项目中NonNull、Nullable等类无法解析，求定位修复方案

Hey there, let's work through this issue together. Those unresolved symbols (NonNull, Nullable, looperProto, Slog, ProtoOutputStream) usually stem from a few common issues, especially given your current dependency setup with Android Support Libraries. Here's how to fix them step by step:

1. Resolve NonNull/Nullable Annotation Issues #

These are Android's null-safety annotations, which are typically included with the AppCompat library, but sometimes need explicit setup:

• Add the support annotations dependency to your module-level build.gradle to ensure the annotations are available:

  implementation 'com.android.support:support-annotations:27.1.1'
  

• After adding the dependency, sync your project with Gradle files (File > Sync Project with Gradle Files) and try a clean rebuild (Build > Clean Project > Rebuild Project). This often fixes annotation resolution glitches.

2. Fix looperProto, Slog, and ProtoOutputStream Errors #

These symbols relate to Android system internals or Protocol Buffers (ProtoBuf) functionality. Here's how to address each scenario:

For Slog #

Slog is part of the Android SDK's android.util package. If it's unresolved, check your SDK version alignment:

• Ensure your module-level build.gradle has compileSdkVersion and targetSdkVersion set to 27 (matching your Support Library version):

  android {
      compileSdkVersion 27
      defaultConfig {
          targetSdkVersion 27
          // ... other configs
      }
  }
  

For ProtoOutputStream and looperProto #

These are tied to Protocol Buffers and system-level proto definitions:

• If your project uses ProtoBuf, add the official Google ProtoBuf dependencies to your module-level build.gradle:

  implementation 'com.google.protobuf:protobuf-java:3.24.4'
  implementation 'com.google.protobuf:protobuf-android:3.24.4'
  

• If you're accidentally referencing hidden system APIs (common if you copied code from internal Android sources), you can temporarily bypass the restriction by adding these lines to your gradle.properties file (note: this is a workaround, not a long-term solution):

  android.useDeprecatedNdk=true
  android.enableJetifier=false
  

3. Track Down the Root Cause of the Unexpected Change #

Since you're unsure which modification triggered the error, try these debugging steps:

• Use your version control tool (like Git) to review recent commits, focusing on changes to build.gradle files, added dependencies, or new code that references these symbols.
• Roll back to the last working commit, then reapply your changes one by one to identify which update broke the build.
• Clear Android Studio's cache: Go to File > Invalidate Caches... > Invalidate and Restart—this fixes many IDE-specific resolution bugs.

内容的提问来源于stack exchange，提问作者Marvin.H