update android demo doc

doc/doc_ch/android_demo.md

@@ -3,7 +3,7 @@
 
 ### 1. 安装最新版本的Android Studio
 
-可以从https://developer.android.com/studio下载。本Demo使用是4.0版本Android Studio编写。
+可以从 https://developer.android.com/studio 下载。本Demo使用是4.0版本Android Studio编写。
 
 ### 2. 创建新项目
 

doc/doc_en/android_demo_en.md

@@ -0,0 +1,60 @@
+# Android Demo quick start
+
+### 1. Install the latest version of Android Studio
+
+It can be downloaded from https://developer.android.com/studio . This Demo is written by Android Studio version 4.0.
+
+### 2. Create a new project
+
+The NDK version 20b is used in the demo test, and the compilation can be successfully supported for version 20 and above.
+
+If you are a beginner, you can install and test the NDK compilation environment in the following ways.
+
+File -> New ->New Project  to create  "Native C++" project
+
+1. Start a new Android Studio project
+
+   Select Native C++ in the project template, select Paddle OCR/deploy/android_demo path
+   After entering the project, it will be automatically compiled. The first compilation
+   will take a long time. It is recommended to add an agent to speed up the download.
+
+**Agent add:**
+
+  Android Studio -> Perferences -> Appearance & Behavior -> System Settings -> HTTP Proxy -> Manual proxy configuration
+
+![](../demo/proxy.png)
+
+2. Start compilation
+
+Click the compile button, connect the phone, and follow the instructions of Android Studio to complete the operation.
+
+When you see the following picture in Android Studio, the compilation is complete:
+
+![](../demo/build.png)
+
+**Tip:** At this time, if the following error message that OpenCV cannot be found appears, please re-click compile,
+exit the project after compiling, and enter again.
+
+![](../demo/error.png)
+
+### 3. Send to mobile
+
+Complete the compilation, click Run, and check the effect on the mobile phone.
+
+### 4. How to customize the demo picture
+
+1. Image storage path: android_demo/app/src/main/assets/images
+
+   Place the custom picture under this path
+
+2. Configuration file: android_demo/app/src/main/res/values/strings.xml
+
+   Modify IMAGE_PATH_DEFAULT to a custom picture name
+
+# Get more support
+
+Go to [EasyEdge](https://ai.baidu.com/easyedge/app/open_source_demo?referrerUrl=paddlelite) to get more development support:
+
+-Demo APP: You can use your mobile phone to scan the code to install, which is convenient for the mobile terminal to quickly experience text recognition
+
+-SDK: The model is packaged to adapt to different chip hardware and operating system SDKs, including a complete interface to facilitate secondary development