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：

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

创建活动 #

The event constructor creates an event object. You can create an event with or without a callback.

Default Usage:
event myEvent;

Overload Usages:
event myEvent(callback);

范围	描述
`myEvent`	活动名称。
`callback`	预先定义好在事件广播时执行的函数。

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

int main() {
  vexcodeInit();

  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();
}

设置事件回调 #

设置回调函数意味着当事件被广播时，该函数将运行。

**注意：**再次设置回调函数会覆盖之前的回调函数。

Usage:
eventName(callback);

范围	描述
`eventName`	先前创建的事件对象的名称。
`callback`	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。

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

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

int main() {
  vexcodeInit();

  // 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();
}

直播活动 #

broadcast #

broadcast starts the event’s callback and continues immediately.

Usage:
myEvent.broadcast();

范围	描述
`myEvent`	先前创建的事件对象的名称。

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

int main() {
  vexcodeInit();

  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 #

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

注意： 仅可用于会结束的回调函数（不能用于无限循环）。

Usage:
myEvent.broadcastAndWait(timeout);

范围	描述
`myEvent`	先前创建的事件对象的名称。
`timeout`	等待的毫秒数（以双精度浮点数表示），之后代码才会再次开始执行。

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

int main() {
  vexcodeInit();

  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!");
}

活动#

介绍#

创建活动#

设置事件回调#

直播活动#

broadcast#

broadcastAndWait#