1、2x 迁移升级

example/android/app/src/main/java/io/flutter/app/FlutterMultiDexApplication.java

@@ -0,0 +1,20 @@
+// Generated file.
+// If you wish to remove Flutter's multidex support, delete this entire file.
+
+package io.flutter.app;
+
+import android.content.Context;
+import androidx.annotation.CallSuper;
+import androidx.multidex.MultiDex;
+
+/**
+ * Extension of {@link io.flutter.app.FlutterApplication}, adding multidex support.
+ */
+public class FlutterMultiDexApplication extends FlutterApplication {
+  @Override
+  @CallSuper
+  protected void attachBaseContext(Context base) {
+    super.attachBaseContext(base);
+    MultiDex.install(this);
+  }
+}