Package io.flutter.plugin.common

Class BasicMessageChannel<T>

java.lang.Object

io.flutter.plugin.common.BasicMessageChannel<T>

public final class BasicMessageChannel<T>
extends Object

A named channel for communicating with the Flutter application using basic, asynchronous message passing.

Messages are encoded into binary before being sent, and binary messages received are decoded into Java objects. The MessageCodec used must be compatible with the one used by the Flutter application. This can be achieved by creating a BasicMessageChannel counterpart of this channel on the Dart side. The static Java type of messages sent and received is Object, but only values supported by the specified MessageCodec can be used.

The logical identity of the channel is given by its name. Identically named channels will interfere with each other's communication.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	BasicMessageChannel.MessageHandler<T>	A handler of incoming messages.
static interface	BasicMessageChannel.Reply<T>	Message reply callback.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	CHANNEL_BUFFERS_CHANNEL

Constructor Summary

Constructors

Constructor	Description
BasicMessageChannel(BinaryMessenger messenger, String name, MessageCodec<T> codec)	Creates a new channel associated with the specified BinaryMessenger and with the specified name and MessageCodec.
BasicMessageChannel(BinaryMessenger messenger, String name, MessageCodec<T> codec, BinaryMessenger.TaskQueue taskQueue)	Creates a new channel associated with the specified BinaryMessenger and with the specified name and MessageCodec.

Method Summary

Modifier and Type	Method	Description
void	resizeChannelBuffer(int newSize)	Adjusts the number of messages that will get buffered when sending messages to channels that aren't fully set up yet.
static void	resizeChannelBuffer(BinaryMessenger messenger, String channel, int newSize)	Adjusts the number of messages that will get buffered when sending messages to channels that aren't fully set up yet.
void	send(T message)	Sends the specified message to the Flutter application on this channel.
void	send(T message, BasicMessageChannel.Reply<T> callback)	Sends the specified message to the Flutter application, optionally expecting a reply.
void	setMessageHandler(BasicMessageChannel.MessageHandler<T> handler)	Registers a message handler on this channel for receiving messages sent from the Flutter application.
void	setWarnsOnChannelOverflow(boolean warns)	Toggles whether the channel should show warning messages when discarding messages due to overflow.
static void	setWarnsOnChannelOverflow(BinaryMessenger messenger, String channel, boolean warns)	Toggles whether the channel should show warning messages when discarding messages due to overflow.

Methods inherited from class java.lang.Object

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

Field Details

CHANNEL_BUFFERS_CHANNEL

public static final String CHANNEL_BUFFERS_CHANNEL

See Also:

• Constant Field Values

Constructor Details

BasicMessageChannel

public BasicMessageChannel(@NonNull
 BinaryMessenger messenger,
 @NonNull
 String name,
 @NonNull
 MessageCodec<T> codec)

Creates a new channel associated with the specified BinaryMessenger and with the specified name and MessageCodec.

Parameters:

messenger - a BinaryMessenger.

name - a channel name String.

codec - a MessageCodec.

BasicMessageChannel

public BasicMessageChannel(@NonNull
 BinaryMessenger messenger,
 @NonNull
 String name,
 @NonNull
 MessageCodec<T> codec,
 BinaryMessenger.TaskQueue taskQueue)

Creates a new channel associated with the specified BinaryMessenger and with the specified name and MessageCodec.

Parameters:

messenger - a BinaryMessenger.

name - a channel name String.

codec - a MessageCodec.

taskQueue - a BinaryMessenger.TaskQueue that specifies what thread will execute the handler. Specifying null means execute on the platform thread. See also BinaryMessenger.makeBackgroundTaskQueue().

Method Details

send

public void send(@Nullable
 T message)

Sends the specified message to the Flutter application on this channel.

Parameters:

message - the message, possibly null.

send

@UiThread
public void send(@Nullable
 T message,
 @Nullable
 BasicMessageChannel.Reply<T> callback)

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

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

Parameters:

message - the message, possibly null.

callback - a BasicMessageChannel.Reply callback, possibly null.

setMessageHandler

@UiThread
public void setMessageHandler(@Nullable
 BasicMessageChannel.MessageHandler<T> handler)

Registers a message handler on this channel for receiving messages sent from the Flutter application.

Overrides any existing handler registration for (the name of) this channel.

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

Parameters:

handler - a BasicMessageChannel.MessageHandler, or null to deregister.

resizeChannelBuffer

public void resizeChannelBuffer(int newSize)

Adjusts the number of messages that will get buffered when sending messages to channels that aren't fully set up yet. For example, the engine isn't running yet or the channel's message handler isn't set up on the Dart side yet.

setWarnsOnChannelOverflow

public void setWarnsOnChannelOverflow(boolean warns)

Toggles whether the channel should show warning messages when discarding messages due to overflow. When 'warns' is false the channel is expected to overflow and warning messages will not be shown.

resizeChannelBuffer

public static void resizeChannelBuffer(@NonNull
 BinaryMessenger messenger,
 @NonNull
 String channel,
 int newSize)

Adjusts the number of messages that will get buffered when sending messages to channels that aren't fully set up yet. For example, the engine isn't running yet or the channel's message handler isn't set up on the Dart side yet.

setWarnsOnChannelOverflow

public static void setWarnsOnChannelOverflow(@NonNull
 BinaryMessenger messenger,
 @NonNull
 String channel,
 boolean warns)

Toggles whether the channel should show warning messages when discarding messages due to overflow. When 'warns' is false the channel is expected to overflow and warning messages will not be shown.