Android Studio添加模块后启动报错：Unable to merge dex

Hey there, let's tackle this dex merging issue you're facing after adding a new module to your Android project. I've run into this plenty of times, so here are the most common fixes that usually get things back on track:

• 排查重复依赖冲突
  This is the #1 culprit. Your new module might be pulling in a library that's already present in your main app module—often with conflicting versions. To spot this, open Android Studio's Terminal and run:

  # Mac/Linux
  ./gradlew app:dependencies
  
  # Windows
  gradlew.bat app:dependencies
  

  Scan the output for duplicate libraries (like different versions of support-v4 or okhttp). Once found, you can either align the versions across modules, or exclude the duplicate from one side. For example:

  implementation('com.example:your-library:1.0.0') {
      exclude group: 'com.android.support', module: 'support-v4'
  }
  

• 启用Multidex支持
  If your project's total method count exceeds the 65536 DEX limit, this error will pop up. To fix it, first enable Multidex in your app/build.gradle:

  android {
      defaultConfig {
          ...
          multiDexEnabled true
      }
  }
  
  dependencies {
      implementation 'com.android.support:multidex:1.0.3'
  }
  

  Then update your Application class: either make it extend MultiDexApplication, or add this override if you're using a custom Application:

  public class MyApp extends Application {
      @Override
      protected void attachBaseContext(Context base) {
          super.attachBaseContext(base);
          MultiDex.install(this);
      }
  }
  

  Don't forget to reference this class in your AndroidManifest.xml.

• 清理缓存并重建项目
  Sometimes stale build cache causes weird merging issues. Start with Build > Clean Project in Android Studio, followed by Build > Rebuild Project. If that doesn't work, manually delete the build folders from both your main app and the new module, then re-run the build.

• 验证Gradle与插件版本兼容性
  Mismatched Android Gradle Plugin and Gradle versions can break dex merging. Check your top-level build.gradle for the plugin version (e.g., com.android.tools.build:gradle:3.1.0) and make sure it's paired with a compatible Gradle version (you can update this in gradle/wrapper/gradle-wrapper.properties via the distributionUrl line).

• 统一minSdkVersion across modules
  Your new module's minSdkVersion can't be higher than your main app's—this causes dependency merging conflicts. Double-check that all modules in your project have matching (or app-compatible) minSdkVersion values in their build.gradle files.

内容的提问来源于stack exchange，提问作者Carlos Cardoso