技術標籤：Dartdart

一 概述

• Dart中的異常
• Dart中的異常處理

二 Dart中的異常

2.1 說明

• Dart使用throw關鍵字丟擲異常
• throw(“異常”)或throw “異常”

2.2 程式碼示例

main() {
  var a = -1;
  if (a < 0) {
    throw "異常";
  }
}

列印：

Unhandled exception:
異常
#0      main (file:///D:/Code/Dart/DartWhile/src/exception/MainException.dart:4:5)
#1      _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:283:19)
#2      _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)
 

三 Dart中的異常處理

3.1 異常處理說明

當使用try處理異常語句時，顯示下列內容(try後可接：on/catch/finally)

A try block must be followed by an 'on', 'catch', or 'finally' clause. 
Try adding either a catch or finally clause, or remove the try statement.

3.2 try…on

main() {
  var a = -1;
  try {
    if (a < 0) {
      throw ("異常");
    }
  } on int {
    print("捕獲了整數型別的異常");
  } on String {
    print("捕獲了字串型別的異常");
  }
  print("程式完成");
}
 

3.3 try…catch

main() {
  var a = -1;
  try {
    if (a < 0) {
      throw ("異常");
    }
  } catch(ex) {
    print("捕獲了異常:$ex");
  }
  print("程式完成");
}

3.4 try…catch…finally

main() {
  var a = -1;
  try {
    if (a < 0) {
      throw ("異常");
    }
  } catch (ex) {
    print("捕獲了異常:$ex");
  } finally {
    print("異常處理結束");
  }
  print("程式完成");
}