Widget 的生命周期
我自己又按照自己的理解整了下流程
關(guān)于構(gòu)造函數(shù)是在父節(jié)點(diǎn)build里調(diào)用的構(gòu)造函數(shù)實例化的子節(jié)點(diǎn)widget冬念，然后父節(jié)點(diǎn)調(diào)用inflateWidget進(jìn)入子節(jié)點(diǎn)的生命周期
inflateWidget要理解為當(dāng)前的element為父節(jié)點(diǎn)氢架，調(diào)用inflateWidget來創(chuàng)建子節(jié)點(diǎn)碌尔，也就是說父節(jié)點(diǎn)的build等流程已經(jīng)走完(build要初始化子節(jié)點(diǎn)實例)
舉例：A 的 child 是 B
Element inflateWidget(Widget newWidget, Object? newSlot) {
//this為A newWidget則是B浇辜，通過Bwidget 創(chuàng)建對應(yīng)的element
final Element newChild = newWidget.createElement();
//新生成的element插入element樹中
newChild.mount(this, newSlot);
return newChild;
}
//可以看到是`createElement`調(diào)起了`widget.createState()`,進(jìn)而`initState`
abstract class StatefulWidget extends Widget {
@override
StatefulElement createElement() => StatefulElement(this);
//...
StatefulElement(StatefulWidget widget)
: _state = widget.createState(),
newChild執(zhí)行該方法 則B element的parent設(shè)置為A券敌，_depth做+1操作
-
ComponentElement重寫Element的mount方法
abstract class Element extends DiagnosticableTree implements BuildContext
_parent = parent;
_depth = _parent != null ? _parent!.depth + 1 : 1;
繼承關(guān)系:
abstract class ComponentElement extends Element
class StatelessElement extends ComponentElement
class StatefulElement extends ComponentElement
abstract class RenderObjectElement extends Element
StatelessElement extends ComponentElement
ComponentElement重寫Element的mount，觸發(fā)build(Element可沒有build方法)
abstract class ComponentElement extends Element {...
void mount(Element? parent, Object? newSlot) {
super.mount(parent, newSlot);
_firstBuild();
}
-
StatefulElement重寫_firstBuild 方法
StatefulElement主要是觸發(fā)initStatedidChangeDependencies_firstBuild
void _firstBuild() {
final Object? debugCheckForReturnedFuture = state.initState() as dynamic;
state.didChangeDependencies();
super._firstBuild();
由此可以看出第一次顯示時柳洋，initState -> didChangeDependencies -> _firstBuild
abstract class RenderObjectElement extends Element重寫mount方法
- ps
stateful...:inflateWidget->createElement()->createState()->newChild.mount->_firstBuild->state.initState()->state.didChangeDependencies()->rebuild()->performRebuild->updateChild
