我有一个为 Android 设置后端的 StatefulWidget:
class ToeKickSettings extends StatefulWidget {
ToeKickSettings({
Key key,
this.backend
}) : super(key: key);
final AndroidBackend backend;
@override
_ToeKickSettingsState createState() => _ToeKickSettingsState();
}
class _ToeKickSettingsState extends State<ToeKickSettings> {
double default_bottom_spacing = 5;
List<Widget> listChildren = [];
_ToeKickSettingsState() {
generateListsFromSoundPacks().then((val) => setState(() {
listChildren = val;
}));
}
Future<List<Widget>> generateListsFromSoundPacks() async {
List<Widget> list = new List<Widget>();
List<String> soundPacks = await widget.backend.common.listSoundPacks();
//...
}
}
我通过执行 StatefulWidget
await widget.backend.common.listSoundPacks();
状态部分的后端
我收到此错误:
E/flutter (23645): [ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: NoSuchMethodError: The getter 'backend' was called on null.
E/flutter (23645): Receiver: null
E/flutter (23645): Tried calling: backend
E/flutter (23645): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
E/flutter (23645): #1 _ToeKickSettingsState.generateListsFromSoundPacks (package:flutter_app/toe_kick.dart:131:44)
这表明在调用 widget
时没有 generateListsFromSoundPacks
属性。我怀疑这与我从 _ToeKickSettingsState()
调用 _ToeKickSettingsState createState() => _ToeKickSettingsState();
的时间有关。可能尚未设置 wodget
属性。
我能做什么?
答案 0 :(得分:1)
不要在widget
的构造函数中使用State class
,将构造函数中的代码移至initState
。
@override
void initState() {
super.initState();
generateListsFromSoundPacks().then((val) => setState(() {
listChildren = val;
}));
}