c++ - Maya Api 中的事件以捕获当前时间/帧更改

Question

我目前正在开发一个 Maya 插件。我如何设置每次在场景中更改帧号/当前时间时触发的回调？
我查看了 MSceneMessage 类，但它似乎不包含我要查找的内容。
谢谢。

Answer 1

您可以使用 MEventMessage 设置每次时间范围/当前时间更改时的回调。代码胜于 Eloquent ，所以这里有一些代码和注释穿插在一起，以说明如何设置它:(对于不耐烦的人来说，TLDR 首先，完整的代码摘录将在下一节中提供)

简单描述:

不耐烦的代码摘要:

    // ...

    // Our callback Id array to 
    // store the Ids of all our callbacks
    // for later removal    
    MCallbackIdArray myCallbackIds;

    // This is where the actual adding callback happens
    // We register our callback to the "timeChanged" event
    MCallbackId callbackId = MEventMessage::addEventCallback("timeChanged",  (MMessage::MBasicFunction) MySampleCmd::userCB);

    // ...

    if(myCallbackIds.length() != 0)
        // Make sure we remove all the callbacks we added
        stat = MEventMessage::removeCallbacks(myCallbackIds);

• 引用 MEventMessage from the docs .
• 列出的事件 here (在 scriptJob 命令中)可以与 MEventMessage 一起使用。

---

带有注释的完整(大概)代码:

MySampleCommand.h

class MySampleCmd : public MPxCommand {
public:
                MySampleCmd();
    virtual     ~MySampleCmd();

    // Our callback - implemented as a static method
    static      void userCB(void* clientData);

    MStatus     doIt( const MArgList& );
    MStatus     redoIt();
    MStatus     undoIt();   
    bool        isUndoable() const;
    static      void* creator();

public:

    // Our callback Id array to 
    // store the Ids of all our callbacks
    // for later removal
    MCallbackIdArray myCallbackIds;
};

MySampleCommand.cpp(节选)

// Constructor
MySampleCmd::MySampleCmd() {

    // Clearing our callback Id array
    // for housekeeping    
    myCallbackIds.clear();
}

// Destructor
MySampleCmd::~MySampleCmd() {

    // Make sure we remove all the callbacks we added
    // Failing to do so will result in fatal error    
    if(myCallbackIds.length() != 0)

        // Remove the MEventMessage callback
        MEventMessage::removeCallbacks(myCallbackIds);
}

MStatus MySampleCmd::redoIt() {

    // This is where the actual adding callback happens
    // We register our callback to the "timeChanged" event
    MCallbackId callbackId = MEventMessage::addEventCallback("timeChanged",  (MMessage::MBasicFunction) MySampleCmd::userCB);

    // Append the newly added callback's ID to our list of callback ids
    // for future removal
    myCallbackIds.append(callbackId);
    return MS::kSuccess;
}

MStatus MySampleCmd::undoIt() {
    MStatus stat;
    if(myCallbackIds.length() != 0)
        // Make sure we remove all the callbacks we added
        stat = MEventMessage::removeCallbacks(myCallbackIds);
    return stat;
}

// Our callback function
void SafeSelect::userCB(void* clientData) {
    MGlobal::displayInfo( "Callback userCB called!\n" );
    return;
}