[webview_flutter_android] Fix bugs in Java Implementation of the Pigeon API (flutter#4459)

Author: bparrishMines

packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/DownloadListenerFlutterApiImpl.java

@@ -0,0 +1,64 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.plugins.webviewflutter;
+
+import android.webkit.DownloadListener;
+import io.flutter.plugin.common.BinaryMessenger;
+import io.flutter.plugins.webviewflutter.GeneratedAndroidWebView.DownloadListenerFlutterApi;
+
+/**
+ * Flutter Api implementation for {@link DownloadListener}.
+ *
+ * <p>Passes arguments of callbacks methods from a {@link DownloadListener} to Dart.
+ */
+public class DownloadListenerFlutterApiImpl extends DownloadListenerFlutterApi {
+  private final InstanceManager instanceManager;
+
+  /**
+   * Creates a Flutter api that sends messages to Dart.
+   *
+   * @param binaryMessenger handles sending messages to Dart
+   * @param instanceManager maintains instances stored to communicate with Dart objects
+   */
+  public DownloadListenerFlutterApiImpl(
+      BinaryMessenger binaryMessenger, InstanceManager instanceManager) {
+    super(binaryMessenger);
+    this.instanceManager = instanceManager;
+  }
+
+  /** Passes arguments from {@link DownloadListener#onDownloadStart} to Dart. */
+  public void onDownloadStart(
+      DownloadListener downloadListener,
+      String url,
+      String userAgent,
+      String contentDisposition,
+      String mimetype,
+      long contentLength,
+      Reply<Void> callback) {
+    onDownloadStart(
+        instanceManager.getInstanceId(downloadListener),
+        url,
+        userAgent,
+        contentDisposition,
+        mimetype,
+        contentLength,
+        callback);
+  }
+
+  /**
+   * Communicates to Dart that the reference to a {@link DownloadListener} was removed.
+   *
+   * @param downloadListener the instance whose reference will be removed
+   * @param callback reply callback with return value from Dart
+   */
+  public void dispose(DownloadListener downloadListener, Reply<Void> callback) {
+    final Long instanceId = instanceManager.removeInstance(downloadListener);
+    if (instanceId != null) {
+      dispose(instanceId, callback);
+    } else {
+      callback.reply(null);
+    }
+  }
+}

packages/webview_flutter/webview_flutter_android/android/src/main/java/io/flutter/plugins/webviewflutter/DownloadListenerHostApiImpl.java

@@ -5,40 +5,92 @@
 package io.flutter.plugins.webviewflutter;
 
 import android.webkit.DownloadListener;
-import io.flutter.plugins.webviewflutter.GeneratedAndroidWebView.DownloadListenerFlutterApi;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import io.flutter.plugins.webviewflutter.GeneratedAndroidWebView.DownloadListenerHostApi;
 
-class DownloadListenerHostApiImpl implements GeneratedAndroidWebView.DownloadListenerHostApi {
+/**
+ * Host api implementation for {@link DownloadListener}.
+ *
+ * <p>Handles creating {@link DownloadListener}s that intercommunicate with a paired Dart object.
+ */
+public class DownloadListenerHostApiImpl implements DownloadListenerHostApi {
   private final InstanceManager instanceManager;
   private final DownloadListenerCreator downloadListenerCreator;
-  private final GeneratedAndroidWebView.DownloadListenerFlutterApi downloadListenerFlutterApi;
-
-  static class DownloadListenerCreator {
-    DownloadListener createDownloadListener(
-        Long instanceId, DownloadListenerFlutterApi downloadListenerFlutterApi) {
-      return (url, userAgent, contentDisposition, mimetype, contentLength) ->
-          downloadListenerFlutterApi.onDownloadStart(
-              instanceId, url, userAgent, contentDisposition, mimetype, contentLength, reply -> {});
+  private final DownloadListenerFlutterApiImpl flutterApi;
+
+  /**
+   * Implementation of {@link DownloadListener} that passes arguments of callback methods to Dart.
+   *
+   * <p>No messages are sent to Dart after {@link DownloadListenerImpl#release} is called.
+   */
+  public static class DownloadListenerImpl implements DownloadListener, Releasable {
+    @Nullable private DownloadListenerFlutterApiImpl flutterApi;
+
+    /**
+     * Creates a {@link DownloadListenerImpl} that passes arguments of callbacks methods to Dart.
+     *
+     * @param flutterApi handles sending messages to Dart
+     */
+    public DownloadListenerImpl(@NonNull DownloadListenerFlutterApiImpl flutterApi) {
+      this.flutterApi = flutterApi;
+    }
+
+    @Override
+    public void onDownloadStart(
+        String url,
+        String userAgent,
+        String contentDisposition,
+        String mimetype,
+        long contentLength) {
+      if (flutterApi != null) {
+        flutterApi.onDownloadStart(
+            this, url, userAgent, contentDisposition, mimetype, contentLength, reply -> {});
+      }
+    }
+
+    @Override
+    public void release() {
+      if (flutterApi != null) {
+        flutterApi.dispose(this, reply -> {});
+      }
+      flutterApi = null;
     }
   }
 
-  DownloadListenerHostApiImpl(
+  /** Handles creating {@link DownloadListenerImpl}s for a {@link DownloadListenerHostApiImpl}. */
+  public static class DownloadListenerCreator {
+    /**
+     * Creates a {@link DownloadListenerImpl}.
+     *
+     * @param flutterApi handles sending messages to Dart
+     * @return the created {@link DownloadListenerImpl}
+     */
+    public DownloadListenerImpl createDownloadListener(DownloadListenerFlutterApiImpl flutterApi) {
+      return new DownloadListenerImpl(flutterApi);
+    }
+  }
+
+  /**
+   * Creates a host API that handles creating {@link DownloadListener}s.
+   *
+   * @param instanceManager maintains instances stored to communicate with Dart objects
+   * @param downloadListenerCreator handles creating {@link DownloadListenerImpl}s
+   * @param flutterApi handles sending messages to Dart
+   */
+  public DownloadListenerHostApiImpl(
       InstanceManager instanceManager,
       DownloadListenerCreator downloadListenerCreator,
-      DownloadListenerFlutterApi downloadListenerFlutterApi) {
+      DownloadListenerFlutterApiImpl flutterApi) {
     this.instanceManager = instanceManager;
     this.downloadListenerCreator = downloadListenerCreator;
-    this.downloadListenerFlutterApi = downloadListenerFlutterApi;
+    this.flutterApi = flutterApi;
   }
 
   @Override
   public void create(Long instanceId) {
     final DownloadListener downloadListener =
-        downloadListenerCreator.createDownloadListener(instanceId, downloadListenerFlutterApi);
+        downloadListenerCreator.createDownloadListener(flutterApi);
     instanceManager.addInstance(downloadListener, instanceId);
   }
-
-  @Override
-  public void dispose(Long instanceId) {
-    instanceManager.removeInstance(instanceId);
-  }
 }