Use aar in Android Java demo. (#1616)

android/SherpaOnnxJavaDemo/README.md

@@ -0,0 +1,44 @@
+# Introduction
+
+Please run the following commands to download model files before you run this Android demo:
+
+```bash
+# Assume we are inside
+# /Users/fangjun/open-source/sherpa-onnx/android/SherpaOnnxJavaDemo
+
+cd app/src/main/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
+rm sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
+
+mv sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/encoder-epoch-99-avg-1.int8.onnx ./
+mv sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/decoder-epoch-99-avg-1.onnx ./
+mv sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/joiner-epoch-99-avg-1.int8.onnx ./
+mv sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/tokens.txt ./
+
+rm -rf sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/*
+
+mv encoder-epoch-99-avg-1.int8.onnx ./
+mv decoder-epoch-99-avg-1.onnx ./
+mv joiner-epoch-99-avg-1.int8.onnx ./
+mv tokens.txt ./
+```
+
+You should have the following directory structure:
+```
+(py38) fangjuns-MacBook-Pro:assets fangjun$ pwd
+/Users/fangjun/open-source/sherpa-onnx/android/SherpaOnnxJavaDemo/app/src/main/assets
+
+(py38) fangjuns-MacBook-Pro:assets fangjun$ tree .
+.
+└── 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.int8.onnx
+    └── tokens.txt
+
+1 directory, 4 files
+```
+
+Remember to remove unused files to reduce the file size of the final APK.