null into the Source for initialization.
  • public display(bundle) -- Same as display, but will apply Bundle to Source first.

All forms are created through a builder, and because of this, hide their constructor. You can create a form through Form.Builder<S,D>. The S and D are the Source and Drain subclasses that you create. Let's take a look at those:


Source is an abstract class that takes some type that you want to wrap. You've got to tell it how to create whatever you're wrapping in onCreate. You'll also, in onCreate, add your Validators, which we'll get to in a minute. Most of Source's functionality is hidden from you, and that's on purpose. Thus, you can see:

  • protected onCreate -- Creates a new instance of your Source object (whatever you're wrapping)
  • protected onSourceCreated -- Returns a list of validators to validate the source in form save
  • public getSource -- returns a source object


Drain is an abstract class that takes some type you want to wrap. You've got to tell it how to create whatever you're wrapping in onCreate. You also need to specify what to do with these objects on form save in onSave, be it writing to a database or emitting an event. Your call. If you pass a null to the constructor, the drain remains null until save or forceSave is called.

  • protectd onCreate -- Where you make an instance of your Drain object (whatever you're wrapping)
  • protected onSave -- where you save your object, emitting events and whatnot.
  • public getDrain -- returns the drain object or null


Form.Mapper is an interface which has two methods, mapForward and mapBackward. These are used for transfering data from Source to Drain or vice versa. They are also used to help you load data from a bundle into a source or drain, for initialization. These should never store any state, and thus can usually be static.

  • public mapForward -- Map from source type to drain type
  • public mapBackward -- Map from drain type to source type


Validator<F> takes a type of object to validate. The objects you can validate are ones who's references don't change. You can't validate a string, per say, but you can validate an EditText, part of which of course is taking it's string and doing some validation on it... get it? There are examples in the samples package. Validators store a weak reference to your field, so it needs a non-null reference to observe. Your Source will call isValid when it runs validation, and delegate to onValid if the reference is not null. The reference is weak, so we aren't holding onto things we shouldn't be. You have access to:

  • protected onValidate(F) -- validate F.

Some simple reusable validators are included for you, and more will be added in the future.

The Builder

Your form is pieced together via Form.Builder<S,D>. S and D are type parameters that refer to the Source and Drain wrapper objects mentioned above. This Builder creates a Form<S,D> for you and returns a new instance of it with every call to build(). The builder's constructor forces you to give non-optional arguments, a Source, a Drain, and a Mapper. You have access to the following methods:

  • withSourceExtrasMapper(Mapper<Bundle, S>) -- Add an optional mapper to map from a bundle into your source (in display(bundle))
  • withDrainExtrasMapper(Mapper<Bundle, D>) -- Add an optional mapper to map from a bundle into your drain (in save(bundle) and forceSave(bundle)

Note that for these bundle mappers, you do not need to support mapBackwards, as it will never be called.


AndroidForms is licensed under the MIT Licnese, (C) 2015 by Alex Hart.


  • Display / Save should return Object wrapped in Source/Drain
  • Losing type information in builder methods
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