Add Android example

examples-android/.gitignore

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+.gradle/
+.idea/
+build/
+*.iml
+/local.properties
+/gradle.properties

examples-android/Procfile

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+web: server/build/install/server/bin/server

examples-android/README.md

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+# gRPC Kotlin Android Sample
+
+## Run Server Locally:
+
+Run the server:
+```
+./gradlew -t :server:run
+```
+
+## Deploy and Run Server on Cloud Run:
+
+[![Run on Google Cloud](https://deploy.cloud.run/button.png)](https://deploy.cloud.run/?cloudshell_context=cloudrun-gbp)
+
+## Run the Client:
+
+1. [Download Android Command Line Tools](https://developer.android.com/studio)
+
+1. Install the SDK:
+    ```
+    mkdir android-sdk
+    cd android-sdk
+    unzip PATH_TO_SDK_ZIP/sdk-tools-linux-VERSION.zip
+    tools/bin/sdkmanager --update
+    tools/bin/sdkmanager "platforms;android-29" "build-tools;29.0.3" "extras;google;m2repository" "extras;android;m2repository"
+    tools/bin/sdkmanager --licenses
+    ```
+
+1. Set an env var pointing to the `android-sdk`
+    ```
+    export ANDROID_HOME=PATH_TO_SDK/android-sdk
+    ```
+
+1. Run the build from this project's dir:
+    ```
+    ./gradlew :android:build
+    ```
+
+1. You can either run on an emulator or a physical device and you can either connect to the server running on your local machine, or connect to a server you deployed on the cloud.
+
+    * Emulator + Local Server:
+        * From the command line:
+            ```
+            ./gradlew :android:installDebug
+            ```
+        * From Android Studio / IntelliJ, navigate to `android/src/main/kotlin/io/grpc/examples/helloworld` and right-click on `MainActivity` and select `Run`.
+
+    * Physical Device + Local Server:
+        * From the command line:
+            1. [Setup adb](https://developer.android.com/studio/run/device)
+            1. `./gradlew :android:installDebug -PserverUrl=http://YOUR_MACHINE_IP:50051/`
+        * From Android Studio / IntelliJ:
+            1. Create a `gradle.properties` file in your root project directory containing:
+                ```
+                serverUrl=http://YOUR_MACHINE_IP:50051/
+                ```
+            1. Navigate to `android/src/main/kotlin/io/grpc/examples/helloworld` and right-click on `MainActivity` and select `Run`.
+
+    * Emulator or Physical Device + Cloud:
+        * From the command line:
+            1. [setup adb](https://developer.android.com/studio/run/device)
+            1. `./gradlew :android:installDebug -PserverUrl=https://YOUR_SERVER/`
+        * From Android Studio / IntelliJ:
+            1. Create a `gradle.properties` file in your root project directory containing:
+                ```
+                serverUrl=https://YOUR_SERVER/
+                ```
+            1. Navigate to `android/src/main/kotlin/io/grpc/examples/helloworld` and right-click on `MainActivity` and select `Run`.

examples-android/android/build.gradle.kts

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+plugins {
+    id("com.android.application")
+    kotlin("android")
+}
+
+dependencies {
+    implementation(kotlin("stdlib"))
+    implementation("androidx.appcompat:appcompat:1.1.0")
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.7")
+    implementation(project(":common"))
+    runtimeOnly("io.grpc:grpc-okhttp:${rootProject.ext["grpcVersion"]}")
+}
+
+android {
+    compileSdkVersion(29)
+    buildToolsVersion = "29.0.3"
+
+    defaultConfig {
+        applicationId = "io.grpc.examples.hello"
+        minSdkVersion(23)
+        targetSdkVersion(29)
+        versionCode = 1
+        versionName = "1.0"
+
+        val serverUrl: String? by project
+        if (serverUrl != null) {
+            resValue("string", "server_url", serverUrl!!)
+        } else {
+            resValue("string", "server_url", "http://10.0.2.2:50051/")
+        }
+    }
+
+    sourceSets["main"].java.srcDir("src/main/kotlin")
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_1_7
+        targetCompatibility = JavaVersion.VERSION_1_7
+    }
+}

examples-android/android/gradle.properties

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+android.useAndroidX=true

examples-android/android/src/main/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="io.grpc.examples.helloworld">
+
+    <uses-permission android:name="android.permission.INTERNET"/>
+
+    <application
+        android:allowBackup="true"
+        android:fullBackupContent="true"
+        android:icon="@android:drawable/btn_star"
+        android:label="@string/app_label">
+        <activity
+            android:theme="@style/Theme.AppCompat.NoActionBar"
+            android:name="io.grpc.examples.helloworld.MainActivity">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>

examples-android/android/src/main/kotlin/io/grpc/examples/helloworld/MainActivity.kt

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+package io.grpc.examples.helloworld
+
+import android.os.Bundle
+import android.text.Editable
+import android.text.TextWatcher
+import android.view.KeyEvent
+import android.widget.Button
+import android.widget.EditText
+import android.widget.TextView
+import androidx.appcompat.app.AppCompatActivity
+import io.grpc.ManagedChannel
+import io.grpc.ManagedChannelBuilder
+import java.net.URL
+import java.util.logging.Logger
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.asExecutor
+import kotlinx.coroutines.runBlocking
+
+// todo: suspend funs
+class MainActivity : AppCompatActivity() {
+    private val logger = Logger.getLogger(this.javaClass.name)
+
+    private fun channel(): ManagedChannel {
+        val url = URL(resources.getString(R.string.server_url))
+        val port = if (url.port == -1) url.defaultPort else url.port
+
+        logger.info("Connecting to ${url.host}:$port")
+
+        val builder = ManagedChannelBuilder.forAddress(url.host, port)
+        if (url.protocol == "https") {
+            builder.useTransportSecurity()
+        } else {
+            builder.usePlaintext()
+        }
+
+        return builder.executor(Dispatchers.Default.asExecutor()).build()
+    }
+
+    // lazy otherwise resources is null
+    private val greeter by lazy { GreeterGrpcKt.GreeterCoroutineStub(channel()) }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_main)
+
+        val button = findViewById<Button>(R.id.button)
+
+        val nameText = findViewById<EditText>(R.id.name)
+        nameText.addTextChangedListener(object : TextWatcher {
+            override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) {
+                button.isEnabled = s.isNotEmpty()
+            }
+            override fun beforeTextChanged(s: CharSequence, start: Int, count: Int, after: Int) { }
+            override fun afterTextChanged(s: Editable) { }
+        })
+
+        val responseText = findViewById<TextView>(R.id.response)
+
+        fun sendReq() = runBlocking {
+            try {
+                val request = HelloRequest.newBuilder().setName(nameText.text.toString()).build()
+                val response = greeter.sayHello(request)
+                responseText.text = "Server says: " + response.getMessage()
+            } catch (e: Exception) {
+                responseText.text = "Server error: " + e.message
+                e.printStackTrace()
+            }
+        }
+
+        button.setOnClickListener {
+            sendReq()
+        }
+
+        nameText.setOnKeyListener { _, keyCode, event ->
+            if ((event.action == KeyEvent.ACTION_DOWN) && (keyCode == KeyEvent.KEYCODE_ENTER)) {
+                sendReq()
+                true
+            } else {
+                false
+            }
+        }
+    }
+}

examples-android/android/src/main/res/layout/activity_main.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    android:gravity="center_horizontal"
+    tools:context="io.grpc.examples.helloworld.MainActivity">
+
+    <EditText android:id="@+id/name"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:inputType="text"
+        android:hint="@string/name_hint"
+        android:autofillHints="name"/>
+
+    <Button android:id="@+id/button"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="@string/say_hello"
+        android:enabled="false"/>
+
+    <TextView android:id="@+id/response"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"/>
+
+</LinearLayout>

examples-android/android/src/main/res/values/strings.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="name_hint">name</string>
+    <string name="say_hello">say hello</string>
+    <string name="app_label">gRPC Kotlin Android</string>
+</resources>

examples-android/build.gradle.kts

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+buildscript {
+    repositories {
+        gradlePluginPortal()
+        google()
+    }
+    dependencies {
+        classpath("com.android.tools.build:gradle:3.6.3")
+    }
+}
+
+plugins {
+    kotlin("jvm") version "1.3.72"
+    id("org.jlleitschuh.gradle.ktlint") version "9.2.1"
+}
+
+// todo: move to subprojects, but how?
+ext["grpcVersion"] = "1.30.0"
+ext["grpcKotlinVersion"] = "0.1.3"
+ext["protobufVersion"] = "3.12.2"
+
+allprojects {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+        jcenter()
+        google()
+    }
+
+    apply(plugin = "org.jlleitschuh.gradle.ktlint")
+}
+
+tasks.replace("assemble").dependsOn(":server:installDist")

examples-android/common/build.gradle.kts

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+import com.google.protobuf.gradle.generateProtoTasks
+import com.google.protobuf.gradle.id
+import com.google.protobuf.gradle.ofSourceSet
+import com.google.protobuf.gradle.plugins
+import com.google.protobuf.gradle.protobuf
+import com.google.protobuf.gradle.protoc
+
+plugins {
+    kotlin("jvm")
+    id("com.google.protobuf") version "0.8.12"
+}
+
+dependencies {
+    implementation(kotlin("stdlib"))
+    implementation("javax.annotation:javax.annotation-api:1.3.2")
+    api("io.grpc:grpc-protobuf-lite:${rootProject.ext["grpcVersion"]}")
+    api("io.grpc:grpc-stub:${rootProject.ext["grpcVersion"]}")
+    api("io.grpc:grpc-kotlin-stub:${rootProject.ext["grpcKotlinVersion"]}") {
+        exclude("io.grpc", "grpc-protobuf")
+    }
+}
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_1_7
+}
+
+protobuf {
+    protoc {
+        artifact = "com.google.protobuf:protoc:${rootProject.ext["protobufVersion"]}"
+    }
+    plugins {
+        id("grpc") {
+            artifact = "io.grpc:protoc-gen-grpc-java:${rootProject.ext["grpcVersion"]}"
+        }
+        id("grpckt") {
+            artifact = "io.grpc:protoc-gen-grpc-kotlin:${rootProject.ext["grpcKotlinVersion"]}"
+        }
+    }
+    generateProtoTasks {
+        ofSourceSet("main").forEach {
+            it.builtins {
+                named("java") {
+                    option("lite")
+                }
+            }
+            it.plugins {
+                id("grpc") {
+                    option("lite")
+                }
+                id("grpckt") {
+                    option("lite")
+                }
+            }
+        }
+    }
+}

examples-android/common/src/main/proto/helloworld.proto

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+// Copyright 2015 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+syntax = "proto3";
+
+option java_multiple_files = true;
+option java_package = "io.grpc.examples.helloworld";
+option java_outer_classname = "HelloWorldProto";
+option objc_class_prefix = "HLW";
+
+package helloworld;
+
+// The greeting service definition.
+service Greeter {
+    // Sends a greeting
+    rpc SayHello (HelloRequest) returns (HelloReply) {}
+}
+
+// The request message containing the user's name.
+message HelloRequest {
+    string name = 1;
+}
+
+// The response message containing the greetings
+message HelloReply {
+    string message = 1;
+}

examples-android/gradle/wrapper/gradle-wrapper.properties

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+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.5-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists