Flutter Dart回顾 —— 异常捕获、抛出

List testList = List();

try {

  var s = testList[3];

  //代码逻辑

} on IntegerDivisionByZeroException {

  //使用on关键字，捕获特定类型的异常

} on NoSuchMethodError catch (e) {

  //使用on关键字，捕获特定类型的异常

  //代码段可以有多个 on / catch 块来处理多个异常

} catch (error, stacktrace) {

  // 没有指定类型，处理所有错误

  //catch 最多提供两个可选参数

  //第一个参数 error 类型为 Object，也就是异常是可以抛出任意对象。

  //第二个参数 stacktrace，表示异常堆栈。

  print('Something really unknown error: $error');

  print('Something really unknown stacktrace: $stacktrace');

  throw '抛出异常关键';

  //throw 之后的代码将不会执行

  //throw new FormatException();

} finally {

  // 在throw之前先执行finally代码块
  print("this is finally");

}

class Custom_exception_Name implements Exception {

   // can contain constructors, variables and methods

}

eg:

class AmtException implements Exception {

   String errMsg() => 'Amount should be greater than zero';

}  

throw new AmtException();

Future(() {

}).then((value){

}).catchError((error, stack) {

});

Future.delayed(Duration(seconds: 1)).then((e) => Future.error("xxx"));

R runZoned<R>(R body(), {

    Map zoneValues, 

    ZoneSpecification zoneSpecification,

    Function onError,

})

runZoned<Future<void>>(() async {

  runApp(MyApp());

}, onError: (error, stackTrace) {

  // Whenever an error occurs, call the `_reportError` function. This sends

  // Dart errors to the dev console or Sentry depending on the environment.

  _reportError(error, stackTrace);

});

runZonedGuarded<Future<void>>(() async {

  runApp(MyApp());

}, (Object error, StackTrace stackTrace) {

  // Whenever an error occurs, call the `_reportError` function. This sends

  // Dart errors to the dev console or Sentry depending on the environment.

  _reportError(error, stackTrace);

});

Future<Null> main() async {

  //重写FlutterError.onError

  FlutterError.onError = (FlutterErrorDetails details) {

    if (isInDebugMode) {

      // In development mode, simply print to console.

      FlutterError.dumpErrorToConsole(details);

    } else {

      // In production mode, report to the application zone to report to

      // Sentry.

      Zone.current.handleUncaughtError(details.exception, details.stack);

    }

  };

  //使用runZonedGuarded捕获日志输出、Timer创建、微任务调度的行为、所有未处理的异常

  runZonedGuarded<Future<Null>>(

    () async {

      runApp(MyApp());

    },

    (error, stackTrace) async {

      await _reportErrorAndLog(error, stackTrace);

    },

    zoneSpecification: ZoneSpecification(

      print: (Zone self, ZoneDelegate parent, Zone zone, String line) async {

        await collectLog(line); // 收集日志

      },

    ),

  );

}

Future<Null> collectLog(String line) async {
  //收集日志
}

//上报错误和日志逻辑

Future<Null> _reportErrorAndLog(dynamic error, dynamic stackTrace) async {

  print('Caught error: $error');

  if (isInDebugMode) {

    print(stackTrace);

    print('In dev mode. Not sending report to Sentry.io.');

    return;
  }

  //TODO: response 为上传请求结果

  if (response.isSuccessful) {
    print('Success!');
  } else {
    print('Failed to report to Sentry.io: ${response}');
  }
}
//判断debug及release环境

bool get isInDebugMode {

  bool inDebugMode = false;

  assert(inDebugMode = true);

  return inDebugMode;
}