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Flutter采坑记录

Flutter采坑记录

作者: 翀鹰精灵 | 来源:发表于2020-09-14 18:19 被阅读0次
在 Flutter 开发中遇到的一些 BUG，避免遗忘，记录一下，如果正在看文章的你也遇到了，那激动的心,颤抖的手，咱们可以握个手。

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
解决方案
2.png

将minsdk提升到19以上

2.flutter打包出来界面空白
这个问题，困扰我两三天了，网上找了千万种方法，无非以下三种情况:
① 升级到flutter SDK stable版本
② flutter clean 并且 flutter build ios --release，最后archive
③更换bundleId
但是都没有卵用
最终我的原因是因为这个界面log有个如下的输出error信息
Incorrect use of ParentDataWidget.
出现这个错误的原因主要是因为Expanded嵌套Column出错了，如下面截图所示：

001.png

解决掉这个错误，打包白屏问题即解决，困扰了两天的问题终于解决了。
Incorrect use of ParentDataWidget

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

这个错误的原因主要是因为当前的widget的context是null

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

当前界面如果有类似(context)代码，好好检查下(context)是否为空。

4.Failed assertion: line 826 pos 14: 'file != null': is not true.
这个问题，我是在拍照选择的时候出现的，模拟器中点击拍照功能，因为模拟器没有摄像头，所以报错，主要原因还是因为代码不严谨的缘故,造成image == null.

原代码为：

  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);
    });
  }

修改后代码为：

    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("模拟器不支持相机！");
    }
  }

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

这个错误，主要是因为模型为空，然后取值模型中的字段造成的，或者是因为字段类型不匹配，需要仔细检查，别无它发。

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

比如说这种情况，如果userModel是null，后面使用了userModel.user.id则会报这种错误。

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

01.png

这种错误一般是因为Row里面为空造成的，比如项目开发中以下代码就出现过相同的错误：

02.png
03.png
上面虽然调用了_buildBottomItem方法，但是这个方法内部并没有返回一个widget，所以就报了上述的错误。
修改方法很简单，直接在_buildBottomItem方法中return Container();即可解决。 
 //解决方法：
 Widget _buildBottomItem(BottomItemType type) {
 // 写自己的业务逻辑，或return一个默认的Container()
   return Container();
 }

7.Failed assertion: line 110 pos 12: '_positions.isNotEmpty'
如下图所示：

03.png
项目中我的主要是因为在SingleChildScrollView里面嵌套了Swiper，,进行swiper count 判断，如果数量为空则不显示，数量不为空在显示 if (null == _swipers || _swipers.isEmpty)
我的解决方案如下
04.png 05.png

8. Looking up a deactivated widget's ancestor is unsafe.
该问题是点击返回的时候报错，意思是不是安全的引用小部件，就是已经销毁的界面然后重复销毁，会爆如下错误，错误信息如下：

06.PNG
根据控制台的错误信息，可以定位到是dispose方法报错了，将FocusScope.of(context).requestFocus(blankFocus);注释掉即可解决。

9.RangeError (index): Invalid value: Only valid value is 0: 1
这个报错主要是因为在创建ListView视图时,漏写itemCount，或者itemCount==null造成的。

10.
The getter 'length' was called on null.
Receiver: null
Tried calling: length
这个报错主要是因为某个字段为空造成的，可能数组空，可能走个字段空，都会引起该问题，一定要仔细排查每个字段，别无他法，同时代码写的要健壮一些，不要碰到null就直接抛错误了。

例：项目中遇到的报错情况如下：

07.png
所以代码需要改为如下,即可消除掉这个报错。
child:Text(formatTime(widget.question.time??""),
style: TextStyle(fontSize: 11,color: infoColor,),),

11. Failed assertion: line 236 pos 16: 'controller != null': is not true.
这个bug是因为用了SmartRefresher控件，但是并没有写controller造成的，如下列所示的错误写法：

   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(),
        );

正确的写法应该是必须有 controller: _refreshController.

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

详细错误信息如下：

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
这个问题不是flutter代码的问题，最主要原因可能是本地缓存的Git库的账号名和密码账号有问题，参考之前 HTTP Basic: Access denied fatal: Authentication failed...文章的处理方案即可解决。

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文件中将这段代码，替换为下面这段：

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
将Build Settings最后一行的VALID_ARCHS这一行删除，以为这里么没有支持模拟器。

09.png

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

10.png

网上查阅很多资料，包括Stack Overflow说的都是clean，方案有多种，如下：

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

网上方案二

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

网上方案三：
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

网上方案四：
解决方法在as的Terminal里面
1.保证在下面根目录下执行下面: flutter clean
2.然后cd到ios目录执行下面: cd iOS
3.最后执行这一步: pod install
4.运行ios模拟器

网上方案五：
1、关闭Xcode，打开终端：
2、进入DerivedData目录
cd ~/Library/Developer/Xcode/DerivedData/
3、然后再终端执行：
xattr -rc .
4、再运行flutter项目，完美解决

但是网上方案千千万，没有一个解决了我的问题，最后我的方案是：
将本地所有的库全部删除，重新pub get新的库，即可解决问题，这个可能是库缓存错乱了，出现的错误。
解决步骤如下：

11.png 12.png
13.png
14.png

至此，这个问题成功解决，耗费了我两天的时长，都是泪~😭

bug 持续采坑中....

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