Expose asset lookup from plugin binding. (#42019)

Author: matthew-carroll

shell/platform/android/io/flutter/embedding/engine/FlutterEnginePluginRegistry.java

@@ -21,6 +21,7 @@
 import java.util.Set;
 
 import io.flutter.Log;
+import io.flutter.embedding.engine.loader.FlutterLoader;
 import io.flutter.embedding.engine.plugins.FlutterPlugin;
 import io.flutter.embedding.engine.plugins.PluginRegistry;
 import io.flutter.embedding.engine.plugins.activity.ActivityAware;
@@ -98,7 +99,8 @@ class FlutterEnginePluginRegistry implements PluginRegistry,
         flutterEngine,
         flutterEngine.getDartExecutor(),
         flutterEngine.getRenderer(),
-        flutterEngine.getPlatformViewsController().getRegistry()
+        flutterEngine.getPlatformViewsController().getRegistry(),
+        new DefaultFlutterAssets(FlutterLoader.getInstance())
     );
   }
 
@@ -532,6 +534,30 @@ public void detachFromContentProvider() {
   }
   //----- End ContentProviderControlSurface -----
 
+  private static class DefaultFlutterAssets implements FlutterPlugin.FlutterAssets {
+    final FlutterLoader flutterLoader;
+
+    private DefaultFlutterAssets(@NonNull FlutterLoader flutterLoader) {
+      this.flutterLoader = flutterLoader;
+    }
+
+    public String getAssetFilePathByName(@NonNull String assetFileName) {
+      return flutterLoader.getLookupKeyForAsset(assetFileName);
+    }
+
+    public String getAssetFilePathByName(@NonNull String assetFileName, @NonNull String packageName) {
+      return flutterLoader.getLookupKeyForAsset(assetFileName, packageName);
+    }
+
+    public String getAssetFilePathBySubpath(@NonNull String assetSubpath) {
+      return flutterLoader.getLookupKeyForAsset(assetSubpath);
+    }
+
+    public String getAssetFilePathBySubpath(@NonNull String assetSubpath, @NonNull String packageName) {
+      return flutterLoader.getLookupKeyForAsset(assetSubpath, packageName);
+    }
+  }
+
   private static class FlutterEngineActivityPluginBinding implements ActivityPluginBinding {
     @NonNull
     private final Activity activity;

shell/platform/android/io/flutter/embedding/engine/plugins/FlutterPlugin.java

@@ -9,6 +9,7 @@
 import android.support.annotation.NonNull;
 
 import io.flutter.embedding.engine.FlutterEngine;
+import io.flutter.embedding.engine.loader.FlutterLoader;
 import io.flutter.plugin.common.BinaryMessenger;
 import io.flutter.plugin.platform.PlatformViewRegistry;
 import io.flutter.view.TextureRegistry;
@@ -91,19 +92,22 @@ class FlutterPluginBinding {
         private final BinaryMessenger binaryMessenger;
         private final TextureRegistry textureRegistry;
         private final PlatformViewRegistry platformViewRegistry;
+        private final FlutterAssets flutterAssets;
 
         public FlutterPluginBinding(
             @NonNull Context applicationContext,
             @NonNull FlutterEngine flutterEngine,
             @NonNull BinaryMessenger binaryMessenger,
             @NonNull TextureRegistry textureRegistry,
-            @NonNull PlatformViewRegistry platformViewRegistry
+            @NonNull PlatformViewRegistry platformViewRegistry,
+            @NonNull FlutterAssets flutterAssets
         ) {
             this.applicationContext = applicationContext;
             this.flutterEngine = flutterEngine;
             this.binaryMessenger = binaryMessenger;
             this.textureRegistry = textureRegistry;
             this.platformViewRegistry = platformViewRegistry;
+            this.flutterAssets = flutterAssets;
         }
 
         @NonNull
@@ -136,5 +140,47 @@ public TextureRegistry getTextureRegistry() {
         public PlatformViewRegistry getPlatformViewRegistry() {
           return platformViewRegistry;
         }
+
+        @NonNull
+        public FlutterAssets getFlutterAssets() {
+          return flutterAssets;
+        }
     }
+
+  /**
+   * Provides Flutter plugins with access to Flutter asset information.
+   */
+  interface FlutterAssets {
+      /**
+       * Returns the relative file path to the Flutter asset with the given name, including the file's
+       * extension, e.g., {@code "myImage.jpg"}.
+       *
+       * <p>The returned file path is relative to the Android app's standard assets directory.
+       * Therefore, the returned path is appropriate to pass to Android's {@code AssetManager},
+       * but the path is not appropriate to load as an absolute path.
+       */
+      String getAssetFilePathByName(@NonNull String assetFileName);
+
+      /**
+       * Same as {@link #getAssetFilePathByName(String)} but with added support for an explicit
+       * Android {@code packageName}.
+       */
+      String getAssetFilePathByName(@NonNull String assetFileName, @NonNull String packageName);
+
+      /**
+       * Returns the relative file path to the Flutter asset with the given subpath, including the file's
+       * extension, e.g., {@code "/dir1/dir2/myImage.jpg"}.
+       *
+       * <p>The returned file path is relative to the Android app's standard assets directory.
+       * Therefore, the returned path is appropriate to pass to Android's {@code AssetManager},
+       * but the path is not appropriate to load as an absolute path.
+       */
+      String getAssetFilePathBySubpath(@NonNull String assetSubpath);
+
+      /**
+       * Same as {@link #getAssetFilePathBySubpath(String)} but with added support for an explicit
+       * Android {@code packageName}.
+       */
+      String getAssetFilePathBySubpath(@NonNull String assetSubpath, @NonNull String packageName);
+  }
 }