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[camera] Dart Interface for camera refactor (flutter-team-archive#1832)
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‎README.md‎

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A Flutter plugin for iOS and Android allowing access to the device cameras.
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*Note*: This plugin is still under development, and some APIs might not be available yet. We are working on a refactor which can be followed here: [issue](https://github.com/flutter/flutter/issues/31225)
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## Features:
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* Display live camera preview in a widget.

‎lib/new/camera.dart‎

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// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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export 'src/camera_controller.dart';
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export 'src/camera_testing.dart';
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export 'src/common/camera_interface.dart';
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export 'src/common/native_texture.dart';

‎lib/new/src/camera_controller.dart‎

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// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'dart:async';
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import 'package:flutter/foundation.dart';
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import 'common/camera_interface.dart';
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/// Controls a device camera.
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///
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/// Use [CameraController.availableCameras] to get a list of available cameras.
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///
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/// This class is used as a simple interface that works for Android and iOS.
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///
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/// When using iOS, simultaneously calling [start] on two [CameraController]s
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/// will throw a [PlatformException].
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///
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/// When using Android, simultaneously calling [start] on two
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/// [CameraController]s may throw a [PlatformException] depending on the
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/// hardware resources of the device.
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class CameraController {
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/// Default constructor.
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///
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/// Use [CameraController.availableCameras] to get a list of available
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/// cameras.
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///
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/// This will choose the best [CameraConfigurator] for the current device.
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factory CameraController({@required CameraDescription description}) {
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assert(description != null);
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return CameraController._(
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description: description,
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configurator: _createDefaultConfigurator(description),
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api: _getCameraApi(description),
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);
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}
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CameraController._({
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@required this.description,
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@required this.configurator,
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@required this.api,
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}) : assert(description != null),
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assert(configurator != null),
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assert(api != null);
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/// Constructor for defining your own [CameraConfigurator].
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///
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/// Use [CameraController.availableCameras] to get a list of available
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/// cameras.
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factory CameraController.customConfigurator({
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@required CameraDescription description,
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@required CameraConfigurator configurator,
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}) {
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return CameraController._(
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description: description,
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configurator: configurator,
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api: _getCameraApi(description),
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);
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}
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/// Details for the camera this controller accesses.
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final CameraDescription description;
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/// Configurator used to control the camera.
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final CameraConfigurator configurator;
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/// Api used by the [configurator].
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final CameraApi api;
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/// Retrieves a list of available cameras for the current device.
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///
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/// This will choose the best [CameraAPI] for the current device.
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static Future<List<CameraDescription>> availableCameras() async {
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throw UnimplementedError('$defaultTargetPlatform not supported');
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}
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/// Begins the flow of data between the inputs and outputs connected the camera instance.
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Future<void> start() => configurator.start();
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/// Stops the flow of data between the inputs and outputs connected the camera instance.
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Future<void> stop() => configurator.stop();
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/// Deallocate all resources and disables further use of the controller.
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Future<void> dispose() => configurator.dispose();
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static CameraConfigurator _createDefaultConfigurator(
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CameraDescription description,
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) {
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final CameraApi api = _getCameraApi(description);
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switch (api) {
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case CameraApi.android:
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throw UnimplementedError();
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case CameraApi.iOS:
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throw UnimplementedError();
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case CameraApi.supportAndroid:
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throw UnimplementedError();
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}
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return null; // Unreachable code
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}
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static CameraApi _getCameraApi(CameraDescription description) {
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throw ArgumentError.value(
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description.runtimeType,
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'description.runtimeType',
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'Failed to get $CameraApi from',
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);
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}
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}

‎lib/new/src/camera_testing.dart‎

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// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/foundation.dart';
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import 'package:flutter/services.dart';
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import 'common/camera_channel.dart';
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@visibleForTesting
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class CameraTesting {
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CameraTesting._();
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static final MethodChannel channel = CameraChannel.channel;
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static int get nextHandle => CameraChannel.nextHandle;
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static set nextHandle(int handle) => CameraChannel.nextHandle = handle;
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}

‎lib/new/src/common/camera_channel.dart‎

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// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/services.dart';
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typedef CameraCallback = void Function(dynamic result);
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// Non exported class
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class CameraChannel {
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static final Map<int, dynamic> callbacks = <int, CameraCallback>{};
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static final MethodChannel channel = const MethodChannel(
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'flutter.plugins.io/camera',
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)..setMethodCallHandler(
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(MethodCall call) async {
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assert(call.method == 'handleCallback');
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final int handle = call.arguments['handle'];
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if (callbacks[handle] != null) callbacks[handle](call.arguments);
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},
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);
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static int nextHandle = 0;
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static void registerCallback(int handle, CameraCallback callback) {
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assert(handle != null);
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assert(CameraCallback != null);
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assert(!callbacks.containsKey(handle));
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callbacks[handle] = callback;
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}
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static void unregisterCallback(int handle) {
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assert(handle != null);
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callbacks.remove(handle);
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}
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}

‎lib/new/src/common/camera_interface.dart‎

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// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'dart:async';
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/// Available APIs compatible with [CameraController].
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enum CameraApi {
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/// [Camera2](https://developer.android.com/reference/android/hardware/camera2/package-summary)
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android,
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/// [AVFoundation](https://developer.apple.com/av-foundation/)
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iOS,
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/// [Camera](https://developer.android.com/reference/android/hardware/Camera)
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supportAndroid,
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}
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/// Location of the camera on the device.
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enum LensDirection { front, back, unknown }
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/// Abstract class used to create a common interface to describe a camera from different platform APIs.
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///
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/// This provides information such as the [name] of the camera and [direction]
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/// the lens face.
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abstract class CameraDescription {
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/// Location of the camera on the device.
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LensDirection get direction;
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/// Identifier for this camera.
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String get name;
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}
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/// Abstract class used to create a common interface across platform APIs.
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abstract class CameraConfigurator {
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/// Texture id that can be used to send camera frames to a [Texture] widget.
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///
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/// You must call [addPreviewTexture] first or this will only return null.
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int get previewTextureId;
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/// Begins the flow of data between the inputs and outputs connected the camera instance.
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///
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/// This will start updating the texture with id: [previewTextureId].
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Future<void> start();
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/// Stops the flow of data between the inputs and outputs connected the camera instance.
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Future<void> stop();
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/// Dispose all resources and disables further use of this configurator.
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Future<void> dispose();
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/// Retrieves a valid texture Id to be used with a [Texture] widget.
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Future<int> addPreviewTexture();
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}

‎lib/new/src/common/camera_mixins.dart‎

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// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'camera_channel.dart';
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mixin NativeMethodCallHandler {
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/// Identifier for an object on the native side of the plugin.
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///
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/// Only used internally and for debugging.
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final int handle = CameraChannel.nextHandle++;
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}
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mixin CameraMappable {
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/// Creates a description of the object compatible with [PlatformChannel]s.
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///
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/// Only used as an internal method and for debugging.
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Map<String, dynamic> asMap();
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}

‎lib/new/src/common/native_texture.dart‎

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// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'dart:async';
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import 'package:flutter/foundation.dart';
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import 'camera_channel.dart';
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import 'camera_mixins.dart';
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/// Used to allocate a buffer for displaying a preview camera texture.
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///
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/// This is used to for a developer to have a control over the
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/// `TextureRegistry.SurfaceTextureEntry` (Android) and FlutterTexture (iOS).
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/// This gives direct access to the textureId and can be reused with separate
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/// camera instances.
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///
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/// The [textureId] can be passed to a [Texture] widget.
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class NativeTexture with CameraMappable {
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NativeTexture._({@required int handle, @required this.textureId})
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: _handle = handle,
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assert(handle != null),
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assert(textureId != null);
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final int _handle;
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bool _isClosed = false;
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/// Id that can be passed to a [Texture] widget.
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final int textureId;
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static Future<NativeTexture> allocate() async {
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final int handle = CameraChannel.nextHandle++;
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final int textureId = await CameraChannel.channel.invokeMethod<int>(
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'$NativeTexture#allocate',
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<String, dynamic>{'textureHandle': handle},
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);
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return NativeTexture._(handle: handle, textureId: textureId);
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}
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/// Deallocate this texture.
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Future<void> release() {
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if (_isClosed) return Future<void>.value();
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_isClosed = true;
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return CameraChannel.channel.invokeMethod<void>(
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'$NativeTexture#release',
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<String, dynamic>{'handle': _handle},
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);
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}
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@override
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Map<String, dynamic> asMap() {
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return <String, dynamic>{'handle': _handle};
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}
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}

‎pubspec.yaml‎

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camera on Android and iOS. Supports previewing the camera feed, capturing images, capturing video,
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and streaming image buffers to dart.
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version: 0.5.2+1
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publish_to: none
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authors:
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- Flutter Team <flutter-dev@googlegroups.com>
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- Luigi Agosti <luigi@tengio.com>
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sdk: flutter
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dev_dependencies:
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flutter_test:
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sdk: flutter
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path_provider: ^0.5.0
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video_player: ^0.10.0
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‎test/camera_test.dart‎

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// Copyright 2019 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/services.dart';
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import 'package:flutter_test/flutter_test.dart';
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import 'package:camera/new/src/camera_testing.dart';
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import 'package:camera/new/src/common/native_texture.dart';
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void main() {
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group('Camera', () {
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final List<MethodCall> log = <MethodCall>[];
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setUpAll(() {
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CameraTesting.channel
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.setMockMethodCallHandler((MethodCall methodCall) async {
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log.add(methodCall);
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switch (methodCall.method) {
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case 'NativeTexture#allocate':
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return 15;
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}
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throw ArgumentError.value(
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methodCall.method,
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'methodCall.method',
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'No method found for',
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);
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});
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});
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setUp(() {
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log.clear();
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CameraTesting.nextHandle = 0;
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});
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group('$NativeTexture', () {
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test('allocate', () async {
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final NativeTexture texture = await NativeTexture.allocate();
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expect(texture.textureId, 15);
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expect(log, <Matcher>[
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isMethodCall(
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'$NativeTexture#allocate',
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arguments: <String, dynamic>{'textureHandle': 0},
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)
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]);
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});
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});
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});
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}

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