[webview_flutter_android] Adds support for receiving Java callback WebChromeClient.onShowFileChooser (#6881)

* some progress

* more work

* compiling code

* dart side should be correct

* maybe working code

* fix plugin class

* formatting

* some docs and polish

* foramtting tests and docs

* version bump

* doc improvements

* flutterapi create test

* working java test

* unused imports

* formatting and more tests

* formatting and more tests

* formatting

* copy and tests

* add more description to the custom method

* formatting

* change doc wording

* more docs

* null out result early

* remove the open option

* fix spelling

* interface implementation

* version bump

* move webchromeclient to webview controller

* tests

* reference method in changelong

* missing typed data import

* undo changes

* use stateerror instead

* updated lints

Author: bparrishMines

packages/webview_flutter/webview_flutter_android/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 3.2.0
+
+* Adds support for handling file selection. See `AndroidWebViewController.setOnShowFileSelector`.
+* Updates pigeon dev dependency to `4.2.14`.
+
 ## 3.1.3
 
 * Fixes crash when the Java `InstanceManager` was used after plugin was removed from the engine.

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

@@ -0,0 +1,74 @@
+// 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.os.Build;
+import android.webkit.WebChromeClient;
+import androidx.annotation.RequiresApi;
+import io.flutter.plugin.common.BinaryMessenger;
+import java.util.Arrays;
+
+/**
+ * Flutter Api implementation for {@link android.webkit.WebChromeClient.FileChooserParams}.
+ *
+ * <p>Passes arguments of callbacks methods from a {@link
+ * android.webkit.WebChromeClient.FileChooserParams} to Dart.
+ */
+@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
+public class FileChooserParamsFlutterApiImpl
+    extends GeneratedAndroidWebView.FileChooserParamsFlutterApi {
+  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 FileChooserParamsFlutterApiImpl(
+      BinaryMessenger binaryMessenger, InstanceManager instanceManager) {
+    super(binaryMessenger);
+    this.instanceManager = instanceManager;
+  }
+
+  private static GeneratedAndroidWebView.FileChooserModeEnumData toFileChooserEnumData(int mode) {
+    final GeneratedAndroidWebView.FileChooserModeEnumData.Builder builder =
+        new GeneratedAndroidWebView.FileChooserModeEnumData.Builder();
+
+    switch (mode) {
+      case WebChromeClient.FileChooserParams.MODE_OPEN:
+        builder.setValue(GeneratedAndroidWebView.FileChooserMode.OPEN);
+        break;
+      case WebChromeClient.FileChooserParams.MODE_OPEN_MULTIPLE:
+        builder.setValue(GeneratedAndroidWebView.FileChooserMode.OPEN_MULTIPLE);
+        break;
+      case WebChromeClient.FileChooserParams.MODE_SAVE:
+        builder.setValue(GeneratedAndroidWebView.FileChooserMode.SAVE);
+        break;
+      default:
+        throw new IllegalArgumentException(String.format("Unsupported FileChooserMode: %d", mode));
+    }
+
+    return builder.build();
+  }
+
+  /**
+   * Stores the FileChooserParams instance and notifies Dart to create a new FileChooserParams
+   * instance that is attached to this one.
+   *
+   * @return the instanceId of the stored instance
+   */
+  public long create(WebChromeClient.FileChooserParams instance, Reply<Void> callback) {
+    final long instanceId = instanceManager.addHostCreatedInstance(instance);
+    create(
+        instanceId,
+        instance.isCaptureEnabled(),
+        Arrays.asList(instance.getAcceptTypes()),
+        toFileChooserEnumData(instance.getMode()),
+        instance.getFilenameHint(),
+        callback);
+    return instanceId;
+  }
+}