所属的包不同：

implementation 'androidx.appcompat:appcompat:1.0.2'

appcompat-1.1.0-alpha01-sources.jar/androidx/appcompat/app/AppCompatActivity.java

class AppCompatActivity extends FragmentActivity

class FragmentActivity extends ComponentActivity

class ComponentActivity extends androidx.core.app.ComponentActivity implements

LifecycleOwner,

ViewModelStoreOwner

class ComponentActivity extends Activity

implementation 'com.android.support:appcompat-v7:28.0.0'

android/support/v7/app/AppCompatActivity.java

class AppCompatActivity extends FragmentActivity

class FragmentActivity extends SupportActivity implements ViewModelStoreOwner

class SupportActivity extends Activity implements LifecycleOwner

targetSdkVersion 28

implementation 'com.android.support:support-v4:28.0.0'

android-28/android/app/Activity.java