List<Attachment> 无效值：唯一有效值为 0:1

Question

我有 3 个按钮，当用户单击它时，他们会拍照，并且长按 photo.And 的预览中的按钮会发生变化，图片会被删除并替换为第一个按钮。当我尝试删除照片时出现以下错误：

Unhandled Exception: RangeError (index): Invalid value: Only valid value is 0: 1
E/flutter ( 4122): #0      List.[] (dart:core-patch/growable_array.dart:146:60)
E/flutter ( 4122): #1      _HomePageNoticeProblemState.removePicture.<anonymous closure> (package:flutterapperadauti/notice_a_problem/main_page.dart:117:23)
E/flutter ( 4122): #2      State.setState (package:flutter/src/widgets/framework.dart:1233:30)
E/flutter ( 4122): #3      _HomePageNoticeProblemState.removePicture (package:flutterapperadauti/notice_a_problem/main_page.dart:113:5)
E/flutter ( 4122): #4      _HomePageNoticeProblemState.build.<anonymous closure> (package:flutterapperadauti/notice_a_problem/main_page.dart:509:23)
E/flutter ( 4122): #5      _InkResponseState._handleLongPress (package:flutter/src/material/ink_well.dart:805:25)
E/flutter ( 4122): #6      _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:865:61)
E/flutter ( 4122): #7      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24)
E/flutter ( 4122): #8      LongPressGestureRecognizer._checkLongPressStart (package:flutter/src/gestures/long_press.dart:304:7)
E/flutter ( 4122): #9      LongPressGestureRecognizer.didExceedDeadline (package:flutter/src/gestures/long_press.dart:253:5)
E/flutter ( 4122): #10     PrimaryPointerGestureRecognizer.didExceedDeadlineWithEvent (package:flutter/src/gestures/recognizer.dart:501:5)
E/flutter ( 4122): #11     PrimaryPointerGestureRecognizer.addAllowedPointer.<anonymous closure> (package:flutter/src/gestures/recognizer.dart:454:40)
E/flutter ( 4122): #12     _rootRun (dart:async/zone.dart:1180:38)
E/flutter ( 4122): #13     _CustomZone.run (dart:async/zone.dart:1077:19)
E/flutter ( 4122): #14     _CustomZone.runGuarded (dart:async/zone.dart:979:7)
E/flutter ( 4122): #15     _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1019:23)
E/flutter ( 4122): #16     _rootRun (dart:async/zone.dart:1184:13)
E/flutter ( 4122): #17     _CustomZone.run (dart:async/zone.dart:1077:19)
E/flutter ( 4122): #18     _CustomZone.bindCallback.<anonymous closure> (dart:async/zone.dart:1003:23)
E/flutter ( 4122): #19     Timer._createTimer.<anonymous closure> (dart:async-patch/timer_patch.dart:23:15)
E/flutter ( 4122): #20     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:398:19)
E/flutter ( 4122): #21     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:429:5)
E/flutter ( 4122): #22     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)
E/flutter ( 4122):

这一行：if(attachments[1] != null) {

我的列表是附件类型

我的删除图片代码：

void removePicture(int i) async {
setState(() {
  if(i==1) {
    attachments.removeAt(0);
    recordedImage1 = null;
    if(attachments[1] != null) {
      attachments[0] = attachments[1];
      recordedImage1 = recordedImage2;
    }
    if(attachments[2] != null) {
      attachments[1] = attachments[2];
      recordedImage2 = recordedImage3;
      recordedImage3 = null;
    }
  }
  if(i==2) {
    recordedImage2 = null;
    attachments.removeAt(1);
    if(attachments[2] != null) {
      attachments[1] = attachments[2];
      recordedImage2 = recordedImage3;
      recordedImage3 = null;
    }
  }
  if(i==3) {
    attachments.removeAt(2);
    recordedImage3 = null;
  }
});

}

而且我观察到图片实际上被删除了（如果我点击另一个按钮拍照，它将被一张新图片替换）但是如果用户不拍摄另一张照片，该按钮将不会更新。

如果我长按第一张图片我得到错误但是如果我按下最后一个按钮并制作一张新图片，新图片将替换第一张图片（因为它已被删除）

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Answer 1

我认为这更像是一种评论，但根据我的声誉，我不能这样做。这是我认为正在发生的事情：

您有这条指令：attachments.removeAt(0); 删除列表中的第一个元素，就在您检查 attachments[1] 中的值之前。

我认为您应该检查数组的长度或在删除值时使用 attachements[i] = null。

List<Attachment> 无效值：唯一有效值为 0:1

List<Attachment> Invalid value: Only valid value is 0: 1

image

attachment

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