This is a plugin project that allows for getting the native device orientation.
Flutter provides a couple of way to get the 'orientation', but they all amount to basically checking whether the screen is taller or wider. This could fail for a strangely shaped device, but that isn't the primary issue.
The primary issue is that this method doesn't differentiate between landscape left and landscape right (what you get from rotation an upright phone left or right).
This isn't an issue for most applications, but when I was writing a plugin which displays a camera image, it became a problem as I need to know which way the screen is rotated.
When using either the build-in widget or the plugin directly, there is an option you can pass in
which is called useSensor. When it is true, the device's sensors are used directly rather
than simply using the window/page orientation. By default it is false, which means the plugin
doesn't to much more than simply tell you whether the window is oriented landscapeLeft or landscapeRight.
This has been tested less thoroughly than other parts of the plugin so your mileage may vary and if you run into any issues please open an issue!
There are three ways of using the plugin. The simplest entails encapsulating your code in a
NativeDeviceOrientationReader widget, and then using
NativeDeviceOrientationReader.orientation(context); in a widget encapsulated within the context.
This allows you to control when the device starts listening for orientation changes (which could
use a bit of energy) by deciding where the NativeDeviceOrientationReader is instantiated,
while being able to access the orientation in a simple way.
Note that there could be a very slight time between when the NativeDeviceOrientationReader widget
is instantiated and when the orientation is read where the widget could be built with an incorrect
orientation; it uses flutter's method of size until the first message it receives
back from the native code (which should be fairly immediate anyways). It
assumes that landscape is right and portrait is upright during this time.
See the source code for more details.
The second approach is more involved, but involves slightly less boilerplate, and may be a bit more
obvious to use. It wraps the NativeDeviceOrientationReader widget, then automatically checks the
orientation for you. Instead of passing in a single builder function, you pass one for each
orientation you wish to define: landscapeLeft, landscapeRight, portraitUp, and portaitDown
are the most obvious, followed by simply landscape and portrait for situations where you don't
care to define different layouts for either of those, and finally the (required) fallback,
used in cases where either you don't have a more specific builder defined, or something goes horribly
horribly wrong.
You sacrifice a bit of control over when to actually retrieve the orientation info in exchange for
the plugin handling orientation updates automatically. Since this approach does a bit more hand
holding, processing things like NativeDeviceOrientation.unknown for you, it's the approach in the
example app.
See example and source code for more details.
It is also possible to bypass the helper widget to access the native calls directly.
This is done by using the NativeDeviceOrientationCommunicator class. It is a singleton
but can be instantiated like a normal class, and handles the communication between the
ios/android code and the flutter code.
This class has two interesting methods:
-
Future<NativeDeviceOrientation> orientation(useSensor: false): This can be called to get the orientation asynchronously. -
Stream<NativeDeviceOrientation> onOrientationChanged(useSensor: false): This can be called to get a stream which receives new events whenever the orientation changes. It should also get an initial value pretty much immediately.