Add support for language hints in TextFields (Android only) (flutter#165554)

## Description

This PR adds support for language hints in TextFields.
This is supported only on Android for the moment and the property name,
aka `TextField.hintLocales`, is based on Android's
`EditorInfo.hintLocales` property, see
https://developer.android.com/reference/android/view/inputmethod/EditorInfo#hintLocales.

## Related Issue

Fixes [Support for language hints in
TextFields](flutter#163698)

## Tests

Adds 4 tests.
Updates several tests.

Author: bleroux

engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/systemchannels/TextInputChannel.java

@@ -19,6 +19,7 @@
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
 import org.json.JSONArray;
@@ -478,6 +479,16 @@ public static Configuration fromJson(@NonNull JSONObject json)
         }
       }
 
+      // Build an array of hint locales from the data in the JSON list.
+      Locale[] hintLocales = null;
+      if (!json.isNull("hintLocales")) {
+        JSONArray hintLocalesJson = json.getJSONArray("hintLocales");
+        hintLocales = new Locale[hintLocalesJson.length()];
+        for (int i = 0; i < hintLocalesJson.length(); i++) {
+          hintLocales[i] = Locale.forLanguageTag(hintLocalesJson.optString(i));
+        }
+      }
+
       return new Configuration(
           json.optBoolean("obscureText"),
           json.optBoolean("autocorrect", true),
@@ -490,7 +501,8 @@ public static Configuration fromJson(@NonNull JSONObject json)
           json.isNull("actionLabel") ? null : json.getString("actionLabel"),
           json.isNull("autofill") ? null : Autofill.fromJson(json.getJSONObject("autofill")),
           contentList.toArray(new String[contentList.size()]),
-          fields);
+          fields,
+          hintLocales);
     }
 
     @NonNull
@@ -649,6 +661,7 @@ public Autofill(
     @Nullable public final Autofill autofill;
     @Nullable public final String[] contentCommitMimeTypes;
     @Nullable public final Configuration[] fields;
+    @Nullable public final Locale[] hintLocales;
 
     public Configuration(
         boolean obscureText,
@@ -662,7 +675,8 @@ public Configuration(
         @Nullable String actionLabel,
         @Nullable Autofill autofill,
         @Nullable String[] contentCommitMimeTypes,
-        @Nullable Configuration[] fields) {
+        @Nullable Configuration[] fields,
+        @Nullable Locale[] hintLocales) {
       this.obscureText = obscureText;
       this.autocorrect = autocorrect;
       this.enableSuggestions = enableSuggestions;
@@ -675,6 +689,7 @@ public Configuration(
       this.autofill = autofill;
       this.contentCommitMimeTypes = contentCommitMimeTypes;
       this.fields = fields;
+      this.hintLocales = hintLocales;
     }
   }
 

engine/src/flutter/shell/platform/android/io/flutter/plugin/editing/TextInputPlugin.java

@@ -11,6 +11,7 @@
 import android.graphics.Rect;
 import android.os.Build;
 import android.os.Bundle;
+import android.os.LocaleList;
 import android.text.Editable;
 import android.text.InputType;
 import android.util.SparseArray;
@@ -349,6 +350,10 @@ public InputConnection createInputConnection(
     }
     outAttrs.imeOptions |= enterAction;
 
+    if (Build.VERSION.SDK_INT >= API_LEVELS.API_24 && configuration.hintLocales != null) {
+      outAttrs.hintLocales = new LocaleList(configuration.hintLocales);
+    }
+
     if (configuration.contentCommitMimeTypes != null) {
       String[] imgTypeString = configuration.contentCommitMimeTypes;
       EditorInfoCompat.setContentMimeTypes(outAttrs, imgTypeString);

engine/src/flutter/shell/platform/android/test/io/flutter/embedding/engine/systemchannels/TextInputChannelTest.java

@@ -5,6 +5,7 @@
 package io.flutter.embedding.engine.systemchannels;
 
 import static io.flutter.Build.API_LEVELS;
+import static org.junit.Assert.assertEquals;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 
@@ -13,6 +14,7 @@
 import io.flutter.embedding.engine.dart.DartExecutor;
 import io.flutter.plugin.common.MethodCall;
 import io.flutter.plugin.common.MethodChannel;
+import java.util.Locale;
 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;
@@ -39,4 +41,27 @@ public void setEditableSizeAndTransformCompletes() throws JSONException {
     textInputChannel.parsingMethodHandler.onMethodCall(call, result);
     verify(result).success(null);
   }
+
+  @Test
+  @TargetApi(API_LEVELS.API_24)
+  @Config(sdk = API_LEVELS.API_24)
+  public void configurationFromJsonParsesHintLocales() throws JSONException, NoSuchFieldException {
+    JSONObject arguments = new JSONObject();
+
+    // Mandatory parameters.
+    arguments.put("inputAction", "TextInputAction.done");
+    arguments.put("textCapitalization", "TextCapitalization.none");
+    JSONObject inputType = new JSONObject();
+    inputType.put("name", "TextInputType.text");
+    arguments.put("inputType", inputType);
+
+    arguments.put("hintLocales", new JSONArray(new String[] {"en", "fr"}));
+    final TextInputChannel.Configuration configuration =
+        TextInputChannel.Configuration.fromJson(arguments);
+
+    final Locale[] hintLocales = {new Locale("en"), new Locale("fr")};
+    assertEquals(configuration.hintLocales.length, hintLocales.length);
+    assertEquals(configuration.hintLocales[0], hintLocales[0]);
+    assertEquals(configuration.hintLocales[1], hintLocales[1]);
+  }
 }