iOS

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：

算法

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

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//字符串分成数组
NSMutableArray *convertStringToArray(NSString *str){
    NSMutableArray *marr = [NSMutableArray array];
    for (NSInteger i = 0; i < str.length; i++) {
        [marr addObject:[str substringWithRange:NSMakeRange(i, 1)]];
    }
    return marr;
}

//数组拼成字符串
NSString *convertArrayToString(NSArray *arr){
    NSMutableString *mstr = [NSMutableString string];
    for (NSString *str in arr) {
        [mstr appendString:str];
    }
    return mstr;
}

//冒泡排序 从小到大
NSString *bubbleSort(NSString *str){
    NSArray *sortedArray = convertStringToArray(str);
    NSMutableArray *marr = [NSMutableArray arrayWithArray:sortedArray];
    //最后一位的索引
    unsigned long j = marr.count-1;
    for (;j>0;j--) {
      
        BOOL didSort = NO;
        //第一轮结束
        for (int i=0; i<j; i++) {
            NSString *pre = marr[i];
            NSString *next = marr[i+1];
            if (pre.integerValue > next.integerValue) {
                [marr exchangeObjectAtIndex:i+1 withObjectAtIndex:i];
                didSort = YES;
            }
        }
        
        if (!didSort) {
            break;
        }
    }
    
    NSMutableString *mstr = [NSMutableString string];
    for (NSString *str in marr) {
        [mstr appendString:str];
    }
    return  mstr;
    
}


NSString *findNextLargerNum(NSString *oriNum){
    NSString *resultStr = oriNum;
    NSMutableArray *oriNumMArr =[NSMutableArray arrayWithArray:convertStringToArray(oriNum)];
    
    for (int j = oriNumMArr.count-1; j>0; j--) {
        
        BOOL getResult = NO;
        NSString *last = oriNumMArr[j];
        for (int i = j-1; i>=0; i--) {
            NSString *pre = oriNumMArr[i];
            if (last.integerValue > pre.integerValue) {
                 [oriNumMArr exchangeObjectAtIndex:i withObjectAtIndex:j];
                NSRange range = NSMakeRange(i+1, oriNumMArr.count - 1 - i);
                NSString *surfixStr = convertArrayToString([oriNumMArr subarrayWithRange:range]);
                NSString *surResultStr = bubbleSort(surfixStr);
                NSString *preStr = convertArrayToString([oriNumMArr subarrayWithRange:NSMakeRange(0,i+1)]);
                resultStr = [NSString stringWithFormat:@"%@%@",preStr,surResultStr];
                getResult = YES;
                break;
            }
        }
        
        
        if (getResult) {
            break;
        }
        
    }
    return resultStr;
}
使用：
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NSString *str = findNextLargerNum(@"8976");
NSLog(@"======%@",str);
//打印结果
======9678
flutter

flutter App 优化实操

  • 抽取widget，尽量成为一个stateless widget

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    class MainWidget extends StatelessWidget {
      @override
      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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      //------ 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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    class _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];
      }

      @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: 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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    class BackgroundWidget extends StatelessWidget {
      const BackgroundWidget();

      @override
      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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    class 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,
        );
      }

      @override
      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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    @override
      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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      class _MyHomePageState extends State<MyHomePage>
          with SingleTickerProviderStateMixin {
        AnimationController _controller;
        int counter = 0;

        void _onPressed() {
          setState(() {
            counter++;
          });
          _controller.forward(from: 0.0);
        }

        @override
        void initState() {
          _controller = AnimationController(
              vsync: this, duration: const Duration(milliseconds: 600));
          _controller.addStatusListener((status) {
            if (status == AnimationStatus.completed) {
              _controller.reverse();
            }
          });
          super.initState();
        }

        @override
        void dispose() {
          _controller.dispose();
          super.dispose();
        }

        @override
        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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    const 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;
        });
      }

      @override
      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

flutter安卓release包代码无法执行

问题描述：

flutter工程打包apk文件后

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try {
    val method = javaClass.getDeclaredMethod(call.method, MethodCall::class.java, MethodChannel.Result::class.java)
    method.invoke(this, call, result)
} catch (e: NoSuchMethodException) {
    e.printStackTrace()
} catch (e: IllegalAccessException) {
    e.printStackTrace()
} catch (e: InvocationTargetException) {
    e.printStackTrace()
}

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

参考：1. https://stackoverflow.com/questions/41525867/reflection-not-working-on-android-release-apk-even-with-proguard-minify-disable

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

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

English

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

image

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

image

relay

/ˈriːleɪ/

verb

1
to pass a message from one person to another

relay something to somebody

image

semaphore

/ˈseməfɔː $ -fɔːr/

noun

1
a system of sending messages useing two flags,which you hold in different positions to represent letters and numbers

image

circuit

/ˈsɜːkɪt/

noun

1
a path that forms a circle around an area

we did a circuit of the old city

image

magnetism

/ˈmæɡnɪtɪzəm/

noun

1
the physical force that makes two metal objects pull toward each other or push each other apart

personal magnetism

image

squiggle

/ˈskwɪɡəl/

noun

1
a line with irregular curves

Shorthand just looks like a series of funny squiggles to me

image

paradigm

/ˈpærədaɪm/

noun

1
a very clear example of something

the basic paradigm of the family tree

image

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

image

to be continued

flutter

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

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//错误
import 'package:xxx_app/utils/app_helper.dart';
//正确
import '../utils/app_helper.dart';

B类结构

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class AppHelper {
  static String name = "";
  
  someFunction(){
    name = "testName";
  }
}

参考：https://stackoverflow.com/questions/45772318/flutter-dart-static-variables-lost-keep-getting-reinitialized

新词：

1
toy around
flutter

flutter NoMethodError - undefined method `size' for nil:NilClass错误排查

错误描述: pod install时发生错误

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### Error

​```
NoMethodError - undefined method `size' for nil:NilClass
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/macho_file.rb:455:in `populate_mach_header'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/macho_file.rb:233:in `populate_fields'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/macho_file.rb:55:in `initialize_from_bin'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/macho_file.rb:33:in `new_from_bin'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/fat_file.rb:365:in `block in populate_machos'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/fat_file.rb:364:in `each'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/fat_file.rb:364:in `populate_machos'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/fat_file.rb:156:in `populate_fields'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/fat_file.rb:95:in `initialize'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho.rb:31:in `new'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho.rb:31:in `open'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/xcode/linkage_analyzer.rb:16:in `dynamic_binary?'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/sandbox/file_accessor.rb:171:in `block in vendored_dynamic_frameworks'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/sandbox/file_accessor.rb:170:in `select'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/sandbox/file_accessor.rb:170:in `vendored_dynamic_frameworks'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/sandbox/file_accessor.rb:179:in `vendored_static_frameworks'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/sandbox/file_accessor.rb:292:in `vendored_static_artifacts'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/installer/xcode/target_validator.rb:82:in `each'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/installer/xcode/target_validator.rb:82:in `flat_map'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/installer/xcode/target_validator.rb:82:in `block (2 levels) in verify_no_static_framework_transitive_dependencies'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/installer/xcode/target_validator.rb:74:in `each_key'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/installer/xcode/target_validator.rb:74:in `block in verify_no_static_framework_transitive_dependencies'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/installer/xcode/target_validator.rb:73:in `each'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/installer/xcode/target_validator.rb:73:in `verify_no_static_framework_transitive_dependencies'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/installer/xcode/target_validator.rb:38:in `validate!'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/installer.rb:595:in `validate_targets'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/installer.rb:162:in `install!'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/command/install.rb:52:in `run'
/Library/Ruby/Gems/2.6.0/gems/claide-1.0.3/lib/claide/command.rb:334:in `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/lib/cocoapods/command.rb:52:in `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.0/bin/pod:55:in `<top (required)>'
/usr/local/bin/pod:23:in `load'
/usr/local/bin/pod:23:in `<main>'
​```

――― TEMPLATE END ――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

[!] Oh no, an error occurred.

Search for existing GitHub issues similar to yours:
https://github.com/CocoaPods/CocoaPods/search?q=undefined+method+%60size%27+for+nil%3ANilClass&type=Issues

If none exists, create a ticket, with the template displayed above, on:
https://github.com/CocoaPods/CocoaPods/issues/new

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https://github.com/CocoaPods/CocoaPods/blob/master/CONTRIBUTING.md

Don't forget to anonymize any private data!

Looking for related issues on cocoapods/cocoapods...
 -  NoMethodError - undefined method `size' for nil:NilClass
   https://github.com/CocoaPods/CocoaPods/issues/10426 [closed] [3 comments]
   a week ago

 - NoMethodError - undefined method `size' for nil:NilClass
   https://github.com/CocoaPods/CocoaPods/issues/10273 [closed] [3 comments]
   7 weeks ago

 - NoMethodError - undefined method `size' for nil:NilClass
   https://github.com/CocoaPods/CocoaPods/issues/8377 [closed] [24 comments]
   a week ago

and 8 more at:
https://github.com/cocoapods/cocoapods/search?q=undefined%20method%20%60size%27%20for%20nil&type=Issues&utf8=✓

解决办法：在flutter目录运行以下命令

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flutter clean
rm -Rf ios/Pods
rm -Rf ios/.symlinks
rm -Rf ios/Flutter/Flutter.framework
rm -Rf ios/Flutter/Flutter.podspec

参考：https://github.com/CocoaPods/CocoaPods/issues/8377

iOS

framework not found

问题：在build的时候framework not found

解决：

  • 添加需要的framework
  • 确定framework齐全的情况下，就是系统添加了冗余的framework编译需求，找到require列表删除即可
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project.xcodeproj文件--->显示包内容--->project.pbxproj文件 全局查找删除

ps:版本对不上处理方法同理，修改版本号和实际pods下载过来一致

计算机

hexo部署文章到github 443问题

问题：

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fatal: unable to access 'https://github.com/xxx/xxx.github.io.git/': LibreSSL SSL_connect: SSL_ERROR_SYSCALL in connection to github.com:443 
FATAL {
  err: Error: Spawn failed
      at ChildProcess.<anonymous> (/Users/kevin/Desktop/xxx.github.io/node_modules/hexo-deployer-git/node_modules/hexo-util/lib/spawn.js:51:21)
      at ChildProcess.emit (events.js:315:20)
      at Process.ChildProcess._handle.onexit (internal/child_process.js:277:12) {
    code: 128
  }
} Something's wrong. Maybe you can find the solution here: %s https://hexo.io/docs/troubleshooting.html

解决：在_config.yml文件里把deploy的地址从http换成git

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deploy:
  type: git
  #repo: https://github.com/xxx/xxx.github.io.git
  repo: git@github.com:xxx/xxx.github.io.git
  branch: master