UI Drawing in Android

• Android drawing process (Android 6.0): from ViewRootImpl.performTraversals → to child View.draw.

Reference: Android硬件加速原理与实现简介

• What happens after calling View.invalidate()?

  Reference: i) 源码分析-Android-View-invalidate 绘制流程, ii) Android-requestLayout与invalidate方法解析.

  View.invalidate()
  -View.invalidate(boolean invalidateCache)
  --View.invalidateInternal(..)
  ---ViewGroup.invalidateChild(..)
  ----ViewParent.invalidateChildInParent(..)
  ----ViewRootImpl.invalidateChildInParent(..)
  -----ViewRootImpl.invalidateRectOnScreen(..)
  ------ViewRootImpl.scheduleTraversals(..)
  -------ViewRootImpl.mTraversalRunnable.run()
  --------ViewRootImpl.performTraversals()
  ---------ViewRootImpl.performMeasure(..)
  ----------View.measure(..)
  ---------ViewRootImpl.performLayout(..)
  ----------..
  ---------ViewRootImpl.performDraw()
  ----------..
  

  • From ViewRootImpl.performDraw() to View.onDraw() calling, print the stack trace of calling hierarchy.
  • For View.requestLayout(), it will call ViewRootImpl.requestLayout(), then ViewRootImpl.mLayoutRequested would be set to true, and this true variable would be used in the processing of deciding whether to perform measure & layout.

• How does Choreographer receive the VSync time plusing?

  android drawing note.pdf

  

• Main works done by Choreographer for each frame after receiving a VSync signal:

  Reference: Android基于Choreographer的渲染机制详解

  // Choreographer.java (android.view)
  
  // From onVSync() to self.run(), then doFrame()
  void doFrame(long frameTimeNanos, int frame) {
      // i) calculate skipped frames
      // ii) log frames in FrameInfo
      // iii) doCallbacks()
      ...
      doCallbacks(Choreographer.CALLBACK_INPUT, frameIntervalNanos);
      doCallbacks(Choreographer.CALLBACK_ANIMATION, frameIntervalNanos);
      doCallbacks(Choreographer.CALLBACK_INSETS_ANIMATION, frameIntervalNanos);
      doCallbacks(Choreographer.CALLBACK_TRAVERSAL, frameIntervalNanos);
      doCallbacks(Choreographer.CALLBACK_COMMIT, frameIntervalNanos);
      ...
  }
  

• A Stack dumped within a custom imageView’s onDraw().

  onDraw:34, LogImageView (com.tbuonomo.viewpagerdotsindicator.log)
  draw:24289, View (android.view)
  updateDisplayListIfDirty:23099, View (android.view)
  draw:23997, View (android.view)
  drawChild:4662, ViewGroup (android.view)
  dispatchDraw:4415, ViewGroup (android.view)
  updateDisplayListIfDirty:23090, View (android.view)
  draw:23997, View (android.view)
  drawChild:4662, ViewGroup (android.view)
  dispatchDraw:4415, ViewGroup (android.view)
  updateDisplayListIfDirty:23090, View (android.view)
  draw:23997, View (android.view)
  drawChild:4662, ViewGroup (android.view)
  drawChild:233, BaseDotsIndicator (com.tbuonomo.viewpagerdotsindicator)
  dispatchDraw:4415, ViewGroup (android.view)
  updateDisplayListIfDirty:23090, View (android.view)
  draw:23997, View (android.view)
  drawChild:4662, ViewGroup (android.view)
  dispatchDraw:4415, ViewGroup (android.view)
  1 hidden frame
  draw:24292, View (android.view)
  updateDisplayListIfDirty:23099, View (android.view)
  draw:23997, View (android.view)
  drawChild:4662, ViewGroup (android.view)
  dispatchDraw:4415, ViewGroup (android.view)
  updateDisplayListIfDirty:23090, View (android.view)
  draw:23997, View (android.view)
  drawChild:4662, ViewGroup (android.view)
  dispatchDraw:4415, ViewGroup (android.view)
  updateDisplayListIfDirty:23090, View (android.view)
  draw:23997, View (android.view)
  drawChild:4662, ViewGroup (android.view)
  dispatchDraw:4415, ViewGroup (android.view)
  updateDisplayListIfDirty:23090, View (android.view)
  draw:23997, View (android.view)
  drawChild:4662, ViewGroup (android.view)
  dispatchDraw:4415, ViewGroup (android.view)
  updateDisplayListIfDirty:23090, View (android.view)
  draw:23997, View (android.view)
  drawChild:4662, ViewGroup (android.view)
  dispatchDraw:4415, ViewGroup (android.view)
  updateDisplayListIfDirty:23090, View (android.view)
  draw:23997, View (android.view)
  drawChild:4662, ViewGroup (android.view)
  dispatchDraw:4415, ViewGroup (android.view)
  draw:24292, View (android.view)
  draw:909, DecorView (com.android.internal.policy)
  updateDisplayListIfDirty:23099, View (android.view)
  updateViewTreeDisplayList:713, ThreadedRenderer (android.view)
  updateRootDisplayList:719, ThreadedRenderer (android.view)
  draw:821, ThreadedRenderer (android.view)
  draw:5634, ViewRootImpl (android.view)
  performDraw:5279, ViewRootImpl (android.view)
  performTraversals:4309, ViewRootImpl (android.view)
  doTraversal:2799, ViewRootImpl (android.view)
  run:10351, ViewRootImpl$TraversalRunnable (android.view)
  run:1525, Choreographer$CallbackRecord (android.view)
  run:1534, Choreographer$CallbackRecord (android.view)
  doCallbacks:1089, Choreographer (android.view)
  doFrame:979, Choreographer (android.view)
  run:1508, Choreographer$FrameDisplayEventReceiver (android.view)
  handleCallback:958, Handler (android.os)
  dispatchMessage:99, Handler (android.os)
  loopOnce:255, Looper (android.os)
  loop:364, Looper (android.os)
  main:8938, ActivityThread (android.app)
  1 hidden frame
  run:572, RuntimeInit$MethodAndArgsCaller (com.android.internal.os)
  main:1053, ZygoteInit (com.android.internal.os)
  

/Android/ /Note/ /UI/ /render/