在handleDrawFrame()中，您可以看到以下部分：

try {
  // PERSISTENT FRAME CALLBACKS
  _schedulerPhase = SchedulerPhase.persistentCallbacks;
  for (final FrameCallback callback in _persistentCallbacks) {
    _invokeFrameCallback(callback, _currentFrameTimeStamp!);
  }

我不知道它被添加到persistenCallbacks的确切位置，但是查看代码中的变量可以看到

/// The persistent callbacks (scheduled by
  /// [SchedulerBinding.addPersistentFrameCallback]) are currently executing.
  ///
  /// Typically, this is the build/layout/paint pipeline. See
  /// [WidgetsBinding.drawFrame] and [SchedulerBinding.handleDrawFrame].
  persistentCallbacks,

这意味着它调用drawFrame
在drawFrame中，你会发现这行代码：

buildOwner!.buildScope(rootElement!);

在这个方法中，它查看_dirtyElements中的所有元素。请注意，在scheduleBuildFor中，你在这个问题中发布了它。在这个buildScope中，它调用

element.rebuild();

这反过来又叫

performRebuild():

对于ComponentElements来说

/// Calls the [StatelessWidget.build] method of the [StatelessWidget] object
  /// (for stateless widgets) or the [State.build] method of the [State] object
  /// (for stateful widgets) and then updates the widget tree.
  ///
  /// Called automatically during [mount] to generate the first build, and by
  /// [rebuild] when the element needs updating.
  @override
  @pragma('vm:notify-debugger-on-exception')
  void performRebuild() {