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flutter::EventChannel< T > Class Template Reference

`#include <event_channel.h>`

## Public Member Functions
| EventChannel (BinaryMessenger *messenger, const std::string &name, const MethodCodec< T > *codec)
| ~EventChannel ()=default
| EventChannel (EventChannel const &)=delete
EventChannel & | operator= (EventChannel const &)=delete
void | SetStreamHandler (std::unique_ptr< StreamHandler< T >> handler)

## Detailed Description

### template<typename T = EncodableValue>
class flutter::EventChannel< T >

Definition at line 33 of file event_channel.h.

## Constructor & Destructor Documentation

## ◆ EventChannel() [1/2]

template<typename T = EncodableValue>

flutter::EventChannel< T >::EventChannel | ( | BinaryMessenger * | messenger,
|  | const std::string & | name,
|  | const MethodCodec< T > * | codec
| ) |  |
| inline

Definition at line 37 of file event_channel.h.

40 : messenger_(messenger), name_(name), codec_(codec) {}

## ◆ ~EventChannel()

template<typename T = EncodableValue>

flutter::EventChannel< T >::~EventChannel | ( |  | ) |
| default

## ◆ EventChannel() [2/2]

template<typename T = EncodableValue>

flutter::EventChannel< T >::EventChannel | ( | EventChannel< T > const & |  | ) |
| delete

## Member Function Documentation

## ◆ operator=()

template<typename T = EncodableValue>

EventChannel& flutter::EventChannel< T >::operator= | ( | EventChannel< T > const & |  | ) |
| delete

## ◆ SetStreamHandler()

template<typename T = EncodableValue>

void flutter::EventChannel< T >::SetStreamHandler | ( | std::unique_ptr< StreamHandler< T >> | handler | ) |
| inline

Definition at line 54 of file event_channel.h.

54 {
55 if (!handler) {
56 messenger_->SetMessageHandler(name_, nullptr);
57 return;
58 }
59
60 // std::function requires a copyable lambda, so convert to a shared pointer.
61 // This is safe since only one copy of the shared_pointer will ever be
62 // accessed.
63 std::shared_ptr<StreamHandler<T>> shared_handler(handler.release());
64 const MethodCodec<T>* codec = codec_;
65 const std::string channel_name = name_;
66 const BinaryMessenger* messenger = messenger_;
67 BinaryMessageHandler binary_handler =
68 [shared_handler, codec, channel_name, messenger,
69 // Mutable state to track the handler's listening status.
70 is_listening = bool(false)](const uint8_t* message,
71 const size_t message_size,
72 const BinaryReply& reply) mutable {
73 constexpr char kOnListenMethod[] = "listen";
74 constexpr char kOnCancelMethod[] = "cancel";
75
76 std::unique_ptr<MethodCall<T>> method_call =
77 codec->DecodeMethodCall(message, message_size);
78 if (!method_call) {
79 std::cerr
80 << "Unable to construct method call from message on channel: "
81 << channel_name << std::endl;
82 reply(nullptr, 0);
83 return;
84 }
85
86 const std::string& method = method_call->method_name();
87 if (method.compare(kOnListenMethod) == 0) {
88 if (is_listening) {
89 std::unique_ptr<StreamHandlerError<T>> error =
90 shared_handler->OnCancel(nullptr);
91 if (error) {
92 std::cerr << "Failed to cancel existing stream: "
93 << (error->error_code) << ", "
94 << (error->error_message) << ", "
95 << (error->error_details);
96 }
97 }
98 is_listening = true;
99
100 std::unique_ptr<std::vector<uint8_t>> result;
101 auto sink = std::make_unique<EventSinkImplementation>(
102 messenger, channel_name, codec);
103 std::unique_ptr<StreamHandlerError<T>> error =
104 shared_handler->OnListen(method_call->arguments(),
105 std::move(sink));
106 if (error) {
107 result = codec->EncodeErrorEnvelope(error->error_code,
108 error->error_message,
109 error->error_details.get());
110 } else {
111 result = codec->EncodeSuccessEnvelope();
112 }
113 reply(result->data(), result->size());
114 } else if (method.compare(kOnCancelMethod) == 0) {
115 std::unique_ptr<std::vector<uint8_t>> result;
116 if (is_listening) {
117 std::unique_ptr<StreamHandlerError<T>> error =
118 shared_handler->OnCancel(method_call->arguments());
119 if (error) {
120 result = codec->EncodeErrorEnvelope(error->error_code,
121 error->error_message,
122 error->error_details.get());
123 } else {
124 result = codec->EncodeSuccessEnvelope();
125 }
126 is_listening = false;
127 } else {
128 result = codec->EncodeErrorEnvelope(
129 "error", "No active stream to cancel", nullptr);
130 }
131 reply(result->data(), result->size());
132 } else {
133 reply(nullptr, 0);
134 }
135 };
136 messenger_->SetMessageHandler(name_, std::move(binary_handler));
137 }

References flutter::BinaryMessenger::SetMessageHandler().

Referenced by flutter::TEST().

The documentation for this class was generated from the following file:

- shell/platform/common/client_wrapper/include/flutter/event_channel.h

flutter::BinaryMessenger::SetMessageHandler
virtual void SetMessageHandler(const std::string &channel, BinaryMessageHandler handler)=0
flutter::BinaryReply
std::function< void(const uint8_t *reply, size_t reply_size)> BinaryReply
Definition: binary_messenger.h:17
flutter::BinaryMessageHandler
std::function< void(const uint8_t *message, size_t message_size, BinaryReply reply)> BinaryMessageHandler
Definition: binary_messenger.h:24