【Unity博客节选】PlayableGraph 的生命周期

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

完整生命周期：