feat(ui): add firebase_ui_database (#9341)

packages/firebase_ui_database/.gitignore

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+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+migrate_working_dir/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+# Libraries should not include pubspec.lock, per https://dart.dev/guides/libraries/private-files#pubspeclock.
+/pubspec.lock
+**/doc/api/
+.dart_tool/
+.packages
+build/

packages/firebase_ui_database/.metadata

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+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+  channel: stable
+
+project_type: package

packages/firebase_ui_database/CHANGELOG.md

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+## 1.0.0-dev.0
+
+ - Bump "firebase_ui_database" to `1.0.0-dev.0`.
+
+## 0.0.1
+
+* TODO: Describe initial release.

packages/firebase_ui_database/LICENSE

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+Copyright 2017, the Chromium project authors. All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+    * Neither the name of Google Inc. nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

packages/firebase_ui_database/README.md

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+# Firebase UI for Realtime Database
+
+Firebase UI enables you to easily integrate your application UI with your Realtime database.
+
+## Installation
+
+```sh
+flutter pub add firebase_database
+flutter pub add firebase_ui_database
+```
+
+## Usage
+
+Import the Firebase UI for Realtime Database package.
+
+```dart
+import 'package:firebase_ui_database/firebase_ui_database.dart';
+```
+
+### Infinite scrolling
+
+Infinite scrolling is the concept of continuously loading more data from a database
+as the user scrolls through your application. This is useful when you have a large
+datasets, as it enables the application to render faster as well as reducing network
+overhead for data the user might never see.
+
+Firebase UI for Realtime Database provides a convenient way to implement infinite scrolling
+using the Realtime Database database with the `FirebaseDatabaseListView` widget.
+
+At a minimum, the widget accepts a Realtime Database query and an item builder. As the user scrolls
+down (or across) your list, more data will be automatically fetched from the database (whilst
+respecting query conditions such as ordering).
+
+To get started, create a query and provide an item builder. For this example, we'll display
+a list of users from the `users` collection:
+
+```dart
+final usersQuery = FirebaseDatabase.instance.ref('users').orderByChild('name');
+
+FirebaseDatabaseListView(
+  query: usersQuery,
+  itemBuilder: (context, snapshot) {
+    Map<String, dynamic> user = snapshot.value as Map<String, dynamic>;
+
+    return Text('User name is ${user['name']}');
+  },
+);
+```
+
+The `FirebaseDatabaseListView` widget is built on-top of Flutter's own [`ListView`](https://api.flutter.dev/flutter/widgets/ListView-class.html)
+widget, and accepts the same parameters which we can optionally provide. For example, to change the scroll-direction to horizontal:
+
+```dart
+FirebaseDatabaseListView(
+  scrollDirection: Axis.horizontal,
+  // ...
+);
+```
+
+### Controlling page size
+
+By default, the widget will fetch 10 items from the collection at a time. This can be changed by providing a `pageSize` parameter:
+
+```dart
+FirebaseDatabaseListView(
+  pageSize: 20,
+  // ...
+);
+```
+
+In general, it is good practice to keep this value as small as possible to reduce network overhead. If the height (or width)
+of an individual item is large, it is recommended to lower the page size.
+
+### Loading and error handling
+
+By default, the widget will display a loading indicator while data is being fetched from the database, and ignore any errors which might be thrown
+(such as permission denied). You can override this behavior by providing a `loadingBuilder` and `errorBuilder` parameters to the widget:
+
+```dart
+FirebaseDatabaseListView(
+  loadingBuilder: (context) => MyCustomLoadingIndicator(),
+  errorBuilder: (context, error, stackTrace) => MyCustomError(error, stackTrace),
+  // ...
+);
+```
+
+### Advanced configuration
+
+In many cases, the `FirebaseDatabaseListView` widget is enough to render simple lists of collection data.
+However, you may have specific requirements which require more control over the widget's behavior
+(such as using a [`GridView`](https://api.flutter.dev/flutter/widgets/GridView-class.html)).
+
+The `FirebaseDatabaseQueryBuilder` provides the building blocks for advanced configuration at the expense of
+requiring more boilerplate code. The widget does not provide any underlying list implementation, instead
+you are expected to provide this yourself.
+
+Much like the `FirebaseDatabaseListView` widget, provide a query and builder:
+
+```dart
+final usersQuery = FirebaseDatabase.instance.ref('users').orderByChild('name');
+
+FirebaseDatabaseQueryBuilder(
+  query: usersQuery,
+  builder: (context, snapshot, _) {
+    // ... TODO!
+  },
+);
+```
+
+The main difference to note here is that the `builder` property returns a `FirebaseQueryBuilderSnapshot`, rather
+than an individual document. The builder returns the current state of the entire query, such as whether
+data is loading, an error has occurred and the documents.
+
+This requires us to implement our own list based implementation. Firstly, let's handle the loading and error
+states:
+
+```dart
+FirebaseDatabaseQueryBuilder(
+  query: usersQuery,
+  builder: (context, snapshot, _) {
+    if (snapshot.isFetching) {
+      return const CircularProgressIndicator();
+    }
+
+    if (snapshot.hasError) {
+      return Text('Something went wrong! ${snapshot.error}');
+    }
+
+    // ...
+  },
+);
+```
+
+Next, we now need to return a list-view based implementation for our application to display the data. For example,
+to display a grid of users, we can use the [`GridView`](https://api.flutter.dev/flutter/widgets/GridView-class.html) widget:
+
+```dart
+FirebaseDatabaseQueryBuilder(
+  query: usersQuery,
+  builder: (context, snapshot, _) {
+    // ...
+
+    return GridView.builder(
+      itemCount: snapshot.docs.length,
+      itemBuilder: (context, index) {
+        // if we reached the end of the currently obtained items, we try to
+        // obtain more items
+        if (snapshot.hasMore && index + 1 == snapshot.docs.length) {
+          // Tell FirebaseDatabaseQueryBuilder to try to obtain more items.
+          // It is safe to call this function from within the build method.
+          snapshot.fetchMore();
+        }
+
+        final user = snapshot.docs[index].value as Map<String, dynamic>;
+
+        return Container(
+          padding: const EdgeInsets.all(8),
+          color: Colors.teal[100],
+          child: const Text("User name is ${user['name']}"),
+        );
+      },
+    );
+  },
+);
+```
+
+With more power comes more responsibility:
+
+1. Within the `itemBuilder` of our `GridView`, we have to manually ensure that we call the `fetchMore()` method on the snapshot when more data is required.
+1. The `FirebaseDatabaseQueryBuilder` does not provide a list-view based handler, instead you must provide your own implementation.

packages/firebase_ui_database/analysis_options.yaml

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+include: package:flutter_lints/flutter.yaml
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

packages/firebase_ui_database/example/.gitignore

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+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+migrate_working_dir/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+**/ios/Flutter/.last_build_id
+.dart_tool/
+.flutter-plugins
+.flutter-plugins-dependencies
+.packages
+.pub-cache/
+.pub/
+/build/
+
+# Web related
+lib/generated_plugin_registrant.dart
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json
+
+# Android Studio will place build artifacts here
+/android/app/debug
+/android/app/profile
+/android/app/release

packages/firebase_ui_database/example/.metadata

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+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled.
+
+version:
+  revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+  channel: stable
+
+project_type: app
+
+# Tracks metadata for the flutter migrate command
+migration:
+  platforms:
+    - platform: root
+      create_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+      base_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+    - platform: android
+      create_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+      base_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+    - platform: ios
+      create_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+      base_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+    - platform: linux
+      create_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+      base_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+    - platform: macos
+      create_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+      base_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+    - platform: web
+      create_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+      base_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+    - platform: windows
+      create_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+      base_revision: f1875d570e39de09040c8f79aa13cc56baab8db1
+
+  # User provided section
+
+  # List of Local paths (relative to this file) that should be
+  # ignored by the migrate tool.
+  #
+  # Files that are not part of the templates will be ignored by default.
+  unmanaged_files:
+    - 'lib/main.dart'
+    - 'ios/Runner.xcodeproj/project.pbxproj'

packages/firebase_ui_database/example/README.md

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+# firebase_ui_database_example
+
+A new Flutter project.
+
+## Getting Started
+
+This project is a starting point for a Flutter application.
+
+A few resources to get you started if this is your first Flutter project:
+
+- [Lab: Write your first Flutter app](https://docs.flutter.dev/get-started/codelab)
+- [Cookbook: Useful Flutter samples](https://docs.flutter.dev/cookbook)
+
+For help getting started with Flutter development, view the
+[online documentation](https://docs.flutter.dev/), which offers tutorials,
+samples, guidance on mobile development, and a full API reference.

packages/firebase_ui_database/example/analysis_options.yaml

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+# This file configures the analyzer, which statically analyzes Dart code to
+# check for errors, warnings, and lints.
+#
+# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
+# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
+# invoked from the command line by running `flutter analyze`.
+
+# The following line activates a set of recommended lints for Flutter apps,
+# packages, and plugins designed to encourage good coding practices.
+include: package:flutter_lints/flutter.yaml
+
+linter:
+  # The lint rules applied to this project can be customized in the
+  # section below to disable rules from the `package:flutter_lints/flutter.yaml`
+  # included above or to enable additional rules. A list of all available lints
+  # and their documentation is published at
+  # https://dart-lang.github.io/linter/lints/index.html.
+  #
+  # Instead of disabling a lint rule for the entire project in the
+  # section below, it can also be suppressed for a single line of code
+  # or a specific dart file by using the `// ignore: name_of_lint` and
+  # `// ignore_for_file: name_of_lint` syntax on the line or in the file
+  # producing the lint.
+  rules:
+    # avoid_print: false  # Uncomment to disable the `avoid_print` rule
+    # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options