22 April 2015

New Android Code Samples

Posted by Rich Hyndman, Developer Advocate

A new set of Android code samples, covering Android Wear, Android for Work, NFC and Screen capturing, have been committed to our Google Samples repository on GitHub. Here’s a summary of the new code samples:

XYZTouristAttractions

This sample mimics a real world mobile and Android Wear app. It has a more refined design and also provides a practical example of how a mobile app would interact and communicate with its Wear counterpart.

The app itself is modeled after a hypothetical tourist attractions experience that notifies the user when they are in close proximity to notable points of interest. In parallel,the Wear component shows tourist attraction images and summary information, and provides quick actions for nearby tourist attractions in a GridViewPager UI component.

DeviceOwner - A Device Owner is a specialized type of device administrator that can control device security and configuration. This sample uses the DevicePolicyManager to demonstrate how to use device owner features, including configuring global settings (e.g.automatic time and time-zone) and setting the default launcher.

NfcProvisioning - This sample demonstrates how to use NFC to provision a device with a device owner. This sample sets up the peer device with the DeviceOwner sample by default. You can rewrite the configuration to use any other device owner.

NFC BeamLargeFiles - A demonstration of how to transfer large files via Android Beam on Android 4.1 and above. After the initial handshake over NFC, file transfer will take place over a secondary high-speed communication channel such as Bluetooth or WiFi Direct.

ScreenCapture - The MediaProjection API was added in Android Lollipop and allows you to easily capture screen contents and/or record system audio. The ScreenCapture sample demonstrates how to use the API to capture device screen in real time and show it on a SurfaceView.

As an additional bonus, the Santa Tracker Android app, including three games, two watch-faces and other goodies, was also recently open sourced and is now available on GitHub.

As with all the Android samples, you can also easily access these new additions in Android Studio using the built in Import Samples feature and they’re also available through our Samples Browser.

Check out a sample today to help you with your development!

Game Performance: Explicit Uniform Locations

Posted by Shanee Nishry, Games Developer Advocate

Uniforms variables in GLSL are crucial for passing data between the game code on the CPU and the shader program on the graphics card. Unfortunately, up until the availability of OpenGL ES 3.1, using uniforms required some preparation which made the workflow slightly more complicated and wasted time during loading.

Let us examine a simple vertex shader and see how OpenGL ES 3.1 allows us to improve it:

#version 300 es

layout(location = 0) in vec4 vertexPosition;
layout(location = 1) in vec2 vertexUV;

uniform mat4 matWorldViewProjection;

out vec2 outTexCoord;

void main()
{
    outTexCoord = vertexUV;
    gl_Position = matWorldViewProjection * vertexPosition;
}

Note: You might be familiar with this shader from a previous Game Performance article on Layout Qualifiers. Find it here.

We have a single uniform for our world view projection matrix:

uniform mat4 matWorldViewProjection;

The inefficiency appears when you want to assign the uniform value.

You need to use glUniformMatrix4fv or glUniform4f to set the uniform’s value but you also need the handle for the uniform’s location in the program. To get the handle you must call glGetUniformLocation.

GLuint program; // the shader program
float matWorldViewProject[16]; // 4x4 matrix as float array

GLint handle = glGetUniformLocation( program, “matWorldViewProjection” );
glUniformMatrix4fv( handle, 1, false, matWorldViewProject );

That pattern leads to having to call glGetUniformLocation for each uniform in every shader and keeping the handles or worse, calling glGetUniformLocation every frame.

Warning! Never call glGetUniformLocation every frame! Not only is it bad practice but it is slow and bad for your game’s performance. Always call it during initialization and save it somewhere in your code for use in the render loop.

This process is inefficient, it requires you to do more work and costs precious time and performance.

Also take into consideration that you might have multiple shaders with the same uniforms. It would be much better if your code was deterministic and the shader language allowed you to explicitly set the locations of your uniforms so you don’t need to query and manage access handles. This is now possible with Explicit Uniform Locations.

You can set the location for uniforms directly in the shader’s code. They are declared like this

layout(location = index) uniform type name;

For our example shader it would be:

layout(location = 0) uniform mat4 matWorldViewProjection;

This means you never need to use glGetUniformLocation again, resulting in simpler code, initialization process and saved CPU cycles.

This is how the example shader looks after the change. Changes are marked in bold:

#version 310 es

layout(location = 0) in vec4 vertexPosition;
layout(location = 1) in vec2 vertexUV;

layout(location = 0) uniform mat4 matWorldViewProjection;

out vec2 outTexCoord;

void main()
{
    outTexCoord = vertexUV;
    gl_Position = matWorldViewProjection * vertexPosition;
}

As Explicit Uniform Locations are only supported from OpenGL ES 3.1 we also changed the version declaration to 310.

Now all you need to do to set your matWorldViewProjection uniform value is call glUniformMatrix4fv for the handle 0:

const GLint UNIFORM_MAT_WVP = 0; // Uniform location for WorldViewProjection
float matWorldViewProject[16]; // 4x4 matrix as float array

glUniformMatrix4fv( UNIFORM_MAT_WVP, 1, false, matWorldViewProject );

This change is extremely simple and the improvements can be substantial, producing cleaner code, asset pipeline and improved performance. Be sure to make these changes If you are targeting OpenGL ES 3.1 or creating multiple APKs to support a wide range of devices.

To learn more about Explicit Uniform Locations check out the OpenGL wiki page for it which contains valuable information on different layouts and how arrays are represented.

21 April 2015

Android Support Library 22.1

Posted by Ian Lake, Developer Advocate

You may have heard the phrase ‘the best code is no code.’ While we don’t recommend not writing any code at all, the code you do write should be adding unique value to your app rather than replicating common boilerplate code. The Android Support Library is one of the best resources for accomplishing this by taking care of the little things for you.

The latest release of the Android Support Library is no different, adding a number of extremely helpful components and changes across the Support V4, AppCompat, Leanback, RecyclerView, Palette, and Renderscript libraries. From the new AppCompatActivity and AppCompatDialog to a new guided step flow for Android TV, there’s a lot to get excited about in this release.

Support V4

The Support V4 library serves as the base of much of the Android Support Library and contains many of the classes focused on making backward compatibility much easier.

DrawableCompat now brings drawable tinting back to API 4: simply wrap your Drawable via DrawableCompat.wrap(Drawable) and setTint(), setTintList(), and setTintMode() will just work: no need to create and maintain separate drawables only to support multiple colors!

In addition, we’re making some of the internals of Palette available to all via the ColorUtils class, giving you pre-built tools to better work with colors. ColorUtils makes it easy to calculate the contrast ratio between colors, determine the minimum alpha value to maintain a minimum contrast (perfect for ensuring readable text), or convert colors to their HSL components.

Interpolators are an important part of any animation system, controlling the rate of change in an animation (say accelerating, decelerating, etc). A number of interpolators were added in Lollipop to android.R.interpolator including fast_out_linear_in, fast_out_slow_in, and linear_out_slow_in: important parts of building authentic motion. These are now available via the Support Library via the FastOutLinearInInterpolator, FastOutSlowInInterpolator, and LinearOutSlowInInterpolator classes, making it possible to use these via code for all animations. In addition to those pre-built interpolators, we’ve also created PathInterpolatorCompat, allowing you to build quadratic and cubic Bezier curves as well.

This release also moves the Space widget from the GridLayout library into Support V4, making it available without requiring a separate dependency. The Space widget is a lightweight, invisible View that can be used to create gaps between components.

AppCompat

The AppCompat Support Library started with humble, but important beginnings: a single consistent Action Bar for all API 7 and higher devices. In revision 21, it took on new responsibility: bringing material color palette, widget tinting, Toolbar support, and more to all API 7+ devices. With that, the name ActionBarActivity didn’t really cover the full scope of what it really did.

In this release, ActionBarActivity has been deprecated in favor of the new AppCompatActivity. However, this wasn’t just a rename. In fact, the internal logic of AppCompat is now available via AppCompatDelegate - a class you can include in any Activity, hook up the appropriate lifecycle methods, and get the same consistent theming, color tinting, and more without requiring you to use AppCompatActivity (although that remains the easiest way to get started).

With the help of the new AppCompatDelegate, we’ve also added support for consistent, material design dialogs via the AppCompatDialog class. If you’ve used AlertDialog before, you’ll be happy to know there is also now a Support Library version in support.v7.app.AlertDialog, giving you the same API as well as all the benefits of AppCompatDialog.

The ability to tint widgets automatically when using AppCompat is incredibly helpful in keeping strong branding and consistency throughout your app. This is done automatically when inflating layouts - replacing Button with AppCompatButton, TextView with AppCompatTextView, etc. to ensure that each could support tinting. In this release, those tint aware widgets are now publicly available, allowing you to keep tinting support even if you need to subclass one of the supported widgets.

The full list of tint aware widgets at this time is:
  • AppCompatAutoCompleteTextView
  • AppCompatButton
  • AppCompatCheckBox
  • AppCompatCheckedTextView
  • AppCompatEditText
  • AppCompatMultiAutoCompleteTextView
  • AppCompatRadioButton
  • AppCompatRatingBar
  • AppCompatSpinner
  • AppCompatTextView

Lollipop added the ability to overwrite the theme at a view by view level by using the android:theme XML attribute - incredibly useful for things such as dark action bars on light activities. Now, AppCompat allows you to use android:theme for Toolbars (deprecating the app:theme used previously) and, even better, brings android:theme support to all views on API 11+ devices.

If you’re just getting started with AppCompat, check out how easy it is to get started and bring a consistent design to all of your users:


Leanback

With the Leanback library serving as the collection of best practices for Android TV apps, we’d be remiss to not make an even better 10’ experience as part of the release with the new guided step functionality.

This set of classes and themes can be used to build a multiple step process that looks great on Android TV. It is constructed from a guidance view on the left and a list of actions on the right. Each is customizable via themes with a parent of Theme.Leanback.GuidedStep or, if even more customization is needed, through custom a GuidanceStylist and GuidedActionsStylist.

You’ll also find a large number of bug fixes, performance improvements, and an extra coat of polish throughout the library - all with the goal of making the Leanback experience even better for users and developers alike.

RecyclerView

Besides a healthy set of bug fixes, this release adds a new SortedList data structure. This collection makes it easy to maintain a sorted list of custom objects, correctly dispatching change events as the data changes through to RecyclerView.Adapter: maintaining the item added/deleted/moved/changed animations provided by RecyclerView.

In addition, SortedList also supports batching changes together, dispatching just a single set of operations to the Adapter, ensuring the best user experience when a large number of items change simultaneously.

Palette

If you’ve been using Palette to extract colors from images, you’ll be happy to know that it is now 6-8 times faster without sacrificing quality!

Palette now uses a Builder pattern for instantiation. Rather than directly calling Palette.generate(Bitmap) or their equivalents, you’ll use Palette.from(Bitmap) to retrieve a Palette.Builder. You can then optionally change the maximum number of colors to generate and set the maximum size of the image to run Palette against before calling generate() or generateAsync() to retrieve the color Swatches.

Renderscript

Renderscript gives you massive compute potential and the Support Library version makes a number of the pre-defined scripts, called script intrinsics, available to all API 8+ devices. This release improves reliability and performance across all devices with an improved detection algorithm in determining whether the native Renderscript functionality can be used - ensuring the fastest, most reliable implementation is always chosen. Two additional intrinsics are also added in this release: ScriptIntrinsicHistogram and ScriptIntrinsicResize, rounding out the collection to ten.

SDK available now!

There’s no better time to get started with the Android Support Library. You can get started developing today by downloading the Android Support Library and Android Support Repository from the Android SDK Manager.

To learn more about the Android Support Library and the APIs available to you through it, visit the Support Library section on the Android Developer site.

Android Developer Story: Jelly Button Games grows globally through data driven development

Posted by Leticia Lago, Google Play team

For Jelly Button Games, understanding users is the key to creating and maintaining a successful game, particularly when growth relies on moving into overseas markets. The team makes extensive use of Google Analytics and Google BigQuery to analyze more than 3 billion events each month. By using this data, Jelly Button can pinpoint exactly where, when, and why people play their highly-rated game, Pirate Kings. Feeding this information back into development has driven active daily users up 1500 percent in just five months.

We caught up with Mor Shani, Moti Novo, and Ron Rejwan — some of the co-founders — in Tel Aviv, Israel, to discover how they created an international hit and keep it growing.


Learn about Google Analytics and taking your game to an international audience:

  • Analyze — discover the power of data from the Google Play Developer Console and Google Analytics.
  • Query — find out how Google BigQuery can help you extract the essential information you need from millions or billions of data points.
  • Localize — guide the localization of your app with best practices and tools.

16 April 2015

Drive app installs through App Indexing

Posted by Lawrence Chang, Product Manager

You’ve invested time and effort into making your app an awesome experience, and we want to help people find the great content you’ve created. App Indexing has already been helping people engage with your Android app after they’ve installed it — we now have 30 billion links within apps indexed. Starting this week, people searching on Google can also discover your app if they haven’t installed it yet. If you’ve implemented App Indexing, when indexed content from your app is relevant to a search done on Google on Android devices, people may start to see app install buttons for your app in search results. Tapping these buttons will take them to the Google Play store where they can install your app, then continue straight on to the right content within it.

App installs through app indexing

With the addition of these install links, we are starting to use App Indexing as a ranking signal for all users on Android, regardless of whether they have your app installed or not. We hope that Search will now help you acquire new users, as well as re-engage your existing ones. To get started, visit g.co/AppIndexing and to learn more about the other ways you can integrate with Google Search, visit g.co/DeveloperSearch.

14 April 2015

Helping developers connect with families on Google Play

Posted by Eunice Kim, Product Manager, Google Play

There are thousands of Android developers creating experiences for families and children — apps and games that broaden the mind and inspire creativity. These developers, like PBS Kids, Tynker and Crayola, carefully tailor their apps to provide high quality, age appropriate content; from optimizing user interface design for children to building interactive features that both educate and entertain.

Google Play is committed to the success of this emerging developer community, so today we’re introducing a new program called Designed for Families, which allows developers to designate their apps and games as family-friendly. Participating apps will be eligible for upcoming family-focused experiences on Google Play that will help parents discover great, age-appropriate content and make more informed choices.

Starting now, developers can opt in their app or game through the Google Play Developer Console. From there, our team will review the submission to verify that it meets the Designed for Families program requirements. In the coming weeks, we’ll be adding new ways to promote family content to users on Google Play — we’ll have more to share on this soon.

08 April 2015

New course: Take Android app performance to the next level

Posted by Jocelyn Becker, Developer Advocate

Building the next great Android app isn't enough. You can have the most amazing social integration, best API coverage, and coolest photo filters, but none of that matters if your app is slow and frustrating to use.

That's why we've launched our new online training course at Udacity, focusing entirely on improving Android performance. This course complements the Android Performance Patterns video series, focused on giving you the resources to help make fast, smooth, and awesome experiences for users.

Created by Android Performance guru Colt McAnlis, this course reviews the main pillars of performance (rendering, compute, and battery). You'll work through tutorials on how to use the tools in Android Studio to find and fix performance problems.

By the end of the course, you'll understand how common performance problems arise from your hardware, OS, and application code. Using profiling tools to gather data, you'll learn to identify and fix performance bottlenecks so users can have that smooth 60 FPS experience that will keep them coming back for more.

Take the course: https://www.udacity.com/course/ud825. Join the conversation and follow along on social at #PERFMATTERS.