add android readme

examples/minicpmv/README.md

@@ -1,5 +1,5 @@
-# 所有命令在 llama.cpp 根目录执行，模型位于根目录上级目录处
-# All command should be executed under the root path of llama.cpp repo. We assume the MiniCPM-V-2.5 model are put in its parent folder.
+### 所有命令在 llama.cpp 根目录执行，模型位于根目录上级目录处
+### All command should be executed under the root path of llama.cpp repo. We assume the MiniCPM-V-2.5 model are put in its parent folder.
 
 ```bash
 make
@@ -18,15 +18,54 @@ python ./convert.py ../MiniCPM-V-2_5/model  --outtype f16 --vocab-type bpe
 ./minicpmv-cli -m ../MiniCPM-V-2_5/model/ggml-model-Q4_K_M.gguf --mmproj ../MiniCPM-V-2_5/mmproj-model-f16.gguf -c 4096 --temp 0.7 --top-p 0.8 --top-k 100 --repeat-penalty 1.05 --image xx.jpg -i
 ```
 
-# 在 Android 上运行
-# Run on android
+### Android
+
+#### Build on Android using Termux
+[Termux](https://github.com/termux/termux-app#installation) is a method to execute `llama.cpp` on an Android device (no root required).
+```
+apt update && apt upgrade -y
+apt install git make cmake
+```
+
+It's recommended to move your model inside the `~/` directory for best performance:
+```
+cd storage/downloads
+mv model.gguf ~/
+```
+
+#### Building the Project using Android NDK
+Obtain the [Android NDK](https://developer.android.com/ndk) and then build with CMake.
+
+Execute the following commands on your computer to avoid downloading the NDK to your mobile. Alternatively, you can also do this in Termux:
 
 ```bash
 mkdir build-android
 cd build-android
 export NDK=/your_ndk_path
 cmake -DCMAKE_TOOLCHAIN_FILE=$NDK/build/cmake/android.toolchain.cmake -DANDROID_ABI=arm64-v8a -DANDROID_PLATFORM=android-23 -DCMAKE_C_FLAGS=-march=armv8.4a+dotprod ..
 make
-cd bin
-# then llava-cli is the file you need to put on the phone.
+```
+
+Install [termux](https://github.com/termux/termux-app#installation) on your device and run `termux-setup-storage` to get access to your SD card (if Android 11+ then run the command twice).
+
+Finally, copy these built `llama` binaries and the model file to your device storage. Because the file permissions in the Android sdcard cannot be changed, you can copy the executable files to the `/data/data/com.termux/files/home/bin` path, and then execute the following commands in Termux to add executable permission:
+
+(Assumed that you have pushed the built executable files to the /sdcard/llama.cpp/bin path using `adb push`)
+```
+$cp -r /sdcard/llama.cpp/bin /data/data/com.termux/files/home/
+$cd /data/data/com.termux/files/home/bin
+$chmod +x ./*
+```
+
+Download models and push them to `/sdcard/llama.cpp/`, then move it to `/data/data/com.termux/files/home/model/`
+
+```
+$mv /sdcard/llama.cpp/ggml-model-Q4_K_M.gguf /data/data/com.termux/files/home/model/
+$mv /sdcard/llama.cpp/mmproj-model-f16.gguf /data/data/com.termux/files/home/model/
+```
+
+Now, you can start chatting:
+```
+$cd /data/data/com.termux/files/home/bin
+$./minicpmv-cli -m ../MiniCPM-V-2_5/model/ggml-model-Q4_K_M.gguf --mmproj ../MiniCPM-V-2_5/mmproj-model-f16.gguf -c 4096 --temp 0.7 --top-p 0.8 --top-k 100 --repeat-penalty 1.05 --image xx.jpg  -p "What is in the image?"
 ```