Android Java GRPC Tutorial

Fernie — Mon, 22 Feb 2021 13:22:17 +0000

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

In the Welcome to Android Studio window, click Create New Project.
In the Select a Project Template window, select Empty Activity and click Next.
In the Configure your project window, complete the following:
- Enter HelloWorldGrpc in the Name field.
- Select Java Language drop-down menu.
- Click Finish
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
Open the project gradle file and add this line to the dependencies section
- classpath "com.google.protobuf:protobuf-gradle-plugin:0.8.14"
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
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
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
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
Now we move on to the code of the MainActivity. Open up the MainActivity file and declare these vars
- hostEdit
- portEdit
- messageEdit
- sendButton
- resultText
Add this code to onCreate
Add the GrpcTask and code
Add the sendGrpcMessage function that will tie to the submit button
Go back to activity_main.xml and set the button onClick listener to sendGrpcMessage
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

DEV Community: Fernie

Android Java GRPC Tutorial