Android Java GRPC Tutorial

This tutorial is to show you the basic set up to get GRPC working with an Android app using Java as the primary language.

Prerequisites

• https://developer.android.com/studio

Set Up

Were going to be borrowing the example java server from the main grpc-java repo

• clone https://github.com/grpc/grpc-java

• change directories to the examples folder

• execute ./gradlew installDist

• then run ./build/install/examples/bin/hello-world-server

1. In the Welcome to Android Studio window, click Create New Project.

2. In the Select a Project Template window, select Empty Activity and click Next.
   

3. In the Configure your project window, complete the following:

   • Enter HelloWorldGrpc in the Name field.
   • Select Java Language drop-down menu.
   • Click Finish

4. Open AndroidManifest.xml add this line above the application block.

   • <uses-permission android:name="android.permission.INTERNET" />
   • For reference here is what it should look like

5. Open the project gradle file and add this line to the dependencies section

   • classpath "com.google.protobuf:protobuf-gradle-plugin:0.8.14"

6. Next we add some lines to the module gradle file
   

   • Add com.google.protobuf to the top in the plugins object
   • Add the protobuf block, I add this right above the dependencies block
   • Add the dependencies to the block, the okhttp, grpc-protobuf-lite, grpc-stub, annotations-api

7. Now time to add the proto file

   • Your going to want to go to the terminal and create the proto directory in the main folder
   • Then create the proto file, whats great about using gradle and GRPC dependencies is that the proto files are automatically compiled for you touch HelloWorld.proto
   • Add this to the file

8. Lets now add the text fields and buttons to the main activity

   • Open the activity_main.xml file
   • Your going to want to delete the TextView component Your going to want to add these components to the view
   • PlainText three of them, one for the host input, another for the port input and a third for the message
   • TextView for the result message
   • Button for the sending action
   • It doesn't matter how you arrange them, if you wanted to get this done quickly then copy the xml file from step 9

9. Add ID's and settings for the components
   For the host and port, I like to default those to the grpc server

   • Host PlainText component id should equal host
   • Port PlainText component id should equal port
   • Message PlainText component id should equal message
   • Send/Submit Button component id should equal send
   • Result TextView component id should equal result
     

10. Now we move on to the code of the MainActivity. Open up the MainActivity file and declare these vars

    • hostEdit
    • portEdit
    • messageEdit
    • sendButton
    • resultText

11. Add this code to onCreate
    

12. Add the GrpcTask and code
    

13. Add the sendGrpcMessage function that will tie to the submit button
    

14. Go back to activity_main.xml and set the button onClick listener to sendGrpcMessage
    

15. Run the app on the emulator

    • For the host use 10.0.2.2
    • For the port use 50051
    • Then add a message
    • Click Submit
    • You should get back Hello and what ever you placed in the message component and see it in the result component

Link to the code for https://github.com/efernie/Android-Java-Grpc-Tutorial

A Kotlin version is coming soon