症状：
除了电源按钮，键盘和触摸板全部失灵，触摸板可以按下去，鼠标无法滑动，外接usb键盘鼠标可以使用
处理办法:
重置NVRAM
步骤：首先按住 option+commamd+P+R键，再按住电源键开机，等待听duang的开机声，听到四声后，松开按键，按电源键开机，恢复正常
参考：https://www.jianshu.com/p/51d6142b564a
完。
pod下载三方库github 443问题
报错原文：
1 | Cloning into '/var/folders/nd/n2mbp09n1lqbyyf586wntcww0000gn/T/d20210428-5764-pwxnoe'... |
原因分析：
本地git使用代理连接github，代理出了问题
问题解决：
让代理恢复正常或者不使用代理
1 | git config --global --unset http.https://github.com.proxy |
去除了http 和 https的代理
完。
Why use WKWebview
WK is run in a separate process so that it can draw on native Safari JavaScript optimizations,this means WK loads web pages faster than UIWeb,UIWeb uses traditional JS engines which are basic interpreters,Apple’s Nitro engine uses a 4 tier compiling strategy which can execute JS 40 times faster than a traditional JS interpreter.
Nitro means Nitromethane, is a kind of fuel for car engine.
source：
寻找下一个数
早上开车等红绿灯时想到几个月前写的一个算法，应该可以更简单，今天重新写了一遍
寻找下一个数字，例如输入345，输出354
思路：从最右边位和上一位对比，如果大，就往前移，移动完，尾数排序，从小到大，保证次大
代码
1 | //字符串分成数组 |
使用：
1 | NSString *str = findNextLargerNum(@"8976"); |
flutter App 优化实操
抽取widget，尽量成为一个stateless widget
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16class MainWidget extends StatelessWidget {
Widget build(BuildContext context) {
return Expanded(
child: Container(
color: Colors.grey[700],
child: Center(
child: Text(
'Hello Flutter',
style: Theme.of(context).textTheme.display1,
),
),
),
);
}
}
更新属性值，用传值的方式
ChangeNotifier
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54//------ ChangeNotifier class ----//
class MyColorNotifier extends ChangeNotifier {
Color myColor = Colors.grey;
Random _random = new Random();
void changeColor() {
int randomNumber = _random.nextInt(30);
myColor = Colors.primaries[randomNumber % Colors.primaries.length];
notifyListeners();
}
}
//------ State class ----//
class _MyHomePageState extends State<MyHomePage> {
final _colorNotifier = MyColorNotifier();
void _onPressed() {
_colorNotifier.changeColor();
}
@override
void dispose() {
_colorNotifier.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
print('building `MyHomePage`');
return Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: _onPressed,
child: Icon(Icons.colorize),
),
body: Stack(
children: [
Positioned.fill(
child: BackgroundWidget(),
),
Center(
child: AnimatedBuilder(
animation: _colorNotifier,
builder: (_, __) => Container(
height: 150,
width: 150,
color: _colorNotifier.myColor,
),
),
),
],
),
);
}
}
ValueNotifier
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44class _MyHomePageState extends State<MyHomePage> {
final _colorNotifier = ValueNotifier<Color>(Colors.grey);
Random _random = new Random();
void _onPressed() {
int randomNumber = _random.nextInt(30);
_colorNotifier.value =
Colors.primaries[randomNumber % Colors.primaries.length];
}
void dispose() {
_colorNotifier.dispose();
super.dispose();
}
Widget build(BuildContext context) {
print('building `MyHomePage`');
return Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: _onPressed,
child: Icon(Icons.colorize),
),
body: Stack(
children: [
Positioned.fill(
child: BackgroundWidget(),
),
Center(
child: ValueListenableBuilder(
valueListenable: _colorNotifier,
builder: (_, value, __) => Container(
height: 150,
width: 150,
color: value,
),
),
),
],
),
);
}
}使用const修饰stateless widget，set state不会重复刷新
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12class BackgroundWidget extends StatelessWidget {
const BackgroundWidget();
Widget build(BuildContext context) {
print('building `BackgroundWidget`');
return Image.network(
'https://cdn.pixabay.com/photo/2017/08/30/01/05/milky-way-2695569_960_720.jpg',
fit: BoxFit.cover,
);
}
}
生成列表的时候使用itemExtent属性告诉系统item高度，更高效的滑动
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35class MyHomePage extends StatelessWidget {
final widgets = List.generate(
10000,
(index) => Container(
color: Colors.primaries[index % Colors.primaries.length],
child: ListTile(
title: Text('Index: $index'),
),
),
);
final _scrollController = ScrollController();
void _onPressed() async {
_scrollController.jumpTo(
_scrollController.position.maxScrollExtent,
);
}
Widget build(BuildContext context) {
return Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: _onPressed,
splashColor: Colors.red,
child: Icon(Icons.slow_motion_video),
),
body: ListView(
controller: _scrollController,
children: widgets,
itemExtent: 200,
),
);
}
}
需要动画的子控件设置给AnimatedBuilder的child，避免重复绘制
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Widget build(BuildContext context) {
return Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: _onPressed,
splashColor: Colors.red,
child: Icon(Icons.slow_motion_video),
),
body: AnimatedBuilder(
animation: _controller,
child: CounterWidget(
counter: counter,
),
builder: (_, child) => Transform(
alignment: Alignment.center,
transform: Matrix4.identity()
..setEntry(3, 2, 0.001)
..rotateY(360 * _controller.value * (pi / 180.0)),
child: child,
),
),
);
}
合理使用opacity属性，减少调用setlayer方法，触发离屏渲染
使用fadeTransition
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47class _MyHomePageState extends State<MyHomePage>
with SingleTickerProviderStateMixin {
AnimationController _controller;
int counter = 0;
void _onPressed() {
setState(() {
counter++;
});
_controller.forward(from: 0.0);
}
void initState() {
_controller = AnimationController(
vsync: this, duration: const Duration(milliseconds: 600));
_controller.addStatusListener((status) {
if (status == AnimationStatus.completed) {
_controller.reverse();
}
});
super.initState();
}
void dispose() {
_controller.dispose();
super.dispose();
}
Widget build(BuildContext context) {
return Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: _onPressed,
splashColor: Colors.red,
child: Icon(Icons.slow_motion_video),
),
body: FadeTransition(
opacity: Tween(begin: 1.0, end: 0.0).animate(_controller),
child: CounterWidget(
counter: counter,
),
),
);
}
}
使用animatedOpacity
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35const duration = const Duration(milliseconds: 600);
class _MyHomePageState extends State<MyHomePage> {
int counter = 0;
double opacity = 1.0;
void _onPressed() async {
counter++;
setState(() {
opacity = 0.0;
});
await Future.delayed(duration);
setState(() {
opacity = 1.0;
});
}
Widget build(BuildContext context) {
return Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: _onPressed,
splashColor: Colors.red,
child: Icon(Icons.slow_motion_video),
),
body: AnimatedOpacity(
opacity: opacity,
duration: duration,
child: CounterWidget(
counter: counter,
),
),
);
}
}
完。
sources:
flutter安卓release包代码无法执行
问题描述：
flutter工程打包apk文件后
1 | try { |
这段代码无法执行
原因分析
经过咨询，安卓release包会代码混淆，使用反射会让代码无法精确匹配
解决:
- 使用反射的类不参与混淆，降低安全性
- 不使用反射，改用if判断或者switch case
2.https://blog.csdn.net/guohesheng/article/details/53696652
3.https://www.jianshu.com/p/b5b2a5dfaaf4
感谢王志浩同学提供帮助！
flutter App optimization
avoid costly work in build() since build() can be invoked frequently when ancestor Widgets rebuild
avoid calling setState() high up in the tree
Use the lazy methods, with callbacks,when building large grids or lists, that way only the visible portion of the screen is built at startup time
avoid invoke saveLayer(),including
- opacity widget
- shaderMask
- colorFilter
- Clip
- Text
- addition:Clipping doesn’t call saveLayer() but is still costly
Ways to avoid calls to saveLayer():
- To implement fading in an image, consider using the FadeInImage
- using the border Radius property instead of applying a clipping rectangle
build and display frames in 16ms
build subtree widget once and pass it as a child to the AnimatedBuilder
pre-clip image before animating it
avoid using constructors with a concrete List of children if most of the children are not visible on screen
source:https://flutter.dev/docs/perf/rendering/best-practices
new words
ratify
[ˈrætɪfaɪ]
verb
1 | to make a written agreement official by signing it |
We hope that the republics will be willing to ratify the treaty.
instantaneous
/ˌɪnstənˈteɪniəs◂/
adj
1 | happening immediately |
modern methods of instantaneous communication
aid
/eɪd/
noun
1 | something such as a machine or tool that helps someone do something |
A video is a useful aid in the classroom
relay
/ˈriːleɪ/
verb
1 | to pass a message from one person to another |
relay something to somebody
semaphore
/ˈseməfɔː $ -fɔːr/
noun
1 | a system of sending messages useing two flags,which you hold in different positions to represent letters and numbers |
circuit
/ˈsɜːkɪt/
noun
1 | a path that forms a circle around an area |
we did a circuit of the old city
magnetism
/ˈmæɡnɪtɪzəm/
noun
1 | the physical force that makes two metal objects pull toward each other or push each other apart |
personal magnetism
squiggle
/ˈskwɪɡəl/
noun
1 | a line with irregular curves |
Shorthand just looks like a series of funny squiggles to me
paradigm
/ˈpærədaɪm/
noun
1 | a very clear example of something |
the basic paradigm of the family tree
patent
/ˈpeɪtnt/
noun
1 | a special document that gives you the right to make or sell a new invention or product that no one else is allowed to copy |
The drugs are protected by patent
refer
/rɪˈfɜː $ -ɜːr/
verb
1 | 1.to mention about something |
We agreed never to refer to the matter again.
to be continued
flutter无法访问另一个类的全局变量
错误描述:在A类访问B类里的static 变量，永远是初始值，即使已经设置过新值
解决办法：A类import B类头文件时使用绝对路径，不使用系统默认
1 | //错误 |
B类结构
1 | class AppHelper { |
新词：
1 | toy around |
flutter NoMethodError - undefined method `size' for nil:NilClass错误排查
错误描述: pod install时发生错误
1 | ## Error |
解决办法：在flutter目录运行以下命令
1 | flutter clean |