Witch for Android

Functional view data binding.

Getting started

    compile "se.snylt:witch:0.0.1"
    annotationProcessor "se.snylt:witch-processor:0.0.1"

Add snapshot repository

  repositories {
    mavenCentral()
    maven {
        url "https://oss.sonatype.org/content/repositories/snapshots/"
    }
  }

How to use:

Define view model

public class MyViewModel {

  @BindToTextView(id = R.id.title_tv)
  public String title;
  ...
}

Bind view model to view

MyViewModel model = new MyViewModel("Hello Witch!"));
Witch.bind(model, activity); // Binds to anything that contains the views defined in view model.

Set custom properties

Each specific bind-view-annotation sets a default property. For example, @BindTextView sets text by default.

@BindToTextView(id = R.id.text_view_title)
// Generates =>
((TextView)view).setText(property);

To set a property different from default one, use set=<property>:

@BindToTextView(id = R.id.text_view_title, set="color")
// Generates =>
((TextView)view).setColor(property);

Bind to any view type

Views not backed up by a specific annotation is supported by the @BindToView

@BindToView(id = R.id.my_view, class = UnknownView.class, set = "myProperty")
// Generates =>
((UnknownView)view).setMyProperty(property)

ViewHolders built in

Each view model will have its own view holder which eliminates the need for defining view holders in adapters:

   @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        // An empty view holder just containing the root view.
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        return new SimpleViewHolder(inflater.inflate(R.layout.recycler_view_item, parent, false));
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        Witch.bind(items.get(position), holder.itemView);
    }

Supported annotations

Direct view binding

@BindToTextView
@BindToEditText
@BindToCompoundButton
@BindToImageView
@BindToRecyclerView
@BindToViewPager
@AlwaysBind
@BindToView
@BindTo
// More to come!

Custom bind composition with Binder

One or more bind actions can be chained for more advanced bindings:

Binder b = Binder.create(
    new SyncOnBind<TextView, String>(){
      @Override
      void onBind(TextView view, String text) {
        view.setText(text);
      }
    })
  .next(
    new SyncOnBind<TextView, String>(){
      @Override
      void onBind(TextView view, String text) {
        view.setVisibility(text == null ? View.INVISIBLE : View.VISIBLE);
      }
    });

    b.bind(view, "Hello Witch!");

Use ValueBinder with @BindTo annotation

class ViewModel {

  private final String amount;

  @BindTo(R.id.amount_tv)
  public ValueBinder<TextView, String> amount(){
    // Binds amount and adds "dollars"
    return ValueBinder.create(amount,  Binder.create(
      new SyncOnBind<TextView, String> {
        @Override
        public void onBind(TextView view, String amount) {
          view.setText(amount + " dollars");
        }
      }
    ));
  }
}

Define actions in separate classes for better re-use:

Binder.create(new SetText<TextView, String>())
.next(new AppendText<TextView, String>("dollars"))
.next(new InvisibleIfNull<TextView, String>());

AsyncOnBind

Bind actions that has async dependencies, like animations, can delay bind chain with a callback.

  Binder.create(
    new AsyncOnBind<TextView, String>(){
      @Override
      void onBind(TextView view, String text, final OnBindListener listener) {
        ObjectAnimator a = ObjectAnimator.ofFloat(view, View.ALPHA, 0f, 1f);
        a.setDuration(300);
        a.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                listener.onBindDone();
            }
        });
        a.start();
      }
    })
  .next(
    new SyncOnBind<TextView, String>(){
      @Override
      void onBind(TextView view, String text) {
        view.setText(text);
      }
    })
    .bind(view, "Hello world!");

@AlwaysBind

By default Witch wont re-bind values that has not changed in the view model. If the view model is out of sync with the actual value in the view, for example when a seekbar is changed by the user, @AlwaysBind can be used to always refresh the binding.

public class MyViewModel {

  @BindToView(R.id.my_seek_bar, class = SeekBar.class, set = "progress")
  @AlwaysBind
  public Integer progress;
}

License

Copyright 2017 Simon Edström

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.