It seems likely that Android N will get its first proper outing in May, at this year's Google I/O conference, but there's no need to wait until then to start developing for the next major release of the Android platform. Thanks to Google's decision to release preview versions early you can start getting your apps ready for Android N today.

In this article by Jessica Thornsby, author of the book Android UI Design, going to look at the major new UI features that you can start experimenting with right now. And since you'll need something to develop your Android N-ready apps in, we're also going to look at Android Studio 2.1, which is currently the recommended development environment for Android N.

(For more resources related to this topic, see here.)

Multi-window mode

Beginning with Android N, the Android operating system will give users the option to display more than one app at a time, in a split-screen environment known as multi-window mode. Multi-window paves the way for some serious multi-app multi-tasking, allowing users to perform tasks such as replying to an email without abandoning the video they were halfway through watching on YouTube, and reading articles in one half of the screen while jotting down notes in Google Keep on the other.

When two activities are sharing the screen, users can even drag data from one activity and drop it into another activity directly, for example dragging a restaurant's address from a website and dropping it into Google Maps.

Android N users can switch to multi-window mode either by:

• Making sure one of the apps they want to view in multi-window mode is visible onscreen, then tapping their device's Recent Apps softkey (that's the square softkey). The screen will split in half, with one side displaying the current activity and the other displaying the Recent Apps carousel. The user can then select the secondary app they want to view, and it'll fill the remaining half of the screen.
• Navigating to the home screen, and then pressing the Recent Apps softkey to open the Recent Apps carousel. The user can then drag one of these apps to the edge of the screen, and it'll open in multi-window mode. The user can then repeat this process for the second activity.

If your app targets Android N or higher, the Android operating system assumes that your app supports multi-window mode unless you explicitly state otherwise. To prevent users from displaying your app in multi-window mode, you'll need to add android:resizeableActivity="false" to the <activity> or <application> section of your project's Manifest file.

If your app does support multi-window mode, you may want to prevent users from shrinking your app's UI beyond a specified size, using the android:minimalSize attribute. If the user attempts to resize your app so it's smaller than the android:minimalSize value, the system will crop your UI instead of shrinking it.

Direct reply notifications

Google are adding a few new features to notifications in Android N, including an inline reply action button that allows users to reply to notifications directly from the notification UI.

This is particularly useful for messaging apps, as it means users can reply to messages without even having to launch the messaging application. You may have already encountered direct reply notifications in Google Hangouts.

To create a notification that supports direct reply, you need to create an instance of RemoteInput.Builder and then add it to your notification action.

The following code adds a RemoteInput to a Notification.Action, and creates a Quick Reply key. When the user triggers the action, the notification prompts the user to input their response:

private static final String KEY_QUICK_REPLY = "key_quick_reply";
String replyLabel = getResources().getString(R.string.reply_label);
RemoteInput remoteInput = new RemoteInput.Builder(KEY_QUICK_REPLY)
       .setLabel(replyLabel)
       .build();

To retrieve the user's input from the notification interface, you need to call: getResultsFromIntent(Intent) and pass the notification action's intent as the input parameter:

Bundle remoteInput = RemoteInput.getResultsFromIntent(intent);
 
//This method returns a Bundle that contains the text response//
 
   if (remoteInput != null) {
           return remoteInput.getCharSequence(KEY_QUICK_REPLY);
 
//Query the bundle using the result key, which is provided to the RemoteInput.Builder constructor//

Bundled notifications

Don't you just hate it when you connect to the World Wide Web first thing in the morning, and Gmail bombards you with multiple new message notifications, but doesn't give you anymore information about the individual emails? Not particularly helpful!

When you receive a notification that consists of multiple items, the only thing you can really do is launch the app in question and take a closer look at the events that make up this grouped notification.

Android N overcomes this drawback, by letting you group multiple notifications from the same app into a single, bundled notification via a new notification style: bundled notifications. A bundled notification consists of a parent notification that displays summary information for that group, plus individual notification items.

If the user wants to see more information about one or more individual items, they can unfurl the bundled notification into separate notifications by swiping down with two fingers. The user can then act on each mini-notification individually, for example they might choose to dismiss the first three notifications about spam emails, but open the forth e-mail.

To group notifications, you need to call setGroup() for each notification you want to add to the same notification stack, and then assign these notifications the same key.

final static String GROUP_KEY_MESSAGES = "group_key_messages";
Notification notif = new NotificationCompat.Builder(mContext)
        .setContentTitle("New SMS from " + sender1)
        .setContentText(subject1)
        .setSmallIcon(R.drawable.new_message)
        .setGroup(GROUP_KEY_MESSAGES)
        .build();

Then when you create another notification that belongs to this stack, you just need to assign it the same group key.

Notification notif2 = new NotificationCompat.Builder(mContext)
   .setContentTitle("New SMS from " + sender1)
    .setContentText(subject2)
     .setGroup(GROUP_KEY_MESSAGES)
  .build();

The second Android N developer preview introduced an Android-specific implementation of the Vulkan API. Vulkan is a cross-platform, 3D rendering API for providing high-quality, real-time 3D graphics. For draw-call heavy applications, Vulkan also promises to deliver a significant performance boost, thanks to a threading-friendly design and a reduction of CPU overhead.

You can try Vulkan for yourself on devices running Developer Preview 2, or learn more about Vulkan at the official Android docs (https://developer.android.com/ndk/guides/graphics/index.html?utm_campaign=android_launch_npreview2_041316&utm_source=anddev&utm_medium=blog).

Android N Support in Android Studio 2.1

The two Developer Previews aren't the only important releases for developers who want to get their apps ready for Android N. Google also recently released a stable version of Android Studio 2.1, which is the recommended IDE for developing Android N apps.

Crucially, with the release of Android Studio 2.1 the emulator can now run the N Developer Preview Emulator System Images, so you can start testing your apps against Android N. Particularly with features like multi-window mode, it's important to test your apps across multiple screen sizes and configurations, and creating various Android N Android Virtual Devices (AVDs) is the quickest and easiest ways to do this.

Android 2.1 also adds the ability to use the new Jack compiler (Java Android Compiler Kit), which compiles Java source code into Android dex bytecode. Jack is particularly important as it opens the door to using Java 8 language features in your Android N projects, without having to resort to additional tools or resources.

Although not Android N-specific, Android 2.1 makes some improvements to the Instant Run feature, which should result in faster editing and deploy builds for all your Android projects.

Previously, one small change in the Java code would cause all Java sources in the module to be recompiled. Instant Run aims to reduce compilation time by analyzing the changes you've made and determining how it can deploy them in the fastest way possible. This is instead of Android Studio automatically going through the lengthy process of recompiling the code, converting it to dex format, generating an APK and installing it on the connected device or emulator every time you make even a small change to your project.

To start using Instant Run, select Android Studio from the toolbar followed by Preferences…. In the window that appears, select Build, Execution, Deployment from the side-menu and select Instant Run. Uncheck the box next to Restart activity on code changes.

Instant Run is supported only when you deploy a debug build for Android 4.0 or higher. You'll also need to be using Android Plugin for Gradle version 2.0 or higher. Instant Run isn't currently compatible with the Jack toolchain.

To use Instant Run, deploy your app as normal. Then if you make some changes to your project you'll notice that a yellow thunderbolt icon appears within the Run icon, indicating that Android Studio will push updates via Instant Run when you click this button.

You can update to the latest version of Android Studio by launching the IDE and then selecting Android Studio from the toolbar, followed by Check for Updates….

Summary

In this article, we looked at the major new UI features currently available in the Android N Developer Preview. We also looked at the Android Studio 2.1 features that are particularly useful for developing and testing apps that target the upcoming Android N release.

Although we should expect some pretty dramatic changes between these early previews and the final release of Android N, taking the time to explore these features now means you'll be in a better position to update your apps when Android N is finally released.

Resources for Article:

Further resources on this subject:

• Drawing and Drawables In Android Canvas [article]
• Behavior-Driven Development With Selenium Webdriver [article]
• Development of Iphone Applications [article]