Flutter采坑記錄

在 Flutter 開發中遇到的一些 BUG，避免遺忘，記錄一下，如果正在看文章的你也遇到了，那激動的心,顫抖的手，咱們可以握個手。

1.Suggestion:use a compatible library with a minSdk of at most 16,
or increase this project's minSdk version to at least 19，

1.png

解決方案
2.png

將minsdk提升到19以上

2.flutter打包出來界面空白
這個問題，困擾我兩三天了，網上找了千萬種方法，無非以下三種情況:
① 升級到flutter SDK stable版本
② flutter clean 并且 flutter build ios --release，最后archive
③更換bundleId
但是都沒有卵用
最終我的原因是因為這個界面log有個如下的輸出error信息
Incorrect use of ParentDataWidget.
出現這個錯誤的原因主要是因為Expanded嵌套Column出錯了，如下面截圖所示：

001.png

解決掉這個錯誤，打包白屏問題即解決，困擾了兩天的問題終于解決了。
Incorrect use of ParentDataWidget

3.Looking up a deactivated widget's ancestor is unsafe.

這個錯誤的原因主要是因為當前的widget的context是null

StyleConfig styleConfig = Provider.of<StyleConfig>(context);

當前界面如果有類似(context)代碼，好好檢查下(context)是否為空。

4.Failed assertion: line 826 pos 14: 'file != null': is not true.
這個問題，我是在拍照選擇的時候出現的，模擬器中點擊拍照功能，因為模擬器沒有攝像頭，所以報錯，主要原因還是因為代碼不嚴謹的緣故,造成image == null.

原代碼為：

  Future getImage(bool isTakePhoto) async {
    Navigator.pop(context);
    var image = await ImagePicker.pickImage(
        source:isTakePhoto ? ImageSource.camera :ImageSource.gallery);
    setState(() {
      // _image = image;
      _images.add(image);
    });
  }

修改后代碼為：

    Navigator.pop(context);
    try {
      var image = await ImagePicker.pickImage(
          source:isTakePhoto ? ImageSource.camera :ImageSource.gallery
      );
      if (image == null) {
        return;
      } else {
        setState(() {
          // _image = image;
          _images.add(image);
        });
      }
    } catch (e) {
      print("模擬器不支持相機！");
    }
  }

5.
The getter 'id' was called on null.
Receiver: null
Tried calling: id

這個錯誤，主要是因為模型為空，然后取值模型中的字段造成的，或者是因為字段類型不匹配，需要仔細檢查，別無它發。

UserModel userModel = Provider.of<UserModel>(context, >listen: false);
print("用戶ID: ${userModel.user.id}");

比如說這種情況，如果userModel是null，后面使用了userModel.user.id則會報這種錯誤。

6. Row's children must not contain any null values, but a null value was found at index 0

01.png

這種錯誤一般是因為Row里面為空造成的，比如項目開發中以下代碼就出現過相同的錯誤：

02.png

03.png

上面雖然調用了_buildBottomItem方法，但是這個方法內部并沒有返回一個widget，所以就報了上述的錯誤。
修改方法很簡單，直接在_buildBottomItem方法中return Container();即可解決。

 //解決方法：
 Widget _buildBottomItem(BottomItemType type) {
 // 寫自己的業務邏輯，或return一個默認的Container()
   return Container();
 }

7.Failed assertion: line 110 pos 12: '_positions.isNotEmpty'
如下圖所示：

03.png

項目中我的主要是因為在SingleChildScrollView里面嵌套了Swiper，,進行swiper count 判斷，如果數量為空則不顯示，數量不為空在顯示 if (null == _swipers || _swipers.isEmpty)
我的解決方案如下
04.png

05.png

8. Looking up a deactivated widget's ancestor is unsafe.
該問題是點擊返回的時候報錯，意思是不是安全的引用小部件，就是已經銷毀的界面然后重復銷毀，會爆如下錯誤，錯誤信息如下：

06.PNG

根據控制臺的錯誤信息，可以定位到是dispose方法報錯了，將FocusScope.of(context).requestFocus(blankFocus);注釋掉即可解決。

9.RangeError (index): Invalid value: Only valid value is 0: 1
這個報錯主要是因為在創建ListView視圖時,漏寫itemCount，或者itemCount==null造成的。

10.
The getter 'length' was called on null.
Receiver: null
Tried calling: length
這個報錯主要是因為某個字段為空造成的，可能數組空，可能走個字段空，都會引起該問題，一定要仔細排查每個字段，別無他法，同時代碼寫的要健壯一些，不要碰到null就直接拋錯誤了。

例：項目中遇到的報錯情況如下：

07.png

所以代碼需要改為如下,即可消除掉這個報錯。
child:Text(formatTime(widget.question.time??""),
style: TextStyle(fontSize: 11,color: infoColor,),),

11. Failed assertion: line 236 pos 16: 'controller != null': is not true.
這個bug是因為用了SmartRefresher控件，但是并沒有寫controller造成的，如下列所示的錯誤寫法：

   return SmartRefresher(
         // controller:_refreshController,
          enableTwoLevel:false ,
          enablePullDown: true,
          header: WaterDropHeader(),
          footer: null,
          onRefresh: () async {
            await pageModel.refresh();
            pageModel.showErrorMessage(context);
          },
          onLoading: null,
          enablePullUp: false,
          child: Container(),
        );

正確的寫法應該是必須有 controller: _refreshController.

12.BUILD FAILED in 36s Exception: Gradle task assembleDebug failed with exit code 1.

詳細錯誤信息如下：

Launching lib/main.dart on V1818CT in debug mode...
Running Gradle task 'assembleDebug'...

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring root project 'android'.
> Could not resolve all artifacts for configuration ':classpath'.
   > Could not resolve com.mob.sdk:MobSDK:+.
     Required by:
         project :
      > Failed to list versions for com.mob.sdk:MobSDK.
         > Unable to load Maven meta-data from https://maven.aliyun.com/repository/public/com/mob/sdk/MobSDK/maven-metadata.xml.
            > Could not get resource 'https://maven.aliyun.com/repository/public/com/mob/sdk/MobSDK/maven-metadata.xml'.
               > Could not GET 'https://maven.aliyun.com/repository/public/com/mob/sdk/MobSDK/maven-metadata.xml'.
                  > Connect to 127.0.0.1:11085 [/127.0.0.1] failed: Connection refused (Connection refused)
      > Failed to list versions for com.mob.sdk:MobSDK.
         > Unable to load Maven meta-data from https://maven.aliyun.com/repository/jcenter/com/mob/sdk/MobSDK/maven-metadata.xml.
            > Could not get resource 'https://maven.aliyun.com/repository/jcenter/com/mob/sdk/MobSDK/maven-metadata.xml'.
               > Could not GET 'https://maven.aliyun.com/repository/jcenter/com/mob/sdk/MobSDK/maven-metadata.xml'.
                  > Connect to 127.0.0.1:11085 [/127.0.0.1] failed: Connection refused (Connection refused)
      > Failed to list versions for com.mob.sdk:MobSDK.
         > Unable to load Maven meta-data from http://maven.aliyun.com/nexus/content/groups/public/com/mob/sdk/MobSDK/maven-metadata.xml.
            > Could not get resource 'http://maven.aliyun.com/nexus/content/groups/public/com/mob/sdk/MobSDK/maven-metadata.xml'.
               > Could not GET 'http://maven.aliyun.com/nexus/content/groups/public/com/mob/sdk/MobSDK/maven-metadata.xml'.
                  > Connect to 127.0.0.1:11085 [/127.0.0.1] failed: Connection refused (Connection refused)
      > Failed to list versions for com.mob.sdk:MobSDK.
         > Unable to load Maven meta-data from http://mvn.mob.com/android/com/mob/sdk/MobSDK/maven-metadata.xml.
            > Could not get resource 'http://mvn.mob.com/android/com/mob/sdk/MobSDK/maven-metadata.xml'.
               > Could not GET 'http://mvn.mob.com/android/com/mob/sdk/MobSDK/maven-metadata.xml'.
                  > Connect to 127.0.0.1:11085 [/127.0.0.1] failed: Connection refused (Connection refused)
      > Failed to list versions for com.mob.sdk:MobSDK.
         > Unable to load Maven meta-data from https://maven.aliyun.com/repository/google/com/mob/sdk/MobSDK/maven-metadata.xml.
            > Could not get resource 'https://maven.aliyun.com/repository/google/com/mob/sdk/MobSDK/maven-metadata.xml'.
               > Could not GET 'https://maven.aliyun.com/repository/google/com/mob/sdk/MobSDK/maven-metadata.xml'.
                  > Connect to 127.0.0.1:11085 [/127.0.0.1] failed: Connection refused (Connection refused)
      > Failed to list versions for com.mob.sdk:MobSDK.
         > Unable to load Maven meta-data from https://maven.aliyun.com/repository/central/com/mob/sdk/MobSDK/maven-metadata.xml.
            > Could not get resource 'https://maven.aliyun.com/repository/central/com/mob/sdk/MobSDK/maven-metadata.xml'.
               > Could not GET 'https://maven.aliyun.com/repository/central/com/mob/sdk/MobSDK/maven-metadata.xml'.
                  > Connect to 127.0.0.1:11085 [/127.0.0.1] failed: Connection refused (Connection refused)
      > Failed to list versions for com.mob.sdk:MobSDK.
         > Unable to load Maven meta-data from http://download.flutter.io/com/mob/sdk/MobSDK/maven-metadata.xml.
            > Could not get resource 'http://download.flutter.io/com/mob/sdk/MobSDK/maven-metadata.xml'.
               > Could not GET 'http://download.flutter.io/com/mob/sdk/MobSDK/maven-metadata.xml'.
                  > Connect to 127.0.0.1:11085 [/127.0.0.1] failed: Connection refused (Connection refused)

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 36s
Exception: Gradle task assembleDebug failed with exit code 1

13. fatal：could not username for 'xxxxxx'

08.png

這個問題不是flutter代碼的問題，最主要原因可能是本地緩存的Git庫的賬號名和密碼賬號有問題，參考之前 HTTP Basic: Access denied fatal: Authentication failed...文章的處理方案即可解決。

14.versions is 9.0 to 14.0.99. (in target 'UMCCommon' from project 'Pods')
warning: The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 14.0.99. (in target 'mob_sharesdk' from project 'Pods')

Could not build the application for the simulator.
Error launching application on iPhone 11 Pro Max.

方案一：

post_install do |installer|
 installer.pods_project.targets.each do |target|
   flutter_additional_ios_build_settings(target)
 end
end

Podfile文件中將這段代碼，替換為下面這段：

post_install do |installer|
 installer.pods_project.targets.each do |target|
     target.build_configurations.each do |config|
         >config.build_settings['IPHONEOS_DEPLOYMENT_T>ARGET'] = '9.0'
     end
    flutter_additional_ios_build_settings(target)
 end
end

方案二
將Build Settings最后一行的VALID_ARCHS這一行刪除，以為這里么沒有支持模擬器。

09.png

15.Could not build the application for the simulator..
Error launching application on iPhone 11 Pro Max..

10.png

網上查閱很多資料，包括Stack Overflow說的都是clean，方案有多種，如下：

網上方案一：
Please follow these steps/run commands
flutter clean (in terminal)
flutter build (in terminal)
In Xcode, then clean project
In Xcode, then build project

網上方案二

1- Open xcode for the iOS project by clicking on Runner.xcworkspacefile located in iOS directory
2- Click Runner (on the left of the Xcode)
3- Click on Build Settings tab (in the middle of Xcode)
4- Change iOS Deployment Target to 12.1 for example
5- Save your action
6- Run flutter clean then run your app

網上方案三：
rm iOS/Podfile
Then upgrade your packages:
pub upgrade
pub run
And update your podfile:
cd ios && pod update
Then clean and run:
flutter clean && flutter run

網上方案四：
解決方法在as的Terminal里面
1.保證在下面根目錄下執行下面: flutter clean
2.然后cd到ios目錄執行下面: cd iOS
3.最后執行這一步: pod install
4.運行ios模擬器

網上方案五：
1、關閉Xcode，打開終端：
2、進入DerivedData目錄
cd ~/Library/Developer/Xcode/DerivedData/
3、然后再終端執行：
xattr -rc .
4、再運行flutter項目，完美解決

但是網上方案千千萬，沒有一個解決了我的問題，最后我的方案是：
將本地所有的庫全部刪除，重新pub get新的庫，即可解決問題，這個可能是庫緩存錯亂了，出現的錯誤。
解決步驟如下：

11.png
12.png

13.png
14.png

至此，這個問題成功解決，耗費了我兩天的時長，都是淚~??

bug 持續采坑中....
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