NSMutableOrderedSet到NSMutableArray(NSMutableOrderedSet to NSMutableArray)

 该字符串资源在Material Design支持库中定义。 
 
 由于您没有使用Material Design支持库中的CoordinatorLayout ，因此您应该能够安全地移除app:layout_behavior属性。 它可能是从其他代码中剪切和粘贴的。 
 
 注意：如果您实际使用CoordinatorLayout并希望协作滚动行为起作用，则需要将最新版本的Material Design Support库的依赖项添加到您的Gradle构建文件中： 
 
compile 'com.android.support:design:23.0.1'
 
 
 更新：请注意，使用Gradle的最新版本， compile配置已被弃用，以支持implementation和api配置，因此您的依赖关系可能如下所示： 
 
implementation 'com.android.support:design:27.0.2'
 
 这只是一个例子; 在阅读本文时，版本号可能会过时，因此请确保您的版本与您要使用的支持库的版本相匹配。 
 
 更多信息： 在Gradle中实现和编译有什么区别 

That string resource is defined within the Material Design support library.
 
Since you're not using the CoordinatorLayout from the Material Design support library, you should be able to safely remove the app:layout_behavior attribute. It was probably cut & paste from other code.
 
NOTE: If you are actually using CoordinatorLayout and want the cooperative scrolling behaviors to work, you need to add the dependency for the latest version of the Material Design Support library to your Gradle build file:
 
compile 'com.android.support:design:23.0.1'
 
 
UPDATE: Note that with the latest versions of Gradle the compile configuration has been deprecated in favor of implementation and api configurations so your dependency could look like this:
 
implementation 'com.android.support:design:27.0.2'
 
This is only an example; the version numbers may be out of date when you read this, so make sure your version matches the version of the support library that you want to use.
 
For more info: What's the difference between implementation and compile in gradle