【Unity博客节选】PlayableGraph 的生命周期-海口c网

注：软件版本Unity 6.0 + Timeline 1.8.7

作者：CSDN @ RingleaderWang
原文：《Unity第25期——Timeline结构及其源码浅析》
文章首发Github👍：《Timeline结构及其源码浅析》

Bilibili 视频版👍👍：《Timeline结构及其源码解析》https://www.bilibili.com/video/BV1bHjYzNE35

PlayableGraph 的生命周期

原文运行时多次提到了 PrepareFrame、ProcessFrame，其实这就是ScriptPlayable在某段生命周期执行的回调函数，我们可以利用 ScriptPlayable 传入自定义PlayableBehaviour 来干涉Playable的生命周期。

Playable的生命周期有：

GraphStart：graph play 开始时
GraphStop：graph stop时
PlayableCreate：Playable Create时
PlayableDestroy：Playable Destroy时
BehaviourPlay：Playable 运行时
BehaviourPause：Playable 暂停时
PrepareFrame：每帧处理数据前
ProcessFrame：每帧开始处理数据时

当然可能并非都是这些生命周期，比如AnimationScriptPlayable就有个ProcessAnimation和ProcessRootMotion过程，可能就没有所谓的ProcessFrame了。

当然对于ScriptPlayable，上面的生命周期是确定的，在Playable处于上面的生命周期时，便会执行对应的回调函数（注册在PlayableBehaviour里）。

下面的自定义PlayableBehaviour就是简单打印回调方法和playable：

public class TimelineTestForAnimationScriptBehaviour : PlayableBehaviour{public override void OnGraphStart(Playable playable){DebugLog(playable,"OnGraphStart");}private static void DebugLog(Playable playable, string methodName){Debug.Log($"Playable by in/output cnt_{playable.GetInputCount()}{playable.GetOutputCount()} Behaviour:{methodName}");}public override void OnGraphStop(Playable playable){DebugLog(playable,"OnGraphStop");}public override void OnPlayableCreate(Playable playable){DebugLog(playable,"OnPlayableCreate");}public override void OnPlayableDestroy(Playable playable){DebugLog(playable,"OnPlayableDestroy");}public override void OnBehaviourPlay(Playable playable, FrameData info){DebugLog(playable,"OnBehaviourPlay");}public override void OnBehaviourPause(Playable playable, FrameData info){DebugLog(playable,"OnBehaviourPause");}public override void PrepareFrame(Playable playable, FrameData info){DebugLog(playable,"PrepareFrame");}public override void ProcessFrame(Playable playable, FrameData info, object playerData){DebugLog(playable,"ProcessFrame");}}

生命周期验证

上面生命周期的理解还比较模糊，尤其父子节点回调执行顺序是什么需要验证。

验证代码如下（给不同节点设置不同端口数能很方便辨析是哪个节点的回调）：

using System;
using Scenes.TimelineTest.scripts;
using UnityEditor;
using UnityEngine;
using UnityEngine.Playables;public class TimelineTestForLifeCycle : MonoBehaviour
{public PlayableGraph graph;private ScriptPlayable<TimelineTestForAnimationScriptBehaviour> playable3;public void CreateGraph(){DestroyGraph();graph = PlayableGraph.Create("TimelineTestForLifeCycle");ScriptPlayableOutput output = ScriptPlayableOutput.Create(graph,"LifeCycleTestOutput");var playable5 = ScriptPlayable<TimelineTestForAnimationScriptBehaviour>.Create(graph,5);var playable4 = ScriptPlayable<TimelineTestForAnimationScriptBehaviour>.Create(graph,4);playable3 = ScriptPlayable<TimelineTestForAnimationScriptBehaviour>.Create(graph,3);var playable2 = ScriptPlayable<TimelineTestForAnimationScriptBehaviour>.Create(graph,2);var playable1 = ScriptPlayable<TimelineTestForAnimationScriptBehaviour>.Create(graph,1);output.SetSourcePlayable(playable5,0);output.SetWeight(1);playable5.ConnectInput(0,playable1,0,1);playable5.ConnectInput(1,playable2,0,0.5f);playable3.Pause();playable5.ConnectInput(2,playable3,0,1);playable5.ConnectInput(3,playable4,0,0);var playable9 = ScriptPlayable<TimelineTestForAnimationScriptBehaviour>.Create(graph,9);var playable8 = ScriptPlayable<TimelineTestForAnimationScriptBehaviour>.Create(graph,8);playable9.ConnectInput(0,playable8,0,1);}public void PlayPlayable3(){playable3.Play();}public void PausePlayable3(){playable3.Pause();}public void DestroyPlayable3(){playable3.Destroy();}public void PlayGraph(){graph.Play();}private void OnDestroy(){DestroyGraph();}public void DestroyGraph(){if (graph.IsValid()){Debug.Log("Execute Graph Destroy");graph.Destroy();Debug.Log("Graph destroyed");}}
}[CustomEditor(typeof(TimelineTestForLifeCycle))]
class TimelineTestForLifeCycleEditor : Editor
{public override void OnInspectorGUI(){base.OnInspectorGUI();TimelineTestForLifeCycle script = (TimelineTestForLifeCycle) target;if (GUILayout.Button("CreateGraph")){script.CreateGraph();}if (GUILayout.Button("PlayGraph")){script.PlayGraph();}if (GUILayout.Button("Destroy graph")){script.DestroyGraph();}if (GUILayout.Button("Play Playable3")){script.PlayPlayable3();}if (GUILayout.Button("Pause Playable3")){script.PausePlayable3();}if (GUILayout.Button("Destroy Playable3")){script.DestroyPlayable3();}}
}

点击 “CreateGraph” 后的 graph 结构（图中标注的是节点设置的play state和连接权重）：

生命周期验证示例的graph图

当前脚本主要测试graph的 create与play（除了prepareFrame、processFrame），验证：

graph不play，playable节点是否会运行
没有playableOutput，playable节点是否会运行
输出权重为0，playable节点是否会运行
pause状态，playable节点是否会运行
PrepareFrame、ProcessFrame顺序
Graph destroy执行效果

打印结果：

// 打印
Playable by in/output cnt_51 Behaviour:OnPlayableCreate  
Playable by in/output cnt_41 Behaviour:OnPlayableCreate  
Playable by in/output cnt_31 Behaviour:OnPlayableCreate  
Playable by in/output cnt_21 Behaviour:OnPlayableCreate  
Playable by in/output cnt_11 Behaviour:OnPlayableCreate  
Playable by in/output cnt_91 Behaviour:OnPlayableCreate  
Playable by in/output cnt_81 Behaviour:OnPlayableCreate  
Playable by in/output cnt_51 Behaviour:OnGraphStart  
Playable by in/output cnt_51 Behaviour:OnBehaviourPlay  
Playable by in/output cnt_11 Behaviour:OnGraphStart  
Playable by in/output cnt_11 Behaviour:OnBehaviourPlay  
Playable by in/output cnt_21 Behaviour:OnGraphStart  
Playable by in/output cnt_21 Behaviour:OnBehaviourPlay  
Playable by in/output cnt_31 Behaviour:OnGraphStart  
Playable by in/output cnt_31 Behaviour:OnBehaviourPause  
Playable by in/output cnt_41 Behaviour:OnGraphStart  
Playable by in/output cnt_41 Behaviour:OnBehaviourPlay  Playable by in/output cnt_51 Behaviour:PrepareFrame  
Playable by in/output cnt_11 Behaviour:PrepareFrame  
Playable by in/output cnt_21 Behaviour:PrepareFrame  
Playable by in/output cnt_41 Behaviour:PrepareFrame  
Playable by in/output cnt_11 Behaviour:ProcessFrame  
Playable by in/output cnt_21 Behaviour:ProcessFrame  
Playable by in/output cnt_41 Behaviour:ProcessFrame  
Playable by in/output cnt_51 Behaviour:ProcessFrame  Graph destroyed  
Playable by in/output cnt_51 Behaviour:OnBehaviourPause  
Playable by in/output cnt_11 Behaviour:OnBehaviourPause  
Playable by in/output cnt_21 Behaviour:OnBehaviourPause  
Playable by in/output cnt_41 Behaviour:OnBehaviourPause  
Playable by in/output cnt_51 Behaviour:OnGraphStop  
Playable by in/output cnt_51 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_41 Behaviour:OnGraphStop  
Playable by in/output cnt_41 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_31 Behaviour:OnGraphStop  
Playable by in/output cnt_31 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_21 Behaviour:OnGraphStop  
Playable by in/output cnt_21 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_11 Behaviour:OnGraphStop  
Playable by in/output cnt_11 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_91 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_81 Behaviour:OnPlayableDestroy

结合Graph Monitor 可以得出结论：

graph不play，playable节点不会运行
没有连ScriptPlayableOutput，ScriptPlayable节点不会运行（playable time不随时间增加），且除了OnPlayableCreate和OnPlayableDestroy，其他回调方法不会触发
输出权重为0，playable节点依然运行
pause状态，playable节点不会运行
graph未play，playable执行pause并不会触发OnBehaviourPause
graph 执行Play() 后：若playable是playing状态时，则触发OnBehaviourPlay回调；是paused状态时，则触发OnBehaviourPause回调
会以前序遍历（父节点优先）的方式触发OnGraphStart 和 OnBehaviourPlay/Pause
会以前序遍历（父节点优先）的方式触发PrepareFrame回调
会以后序遍历（子节点优先）的方式触发ProcessFrame回调
没有连接playableOutput的playable节点不会触发OnGraphStart/OnGraphStop回调
直接Destroy graph时，如果graph未stop会先触发OnBehaviourPause、OnGraphStop回调，这两个回调的触发逻辑与先Stop Graph后Destroy Graph 略有不同，如下日志：

// 先Stop graph 再 Destroy graph的日志（与直接Destroy graph有差异）
graph.Stop()Playable by in/output cnt_51 Behaviour:OnBehaviourPause  
Playable by in/output cnt_51 Behaviour:OnGraphStop  
Playable by in/output cnt_11 Behaviour:OnBehaviourPause  
Playable by in/output cnt_11 Behaviour:OnGraphStop  
Playable by in/output cnt_21 Behaviour:OnBehaviourPause  
Playable by in/output cnt_21 Behaviour:OnGraphStop  
Playable by in/output cnt_31 Behaviour:OnBehaviourPause  
Playable by in/output cnt_31 Behaviour:OnGraphStop  
Playable by in/output cnt_41 Behaviour:OnBehaviourPause  
Playable by in/output cnt_41 Behaviour:OnGraphStop  Graph.Destroy()  Playable by in/output cnt_51 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_41 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_31 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_21 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_11 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_91 Behaviour:OnPlayableDestroy  
Playable by in/output cnt_81 Behaviour:OnPlayableDestroy