写在前面
项目地址
WanAndroid项目Release版运行效果开发环境搭建及模拟器相关
PANIC: Missing emulator engine program for 'x86' CPU.
在启动模拟器运行Flutter时可能出现如上错误,原因是 Sdk(AndroidSDK安装位置 )/ tools下文件丢失,删除重新安装就好了。步骤如下图:
取消2中Andrid SDK Tools的勾选,然后点击Apply开始卸载,卸载完成之后,勾选Andrid SDK Tools,然后点击Apply开始安装。完成之后重启AndroidStudio(记得重启)
操作图Error while initializing the Dart VM
Windows开发环境下,Android在打包之后成功之后,安装release版apk时闪退,并且出现错误日志
Error while initializing the Dart VM
WanAndroid项目相关
首页直接在MaterialApp中直接使用Navigator.push
class WanAndroidApp extends StatefulWidget {
@override
_WanAndroidState createState() => new _WanAndroidState();
}
class _WanAndroidState extends State<WanAndroidApp>
with TickerProviderStateMixin {
@override
Widget build(BuildContext context) {
initData();
return new MaterialApp(
home: new Scaffold(
appBar: new AppBar(
title: new Text('标题'),
actions: <Widget>[
new IconButton(
icon: new Icon(Icons.search),
onPressed: () {
Navigator.push(context,new MaterialPageRoute(
builder: (context) => new SearchPage()));
})
],
),
body: ...
);
}
}
直接点击是搜索按钮,会报错,具体信息如下,为什么呢?
The following assertion was thrown while handling a gesture: Navigator operation requested with a context that does not include a Navigator. The context used to push or pop routes from the Navigator must be that of a widget that is a descendant of a Navigator widget.
Another exception was thrown: Navigator operation requested with a context that does not include a Navigator.
stackoverflow上有人给出了答案,如下
Think of the widgets in Flutter as a tree, with the context pointing to whichever node is being built with the build function. In your case, you have
--------------------------------------------------------------
MainScreen <------ context
--> MaterialApp
(--> Navigator built within MaterialApp)
--> Scaffold
--> App Bar
--> ...
--> Center
--> ...
--------------------------------------------------------------
So when you're using the context to find the Navigator, you're using a context for the MainScreen which isn't under the navigator.
意思就是此时Navigator.push(context..中的contexts是MainScreen中的context
RefreshIndicator在ListView条目较少时不触发下拉刷新
RefreshIndicator是根据下拉时的偏移量触发刷新,当条目较少时(未占满一个屏幕),ListView不能滚动,所以无法触发下拉刷新,给ListView的physice属性设置值为new AlwaysScrollableScrollPhysics(),让ListView在任何情况下都可以滑动,也就可以触发RefreshIndicator的刷新。
Widget listView = new ListView.builder(
//注意这里physics
physics: new AlwaysScrollableScrollPhysics(),
itemCount: listData.length,
itemBuilder: (context, i) => buildItem(i),
controller: _contraller,
);
TarBarView每次切换时其条目Widget都会执行initState()
class ArticleListPageState extends State<ArticleListPage>
with AutomaticKeepAliveClientMixin {
// with AutomaticKeepAliveClientMixin 并且get wantKeepAlive返回true,tab切换时,不会每次执行initState
//来自
@override
bool get wantKeepAlive => true;
}
后续会再慢慢完善这篇博客