FlutterEngine Class Reference


                    
                    
                    -init

Default initializer for a FlutterEngine.

Threads created by this FlutterEngine will appear as “FlutterEngine #” in Instruments. The prefix can be customized using initWithName.

The engine will execute the project located in the bundle with the identifier “io.flutter.flutter.app” (the default for Flutter projects).

A newly initialized engine will not run until either -runWithEntrypoint: or -runWithEntrypoint:libraryURI: is called.

FlutterEngine created with this method will have allowHeadlessExecution set to YES. This means that the engine will continue to run regardless of whether a FlutterViewController is attached to it or not, until -destroyContext: is called or the process finishes.

Declaration

Objective-C

- (nonnull instancetype)init;


                    
                    
                    -initWithName:

Initialize this FlutterEngine.

The engine will execute the project located in the bundle with the identifier “io.flutter.flutter.app” (the default for Flutter projects).

A newly initialized engine will not run until either -runWithEntrypoint: or -runWithEntrypoint:libraryURI: is called.

FlutterEngine created with this method will have allowHeadlessExecution set to YES. This means that the engine will continue to run regardless of whether a FlutterViewController is attached to it or not, until -destroyContext: is called or the process finishes.

Declaration

Objective-C

- (nonnull instancetype)initWithName:(nonnull NSString *)labelPrefix;

Parameters


                                labelPrefix

The label prefix used to identify threads for this instance. Should be unique across FlutterEngine instances, and is used in instrumentation to label the threads used by this FlutterEngine.


                    
                    
                    -initWithName:project:

Initialize this FlutterEngine with a FlutterDartProject.

If the FlutterDartProject is not specified, the FlutterEngine will attempt to locate the project in a default location (the flutter_assets folder in the iOS application bundle).

A newly initialized engine will not run the FlutterDartProject until either -runWithEntrypoint: or -runWithEntrypoint:libraryURI: is called.

FlutterEngine created with this method will have allowHeadlessExecution set to YES. This means that the engine will continue to run regardless of whether a FlutterViewController is attached to it or not, until -destroyContext: is called or the process finishes.

Declaration

Objective-C

- (nonnull instancetype)initWithName:(nonnull NSString *)labelPrefix
                             project:(nullable FlutterDartProject *)project;

Parameters

`labelPrefix`	The label prefix used to identify threads for this instance. Should be unique across FlutterEngine instances, and is used in instrumentation to label the threads used by this FlutterEngine.
`project`	The `FlutterDartProject` to run.


                    
                    
                    -initWithName:project:allowHeadlessExecution:

Initialize this FlutterEngine with a FlutterDartProject.

If the FlutterDartProject is not specified, the FlutterEngine will attempt to locate the project in a default location (the flutter_assets folder in the iOS application bundle).

A newly initialized engine will not run the FlutterDartProject until either -runWithEntrypoint: or -runWithEntrypoint:libraryURI: is called.

Declaration

Objective-C

- (nonnull instancetype)initWithName:(nonnull NSString *)labelPrefix
                             project:(nullable FlutterDartProject *)project
              allowHeadlessExecution:(BOOL)allowHeadlessExecution;

Parameters

`labelPrefix`	The label prefix used to identify threads for this instance. Should be unique across FlutterEngine instances, and is used in instrumentation to label the threads used by this FlutterEngine.
`project`	The `FlutterDartProject` to run.
`allowHeadlessExecution`	Whether or not to allow this instance to continue running after passing a nil `FlutterViewController` to `-setViewController:`.


                    
                    
                    -initWithName:project:allowHeadlessExecution:restorationEnabled:

Initialize this FlutterEngine with a FlutterDartProject.

If the FlutterDartProject is not specified, the FlutterEngine will attempt to locate the project in a default location (the flutter_assets folder in the iOS application bundle).

A newly initialized engine will not run the FlutterDartProject until either -runWithEntrypoint: or -runWithEntrypoint:libraryURI: is called.

Declaration

Objective-C

- (nonnull instancetype)initWithName:(nonnull NSString *)labelPrefix
                             project:(nullable FlutterDartProject *)project
              allowHeadlessExecution:(BOOL)allowHeadlessExecution
                  restorationEnabled:(BOOL)restorationEnabled;

Parameters

`labelPrefix`	The label prefix used to identify threads for this instance. Should be unique across FlutterEngine instances, and is used in instrumentation to label the threads used by this FlutterEngine.
`project`	The `FlutterDartProject` to run.
`allowHeadlessExecution`	Whether or not to allow this instance to continue running after passing a nil `FlutterViewController` to `-setViewController:`.
`restorationEnabled`	Whether state restoration is enabled. When true, the framework will wait for the attached view controller to provide restoration data.


                    
                    
                    -run

Runs a Dart program on an Isolate from the main Dart library (i.e. the library that contains main()), using main() as the entrypoint (the default for Flutter projects), and using “/” (the default route) as the initial route.

The first call to this method will create a new Isolate. Subsequent calls will return immediately and have no effect.

Declaration

Objective-C

- (BOOL)run;

Return Value

YES if the call succeeds in creating and running a Flutter Engine instance; NO otherwise.


                    
                    
                    -runWithEntrypoint:

Runs a Dart program on an Isolate from the main Dart library (i.e. the library that contains main()), using “/” (the default route) as the initial route.

The first call to this method will create a new Isolate. Subsequent calls will return immediately and have no effect.

Declaration

Objective-C

- (BOOL)runWithEntrypoint:(nullable NSString *)entrypoint;

Parameters


                                entrypoint

The name of a top-level function from the same Dart library that contains the app’s main() function. If this is FlutterDefaultDartEntrypoint (or nil) it will default to main(). If it is not the app’s main() function, that function must be decorated with @pragma(vm:entry-point) to ensure the method is not tree-shaken by the Dart compiler.

Return Value

YES if the call succeeds in creating and running a Flutter Engine instance; NO otherwise.


                    
                    
                    -runWithEntrypoint:initialRoute:

Runs a Dart program on an Isolate from the main Dart library (i.e. the library that contains main()).

The first call to this method will create a new Isolate. Subsequent calls will return immediately and have no effect.

Declaration

Objective-C

- (BOOL)runWithEntrypoint:(nullable NSString *)entrypoint
             initialRoute:(nullable NSString *)initialRoute;

Parameters

`entrypoint`	The name of a top-level function from the same Dart library that contains the app’s main() function. If this is FlutterDefaultDartEntrypoint (or nil), it will default to `main()`. If it is not the app’s main() function, that function must be decorated with `@pragma(vm:entry-point)` to ensure the method is not tree-shaken by the Dart compiler.
`initialRoute`	The name of the initial Flutter `Navigator` `Route` to load. If this is FlutterDefaultInitialRoute (or nil), it will default to the “/” route.

Return Value

YES if the call succeeds in creating and running a Flutter Engine instance; NO otherwise.


                    
                    
                    -runWithEntrypoint:libraryURI:

Runs a Dart program on an Isolate using the specified entrypoint and Dart library, which may not be the same as the library containing the Dart program’s main() function.

The first call to this method will create a new Isolate. Subsequent calls will return immediately and have no effect.

Declaration

Objective-C

- (BOOL)runWithEntrypoint:(nullable NSString *)entrypoint
               libraryURI:(nullable NSString *)uri;

Parameters

`entrypoint`	The name of a top-level function from a Dart library. If this is FlutterDefaultDartEntrypoint (or nil); this will default to `main()`. If it is not the app’s main() function, that function must be decorated with `@pragma(vm:entry-point)` to ensure the method is not tree-shaken by the Dart compiler.
`uri`	The URI of the Dart library which contains the entrypoint method (example “package:foo_package/main.dart”). If nil, this will default to the same library as the `main()` function in the Dart program.

Return Value

YES if the call succeeds in creating and running a Flutter Engine instance; NO otherwise.


                    
                    
                    -runWithEntrypoint:libraryURI:initialRoute:

Runs a Dart program on an Isolate using the specified entrypoint and Dart library, which may not be the same as the library containing the Dart program’s main() function.

The first call to this method will create a new Isolate. Subsequent calls will return immediately and have no effect.

Declaration

Objective-C

- (BOOL)runWithEntrypoint:(nullable NSString *)entrypoint
               libraryURI:(nullable NSString *)libraryURI
             initialRoute:(nullable NSString *)initialRoute;

Parameters

`entrypoint`	The name of a top-level function from a Dart library. If this is FlutterDefaultDartEntrypoint (or nil); this will default to `main()`. If it is not the app’s main() function, that function must be decorated with `@pragma(vm:entry-point)` to ensure the method is not tree-shaken by the Dart compiler.
`libraryURI`	The URI of the Dart library which contains the entrypoint method (example “package:foo_package/main.dart”). If nil, this will default to the same library as the `main()` function in the Dart program.
`initialRoute`	The name of the initial Flutter `Navigator` `Route` to load. If this is FlutterDefaultInitialRoute (or nil), it will default to the “/” route.

Return Value

YES if the call succeeds in creating and running a Flutter Engine instance; NO otherwise.


                    
                    
                    -runWithEntrypoint:libraryURI:initialRoute:entrypointArgs:

Runs a Dart program on an Isolate using the specified entrypoint and Dart library, which may not be the same as the library containing the Dart program’s main() function.

The first call to this method will create a new Isolate. Subsequent calls will return immediately and have no effect.

Declaration

Objective-C

- (BOOL)runWithEntrypoint:(nullable NSString *)entrypoint
               libraryURI:(nullable NSString *)libraryURI
             initialRoute:(nullable NSString *)initialRoute
           entrypointArgs:(nullable NSArray<NSString *> *)entrypointArgs;

Parameters

`entrypoint`	The name of a top-level function from a Dart library. If this is FlutterDefaultDartEntrypoint (or nil); this will default to `main()`. If it is not the app’s main() function, that function must be decorated with `@pragma(vm:entry-point)` to ensure the method is not tree-shaken by the Dart compiler.
`libraryURI`	The URI of the Dart library which contains the entrypoint method (example “package:foo_package/main.dart”). If nil, this will default to the same library as the `main()` function in the Dart program.
`initialRoute`	The name of the initial Flutter `Navigator` `Route` to load. If this is FlutterDefaultInitialRoute (or nil), it will default to the “/” route.
`entrypointArgs`	Arguments passed as a list of string to Dart’s entrypoint function.

Return Value

YES if the call succeeds in creating and running a Flutter Engine instance; NO otherwise.


                    
                    
                    -destroyContext

Destroy running context for an engine.

This method can be used to force the FlutterEngine object to release all resources. After sending this message, the object will be in an unusable state until it is deallocated. Accessing properties or sending messages to it will result in undefined behavior or runtime errors.

Declaration

Objective-C

- (void)destroyContext;


                    
                    
                    -ensureSemanticsEnabled

Ensures that Flutter will generate a semantics tree.

This is enabled by default if certain accessibility services are turned on by the user, or when using a Simulator. This method allows a user to turn semantics on when they would not ordinarily be generated and the performance overhead is not a concern, e.g. for UI testing. Note that semantics should never be programmatically turned off, as it would potentially disable accessibility services an end user has requested.

This method must only be called after launching the engine via -runWithEntrypoint: or -runWithEntryPoint:libraryURI.

Although this method returns synchronously, it does not guarantee that a semantics tree is actually available when the method returns. It synchronously ensures that the next frame the Flutter framework creates will have a semantics tree.

You can subscribe to semantics updates via NSNotificationCenter by adding an observer for the name FlutterSemanticsUpdateNotification. The object parameter will be the FlutterViewController associated with the semantics update. This will asynchronously fire after a semantics tree has actually built (which may be some time after the frame has been rendered).

Declaration

Objective-C

- (void)ensureSemanticsEnabled;


                    
                    
                    viewController

Sets the FlutterViewController for this instance. The FlutterEngine must be running (e.g. a successful call to -runWithEntrypoint: or -runWithEntrypoint:libraryURI) before calling this method. Callers may pass nil to remove the viewController and have the engine run headless in the current process.

A FlutterEngine can only have one FlutterViewController at a time. If there is already a FlutterViewController associated with this instance, this method will replace the engine’s current viewController with the newly specified one.

Setting the viewController will signal the engine to start animations and drawing, and unsetting it will signal the engine to stop animations and drawing. However, neither will impact the state of the Dart program’s execution.

Declaration

Objective-C

@property (nonatomic, weak) FlutterViewController *_Nullable viewController;


                    
                    
                    localizationChannel

The FlutterMethodChannel used for localization related platform messages, such as setting the locale.

Can be nil after destroyContext is called.

Declaration

Objective-C

@property (nonatomic, readonly, nullable) FlutterMethodChannel *localizationChannel;


                    
                    
                    navigationChannel

The FlutterMethodChannel used for navigation related platform messages.

Can be nil after destroyContext is called.

See

Navigation Channel

See

Navigator Widget

Declaration

Objective-C

@property (nonatomic, readonly) FlutterMethodChannel *_Nonnull navigationChannel;


                    
                    
                    restorationChannel

The FlutterMethodChannel used for restoration related platform messages.

Can be nil after destroyContext is called.

See

Restoration Channel

Declaration

Objective-C

@property (nonatomic, readonly) FlutterMethodChannel *_Nonnull restorationChannel;


                    
                    
                    platformChannel

The FlutterMethodChannel used for core platform messages, such as information about the screen orientation.

Can be nil after destroyContext is called.

Declaration

Objective-C

@property (nonatomic, readonly) FlutterMethodChannel *_Nonnull platformChannel;


                    
                    
                    textInputChannel

The FlutterMethodChannel used to communicate text input events to the Dart Isolate.

Can be nil after destroyContext is called.

See

Text Input Channel

Declaration

Objective-C

@property (nonatomic, readonly) FlutterMethodChannel *_Nonnull textInputChannel;


                    
                    
                    lifecycleChannel

The FlutterBasicMessageChannel used to communicate app lifecycle events to the Dart Isolate.

Can be nil after destroyContext is called.

See

Lifecycle Channel

Declaration

Objective-C

@property (nonatomic, readonly) FlutterBasicMessageChannel *_Nonnull lifecycleChannel;


                    
                    
                    systemChannel

The FlutterBasicMessageChannel used for communicating system events, such as memory pressure events.

Can be nil after destroyContext is called.

See

System Channel

Declaration

Objective-C

@property (nonatomic, readonly) FlutterBasicMessageChannel *_Nonnull systemChannel;


                    
                    
                    settingsChannel

The FlutterBasicMessageChannel used for communicating user settings such as clock format and text scale.

Can be nil after destroyContext is called.

Declaration

Objective-C

@property (nonatomic, readonly) FlutterBasicMessageChannel *_Nonnull settingsChannel;


                    
                    
                    keyEventChannel

The FlutterBasicMessageChannel used for communicating key events from physical keyboards

Can be nil after destroyContext is called.

Declaration

Objective-C

@property (nonatomic, readonly) FlutterBasicMessageChannel *_Nonnull keyEventChannel;


                    
                    
                    observatoryUrl

The NSURL of the observatory for the service isolate.

This is only set in debug and profile runtime modes, and only after the observatory service is ready. In release mode or before the observatory has started, it returns nil.

Declaration

Objective-C

@property (nonatomic, readonly, nullable) NSURL *observatoryUrl;


                    
                    
                    binaryMessenger

The FlutterBinaryMessenger associated with this FlutterEngine (used for communicating with channels).

Declaration

Objective-C

@property (nonatomic, readonly) NSObject<FlutterBinaryMessenger> *_Nonnull binaryMessenger;


                    
                    
                    isolateId

The UI Isolate ID of the engine.

This property will be nil if the engine is not running.

Declaration

Objective-C

@property (nonatomic, copy, readonly, nullable) NSString *isolateId;


                    
                    
                    isGpuDisabled

Whether or not GPU calls are allowed.

Typically this is set when the app is backgrounded and foregrounded.

Declaration

Objective-C

@property (nonatomic) BOOL isGpuDisabled;