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the Solution Explorer.You can run the example app by right-clicking hello_example in |
the Solution Explorer and selecting Set as Startup Project, |
then pressing the run (▶) button. Important: After |
making changes to plugin code, you must select |
Build > Build Solution before running again, otherwise |
an outdated copy of the built plugin will be run instead |
of the latest version containing your changes.<topic_end> |
<topic_start>Step 2g: Connect the API and the platform code |
Finally, you need to connect the API written in Dart code with |
the platform-specific implementations. |
This is done using a platform channel, |
or through the interfaces defined in a platform |
interface package.<topic_end> |
<topic_start> |
Add support for platforms in an existing plugin project |
To add support for specific platforms to an |
existing plugin project, run flutter create with |
the --template=plugin flag again in the project directory. |
For example, to add web support in an existing plugin, run:If this command displays a message about updating the |
pubspec.yaml file, follow the provided instructions.<topic_end> |
<topic_start> |
Dart platform implementations |
In many cases, non-web platform implementations only use the |
platform-specific implementation language, as shown above. However, |
platform implementations can also use platform-specific Dart as well.info Note |
The examples below only apply to non-web platforms. Web |
plugin implementations are always written in Dart, and use |
pluginClass and fileName for their Dart implementations |
as shown above.<topic_end> |
<topic_start>Dart-only platform implementations |
In some cases, some platforms can be |
implemented entirely in Dart (for example, using FFI). |
For a Dart-only platform implementation on a platform other than web, |
replace the pluginClass in pubspec.yaml with a dartPluginClass. |
Here is the hello_windows example above modified for a |
Dart-only implementation:In this version you would have no C++ Windows code, and would instead |
subclass the hello plugin’s Dart platform interface class with a |
HelloPluginWindows class that includes a static |
registerWith() method. This method is called during startup, |
and can be used to register the Dart implementation:<topic_end> |
<topic_start>Hybrid platform implementations |
Platform implementations can also use both Dart and a platform-specific |
language. For example, a plugin could use a different platform channel |
for each platform so that the channels can be customized per platform.A hybrid implementation uses both of the registration systems |
described above. Here is the hello_windows example above modified for a |
hybrid implementation:The Dart HelloPluginWindows class would use the registerWith() |
shown above for Dart-only implementations, while the C++ HelloPlugin |
class would be the same as in a C++-only implementation.<topic_end> |
<topic_start> |
Testing your plugin |
We encourage you test your plugin with automated tests |
to ensure that functionality doesn’t regress |
as you make changes to your code.To learn more about testing your plugins, |
check out Testing plugins. |
If you are writing tests for your Flutter app |
and plugins are causing crashes, |
check out Flutter in plugin tests.<topic_end> |
<topic_start> |
Developing FFI plugin packages |
If you want to develop a package that calls into native APIs using |
Dart’s FFI, you need to develop an FFI plugin package.Both FFI plugin packages and (non-FFI) plugin packages support |
bundling native code, but FFI plugin packages do not support |
method channels and do include method channel registration code. |
If you want to implement a plugin that uses both method channels |
and FFI, use a (non-FFI) plugin. You can chose per platform to |
use an FFI or (non-FFI) plugin.FFI plugin packages were introduced in Flutter 3.0, if you’re |
targeting older Flutter versions, you can use a (non-FFI) plugin.<topic_end> |
<topic_start> |
Step 1: Create the package |
To create a starter FFI plugin package, |
use the --template=plugin_ffi flag with flutter create:This creates an FFI plugin project in the hello |
folder with the following specialized content:lib: The Dart code that defines the API of the plugin, |
and which calls into the native code using dart:ffi.src: The native source code, and a CMakeLists.txt |
file for building that source code into a dynamic library.platform folders (android, ios, windows, etc.): The |
build files for building and bundling the native code |
library with the platform application.<topic_end> |
<topic_start> |
Step 2: Building and bundling native code |
The pubspec.yaml specifies FFI plugins as follows:This configuration invokes the native build |
for the various target platforms and bundles |
the binaries in Flutter applications using these FFI plugins.This can be combined with dartPluginClass, |
such as when FFI is used for the |
implementation of one platform in a federated plugin:A plugin can have both FFI and method channels:The native build systems that are invoked by FFI |
(and method channels) plugins are:<topic_end> |
<topic_start> |
Step 3: Binding to native code |
To use the native code, bindings in Dart are needed.To avoid writing these by hand, |
they are generated from the header file |
(src/hello.h) by package:ffigen. |
Reference the ffigen docs for information |
on how to install this package.Regenerate the bindings by running the following:<topic_end> |
<topic_start> |
Step 4: Invoking native code |
Very short-running native functions can be directly |
invoked from any isolate. |
For an example, see sum in lib/hello.dart.Longer-running functions should be invoked on a |
helper isolate to avoid dropping frames in |
Flutter applications. |
For an example, see sumAsync in lib/hello.dart.<topic_end> |
<topic_start> |
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