Sky apps are written in Dart. To get started, we need to set up Dart SDK:
brew tap dart-lang/dart && brew install dart
$DART_SDK
is set to the path of your Dart SDK and that the dart
and pub
executables are on your $PATH
.Once you have installed Dart SDK, create a new directory and add a pubspec.yaml:
name: your_app_name dependencies: sky: any sky_tools: any
Next, create a lib
directory (which is where your Dart code will go) and use the pub
tool to fetch the Sky package and its dependencies:
mkdir lib
pub upgrade
Sky assumes the entry point for your application is a main
function in lib/main.dart
:
import 'package:sky/widgets.dart'; class HelloWorldApp extends App { Widget build() { return new Center(child: new Text('Hello, world!')); } } void main() { runApp(new HelloWorldApp()); }
Execution starts in main
, which in this example runs a new instance of the HelloWorldApp
. The HelloWorldApp
builds a Text
widget containing the traditional Hello, world!
string and centers it on the screen using a Center
widget. To learn more about the widget system, please see the widgets tutorial.
Currently Sky requires an Android device running the Lollipop (or newer) version of the Android operating system.
Install the adb
tool from the Android SDK:
Mac: brew install android-platform-tools
Linux: sudo apt-get install android-tools-adb
Enable developer mode on your device by visiting Settings > About phone
and tapping the Build number
field five times.
Enable Android debugging
in Settings > Developer options
.
Using a USB cable, plug your phone into your computer. If prompted on your device, authorize your computer to access your device.
The sky
pub package includes a sky_tool
script to assist in running Sky applications inside the SkyShell.apk
harness. The sky_tool
script expects to be run from the root directory of your application's package (i.e., the same directory that contains the pubspec.yaml
file). To run your app, follow these instructions:
./packages/sky/sky_tool start --install --checked && adb logcat -s sky chromium
./packages/sky/sky_tool start --checked && adb logcat -s sky chromium
The sky_tool start
command starts the dev server and uploads your app to the device. The --install
flag installs SkyShell.apk
if it is not already installed on the device. The --checked
flag triggers checked mode, in which types are checked, asserts are run, and various debugging features are enabled. The adb logcat
command logs errors and Dart print()
output from the app. The -s sky chromium
argument limits the output to just output from Sky Dart code and the Sky Engine C++ code (which for historical reasons currently uses the tag chromium
.)
To avoid confusion from old log messages, you may wish to run adb logcat -c
before calling sky_tool start
, to clear the log between runs.
As an alternative to running ./packages/sky/sky_tool start
every time you make a change, you might prefer to have the SkyShell reload your app automatically for you as you edit. To do this, run the following command:
./packages/sky/sky_tool listen
This is a long-running command -- just press ctrl-c
when you want to stop listening for changes to the file system and automatically reloading your app.
Currently sky_tool listen
only works for Android, but iOS device and iOS simulator support are coming soon.
Sky uses Observatory for debugging and profiling. While running your Sky app using sky_tool
, you can access Observatory by navigating your web browser to http://localhost:8181/.
Although it is possible to build a standalone APK containing your application, doing so right now is difficult. If you're feeling brave, you can see how we build the Stocks.apk
in examples/stocks. Eventually we plan to make this much easier and support platforms other than Android, but that work still in progress.