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Android Java GRPC Tutorial

efernie profile image Fernie Originally published at fern.life ・3 min read

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

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.
    Alt Text

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

    • Enter HelloWorldGrpc in the Name field.
    • Select Java Language drop-down menu.
    • Click Finish Alt Text
  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" Alt Text
  6. Next we add some lines to the module gradle file
    Alt Text

    • 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 Alt Text
    • 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 Alt Text 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
      Alt Text
  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
    Alt Text

  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

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