Android 应用启动与 View 绘制 — 三进程图形框架总览Android 应用启动与 View 绘制

Android 应用启动与 View 绘制 — 三进程图形框架总览

基于 Android 16 AOSP（J:\aosp16）源码分析

一、三进程全景架构

graph TB
    subgraph APP["App 进程"]
        AT["ActivityThread\nmain()"]
        ACT["Activity\nonCreate / onResume"]
        VRI["ViewRootImpl\nperformTraversals()"]
        CHO["Choreographer\ndoFrame()"]
        HR["HardwareRenderer\n(UI线程)"]
        RT["RenderThread\n进程单例"]
        BBQ_P["BLASTBufferQueue\n生产者端"]
    end

    subgraph SS["SystemServer 进程"]
        ATMS["ActivityTaskManagerService\n(ATMS)"]
        WMS["WindowManagerService\n(WMS)"]
        WS["WindowState\n单窗口状态"]
        SCC["SurfaceComposerClient\n向SF申请Layer"]
    end

    subgraph SF["SurfaceFlinger 进程"]
        EVT["EventThread\nVsync分发"]
        SFL["SurfaceFlinger\n合成主循环"]
        LAYER["Layer\nBufferQueue消费端"]
        CE["CompositionEngine\nOutput::present()"]
        HWC["HWComposer / GPU\n硬件/软件合成"]
        DISP["Display Driver\n屏幕输出"]
    end

    AT -->|"Binder\nattachApplication"| ATMS
    ATMS -->|"scheduleLaunchActivity"| ACT
    ACT -->|"addView"| VRI
    VRI -->|"Binder\nIWindowSession"| WMS
    WMS --> WS
    WMS --> SCC
    SCC -->|"Binder\nISurfaceComposer"| SF

    CHO -->|"TRAVERSAL回调"| VRI
    VRI --> HR
    HR -->|"syncAndDrawFrame"| RT
    RT -->|"eglSwapBuffers"| BBQ_P

    BBQ_P -->|"queueBuffer\n共享内存"| LAYER
    EVT -->|"Vsync信号"| SFL
    EVT -->|"Vsync信号"| CHO
    SFL --> CE
    CE --> HWC
    HWC --> DISP
    LAYER --> CE

二、应用启动流程

2.1 完整启动时序

sequenceDiagram
    participant User as 用户/Launcher
    participant ATMS as ATMS (SystemServer)
    participant Zygote as Zygote进程
    participant App as App进程
    participant WMS as WMS (SystemServer)
    participant SF as SurfaceFlinger

    User->>ATMS: startActivity() [Binder]
    ATMS->>ATMS: ActivityStarter.execute()
    ATMS->>Zygote: 进程不存在 → Process.start() [Socket]
    Zygote->>App: forkAndSpecialize()
    App->>App: ActivityThread.main()
    App->>App: Looper.prepareMainLooper()
    App->>ATMS: attachApplication() [Binder]
    ATMS->>App: scheduleLaunchActivity() [Binder]
    App->>App: handleLaunchActivity()
    App->>App: Activity.attach() 绑定Window/Context
    App->>App: Activity.onCreate() setContentView()
    App->>App: Activity.onResume()
    App->>WMS: addWindow() [Binder IWindowSession]
    WMS->>WMS: 创建 WindowState
    WMS->>SF: createSurface() [Binder ISurfaceComposer]
    SF->>SF: 创建 Layer + BLASTBufferQueue
    SF-->>WMS: 返回 SurfaceControl
    WMS-->>App: 返回 SurfaceControl
    App->>App: ViewRootImpl 持有 Surface
    App->>App: 请求第一帧绘制 (scheduleTraversals)

2.2 阶段说明

阶段	核心操作	关键文件
进程孵化	Launcher → ATMS → Zygote fork	`ActivityStarter.java` `ActivityTaskSupervisor.java`
Application初始化	ActivityThread.main() → attach()	`ActivityThread.java`
Activity创建	onCreate() → setContentView() → View树构建	`Activity.java`
Window注册	ViewRootImpl.setView() → WMS.addWindow()	`ViewRootImpl.java` `WindowManagerService.java`
Surface创建	WMS → SF创建Layer → BLASTBufferQueue	`SurfaceComposerClient.cpp` `BLASTBufferQueue.cpp`
首帧绘制	scheduleTraversals → Vsync → performTraversals	`ViewRootImpl.java`

三、View 绘制流程

3.1 Vsync 驱动链

graph LR
    HV["HWComposer\n硬件Vsync"] -->|"周期信号"| DS["SF Scheduler\nDispSync软件锁相"]
    DS -->|"INVALIDATE\nREFRESH"| SFMQ["SF MessageQueue\n合成循环"]
    DS -->|"onVsync()"| DER["DisplayEventReceiver\nApp进程"]
    DER --> CHO["Choreographer\ndoFrame(frameTimeNanos)"]
    CHO -->|"INPUT"| INP["输入事件处理"]
    CHO -->|"ANIMATION"| ANI["ValueAnimator\nObjectAnimator"]
    CHO -->|"TRAVERSAL"| TRV["ViewRootImpl\nperformTraversals()"]

3.2 performTraversals — 三大流程

flowchart TD
    PT["ViewRootImpl.performTraversals()"]

    PT --> PM["performMeasure()"]
    PM --> M["View.measure()"]
    M --> OM["onMeasure()\n递归确定宽高\nMeasureSpec传递"]

    PT --> PL["performLayout()"]
    PL --> L["View.layout()"]
    L --> OL["onLayout()\n递归确定位置\nleft/top/right/bottom"]

    PT --> PD["performDraw()"]
    PD --> D["draw()"]
    D --> URDL["updateRootDisplayList()\nUI线程"]
    URDL --> VD["View.draw()\n→ onDraw(canvas)"]
    VD --> RC["RecordingCanvas\n录制绘制指令"]
    RC --> DL["DisplayList\n(RenderNode)"]

    DL --> SADF["RenderProxy.syncAndDrawFrame()\n通知RenderThread"]
    SADF --> DFT["DrawFrameTask.run()\nRenderThread"]
    DFT --> CC["CanvasContext.draw()"]
    CC --> SKIA["Skia Pipeline\nOpenGL ES / Vulkan"]
    SKIA --> GPU["GPU渲染\n→ GraphicBuffer"]

3.3 UI线程与RenderThread分工

sequenceDiagram
    participant UI as UI线程 (Main)
    participant RT as RenderThread
    participant GPU as GPU
    participant SF as SurfaceFlinger

    Note over UI: Choreographer.doFrame()
    UI->>UI: performMeasure / performLayout
    UI->>UI: updateRootDisplayList() 录制DisplayList
    UI->>RT: syncAndDrawFrame() 同步点
    Note over UI,RT: 同步阶段(短暂阻塞): 传递属性/纹理
    RT-->>UI: 同步完成，UI线程解锁
    Note over UI: UI线程继续处理下一帧逻辑
    RT->>RT: CanvasContext.draw()
    RT->>GPU: OpenGL/Vulkan 提交命令
    GPU-->>RT: 渲染完成 (acquireFence)
    RT->>SF: eglSwapBuffers → queueBuffer
    SF->>SF: 下一个Vsync合成
    SF-->>RT: releaseFence (Buffer可复用)

四、图形框架流水线（Buffer生命周期）

4.1 BufferQueue 状态机

stateDiagram-v2
    [*] --> FREE : 初始状态
    FREE --> DEQUEUED : dequeueBuffer()\nApp申请Buffer
    DEQUEUED --> QUEUED : queueBuffer()\nGPU渲染完成，提交
    DEQUEUED --> FREE : cancelBuffer()\n取消（异常路径）
    QUEUED --> ACQUIRED : acquireBuffer()\nSF获取Buffer准备合成
    ACQUIRED --> FREE : releaseBuffer()\nSF合成完毕，释放

4.2 BLASTBufferQueue 跨进程流转

sequenceDiagram
    participant RT as RenderThread (App)
    participant BBQ_P as BLASTBufferQueue-Producer
    participant BQC as BufferQueueCore (共享内存)
    participant BBQ_C as BLASTBufferQueue-Consumer
    participant SF as SurfaceFlinger Layer

    RT->>BBQ_P: eglSwapBuffers()
    BBQ_P->>BQC: queueBuffer(slot, acquireFence)
    Note over BQC: DEQUEUED → QUEUED
    BQC->>BBQ_C: onFrameAvailable() 回调
    BBQ_C->>SF: 通知有新帧
    SF->>BQC: acquireBuffer()
    Note over BQC: QUEUED → ACQUIRED
    SF->>SF: 等待 acquireFence 信号 (GPU写完)
    SF->>SF: HWC/GPU 合成此Layer
    SF->>BQC: releaseBuffer(releaseFence)
    Note over BQC: ACQUIRED → FREE
    BQC->>BBQ_P: onBufferReleased() 回调
    RT->>BQC: dequeueBuffer() 复用该Buffer

4.3 Fence 三种类型

graph LR
    GPU_W["GPU 写入 GraphicBuffer"] -->|"信号ready"| AF["acquireFence\nSF可读取此Buffer"]
    SF_R["SurfaceFlinger 读取合成完毕"] -->|"信号ready"| RF["releaseFence\nApp可dequeue复用"]
    DISP["Display 扫描出帧"] -->|"信号ready"| PF["presentFence\n计算实际帧呈现时间\nFrameTimeline使用"]

五、SurfaceFlinger 合成循环

flowchart TD
    VS["Vsync信号到来"] --> INV["SF::onMessageInvalidate()"]
    INV --> HT["handleTransaction()\n处理Layer属性变更Transaction"]
    HT --> RLS["rebuildLayerStacks()\n重建LayerSnapshot只读快照"]
    RLS --> REF["SF::onMessageRefresh()"]
    REF --> CEP["CompositionEngine::present()"]

    CEP --> PFA["Output::prepareFrameAsync()\n遍历每个Layer"]
    PFA --> DEC{合成策略决策}
    DEC -->|"简单Layer\n无变换/无混合"| DEVICE["DEVICE类型\nHWC硬件Overlay\n最低功耗"]
    DEC -->|"复杂Layer\n模糊/旋转/特效"| CLIENT["CLIENT类型\nGPU SkiaRenderEngine"]
    DEC -->|"纯色填充"| SOLID["SOLID_COLOR\nHWC直接填充"]

    DEVICE --> HWC2["HWComposer\nvalidateDisplay()"]
    CLIENT --> GPU2["SkiaRenderEngine\n离屏渲染到FrameBuffer"]
    SOLID --> HWC2

    GPU2 --> HWC2
    HWC2 --> PRES["presentDisplay()\n提交到Display驱动"]
    PRES --> PF2["presentFence回传\nFrameTimeline记录实际呈现时间"]
    PRES --> RF2["releaseFence回传给App\nBuffer可复用"]

六、关键类与文件索引

App 进程

类	文件路径	核心职责
`ActivityThread`	`base/core/java/android/app/ActivityThread.java`	主线程Loop，分发Activity生命周期
`ViewRootImpl`	`base/core/java/android/view/ViewRootImpl.java`	窗口根，驱动measure/layout/draw
`Choreographer`	`base/core/java/android/view/Choreographer.java`	Vsync回调分发，帧时序协调
`HardwareRenderer`	`base/core/java/android/graphics/HardwareRenderer.java`	UI线程侧硬件加速接口
`RenderProxy`	`base/libs/hwui/renderthread/RenderProxy.cpp`	UI线程→RenderThread任务提交
`DrawFrameTask`	`base/libs/hwui/renderthread/DrawFrameTask.cpp`	单帧同步点，跨线程协调
`CanvasContext`	`base/libs/hwui/renderthread/CanvasContext.cpp`	渲染上下文，管理EGLSurface
`RenderNode`	`base/libs/hwui/RenderNode.cpp`	场景图节点，持有DisplayList

SystemServer 进程

类	文件路径	核心职责
`ActivityTaskManagerService`	`base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java`	Activity调度主体
`ActivityStarter`	`base/services/core/java/com/android/server/wm/ActivityStarter.java`	启动流程控制
`WindowManagerService`	`base/services/core/java/com/android/server/wm/WindowManagerService.java`	窗口管理主体
`WindowState`	`base/services/core/java/com/android/server/wm/WindowState.java`	单窗口服务端状态
`RootWindowContainer`	`base/services/core/java/com/android/server/wm/RootWindowContainer.java`	Window容器树根节点

SurfaceFlinger 进程

类	文件路径	核心职责
`SurfaceFlinger`	`native/services/surfaceflinger/SurfaceFlinger.cpp`	合成主循环、Transaction处理
`Layer`	`native/services/surfaceflinger/Layer.cpp`	Layer属性、Buffer生命周期
`LayerSnapshot`	`native/services/surfaceflinger/FrontEnd/LayerSnapshot.cpp`	合成用只读快照
`Output`	`native/services/surfaceflinger/CompositionEngine/Output.cpp`	合成循环主体
`HWComposer`	`native/services/surfaceflinger/DisplayHardware/HWComposer.cpp`	HWC接口总入口
`EventThread`	`native/services/surfaceflinger/Scheduler/EventThread.cpp`	Vsync事件分发
`FrameTimeline`	`native/services/surfaceflinger/FrameTimeline/FrameTimeline.cpp`	帧时间线追踪，Jank分析

libgui（跨进程共享）

类	文件路径	核心职责
`BLASTBufferQueue`	`native/libs/gui/BLASTBufferQueue.cpp`	App→SF异步缓冲队列（主路径）
`BufferQueueCore`	`native/libs/gui/BufferQueueCore.cpp`	FREE/DEQUEUED/QUEUED/ACQUIRED状态机
`SurfaceComposerClient`	`native/libs/gui/SurfaceComposerClient.cpp`	创建Layer、提交Transaction

路径前缀均为 J:\aosp16\frameworks

七、核心概念速查

合成类型

类型	路径	适用场景
`DEVICE`	HWC 硬件 Overlay	普通矩形Layer，无特殊混合
`CLIENT`	GPU SkiaRenderEngine	模糊、旋转、复杂特效
`SOLID_COLOR`	HWC 纯色填充	背景色Layer
`CURSOR`	硬件光标Plane	系统鼠标光标

关键数据结构

对象	所在进程	含义
`ViewRootImpl`	App	窗口根，驱动 measure/layout/draw
`Surface` (Java)	App	ANativeWindow 的 Java 封装
`BLASTBufferQueue`	App/Native	Android 12+ 统一跨进程缓冲路径
`SurfaceControl`	App + WMS	Layer客户端句柄，Transaction操作对象
`WindowState`	SystemServer	WMS侧单窗口状态
`Layer`	SurfaceFlinger	SF内部合成单元，持有BufferQueue消费端
`LayerSnapshot`	SurfaceFlinger	每帧合成前生成的只读快照
`GraphicBuffer`	跨进程共享	GPU可直接读写的ION/DMA-BUF缓冲区
`Fence`	跨进程传递	GPU同步信号（acquire/release/present）

八、后续深入方向

graph LR
    A["今日：三进程框架总览"] --> B["应用启动细节\nActivityThread + Zygote fork"]
    A --> C["Window/Surface建立\nViewRootImpl.setView()\n→ WMS → SF createLayer"]
    A --> D["三大绘制流程\nperformTraversals逐行追踪"]
    A --> E["RenderThread渲染\nDrawFrameTask → CanvasContext\n→ Skia/EGL"]
    A --> F["SF合成循环\nonMessageRefresh全链路"]
    A --> G["Fence同步机制\nBLASTBufferQueue三Fence"]
    B --> H["进阶：冷启动优化\nJank定位"]
    C --> H
    D --> H
    E --> H
    F --> H
    G --> H