Android ViewModelBinding 2.0

Intro

A lightweight library aiming to speed up Android app development by leveraging the new Android Data Binding and taking the best from the Model-View-ViewModel design pattern.

Why should I use it?

1. Data Binding Android Data Binding is great and if you're not, you should start using it today.
2. You don't need to care about screen rotation (configuration change) at all. Most of the screen lifecycle is moved to ViewModel where the lifecycle is dramatically easier to understand and to use. The ViewModel instance outlives it's Activity/Fragment during configuration change so no more hassle with onSaveInstanceState() or using retained Fragments.
3. ViewModel as the only variable in the layout ViewModel serves as the data provider in layout's binding as well as handler for click or other methods common fro Data Binding. With a construct like android:onClick="@{viewModel.onClickedPlayButton}" you will never have to set an OnClickListener anymore. Also, each ViewModel extends BaseObservable so you have a choice between using BaseObservable approach or ObservableField approach within the DataBinding. (see Data Binding Guide)

How does it work?

The framework extensively uses Java Generics to provide a type-safe link between Activity/Fragment and ViewModel and its binding.

ViewModel instances are stored in a global static Map and reattached automatically to corresponding Activity/Fragment. When there is no need for the ViewModel anymore (Activity finished) the instance is destroyed.

ViewModel Lifecycle

Installation

compile 'cz.kinst.jakub:viewmodelbinding:2.0.0'

Don't forget to enable Data Binding in your module:

android {
    dataBinding.enabled = true
}

Usage

Activity/Fragment

MainActivity.java

public class MainActivity extends ViewModelActivity<ActivityMainBinding, MainViewModel> {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        setupViewModel(R.layout.activity_main, MainViewModel.class);
        super.onCreate(savedInstanceState);
    }

    // handle Activity related stuff here - Options menu, Toolbar, Window config, etc.
}

activity_main.xml

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

        <variable
            name="viewModel"
            type="cz.kinst.jakub.sample.viewmodelbinding.MainViewModel" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="@dimen/activity_padding"
        android:orientation="vertical">

        <android.support.design.widget.TextInputLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

            <EditText
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="@={viewModel.name}"
                android:inputType="textPersonName|textCapWords"
                android:hint="@string/hint_enter_your_name" />
        </android.support.design.widget.TextInputLayout>

        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:animateLayoutChanges="true">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:textAppearance="@style/Base.TextAppearance.AppCompat.Headline"
                android:textColor="@color/colorPrimary"
                android:text="@{@string/hello(viewModel.name)}"
                app:show="@{viewModel.name != null &amp;&amp; !viewModel.name.empty}"
                tools:text="@string/hello" />
        </FrameLayout>

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:onClick="@{() -> viewModel.showDialog()}"
            android:text="@string/button_dialog_fragment"
            style="@style/Widget.AppCompat.Button.Colored" />
    </LinearLayout>
</layout>

ViewModel

MainViewModel.java

public class MainViewModel extends ViewModel {

    public final ObservableField<String> name = new ObservableField<>();

    @Override
    public void onViewModelCreated() {
        super.onViewModelCreated();
        // Do API calls etc.
    }

    @Override
    public void onViewAttached(boolean firstAttachment) {
        super.onViewAttached(firstAttachment);
        // manipulate with the view
    }
}

Android Studio New Screen Template

To deploy new screens even faster, use the included Android Studio Template (revision 2)

Usage

1. Copy the template folder to Android Studio templates folder (/Applications/Android Studio.app/Contents/plugins/android/lib/templates/ on Mac) OR run the following command to download and install the template automatically

   curl -o viewmodelbinding.zip -Lk https://github.com/jakubkinst/Android-ViewModelBinding/archive/master.zip && unzip viewmodelbinding.zip && cp -af Android-ViewModelBinding-master/extras/AndroidStudioTemplate/templates/. "/Applications/Android Studio.app/Contents/plugins/android/lib/templates/" && rm -r Android-ViewModelBinding-master && rm viewmodelbinding.zip

2. Restart Android Studio
3. Use File>New>ViewModelBinding>ViewModelBinding Screen action to add a new screen

Changelog

v2.0.0 (Mar 8, 2017)

• Activity result delivered to ViewModel automatically
• ViewModel is not tied to binding (layout) anymore
• ViewModel has getApplicationContext() which returns Context at all times (even if View is not attached at the moment)
• Included couple of handy BindingAdapters (app:show, app:hide, app:invisible)
• New way of configuring Activity/Fragment (call setupViewModel() before super.onCreate())
• Added onViewModelInitialized() callback to Activity/Fragment to be able to setup ViewModel before onViewModelCreated() is called (example: feeding ViewModel with Extras/Arguments - see ArgumentDialogFragment in sample)
• Optional automatic binding of Activity/Fragment into layout file next to the ViewModel instance (add variable of name view and appropriate type)
• [ALPHA] Added simple permission handling (PermissionManager) to ViewModel - see sample

v0.9.4 (Jul 18, 2016)

• ViewInterface now has to implement startActivityForResult()

v0.9.2 (Jun 28, 2016)

• Tasks added by runOnUiThread() are performed after onViewAttached() method is called when there are some left in the queue

v0.9 (Jun 21, 2016)

• Added safe handling of Runnables in runOnUiThread() - if the ViewModel is not attached to an Activity/Fragment at the time, the Runnable will be executed once it is attached again
• Added getString() method taking formatting arguments to ViewModel
• Added RetrofitCallViewModel extension for handling Retrofit calls (see the source)
• Updated dependencies (support library versions, targetSdkVersion, etc.)

v0.8.3 (Mar 10, 2016)

• Improved internal generics - more type-safety across the library

v0.8.2 (Feb 26, 2016)

• Added isRunning() method to ViewModel telling if Activity/Fragment is in RUNNING state (in between onResume() and onPause())

v0.8.1 (Feb 3, 2016)

• Added runOnUiThread(), postDelayed() and getRootView() methods to ViewModel
• Added ViewModelDialogFragment
• getBinding() is now public in ViewModel

v0.8 (Jan 19, 2016)

• ViewModelConfig can be created without BR.viewModel as long as the name ov the binding variable is viewModel
• Added onViewModelCreated() callback in ViewModel
• BREAKING Renamed onModelRemoved() to onViewModelDestroyed() callback in ViewModel
• Added getResources() convenience method to ViewModel

Contributors

• Jakub Kinst (jakub@kinst.cz)
• Stepan Sanda (stepan.sanda@gmail.com)
• Artem Ufimtcev (alotxo@gmail.com)

The library was inspired by a great AndroidViewModel library by Inloop

License

Copyright 2015 Jakub Kinst & Stepan Sanda

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.