Android – Comparing Models in Kotlin, Java, and C# for Xamarin

Models are an obvious important part of our applications we develop. It’s how we define our data and because of that, we can grow our models to be quite large in number. This post will look at comparing the definition of models between Java, C# (for Xamarin), and Kotlin.

Our example model will be a simple Person that has a Name and Description along with an ID. Let’s look at how we can define our Person model with these fields as well as the ability to access these fields publicly.

Using Java

Java is going to be our largest and most annoying to develop. We need to define our class, private fields, and then public functions/methods to get and set the value of each of the fields. We also need to be able to instantiate a Person with all these properties set in the constructor.

Person.java

public class Person{
    private int id;
    private String name;
    private String description;

    public Person(int id, string name, string description){
        this.id = id;
        this.name = name;
        this.description = description;
    }

    public void setID(int id){
        this.id = id;
    }
    public int getID(){
        return this.id;
    }
    public void setName(String name){
        this.name = name;
    }
    public String getName(){
        return this.name;
    }
    public void setDescription(String description){
        this.description = description;
    }
    public String getDescription(){
        return this.description;
    }
}

That’s exhausting…

Now we can instantiate it and update properties like this:

...
Person bob = new Person(1, "Bob", "He writes code and stuff");
bob.setDescription("He doesn't actually write code");
...

Using C# for Xamarin Applications

C# makes our lives a lot easier with the get and set mechanism built into properties.

Person.cs

public class Person
{
    public int ID { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }

    public Person(int id, string name, string description)
    {
        ID = id;
        Name = name;
        Description = description;
    }
}

Nice and neat!

Now we can instantiate it and update properties like this:

...
var bob = new Person(1, "Bob", "He writes code and stuff");
bob.Description = "He doesn't actually write code";
...

Using Kotlin

Kotlin has some cool tricks that allow us to define and set properties directly in our constructor without having to define and set them separately. This gives us the quickest way to create simple POCO definitions and speed up that development time.

Person.kt

class Person(var id: Int, var name: String, var description: String);

One line.

Now we can instantiate it and update properties like this:

...
val bob = Person(1, "Bob", "He writes code and stuff");
bob.description = "He doesn't actually write code";
...

Conclusion

Each language has their nuances, but I think we can all agree that defining models in Java is just a headache that other languages have solved with better solutions.

If you like what you see, don’t forget to follow me on twitter @Suave_Pirate, check out my GitHub, and subscribe to my blog to learn more mobile developer tips and tricks!

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Android.Basics – Adding a Bottom Navigation View

Changing my pace of steady Xamarin content to go to my roots of native mobile development. This time, we’ll look at implementing the latest control provided by Google and Material Design – The BottomNavigationView.

Resources

Aren’t These Just Tabs?

I mean… yeah, but… it’s new and cool! Google finally realized that stretching to the top of the app can be annoying.
Screen Shot 2017-06-27 at 5.56.48 PM.png

This new control is also a little different from the TabLayout we all know in love from Material Design and Android development in that it is limited to 5 maximum tab items and does not support scrolling. It’s meant to act as top level or sibling level navigation as long as all items are of equal importance in the context of the application/current view. It is also nice to give some variety to our applications navigation scheme; larger apps with many tabbed views can become overwhelming, so tossing something new is relieving to our users.

Code

There are 3 major components to setting up a view with a BottomNavigationView.

  1. First, we need to create a menu resource for our navigation items.
  2. Then we need to create, style, and set up our BottomNavigationView in our layout.
  3. Lastly, add listeners for when an item is selected in our BottomNavigationView and make sure it fits the experience expectation defined in Material Design.

Create a Menu

In our example, we will be building an application for viewing adoptable puppies. Each navigation item will be a different set of these puppies by categorizing them. Let’s create a menu for “all”, “big”, “small”, “trained”, and “active” as categories for our puppies:

res/menu/bottom_bar_menu.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/all_puppies"         android:title="@string/action_all"         android:icon="@drawable/ic_home_white_24dp" />

    <item android:id="@+id/big_puppies"         android:title="@string/action_big"         android:icon="@drawable/ic_dog_white_24dp" />

    <item android:id="@+id/small_puppies"         android:title="@string/action_small"         android:icon="@drawable/ic_small_dog_white_24dp" />

    <item android:id="@+id/trained_puppies"         android:title="@string/action_trained"         android:icon="@drawable/ic_trained_white_24dp" />

    <item android:id="@+id/active_puppies"         android:title="@string/action_active"         android:icon="@drawable/ic_active_white_24dp" />
</menu>

With our menu, we can create our layout.

Updating the Layout

In our example, we are moving from a TabLayout with a ViewPager. However, the Material Design documentation for the BottomNavigationView states that it should NOT be used with side-swiping actions such as a ViewPager. Let’s replace that ViewPager with a FrameLayout that will be used to swap our active Fragment and also remove the TabLayout that is being replaced by the BottomNavigationView:

res/layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:app="http://schemas.android.com/apk/res-auto"     xmlns:tools="http://schemas.android.com/tools"     android:id="@+id/main_content"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:fitsSystemWindows="true"     tools:context="com.suavepirate.bottomnavigationpuppies.activities.MainActivity">

    <android.support.design.widget.AppBarLayout         android:id="@+id/appbar"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:paddingTop="@dimen/appbar_padding_top"         android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar             android:id="@+id/toolbar"             android:layout_width="match_parent"             android:layout_height="?attr/actionBarSize"             android:background="?attr/colorPrimary"             app:layout_scrollFlags="scroll|enterAlways"             app:popupTheme="@style/AppTheme.PopupOverlay">

        </android.support.v7.widget.Toolbar>
    </android.support.design.widget.AppBarLayout>

<FrameLayout     android:id="@+id/container"     android:layout_width="match_parent"     android:layout_height="match_parent"     app:layout_behavior="@string/appbar_scrolling_view_behavior" ></FrameLayout>
<android.support.design.widget.BottomNavigationView     android:id="@+id/bottombar"     android:layout_width="match_parent"     android:layout_height="56dp"     android:layout_gravity="bottom|fill_horizontal|start"     app:menu="@menu/bottom_bar_menu"     android:background="@android:color/white"     app:elevation="8dp"/>
</android.support.design.widget.CoordinatorLayout>

It’s important to layout the BottomNavigationView at the bottom of the page as well as give it a solid background and elevation. Also, notice how we apply our menu we created to the view by setting app:menu="@menu/bottom_bar_men".

With our layout set, let’s wire up listeners to update the current Fragment based on the selected navigation item.

Setting Up Listeners

In our MainActivity.java we can implement the BottomNavigationView.OnNavigationItemSelectedListener interface and override the onNavigationItemSelected method:

MainActivity.java

// imports

public class MainActivity extends AppCompatActivity implements BottomNavigationView.OnNavigationItemSelectedListener {
    private PageAdapter mSectionsPagerAdapter;
    private FrameLayout mContainer;
    private BottomNavigationView mBottomBar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        // Create the adapter that will return a fragment for each of puppy types
        mSectionsPagerAdapter = new PageAdapter(getSupportFragmentManager(), this);

        // Set up the ViewPager with the sections adapter.
        mContainer = (FrameLayout) findViewById(R.id.container);

        // set up the first Fragment
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.add(R.id.container, mSectionsPagerAdapter.getItem(0), "CURRENT_PAGE");
        ft.commit();

        // set up the bottom bar and listener
        mBottomBar = (BottomNavigationView)findViewById(R.id.bottombar);
        mBottomBar.setOnNavigationItemSelectedListener(this);

    }

    // Handles when an item is selected to update the fragment container
    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.setCustomAnimations(android.R.anim.fade_in, android.R.anim.fade_out);

        switch(item.getItemId()){
            case R.id.all_puppies: ft.replace(R.id.container, mSectionsPagerAdapter.getItem(0));
                break;
            case R.id.big_puppies: ft.replace(R.id.container, mSectionsPagerAdapter.getItem(1));
                break;
            case R.id.small_puppies: ft.replace(R.id.container, mSectionsPagerAdapter.getItem(2));
                break;
            case R.id.trained_puppies: ft.replace(R.id.container, mSectionsPagerAdapter.getItem(3));
                break;
            case R.id.active_puppies: ft.replace(R.id.container, mSectionsPagerAdapter.getItem(4));
                break;
        }
        ft.commit();
        return true;
    }
}

Now with all of this, we are able to switch the current Fragment with a fade in and out animation when the selected navigation item is updated. That means our BottomNavigationView is implemented and ready to go!

Screenshot_1497932698

If you like what you see, don’t forget to follow me on twitter @Suave_Pirate, check out my GitHub, and subscribe to my blog to learn more mobile developer tips and tricks!

Interested in sponsoring developer content? Message @Suave_Pirate on twitter for details.