Support the platform iOS for Flutter (#1079)

flutter-examples/streaming_asr/README.md

@@ -1,16 +1,123 @@
-# streaming_asr
+# Real-time speech recognition
 
-A new Flutter project.
+This APP supports the following platforms:
+
+  - Windows
+  - macOS
+  - Android
+  - iOS
+
+Note that it does not support Linux since we are using
+the package [record](https://pub.dev/packages/record), which does not
+support streaming recording on Linux.
+
+If you can find a recording package
+that works on Linux, please let us know and we will update this app to support Linux.
 
 ## Getting Started
 
-This project is a starting point for a Flutter application.
+Remember to use the following steps to download a model. Otherwise, you would
+get errors after you start and run the app.
 
-A few resources to get you started if this is your first Flutter project:
+###  1. Select a streaming model
 
-- [Lab: Write your first Flutter app](https://docs.flutter.dev/get-started/codelab)
-- [Cookbook: Useful Flutter samples](https://docs.flutter.dev/cookbook)
+Please visit <https://github.com/k2-fsa/sherpa-onnx/releases/tag/asr-models>
+to download a streaming ASR model.
 
-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.
+You can find introductions about each streaming model at
+<https://k2-fsa.github.io/sherpa/onnx/pretrained_models/index.html>
+
+
+Note: `Streaming` is the same as `Online` in this context.
+
+### 2. Let the code know which model you are using
+
+We have pre-configured some streaming models in the following file
+
+<https://github.com/k2-fsa/sherpa-onnx/blob/master/flutter-examples/streaming_asr/lib/online_model.dart>
+
+If you select a model that is not in the above file, please add it to the above file
+by yourself by following how existing models are added.
+
+Then you need to update
+
+<https://github.com/k2-fsa/sherpa-onnx/blob/master/flutter-examples/streaming_asr/lib/streaming_asr.dart#L16>
+
+```
+final type = 0;
+```
+
+Please change ``type`` accordingly.
+
+You also need to change [./pubspec.yaml](./pubspec.yaml) so that your APP knows where to find it.
+Please see the example below for how to do that.
+
+### 3. Place your downloaded model inside the directory assets
+
+The downloaded model has to be placed in the [assets](./assets) directory.
+
+**HINT**: Please delete files that are not needed by the code. Otherwise, you put
+unnecessary files in your APP and it will significantly increase the size of your APP.
+
+## Example
+
+Suppose you have selected the following model
+
+<https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2>
+
+Please use the following steps to make it available in your APP.
+
+ - 1. Change [online_model.dart](./lib/online_model.dart)
+
+    This model is already in the file and its type is `0`, so there is no need to change this file.
+
+ - 2. Change [streaming_asr.dart](./lib/streaming_asr.dart)
+
+    The default value for `type` is 0 and our model has also a type of `0`, so there is no need to change this file.
+
+ - 3. Change [pubspec.yaml](./pubspec.yaml)
+
+   At the end of [pubspec.yaml](./pubspec.yaml), please change it exactly like below:
+
+```
+  assets:
+    - assets/
+    - assets/sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/
+```
+
+  - 4. Download the model to the [./assets](./assets) directory.
+
+```
+cd assets
+wget https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
+tar xvf sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
+
+# Remeber to remove unused files.
+rm -rf sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/test_wavs
+rm sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/README.md
+rm sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/bpe*
+rm sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/encoder-epoch-99-avg-1.onnx
+rm sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/decoder-epoch-99-avg-1.int8.onnx
+rm sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/joiner-epoch-99-avg-1.int8.onnx
+```
+
+Your [assets](./assets) directory should look like below at the end.
+
+```
+assets/
+└── sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20
+    ├── decoder-epoch-99-avg-1.onnx
+    ├── encoder-epoch-99-avg-1.int8.onnx
+    ├── joiner-epoch-99-avg-1.onnx
+    └── tokens.txt
+
+1 directory, 4 files
+```
+
+  - 5. Run it!
+
+    For instance
+
+      - `flutter run -d macos` for macOS.
+
+      - `flutter run -d windows` for windows.