Widget 的生命周期
我自己又按照自己的理解整了下流程
关于构造函数是在父节点build里调用的构造函数实例化的子节点widget，然后父节点调用inflateWidget进入子节点的生命周期
inflateWidget要理解为当前的element为父节点，调用inflateWidget来创建子节点，也就是说父节点的build等流程已经走完(build要初始化子节点实例)
举例：A 的 child 是 B
Element inflateWidget(Widget newWidget, Object? newSlot) {
//this为A newWidget则是B，通过Bwidget 创建对应的element
final Element newChild = newWidget.createElement();
//新生成的element插入element树中
newChild.mount(this, newSlot);
return newChild;
}
//可以看到是`createElement`调起了`widget.createState()`,进而`initState`
abstract class StatefulWidget extends Widget {
@override
StatefulElement createElement() => StatefulElement(this);
//...
StatefulElement(StatefulWidget widget)
: _state = widget.createState(),
newChild执行该方法 则B element的parent设置为A，_depth做+1操作
-
ComponentElement重写Element的mount方法
abstract class Element extends DiagnosticableTree implements BuildContext
_parent = parent;
_depth = _parent != null ? _parent!.depth + 1 : 1;
继承关系:
abstract class ComponentElement extends Element
class StatelessElement extends ComponentElement
class StatefulElement extends ComponentElement
abstract class RenderObjectElement extends Element
StatelessElement extends ComponentElement
ComponentElement重写Element的mount，触发build(Element可没有build方法)
abstract class ComponentElement extends Element {...
void mount(Element? parent, Object? newSlot) {
super.mount(parent, newSlot);
_firstBuild();
}
-
StatefulElement重写_firstBuild 方法
StatefulElement主要是触发initStatedidChangeDependencies_firstBuild
void _firstBuild() {
final Object? debugCheckForReturnedFuture = state.initState() as dynamic;
state.didChangeDependencies();
super._firstBuild();
由此可以看出第一次显示时，initState -> didChangeDependencies -> _firstBuild
abstract class RenderObjectElement extends Element重写mount方法
- ps
stateful...:inflateWidget->createElement()->createState()->newChild.mount->_firstBuild->state.initState()->state.didChangeDependencies()->rebuild()->performRebuild->updateChild
