Update

examples/android/binder/java/io/grpc/binder/cpp/exampleclient/ButtonPressHandler.java

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+package io.grpc.binder.cpp.exampleclient;
+
+import android.app.Application;
+
+public class ButtonPressHandler {
+  static {
+    System.loadLibrary("app");
+  }
+
+  public native String native_entry(Application application);
+
+  public String onPressed(Application application) {
+    return native_entry(application);
+  }
+}

examples/android/binder/java/io/grpc/binder/cpp/exampleclient/MainActivity.java

@@ -0,0 +1,26 @@
+package io.grpc.binder.cpp.exampleclient;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.util.Log;
+import android.widget.Button;
+import android.widget.TextView;
+
+/** Main class for the example app. */
+public class MainActivity extends Activity {
+  @Override
+  public void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    Log.v("Example", "hello, world");
+
+    setContentView(R.layout.activity_main);
+
+    Button clickMeButton = findViewById(R.id.clickMeButton);
+    TextView exampleTextView = findViewById(R.id.exampleTextView);
+
+    ButtonPressHandler h = new ButtonPressHandler();
+
+    clickMeButton.setOnClickListener(
+        v -> exampleTextView.setText(h.onPressed(getApplication())));
+  }
+}

examples/android/binder/java/io/grpc/binder/cpp/exampleserver/ButtonPressHandler.java

@@ -0,0 +1,13 @@
+package io.grpc.binder.cpp.exampleserver;
+
+import android.app.Application;
+
+public class ButtonPressHandler {
+  static {
+    System.loadLibrary("app");
+  }
+
+  public String onPressed(Application application) {
+    return "Server Button Pressed";
+  }
+}

examples/android/binder/java/io/grpc/binder/cpp/exampleserver/ExportedEndpointService.java

@@ -0,0 +1,25 @@
+package io.grpc.binder.cpp.exampleserver;
+
+import android.app.Service;
+import android.content.Intent;
+import android.os.IBinder;
+import io.grpc.binder.cpp.GrpcCppServerBuilder;
+
+/** Exposes gRPC services running in the main process */
+public final class ExportedEndpointService extends Service {
+  static {
+    System.loadLibrary("app");
+  }
+
+  public ExportedEndpointService() {
+    init_grpc_server();
+  }
+
+  @Override
+  public IBinder onBind(Intent intent) {
+    // The argument should match the URI passed into grpc::ServerBuilder::AddListeningPort
+    return GrpcCppServerBuilder.GetEndpointBinder("binder:example.service");
+  }
+
+  public native void init_grpc_server();
+}

examples/android/binder/java/io/grpc/binder/cpp/exampleserver/MainActivity.java

@@ -0,0 +1,27 @@
+package io.grpc.binder.cpp.exampleserver;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.util.Log;
+import android.widget.Button;
+import android.widget.TextView;
+import io.grpc.binder.cpp.exampleserver.R;
+
+/** Main class for the example app. */
+public class MainActivity extends Activity {
+  @Override
+  public void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    Log.v("Example", "hello, world");
+
+    setContentView(R.layout.activity_main);
+
+    Button clickMeButton = findViewById(R.id.clickMeButton);
+    TextView exampleTextView = findViewById(R.id.exampleTextView);
+
+    ButtonPressHandler h = new ButtonPressHandler();
+
+    clickMeButton.setOnClickListener(
+        v -> exampleTextView.setText(h.onPressed(getApplication())));
+  }
+}

examples/android/helloworld/app/src/main/java/io/grpc/helloworldexample/cpp/HelloworldActivity.java

@@ -0,0 +1,167 @@
+/*
+ * Copyright 2018, gRPC Authors All rights reserved.
+ *
+ * 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.
+ */
+
+package io.grpc.helloworldexample.cpp;
+
+import android.content.Context;
+import android.os.AsyncTask;
+import android.os.Bundle;
+import android.support.v7.app.AppCompatActivity;
+import android.text.TextUtils;
+import android.text.method.ScrollingMovementMethod;
+import android.view.View;
+import android.view.inputmethod.InputMethodManager;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.TextView;
+import android.widget.Toast;
+import java.lang.ref.WeakReference;
+
+public class HelloworldActivity extends AppCompatActivity {
+
+  static {
+    System.loadLibrary("grpc-helloworld");
+  }
+
+  private Button sendButton;
+  private Button serverButton;
+  private EditText hostEdit;
+  private EditText portEdit;
+  private EditText messageEdit;
+  private EditText serverPortEdit;
+  private TextView resultText;
+  private GrpcTask grpcTask;
+  private RunServerTask runServerTask;
+
+  @Override
+  protected void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    setContentView(R.layout.activity_helloworld);
+    sendButton = (Button) findViewById(R.id.send_button);
+    serverButton = (Button) findViewById(R.id.server_button);
+    hostEdit = (EditText) findViewById(R.id.host_edit_text);
+    portEdit = (EditText) findViewById(R.id.port_edit_text);
+    messageEdit = (EditText) findViewById(R.id.message_edit_text);
+    serverPortEdit = (EditText) findViewById(R.id.server_port_edit_text);
+    resultText = (TextView) findViewById(R.id.grpc_response_text);
+    resultText.setMovementMethod(new ScrollingMovementMethod());
+  }
+
+  @Override
+  protected void onPause() {
+    super.onPause();
+    if (runServerTask != null) {
+      runServerTask.cancel(true);
+      runServerTask = null;
+      serverButton.setText("Start gRPC Server");
+    }
+    if (grpcTask != null) {
+      grpcTask.cancel(true);
+      grpcTask = null;
+    }
+  }
+
+  public void sendMessage(View view) {
+    ((InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE))
+        .hideSoftInputFromWindow(hostEdit.getWindowToken(), 0);
+    sendButton.setEnabled(false);
+    resultText.setText("");
+    grpcTask = new GrpcTask(this);
+    grpcTask.executeOnExecutor(
+        AsyncTask.THREAD_POOL_EXECUTOR,
+        hostEdit.getText().toString(),
+        messageEdit.getText().toString(),
+        portEdit.getText().toString());
+  }
+
+  public void startOrStopServer(View view) {
+    if (runServerTask != null) {
+      runServerTask.cancel(true);
+      runServerTask = null;
+      serverButton.setText("Start gRPC Server");
+      Toast.makeText(this, "Server stopped", Toast.LENGTH_SHORT).show();
+    } else {
+      runServerTask = new RunServerTask(this);
+      String portStr = serverPortEdit.getText().toString();
+      int port = TextUtils.isEmpty(portStr) ? 50051 : Integer.valueOf(portStr);
+      runServerTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, port);
+      serverButton.setText("Stop gRPC Server");
+      Toast.makeText(this, "Server started on port " + port, Toast.LENGTH_SHORT).show();
+    }
+  }
+
+  private static class RunServerTask extends AsyncTask<Integer, Void, Void> {
+    private final WeakReference<HelloworldActivity> activityReference;
+
+    private RunServerTask(HelloworldActivity activity) {
+      this.activityReference = new WeakReference<HelloworldActivity>(activity);
+    }
+
+    @Override
+    protected Void doInBackground(Integer... params) {
+      int port = params[0];
+      HelloworldActivity activity = activityReference.get();
+      if (activity != null) {
+        activity.startServer(port);
+      }
+      return null;
+    }
+  }
+
+  private static class GrpcTask extends AsyncTask<String, Void, String> {
+    private final WeakReference<HelloworldActivity> activityReference;
+
+    private GrpcTask(HelloworldActivity activity) {
+      this.activityReference = new WeakReference<HelloworldActivity>(activity);
+    }
+
+    @Override
+    protected String doInBackground(String... params) {
+      String host = params[0];
+      String message = params[1];
+      String portStr = params[2];
+      int port = TextUtils.isEmpty(portStr) ? 50051 : Integer.valueOf(portStr);
+      return sayHello(host, port, message);
+    }
+
+    @Override
+    protected void onPostExecute(String result) {
+      HelloworldActivity activity = activityReference.get();
+      if (activity == null || isCancelled()) {
+        return;
+      }
+      TextView resultText = (TextView) activity.findViewById(R.id.grpc_response_text);
+      Button sendButton = (Button) activity.findViewById(R.id.send_button);
+      resultText.setText(result);
+      sendButton.setEnabled(true);
+    }
+  }
+
+  /**
+   * Invoked by native code to stop server when RunServerTask has been canceled, either by user
+   * request or upon app moving to background.
+   */
+  public boolean isRunServerTaskCancelled() {
+    if (runServerTask != null) {
+      return runServerTask.isCancelled();
+    }
+    return false;
+  }
+
+  public static native String sayHello(String host, int port, String message);
+
+  public native void startServer(int port);
+}

src/android/test/interop/app/src/androidTest/java/io/grpc/interop/cpp/InteropTest.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2018, gRPC Authors All rights reserved.
+ *
+ * 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.
+ */
+
+package io.grpc.interop.cpp;
+
+import static junit.framework.Assert.assertTrue;
+
+import android.content.Context;
+import android.support.test.InstrumentationRegistry;
+import android.support.test.runner.AndroidJUnit4;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.InputStream;
+import java.io.OutputStream;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(AndroidJUnit4.class)
+public class InteropTest {
+  private String host;
+  private int port;
+  private boolean useTls;
+
+  @Before
+  public void setUp() throws Exception {
+    host =
+        InstrumentationRegistry.getArguments()
+            .getString("server_host", "grpc-test.sandbox.googleapis.com");
+    port = Integer.parseInt(InstrumentationRegistry.getArguments().getString("server_port", "443"));
+    useTls =
+        Boolean.parseBoolean(InstrumentationRegistry.getArguments().getString("use_tls", "true"));
+  }
+
+  @Test
+  public void emptyUnary() {
+    assertTrue(InteropActivity.doEmpty(host, port, useTls));
+  }
+
+  @Test
+  public void largeUnary() {
+    assertTrue(InteropActivity.doLargeUnary(host, port, useTls));
+  }
+
+  @Test
+  public void emptyStream() {
+    assertTrue(InteropActivity.doEmptyStream(host, port, useTls));
+  }
+
+  @Test
+  public void requestStreaming() {
+    assertTrue(InteropActivity.doRequestStreaming(host, port, useTls));
+  }
+
+  @Test
+  public void responseStreaming() {
+    assertTrue(InteropActivity.doResponseStreaming(host, port, useTls));
+  }
+
+  @Test
+  public void pingPong() {
+    assertTrue(InteropActivity.doPingPong(host, port, useTls));
+  }
+}