活动#

介绍#

事件允许你异步启动函数。当一个事件被广播时，该事件的回调函数会在它自己的任务（线程）中启动，因此你的主代码可以同时继续运行。

Important: An event object stores one callback. If you register another function with the same event object, it replaces the previous callback.

如果你希望一个触发器触发多个事件，那么：

  • 从单个回调函数调用多个辅助函数，或者

  • 使用多个事件对象并分别广播它们。

  • 使用单独的线程独立运行任务。

要创建和使用事件，请按以下步骤操作：

  1. Create the event with event.

  2. Set the event’s callback using the event name (ex: myEvent(myCallback);).

  3. Broadcast an event:

    • broadcast — Triggers all registered functions in an event object to run in parallel.

    • broadcastAndWait — Triggers all registered functions in an event object and waits for them to finish before continuing.

Class Constructors#

1 — Creates an event object without a callback function.

event();

2 — Creates an event object with a callback function.

event( void (* callback)(void) );

3 — Creates an event object from another event with a callback function.

event( 
  event v, 
  void v(* callback)(void) );

4 — Creates an event object with a callback function that accepts an argument.

event( void (* callback)(void *), void *arg );

5 — Creates an event object from another event with a callback function that accepts an argument.

event( event v, void (* callback)(void *), void *arg );

Class Destructor#

Destroys the event object and releases associated resources.

~event();

Parameters#

范围

Type

描述

callback

void (*)(void)

预先定义好在事件广播时执行的函数。

v

event

An existing event object to copy from.

callback

void (*)(void *)

A function that accepts a void pointer argument and executes when the event is broadcasted.

arg

void *

A pointer to data that will be passed to the callback function.

Notes#

  • An event object stores one callback. If you register another function with the same event object, it replaces the previous callback.

  • 如果你希望一个触发器触发多个事件，那么：

    • 从单个回调函数调用多个辅助函数，或者

    • 使用多个事件对象并分别广播它们。

    • Use separate threads to run tasks independently.

Example#

// Create a callback function
void onMyEvent() {
  Brain.Screen.print("Callback function executed!");
}

// Create an event called myEvent
// Set onMyEvent as the callback function
event myEvent(onMyEvent);

Member Functions#

The event class includes the following member functions:

  • operator — Sets a callback function for the event.

  • broadcast — Triggers the event’s callback function to run in parallel.

  • broadcastAndWait — Triggers the event’s callback function and waits for completion.

Before calling any event member functions, an event instance must be created, as shown below:

/* This constructor is required when using VS Code.
Event configuration can be created with or without
a callback function as shown in the examples above. */

// Create an event without a callback
event myEvent;

// Or create an event with a callback
event myEvent(onMyEvent);

operator#

Sets a callback function for the event using the function call operator.

Available Functions 
void operator()( void (* callback)() );
Parameters

范围

Type

描述

callback

void (*)(void)

预先定义的回调函数，会在事件广播时自动调用。该函数必须符合所需的回调函数签名。更多信息请参见回调函数。
Return Values

This function does not return a value.

Notes

  • Setting a callback again replaces the previous callback.

  • The callback function must have no parameters and return void.

Examples 
void drawSquare() {
  Brain.Screen.clearScreen();
  Brain.Screen.drawRectangle(40, 40, 120, 120);
}

void drawCircle() {
  Brain.Screen.clearScreen();
  Brain.Screen.drawCircle(100, 100, 60);
}

// Create the event drawEvent
event drawEvent;

Brain.Screen.print("Drawing a square...");

// Set the event to drawSquare
drawEvent(drawSquare);

wait(1, seconds);

// Trigger the event
drawEvent.broadcast();

wait(1, seconds);

Brain.Screen.clearScreen();
Brain.Screen.setCursor(1, 1);
Brain.Screen.print("Drawing a circle...");

// Replace drawSquare with drawCircle
drawEvent(drawCircle);

wait(1, seconds);

// Trigger the event a second time
drawEvent.broadcast();

broadcast#

broadcast starts the event’s callback and continues immediately.

Member Functions 
void broadcast();
Parameters

This function does not take any parameters.

Return Values

This function does not return a value.

Examples 
// Create a callback function
void onMyEvent() {
  Brain.Screen.clearScreen();
  Brain.Screen.setCursor(1, 1)
  Brain.Screen.print("Event fired!");
}

Brain.Screen.print("Broadcasting in 2 seconds...");

// Create an event called myEvent
// Set onMyEvent as the callback function
event myEvent(onMyEvent);

wait(2, seconds);

// Trigger the event
myEvent.broadcast();

broadcastAndWait#

Starts the callback and waits until it finishes (or times out).

Available Functions 
void broadcastAndWait( int32_t timeout = 60000 );
Parameters

范围

Type

描述

timeout

int32_t

The amount of milliseconds to wait before the code starts executing again (defaults to 60000).
Return Values

This function does not return a value.

Notes

  • Use this only with callbacks that end (no infinite loops).

  • This is a waiting function that blocks execution until the callback completes or times out.

Examples 
void startDriving() {
  Drivetrain.drive(forward);
  wait(2, seconds);
}


Brain.Screen.print("Starting drive...");

event driveEvent(startDriving);
// Give the event time to be set
wait(0.25, seconds);

// Run the event and wait until it finishes
driveEvent.broadcastAndWait();

// Stop driving after 2 seconds
Drivetrain.stop();
Brain.Screen.clearScreen();
Brain.Screen.print("Drive complete!");
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