io.flutter.embedding.engine.dart

Class DartExecutor

java.lang.Object

io.flutter.embedding.engine.dart.DartExecutor

All Implemented Interfaces:

BinaryMessenger

public class DartExecutor
extends Object
implements BinaryMessenger

Configures, bootstraps, and starts executing Dart code.

To specify a top-level Dart function to execute, use a DartExecutor.DartEntrypoint to tell DartExecutor where to find the Dart code to execute, and which Dart function to use as the entrypoint. To execute the entrypoint, pass the DartExecutor.DartEntrypoint to executeDartEntrypoint(DartEntrypoint).

To specify a Dart callback to execute, use a DartExecutor.DartCallback. A given Dart callback must be registered with the Dart VM to be invoked by a DartExecutor. To execute the callback, pass the DartExecutor.DartCallback to executeDartCallback(DartCallback).

Once started, a DartExecutor cannot be stopped. The associated Dart code will execute until it completes, or until the FlutterEngine that owns this DartExecutor is destroyed.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	DartExecutor.DartCallback Configuration options that specify which Dart callback function is executed and where to find that callback and other assets required for Dart execution.
static class	DartExecutor.DartEntrypoint Configuration options that specify which Dart entrypoint function is executed and where to find that entrypoint and other assets required for Dart execution.

Nested classes/interfaces inherited from interface io.flutter.plugin.common.BinaryMessenger

BinaryMessenger.BinaryMessageHandler, BinaryMessenger.BinaryReply

Constructor Summary

Constructors

Constructor and Description
DartExecutor(FlutterJNI flutterJNI, AssetManager assetManager)

Method Summary

Modifier and Type	Method and Description
void	executeDartCallback(DartExecutor.DartCallback dartCallback) Starts executing Dart code based on the given dartCallback.
void	executeDartEntrypoint(DartExecutor.DartEntrypoint dartEntrypoint) Starts executing Dart code based on the given dartEntrypoint.
BinaryMessenger	getBinaryMessenger() Returns a BinaryMessenger that can be used to send messages to, and receive messages from, Dart code that this DartExecutor is executing.
String	getIsolateServiceId() Returns an identifier for this executor's primary isolate.
int	getPendingChannelResponseCount() Returns the number of pending channel callback replies.
boolean	isExecutingDart() Is this DartExecutor currently executing Dart code?
void	notifyLowMemoryWarning() Notify the Dart VM of a low memory event, or that the application is in a state such that now is an appropriate time to free resources, such as going to the background.
void	onAttachedToJNI() Invoked when the FlutterEngine that owns this DartExecutor attaches to JNI.
void	onDetachedFromJNI() Invoked when the FlutterEngine that owns this DartExecutor detaches from JNI.
void	send(String channel, ByteBuffer message) Deprecated. Use getBinaryMessenger() instead.
void	send(String channel, ByteBuffer message, BinaryMessenger.BinaryReply callback) Deprecated. Use getBinaryMessenger() instead.
void	setIsolateServiceIdListener(io.flutter.embedding.engine.dart.DartExecutor.IsolateServiceIdListener listener) Set a listener that will be notified when an isolate identifier is available for this executor's primary isolate.
void	setMessageHandler(String channel, BinaryMessenger.BinaryMessageHandler handler) Deprecated. Use getBinaryMessenger() instead.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DartExecutor

public DartExecutor(@NonNull
                    FlutterJNI flutterJNI,
                    @NonNull
                    AssetManager assetManager)

Method Detail

onAttachedToJNI

public void onAttachedToJNI()

Invoked when the FlutterEngine that owns this DartExecutor attaches to JNI.

When attached to JNI, this DartExecutor begins handling 2-way communication to/from the Dart execution context. This communication is facilitate via 2 APIs:

• BinaryMessenger, which sends messages to Dart
• PlatformMessageHandler, which receives messages from Dart

onDetachedFromJNI

public void onDetachedFromJNI()

Invoked when the FlutterEngine that owns this DartExecutor detaches from JNI.

When detached from JNI, this DartExecutor stops handling 2-way communication to/from the Dart execution context.

isExecutingDart

public boolean isExecutingDart()

Is this DartExecutor currently executing Dart code?

Returns:

true if Dart code is being executed, false otherwise

executeDartEntrypoint

public void executeDartEntrypoint(@NonNull
                                  DartExecutor.DartEntrypoint dartEntrypoint)

Starts executing Dart code based on the given dartEntrypoint.

See DartExecutor.DartEntrypoint for configuration options.

Parameters:

dartEntrypoint - specifies which Dart function to run, and where to find it

executeDartCallback

public void executeDartCallback(@NonNull
                                DartExecutor.DartCallback dartCallback)

Starts executing Dart code based on the given dartCallback.

See DartExecutor.DartCallback for configuration options.

Parameters:

dartCallback - specifies which Dart callback to run, and where to find it

getBinaryMessenger

@NonNull
public BinaryMessenger getBinaryMessenger()

Returns a BinaryMessenger that can be used to send messages to, and receive messages from, Dart code that this DartExecutor is executing.

send

@Deprecated
 @UiThread
public void send(@NonNull
                                        String channel,
                                        @Nullable
                                        ByteBuffer message)

Deprecated. Use getBinaryMessenger() instead.

Description copied from interface: BinaryMessenger

Sends a binary message to the Flutter application.

Specified by:

send in interface BinaryMessenger

Parameters:

channel - the name String of the logical channel used for the message.

message - the message payload, a direct-allocated ByteBuffer with the message bytes between position zero and current position, or null.

send

@Deprecated
 @UiThread
public void send(@NonNull
                                        String channel,
                                        @Nullable
                                        ByteBuffer message,
                                        @Nullable
                                        BinaryMessenger.BinaryReply callback)

Deprecated. Use getBinaryMessenger() instead.

Description copied from interface: BinaryMessenger

Sends a binary message to the Flutter application, optionally expecting a reply.

Any uncaught exception thrown by the reply callback will be caught and logged.

Specified by:

send in interface BinaryMessenger

Parameters:

channel - the name String of the logical channel used for the message.

message - the message payload, a direct-allocated ByteBuffer with the message bytes between position zero and current position, or null.

callback - a BinaryMessenger.BinaryReply callback invoked when the Flutter application responds to the message, possibly null.

setMessageHandler

@Deprecated
 @UiThread
public void setMessageHandler(@NonNull
                                                     String channel,
                                                     @Nullable
                                                     BinaryMessenger.BinaryMessageHandler handler)

Deprecated. Use getBinaryMessenger() instead.

Description copied from interface: BinaryMessenger

Registers a handler to be invoked when the Flutter application sends a message to its host platform.

Registration overwrites any previous registration for the same channel name. Use a null handler to deregister.

If no handler has been registered for a particular channel, any incoming message on that channel will be handled silently by sending a null reply.

Specified by:

setMessageHandler in interface BinaryMessenger

Parameters:

channel - the name String of the channel.

handler - a BinaryMessenger.BinaryMessageHandler to be invoked on incoming messages, or null.

getPendingChannelResponseCount

@UiThread
public int getPendingChannelResponseCount()

Returns the number of pending channel callback replies.

When sending messages to the Flutter application using BinaryMessenger.send(String, ByteBuffer, io.flutter.plugin.common.BinaryMessenger.BinaryReply), developers can optionally specify a reply callback if they expect a reply from the Flutter application.

This method tracks all the pending callbacks that are waiting for response, and is supposed to be called from the main thread (as other methods). Calling from a different thread could possibly capture an indeterministic internal state, so don't do it.

Currently, it's mainly useful for a testing framework like Espresso to determine whether all the async channel callbacks are handled and the app is idle.

getIsolateServiceId

@Nullable
public String getIsolateServiceId()

Returns an identifier for this executor's primary isolate. This identifier can be used in queries to the Dart service protocol.

setIsolateServiceIdListener

public void setIsolateServiceIdListener(@Nullable
                                        io.flutter.embedding.engine.dart.DartExecutor.IsolateServiceIdListener listener)

Set a listener that will be notified when an isolate identifier is available for this executor's primary isolate.

notifyLowMemoryWarning

public void notifyLowMemoryWarning()

Notify the Dart VM of a low memory event, or that the application is in a state such that now is an appropriate time to free resources, such as going to the background.

This does not notify a Flutter application about memory pressure. For that, use the SystemChannel#sendMemoryPressureWarning.