【移动应用开发技术】如何在Flutter中捕获错误

【移动应用开发技术】如何在Flutter中捕获错误

这期内容当中在下将会给大家带来有关如何在Flutter中捕获错误，文章内容丰富且以专业的角度为大家分析和叙述，阅读完这篇文章希望大家可以有所收获。Demo初始状态首先我们新建Flutter项目，修改main.dart代码如下：import

'package:flutter/material.dart';

void

main()

=>

runApp(MyApp());

class

MyApp

extends

StatelessWidget

{

//

This

widget

is

the

root

of

your

application.

@override

Widget

build(BuildContext

context)

{

return

MaterialApp(

home:

Scaffold(

appBar:

AppBar(title:

Text('Flutter

Crash

Capture'),),

body:

MyHomePage(),

),

);

}

}

class

MyHomePage

extends

StatelessWidget

{

@override

Widget

build(BuildContext

context)

{

return

Container();

}

}效果如下：捕获错误我们修改MyHomePage，添加一个List然后进行越界访问，改动部分代码如下：class

MyHomePage

extends

StatelessWidget

{

@override

Widget

build(BuildContext

context)

{

List<String>

numList

=

['1',

'2'];

print(numList[6]);

return

Container();

}

}可以看到控制台报错如下：flutter:══╡EXCEPTIONCAUGHTBYWIDGETSLIBRARY╞═══════════════════════════════════════════════════════════flutter:ThefollowingRangeErrorwasthrownbuildingMyHomePage(dirty):flutter:RangeError(index):Invalidvalue:Notinrange0..1,inclusive:6flutter:══╡EXCEPTIONCAUGHTBYWIDGETSLIBRARY╞═══════════════════════════════════════════════════════════flutter:ThefollowingRangeErrorwasthrownbuildingMyHomePage(dirty):flutter:RangeError(index):Invalidvalue:Notinrange0..1,inclusive:6当然这些错误信息在界面上也有显示（debug模式）。那么我们如何捕获呢？其实很简单，有个通用模板，模板为：import

'dart:async';

import

'package:flutter/material.dart';

Future<Null>

main()

async

{

FlutterError.onError

=

(FlutterErrorDetails

details)

async

{

Zone.current.handleUncaughtError(details.exception,

details.stack);

};

runZoned<Future<void>>(()

async

{

runApp(MyApp());

},

onError:

(error,

stackTrace)

async

{

await

_reportError(error,

stackTrace);

});

}

Future<Null>

_reportError(dynamic

error,

dynamic

stackTrace)

async

{

//

TODO

}在TODO里面就可以执行埋点上报操作或者其他处理了。完整例子如下：import

'dart:async';

import

'package:flutter/material.dart';

Future<Null>

main()

async

{

FlutterError.onError

=

(FlutterErrorDetails

details)

async

{

Zone.current.handleUncaughtError(details.exception,

details.stack);

};

runZoned<Future<void>>(()

async

{

runApp(MyApp());

},

onError:

(error,

stackTrace)

async

{

await

_reportError(error,

stackTrace);

});

}

Future<Null>

_reportError(dynamic

error,

dynamic

stackTrace)

async

{

print('catch

error='+error);

}

class

MyApp

extends

StatelessWidget

{

//

This

widget

is

the

root

of

your

application.

@override

Widget

build(BuildContext

context)

{

return

MaterialApp(

home:

Scaffold(

appBar:

AppBar(title:

Text('Flutter

Crash

Capture'),),

body:

MyHomePage(),

),

);

}

}

class

MyHomePage

extends

StatelessWidget

{

@override

Widget

build(BuildContext

context)

{

List<String>

numList

=

['1',

'2'];

print(numList[6]);

return

Container();

}

}运行可以看到控制台捕获到错误如下：flutter:catcherror=RangeError(index):Invalidvalue:Notinrange0..1,inclusive:6flutter:catcherror=RangeError(index):Invalidvalue:Notinrange0..1,inclusive:6assert妙用我们知道，一般错误上报都是在打包发布到市场后才需要。平时调试的时候如果遇到错误，我们是会定位问题并修复的。因此在debug模式下，我们不希望上报错误，而是希望直接打印到控制台。那么，这个时候就需要一种方式来区分现在是debug模式还是release模式，怎么区分呢？这个时候就需要用到assert了。bool

get

isInDebugMode

{

//

Assume

you're

in

production

mode.

bool

inDebugMode

=

false;

//

Assert

expressions

are

only

evaluated

during

development.

They

are

ignored

//

in

production.

Therefore,

this

code

only

sets

`inDebugMode`

to

true

//

in

a

development

environment.

assert(inDebugMode

=

true);

return

inDebugMode;

}从注释也可以知道，assert表达式只在开发环境下会起作用，在生产环境下会被忽略。因此利用这一个，我们就可以实现我们的需求。上面的结论要验证也很简单，我们就不演示了。完整模板import

'dart:async';

import

'package:flutter/material.dart';

Future<Null>

main()

async

{

FlutterError.onError

=

(FlutterErrorDetails

details)

async

{

if

(isInDebugMode)

{

FlutterError.dumpErrorToConsole(details);

}

else

{

Zone.current.handleUncaughtError(details.exception,

details.stack);

}

};

runZoned<Future<void>>(()

async

{

runApp(MyApp());

},

onError:

(error,

stackTrace)

async

{

await

_reportError(error,

stackTrace);

});

}

Future<Null>

_reportError(dynamic

error,

dynamic

stackTrace)

async

{

//

TODO

}

bool

get

isInDebugMode

{

//

Assume

you're

in

production

mode.

bool

inDebugMode

=

false;

//

Assert

exp