android Surface绘制状态流转-WindowStateAnimator

java 复制代码

/**
 * Keep track of animations and surface operations for a single WindowState.
 **/
class WindowStateAnimator {
    /** This is set when there is no Surface */
    static final int NO_SURFACE = 0;
    /** This is set after the Surface has been created but before the window has been drawn. During
     * this time the surface is hidden. */
    static final int DRAW_PENDING = 1;
    /** This is set after the window has finished drawing for the first time but before its surface
     * is shown.  The surface will be displayed when the next layout is run. */
    static final int COMMIT_DRAW_PENDING = 2;
    /** This is set during the time after the window's drawing has been committed, and before its
     * surface is actually shown.  It is used to delay showing the surface until all windows in a
     * token are ready to be shown. */
    static final int READY_TO_SHOW = 3;
    /** Set when the window has been shown in the screen the first time. */
    static final int HAS_DRAWN = 4;

WindowStateAnimator 是 WMS 中每个窗口对应的 Surface 动画与绘制状态管理器。它维护了从 Surface 创建到最终显示到屏幕的完整生命周期，核心职责包括：

职责	说明
Surface 生命周期管理	创建 (`createSurfaceLocked`)、销毁 (`destroySurfaceLocked`) 窗口的 `SurfaceControl`
绘制状态机	管理 `mDrawState` 的 5 个状态流转（核心机制）
Surface 属性控制	控制透明度 (`setAlpha`)、可见性 (`show`/`hide`)、不透明度 (`setOpaque`)、颜色空间等
入场动画	`applyEnterAnimationLocked()` 为窗口首次显示播放动画
Transaction 提交	`finishDrawingLocked()` 将客户端的 `postDrawTransaction` 合并到 `getSyncTransaction()`

完整时序图
SurfaceControl WindowStateAnimator(绘制状态机) WindowState WindowManagerService 应用客户端(ViewRootImpl) SurfaceControl WindowStateAnimator(绘制状态机) WindowState WindowManagerService 应用客户端(ViewRootImpl) #mermaid-svg-5Todbye6GHBBaUwF{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-5Todbye6GHBBaUwF .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-5Todbye6GHBBaUwF .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-5Todbye6GHBBaUwF .error-icon{fill:#552222;}#mermaid-svg-5Todbye6GHBBaUwF .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-5Todbye6GHBBaUwF .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-5Todbye6GHBBaUwF .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-5Todbye6GHBBaUwF .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-5Todbye6GHBBaUwF .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-5Todbye6GHBBaUwF .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-5Todbye6GHBBaUwF .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-5Todbye6GHBBaUwF .marker{fill:#333333;stroke:#333333;}#mermaid-svg-5Todbye6GHBBaUwF .marker.cross{stroke:#333333;}#mermaid-svg-5Todbye6GHBBaUwF svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-5Todbye6GHBBaUwF p{margin:0;}#mermaid-svg-5Todbye6GHBBaUwF .actor{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-5Todbye6GHBBaUwF text.actor>tspan{fill:black;stroke:none;}#mermaid-svg-5Todbye6GHBBaUwF .actor-line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-5Todbye6GHBBaUwF .innerArc{stroke-width:1.5;stroke-dasharray:none;}#mermaid-svg-5Todbye6GHBBaUwF .messageLine0{stroke-width:1.5;stroke-dasharray:none;stroke:#333;}#mermaid-svg-5Todbye6GHBBaUwF .messageLine1{stroke-width:1.5;stroke-dasharray:2,2;stroke:#333;}#mermaid-svg-5Todbye6GHBBaUwF #arrowhead path{fill:#333;stroke:#333;}#mermaid-svg-5Todbye6GHBBaUwF .sequenceNumber{fill:white;}#mermaid-svg-5Todbye6GHBBaUwF #sequencenumber{fill:#333;}#mermaid-svg-5Todbye6GHBBaUwF #crosshead path{fill:#333;stroke:#333;}#mermaid-svg-5Todbye6GHBBaUwF .messageText{fill:#333;stroke:none;}#mermaid-svg-5Todbye6GHBBaUwF .labelBox{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-5Todbye6GHBBaUwF .labelText,#mermaid-svg-5Todbye6GHBBaUwF .labelText>tspan{fill:black;stroke:none;}#mermaid-svg-5Todbye6GHBBaUwF .loopText,#mermaid-svg-5Todbye6GHBBaUwF .loopText>tspan{fill:black;stroke:none;}#mermaid-svg-5Todbye6GHBBaUwF .loopLine{stroke-width:2px;stroke-dasharray:2,2;stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-5Todbye6GHBBaUwF .note{stroke:#aaaa33;fill:#fff5ad;}#mermaid-svg-5Todbye6GHBBaUwF .noteText,#mermaid-svg-5Todbye6GHBBaUwF .noteText>tspan{fill:black;stroke:none;}#mermaid-svg-5Todbye6GHBBaUwF .activation0{fill:#f4f4f4;stroke:#666;}#mermaid-svg-5Todbye6GHBBaUwF .activation1{fill:#f4f4f4;stroke:#666;}#mermaid-svg-5Todbye6GHBBaUwF .activation2{fill:#f4f4f4;stroke:#666;}#mermaid-svg-5Todbye6GHBBaUwF .actorPopupMenu{position:absolute;}#mermaid-svg-5Todbye6GHBBaUwF .actorPopupMenuPanel{position:absolute;fill:#ECECFF;box-shadow:0px 8px 16px 0px rgba(0,0,0,0.2);filter:drop-shadow(3px 5px 2px rgb(0 0 0 / 0.4));}#mermaid-svg-5Todbye6GHBBaUwF .actor-man line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-5Todbye6GHBBaUwF .actor-man circle,#mermaid-svg-5Todbye6GHBBaUwF line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;stroke-width:2px;}#mermaid-svg-5Todbye6GHBBaUwF :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;} 阶段1: Surface 创建 (NO_SURFACE → DRAW_PENDING) mDrawState = NO_SURFACE Surface 已创建但隐藏 mDrawState = DRAW_PENDING 阶段2: 客户端首次绘制完成 (DRAW_PENDING → COMMIT_DRAW_PENDING) 状态转换合并事务到同步组 alt $mDrawState == DRAW_PENDING$ 阶段3: 布局提交与准备显示 (COMMIT_DRAW_PENDING → READY_TO_SHOW) 状态转换检查 Activity 生命周期 alt $mDrawState == COMMIT_DRAW_PENDING$ 阶段4: 最终显示 (READY_TO_SHOW → HAS_DRAWN) 验证显示条件应用进入动画(如果需要) 状态转换触发动画帧渲染 alt $mDrawState == READY_TO_SHOW \&\& isReadyForDisplay()$ 阶段5: 正常显示循环 (HAS_DRAWN 状态) alt $mDrawState == HAS_DRAWN \&\& !mLastHidden$ $mDrawState != HAS_DRAWN \|\| mLastHidden$ loop $每帧渲染$ 阶段6: 窗口销毁 (任意状态 → NO_SURFACE) 销毁 Surface 资源状态重置 relayoutWindow() 请求创建窗口创建 WindowState构造 WindowStateAnimatorcreateSurfaceLocked()创建 SurfaceControl (HIDDEN标志)resetDrawState()返回 Surface，等待客户端绘制执行 onDraw() 渲染内容finishDrawing() 通知绘制完成finishDrawing(postDrawTransaction, syncSeqId)finishDrawingLocked(postDrawTransaction)mDrawState = COMMIT_DRAW_PENDINGgetSyncTransaction().merge(postDrawTransaction)返回 layoutNeeded = trueperformLayoutAndPlaceSurfaces()commitFinishDrawingLocked()commitFinishDrawingLocked()mDrawState = READY_TO_SHOWperformShowLocked()performShowLocked()检查 showToCurrentUser()检查 mActivityRecord.canShowWindows()applyEnterAnimationLocked()mDrawState = HAS_DRAWNscheduleAnimationLocked()递归调用子窗口 performShowLocked()prepareSurfaceLocked(transaction)transaction.show(mSurfaceControl)setShown(true)transaction.hide(mSurfaceControl)setShown(false)移除窗口或 Activity 停止destroySurface(cleanupOnResume, appStopped)destroySurfaceUnchecked()destroySurfaceLocked(transaction)transaction.remove(mSurfaceControl)setShown(false)mSurfaceControl = nullmDrawState = NO_SURFACEmAnimatingExit = false

BUFFER 的 fence 机制

当 App 通过 eglSwapBuffers / queueBuffer 将 buffer 提交给 BLASTBufferQueue 时，buffer 带有一个 fence（GraphicBuffer 的 acquireFence）：

当 App 通过 eglSwapBuffers / queueBuffer 将 buffer 提交给 BLASTBufferQueue 时，buffer 带有一个 fence（GraphicBuffer 的 acquireFence）：

text 复制代码

queueBuffer(buffer, fence) → BBQ
                               │
                               ├── buffer 进入 BBQ 的待处理队列
                               ├── fence 被附加到 Transaction 中
                               └── Transaction → SF
                                     │
                                     ├── SF: t.show() → Surface 可见
                                     ├── SF: 尝试合成 buffer
                                     ├── SF: 发现 fence 未 signal
                                     ├── SF: 等待 fence  ← GPU 仍在渲染
                                     ├── ... GPU 完成 → fence signal
                                     └── SF: 合成并显示

绘制状态与屏显的关系

时间点	事件	GPU 状态	`mDrawState`
T1	GPU 命令提交，`queueBuffer`	渲染中	`DRAW_PENDING`
T2	`finishDrawing()` → WMS	渲染中	`COMMIT_DRAW_PENDING`
T3	`commitFinishDrawingLocked()`	渲染中	`READY_TO_SHOW`
T4	`performShowLocked()`	渲染中	`HAS_DRAWN` ✅
T5	`showRobustly()` → `t.show()`	渲染中	`HAS_DRAWN`
T6	GPU fence signal	完成 ✅	`HAS_DRAWN`
T7	SF 合成并显示	完成	`HAS_DRAWN`

HAS_DRAWN 是 WMS 侧的"决策状态"，不是 GPU 侧的"完成状态"。从 HAS_DRAWN 设置到 GPU 真正完成渲染之间的时间差，由 buffer 的 acquire fence 机制来保证画面正确性------SF 会在合成前自动等待 fence，不会出现显示不完整帧的问题。