Create a simple fallback activity for supervised user creation

Create a simple fallback activity to be started if no other activity could be
resolved when Add supervised user option is tapped in Multi User settings.

Bug: 207495450
Test: croot && make RunSettingsRoboTests -j40 ROBOTEST_FILTER="com.android.settings.users.UserSettingsTest"
Change-Id: I850a2798567787c2494c75aa5fa451ddf373410d

AndroidManifest.xml

@@ -2963,6 +2963,12 @@
                        android:value="true" />
         </activity>
 
+        <activity
+            android:name=".users.AddSupervisedUserActivity"
+            android:label="@*android:string/supervised_user_creation_label"
+            android:icon="@drawable/ic_settings_multiuser">
+        </activity>
+
         <activity
             android:name="Settings$PaymentSettingsActivity"
             android:label="@string/nfc_payment_settings_title"

res/layout/add_supervised_user.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright (C) 2021 The Android Open Source Project
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~      http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+             android:layout_width="match_parent"
+             android:layout_height="match_parent">
+    <Button
+        android:id="@+id/createSupervisedUser"
+        android:layout_height="wrap_content"
+        android:layout_width="wrap_content"
+        android:text="@*android:string/supervised_user_creation_label" />
+</FrameLayout>

src/com/android/settings/users/AddSupervisedUserActivity.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.users;
+
+import android.app.Activity;
+import android.app.ActivityManager;
+import android.app.AlertDialog;
+import android.os.Bundle;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.NewUserRequest;
+import android.os.NewUserResponse;
+import android.os.UserManager;
+
+import androidx.annotation.Nullable;
+
+import com.android.settings.R;
+
+import java.util.Objects;
+import java.util.concurrent.Executors;
+import java.util.function.Consumer;
+
+/**
+ * Fallback activity for supervised user creation.
+ * Built to test {@link UserManager#createUser(NewUserRequest)} API.
+ */
+// TODO(b/209659998): [to-be-removed] fallback activity for supervised user creation.
+public class AddSupervisedUserActivity extends Activity {
+
+    private UserManager mUserManager;
+    private ActivityManager mActivityManager;
+
+    @Override
+    protected void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        mUserManager = getSystemService(UserManager.class);
+        mActivityManager = getSystemService(ActivityManager.class);
+        setContentView(R.layout.add_supervised_user);
+        findViewById(R.id.createSupervisedUser).setOnClickListener(v -> createUser());
+    }
+
+    private void createUserAsync(final NewUserRequest request,
+            final Consumer<NewUserResponse> onResponse) {
+        Objects.requireNonNull(onResponse);
+
+        final Handler mMainThread = new Handler(Looper.getMainLooper());
+        Executors.newSingleThreadExecutor().execute(() -> {
+            final NewUserResponse response = mUserManager.createUser(request);
+            mMainThread.post(() -> onResponse.accept(response));
+        });
+    }
+
+    private void createUser() {
+        final NewUserRequest request = new NewUserRequest.Builder().build();
+
+        final AlertDialog pleaseWaitDialog = new AlertDialog.Builder(this)
+                .setMessage(getString(R.string.creating_new_user_dialog_message))
+                .setCancelable(false)
+                .create();
+
+        pleaseWaitDialog.show();
+        createUserAsync(request, response -> {
+            pleaseWaitDialog.dismiss();
+
+            if (response.isSuccessful()) {
+                mActivityManager.switchUser(response.getUser());
+                finish();
+            } else {
+                new AlertDialog.Builder(this)
+                        .setTitle(getString(R.string.add_user_failed))
+                        .setMessage(UserManager.UserOperationResult.class.getName()
+                                + " = " + response.getOperationResult())
+                        .setNeutralButton(getString(R.string.okay), null)
+                        .show();
+            }
+        });
+    }
+}

src/com/android/settings/users/UserSettings.java

@@ -504,6 +504,13 @@ public class UserSettings extends SettingsPreferenceFragment
                 .setAction(UserManager.ACTION_CREATE_SUPERVISED_USER)
                 .setPackage(mConfigSupervisedUserCreationPackage);
 
+        // TODO(b/209659998): [to-be-removed] fallback activity for supervised user creation.
+        if (getActivity().getPackageManager().resolveActivity(intent, 0) == null) {
+            intent
+                .setClass(getContext(), AddSupervisedUserActivity.class)
+                .setPackage(null);
+        }
+
         startActivity(intent);
     }