Movie Booking

This is a simple example for booking movie seats in general movie/film mobile application. The concept is simply combined of State Design Pattern, Android Data Binding and Multibinding + Autofactory below.

In the future, we can extend this concept by using RxJava to handle behavior in only a stream, also chain any stream to process our logic.

Hope it will be useful for anyone who are building this context.

Concept

State Design Pattern

A seat has many states, such as:

• EMPTY: this is not a seat, just a blank space, it does not have any action.
• RESERVED: this is a reserved seat, which can not be booked anymore.
• AVAILABLE: this seat can be book by selecting.
• SELECTED: this seat is being selected, it can be deselected to be available.

To manage these states, we use State Design Pattern, also for the definition of state action, current state and switching between different states.

• An available seat can be select to be a selected seat, its state changes from AVAILABLE to SELECTED.
• A selected seat can be deselected to be an available seat, its state changes from SELECTED to AVAILABLE

Android Data Binding

For any state changes, we update the UI of the seat correspondingly by using @BindingAdapter and @Bindable annotations defined in Android Data Binding. Example:

• In a layout of a seat, we bind a state value to UI by: app:state="@{data.state}".
• A state defined in Java code is: @Bindable State mState; and must have getter public State getState() { return mState; }.
• If we want to seatChange the state and update to the UI, we set mState = new NewState(); then notifyPropertyChanged(BR.state);, noted that BR.state is generated after building our application.

Multibinding and Autofactory

For the Dependency Injection, we use Dagger2 to setup. Dagger2 also supports Multibinding, it means that we can inject any ViewHolder into our adapter to render the corresponding layout of an item in a list.

By using Autofactory, we construct some ViewHolders and provide these factory in a module. These factory must go with a key defined by @IntKey, which is an item view type. Example:

@Provides
@IntoMap
@IntKey(Seat.Type.AVAILABLE)
SeatViewHolderFactory provideAvailableSeatViewHolder() {
  return new AvailableSeatViewHolderFactory();
}

public interface SeatViewHolderFactory {
  SeatViewHolder createViewHolder(ViewDataBinding binding);
}

@Override
public SeatViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
  ItemSeatBinding binding = DataBindingUtil.inflate(LayoutInflater.from(parent.getContext()), R.layout.item_seat, parent, false);
  return mSeatViewHolderFactoryMap.get(viewType).createViewHolder(binding);
}

TODO

• Write Unit Test to verify any action from the views.
• Support selecting many seats and handle exception if the selection reaches the maximum.
• Try to use RxJava to extend the concept.

References

• http://frogermcs.github.io/inject-everything-viewholder-and-dagger-2-example/
• https://github.com/google/android-ui-toolkit-demos/tree/master/DataBinding/DataBoundRecyclerView

License

MIT License

Copyright (c) 2017 Lam Tran ([email protected])

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