Package io.flutter.plugin.common

Class MethodChannel

java.lang.Object

io.flutter.plugin.common.MethodChannel

public class MethodChannel
extends Object

A named channel for communicating with the Flutter application using asynchronous method calls.

Incoming method calls are decoded from binary on receipt, and Java results are encoded into binary before being transmitted back to Flutter. The MethodCodec used must be compatible with the one used by the Flutter application. This can be achieved by creating a MethodChannel counterpart of this channel on the Dart side. The Java type of method call arguments and results is Object, but only values supported by the specified MethodCodec 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	MethodChannel.MethodCallHandler	A handler of incoming method calls.
static interface	MethodChannel.Result	Method call result callback.

Constructor Summary

Constructors

Constructor	Description
MethodChannel(BinaryMessenger messenger, String name)	Creates a new channel associated with the specified BinaryMessenger and with the specified name and the standard MethodCodec.
MethodChannel(BinaryMessenger messenger, String name, MethodCodec codec)	Creates a new channel associated with the specified BinaryMessenger and with the specified name and MethodCodec.
MethodChannel(BinaryMessenger messenger, String name, MethodCodec codec, BinaryMessenger.TaskQueue taskQueue)	Creates a new channel associated with the specified BinaryMessenger and with the specified name and MethodCodec.

Method Summary

Modifier and Type	Method	Description
void	invokeMethod(String method, Object arguments)	Invokes a method on this channel, expecting no result.
void	invokeMethod(String method, Object arguments, MethodChannel.Result callback)	Invokes a method on this channel, optionally expecting a result.
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.
void	setMethodCallHandler(MethodChannel.MethodCallHandler handler)	Registers a method call handler on this channel.
void	setWarnsOnChannelOverflow(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

Constructor Details

MethodChannel

public MethodChannel(@NonNull
 BinaryMessenger messenger,
 @NonNull
 String name)

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

Parameters:

messenger - a BinaryMessenger.

name - a channel name String.

MethodChannel

public MethodChannel(@NonNull
 BinaryMessenger messenger,
 @NonNull
 String name,
 @NonNull
 MethodCodec codec)

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

Parameters:

messenger - a BinaryMessenger.

name - a channel name String.

codec - a MessageCodec.

MethodChannel

public MethodChannel(@NonNull
 BinaryMessenger messenger,
 @NonNull
 String name,
 @NonNull
 MethodCodec codec,
 @Nullable
 BinaryMessenger.TaskQueue taskQueue)

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

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

invokeMethod

@UiThread
public void invokeMethod(@NonNull
 String method,
 @Nullable
 Object arguments)

Invokes a method on this channel, expecting no result.

Parameters:

method - the name String of the method.

arguments - the arguments for the invocation, possibly null.

invokeMethod

@UiThread
public void invokeMethod(@NonNull
 String method,
 @Nullable
 Object arguments,
 @Nullable
 MethodChannel.Result callback)

Invokes a method on this channel, optionally expecting a result.

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

Parameters:

method - the name String of the method.

arguments - the arguments for the invocation, possibly null.

callback - a MethodChannel.Result callback for the invocation result, or null.

setMethodCallHandler

@UiThread
public void setMethodCallHandler(@Nullable
 MethodChannel.MethodCallHandler handler)

Registers a method call handler on this channel.

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

If no handler has been registered, any incoming method call on this channel will be handled silently by sending a null reply. This results in a MissingPluginException on the Dart side, unless an OptionalMethodChannel is used.

Parameters:

handler - a MethodChannel.MethodCallHandler, 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.