14 March 2016 |

If you’re an Android developer (and you probably are if you’re reading this blog), you’ve probably heard of the Design Support Library. It was unveiled at Google I/O last year, and comes with several classes to assist you in making your apps follow the Material Design Guidelines. This leads to not only a great user experience, but consistency across apps all over the Android ecosystem. This is something that has been sorely lacking up until the introduction of Lollipop. In this post, I’m going to show you how to use several elements of the Design Support Library in your app, as well as point out a few gotchas I’ve come across.

Before we begin, I should note that this post is based on version 23.1.0 of the library, and with Google’s constant updates there could be changes down the road that are not reflected here.

CoordinatorLayout

CoordinatorLayout is, in Google’s own words, a “super-powered FrameLayout”. It behaves similarly to a FrameLayout in that it uses z-ordering and doesn’t give you many methods for laying out child views (margins and layout gravity are about all you get), but it has special functions: it facilitates Material animations and visual flourishes, as well as coordinates the location and behaviors of child views with respect to other children. Most of the views in this library make use of the CoordinatorLayout so it is essential that you know how to use it. Fortunately, it’s very easy!

Simply put a CoordinatorLayout at the root of your Activity or Fragment's layout xml, and any child views will automatically be able to take advantage of it. It should look something like this:

<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="match_parent"
    android:layout_width="match_parent">

   <!-- 
     Add your layout's views here just like you normally would. Don't forget to add a root 
     LinearLayout, RelativeLayout, etc. if CoordinatorLayout isn't flexible enough for your needs.
   -->

</android.support.design.widget.CoordinatorLayout>

That’s all there is to it. Now let’s take a look at Snackbar, which takes advantage of CoordinatorLayout.

Snackbar

You’ve probably seen Snackbars before. They have essentially replaced Toasts in Lollipop, and all of Google’s apps have been updated to use them.

Snackbar

Snackbars are used to display a brief message to a user and can also take a single input action, such as Undo if you swipe away an email in the Inbox app. Like Toasts, they can be shown for a short or long duration, but they can also be shown indefinitely until the user swipes them away. Here’s where CoordinatorLayout comes in: if you display a Snackbar inside one, you get swipe dismissal for free!

You can display a Snackbar in a couple lines of code:

CoordinatorLayout root = (CoordinatorLayout) findViewById(R.id.root);
Snackbar.make(root, R.string.txt_snackbar, Snackbar.LENGTH_LONG).show();

It’s important to be aware that the view passed in as the first parameter of Snackbar.make() should either be a CoordinatorLayout or be a child of one, otherwise swiping will not work. If you want to also display an action on the right side, you can call setAction(int resId, View.OnClickListener listener) to indicate the action’s text and set a click listener to handle the action.

TextInputLayout

The concept of the “floating label” EditText became pretty popular after the announcement of Lollipop in 2014. In response, Google has added TextInputLayout. This widget has the magical power of adding floating label functionality to any normal EditText inside it. You may be asking, “What does floating label mean?” Here’s an example:

TextInputLayout

To take advantage of this effect, just wrap your EditText with a TextInputLayout like so:

<android.support.design.widget.TextInputLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:hintTextAppearance="@style/TextInputWidgetAppearance">

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="@string/txt_hint_input_1"/>

</android.support.design.widget.TextInputLayout>

When an EditText that is inside a TextInputLayout receives focus, the hint text will automatically shrink and float up above the field. That hint text will stay above the field as long as there is text in it, even if focus is changed to another view. However, if the field is empty and focus changes to, say, a different EditText, the hint text will grow and move back into its origin position inside the field.

Additionally, TextInputLayout comes with a setError(CharSequence error) method. Calling this and passing in some text will cause the text to appear below the EditText in red (by default). It’s an easy way to show a validation error if a user provides invalid input in your field. To hide the error, just call setError(null) and the text will be cleared. Here’s an example:

Resources resources = getResources();
TextInputLayout textInput = (TextInputLayout) findViewById(R.id.txt_input_2);
textInput.setError(resources.getString(R.string.txt_input_error));

A few extra tips on using TextInputLayout:

  • Calling setError() increases the height of the TextInputLayout, so depending on how your layout is structured other views may be shifted when the error is displayed.
  • When setting hint text in XML, set it on the EditText, not TextInputLayout. android:hint is accepted by TextInputLayout but has no effect. Oddly enough though, calling setHint() on the TextInputLayout works fine!
  • You can use app:hintTextAppearance to set the appearance of the floating hint text, and app:errorTextAppearance for the error text that appears underneath the field.

TextInputLayout Error

FloatingActionButton (FAB)

If you’ve used any Google app in the last year or so, you’ve seen FloatingActionButton in use. The FAB is a button that floats on top of an app’s content and provides a single action for the user to take, or in Google’s words, it is “used for a promoted action”. The color of your FAB is dictated by the android:colorAccent value in your app’s theme.

There are many different use cases for FABs. They can be used to bring up a contextual search, expand into other action buttons to provide quick actions, and morph into new pieces of UI. For some examples of such cases, refer to the Material Design Guidelines.

The various uses outlined by the guidelines don’t come for free unfortunately; all you get out of the box is a simple round button with a shadow that you can position where needed.

FloatingActionButton

To add a FAB, simply put it in your layout xml inside a CoordinatorLayout:

<android.support.design.widget.CoordinatorLayout>

  <!-- Rest of your content -->

  <android.support.design.widget.FloatingActionButton
      android:layout_height="wrap_content"
      android:layout_width="wrap_content"
      android:layout_gravity="right|bottom"
      android:visibility="invisible"
      android:src="@android:drawable/ic_input_add"
      app:fabSize="normal"
      android:id="@+id/fab"/>

</android.support.design.widget.CoordinatorLayout>

Remember earlier how Snackbars had extra functionality as a result of being inside a CoordinatorLayout? The same goes for FABs too! If you show a Snackbar and your FAB is anchored to the bottom of the screen (as seen above by layout_gravity="right|bottom"), the FAB will automatically translate up and down when the Snackbar is shown and hidden, with no extra work required. Neat!

FAB with Snackbar

The Material Design Guidelines include several animations for FABs to add that Material flourish to your app. One of them is a grow/shrink animation when a FAB is shown/hidden. The FloatingActionButton class comes with show() and hide() methods that will automatically perform these animations, and it works whether your FAB is inside a CoordinatorLayout or not! There’s also an isShown() method that will tell you if the FAB is already being shown. Here’s a basic example of how to toggle a FAB’s visibility, with animation:

private void toggleFab() {
  FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
  if (fab.isShown()) {
      fab.hide();
  } else {
      fab.show();
  }
}

FloatingActionButtons are an important component of Android apps now, and there’s way more to cover than what this post will allow for. To get some ideas on how to incorporate them into your own apps, I’d recommend looking at the Design Guidelines linked earlier, as well as Google’s apps like Keep, Inbox, Gmail, and Hangouts.

That’s all for Part 1. Next time we’ll have Part 2, which will detail the rest of the Design Support Library, including AppBarLayout, TabLayout, and NavigationView. In the meantime, feel free to check out this sample project on Github. It demonstrates example usage of each element of the library, including the ones not covered in Part 1.


Categories

Tags