Add an example Android app and a README.md file that details how to compile it.

--
MOS_MIGRATED_REVID=98621744

7 files changed, 139 insertions, 0 deletions

diff --git a/examples/android/README.md b/examples/android/README.md
new file mode 100644
index 0000000000..004d05f6ae
--- /dev/null
+++ b/examples/android/README.md
@@ -0,0 +1,35 @@
+In order to build these examples, add the following two rules to the top-level `WORKSPACE` file (two directories above this file):
+
+```python
+android_sdk_repository(
+    name="androidsdk",
+    path="<path to your Android SDK>",
+    api_level=21,
+    build_tools_version="21.1.1")
+android_ndk_repository(
+    name="androidndk",
+    path="<path to your Android NDK>",
+    api_level=21)
+```
+
+Then the following command can be used to build the example app:
+
+```
+bazel build --android_crosstool_top=@androidndk//:toolchain //examples/android/java/bazel:hello_world
+```
+
+Yes, we know that this is a little clunky. We are working on the following things (and more):
+ * Eliminating the need for the `--android_crosstool_top` command line option
+ * Supporting other architectures than `armeabi-v7a` and compilers other than GCC 4.9
+ * Eliminating the big ugly deprecation message from the console output of Bazel
+
+We also have a nice way to speed up the edit-compile-install development cycle for physical Android devices and emulators: Bazel knows what code changed since the last build, and can use this knowledge to install only the changed code to the device. This currently works with L devices and changes to Java code and Android resources. To try this out, take an `android_binary` rule and:
+ * Set the `proguard_specs` attribute to `[]` (the empty list) or just omit it altogether
+ * Set the `multidex` attribute to `native`
+ * Set the `dex_shards` attribute to a number between 2 and 200. This controls the size of chunks the code is split into. As this number is increased, compilation and installation becomes faster but app startup becomes slower. A good initial guess is 10.
+ * Connect your device over USB to your workstation and enable USB debugging on it
+ * Run `bazel mobile-install --android_crosstool_top=@androidndk//:toolchain <android_binary rule>`
+ * Edit Java code or Android resources
+ * Run `blaze mobile-install --android_crosstool_top=@androidndk//:toolchain --incremental <android_binary rule>`
+
+Note that if you change anything other than Java code or Android resources (C++ code or something on the device), you must omit the `--incremental` command line option. Yes, we know that this is also clunky and we are working on improving it.
diff --git a/examples/android/java/bazel/AndroidManifest.xml b/examples/android/java/bazel/AndroidManifest.xml
new file mode 100644
index 0000000000..3ad459c90b
--- /dev/null
+++ b/examples/android/java/bazel/AndroidManifest.xml
@@ -0,0 +1,21 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="bazel.android"
+    android:versionCode="1"
+    android:versionName="1.0" >
+
+    <uses-sdk
+        android:minSdkVersion="21"
+        android:targetSdkVersion="21" />
+
+    <application
+        android:label="Bazel App" >
+        <activity
+            android:name="bazel.MainActivity"
+            android:label="Bazel" >
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+</manifest>
diff --git a/examples/android/java/bazel/BUILD b/examples/android/java/bazel/BUILD
new file mode 100644
index 0000000000..1a6ebe7e76
--- /dev/null
+++ b/examples/android/java/bazel/BUILD
@@ -0,0 +1,22 @@
+android_library(
+    name = "lib",
+    srcs = ["Lib.java"],
+)
+
+android_binary(
+    name = "hello_world",
+    srcs = glob([
+        "MainActivity.java",
+        "Jni.java",
+    ]),
+    manifest = "AndroidManifest.xml",
+    deps = [
+        ":jni",
+        ":lib",
+    ],
+)
+
+cc_library(
+    name = "jni",
+    srcs = ["jni.cc"],
+)
diff --git a/examples/android/java/bazel/Jni.java b/examples/android/java/bazel/Jni.java
new file mode 100644
index 0000000000..5fa92e0baa
--- /dev/null
+++ b/examples/android/java/bazel/Jni.java
@@ -0,0 +1,8 @@
+package bazel;
+
+/**
+ * JNI stubs for the Bazel Android "Hello, World" app.
+ */
+public class Jni {
+  public static native String hello();
+}
diff --git a/examples/android/java/bazel/Lib.java b/examples/android/java/bazel/Lib.java
new file mode 100644
index 0000000000..b2f27bf86d
--- /dev/null
+++ b/examples/android/java/bazel/Lib.java
@@ -0,0 +1,10 @@
+package bazel;
+
+/**
+ * A tiny library for the Bazel Android "Hello, World" app.
+ */
+public class Lib {
+  public static String message() {
+    return "Hello Lib";
+  }
+}
diff --git a/examples/android/java/bazel/MainActivity.java b/examples/android/java/bazel/MainActivity.java
new file mode 100644
index 0000000000..c50cd4ac02
--- /dev/null
+++ b/examples/android/java/bazel/MainActivity.java
@@ -0,0 +1,20 @@
+package bazel;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.util.Log;
+
+/**
+ * Main class for the Bazel Android "Hello, World" app.
+ */
+public class MainActivity extends Activity {
+  @Override
+  public void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+
+    Log.v("Bazel", "Hello, Android");
+    Log.v("Bazel", "Lib says: " + Lib.message());
+    System.loadLibrary("jni");
+    Log.v("Bazel", "JNI says: " + Jni.hello());
+  }
+}
diff --git a/examples/android/java/bazel/jni.cc b/examples/android/java/bazel/jni.cc
new file mode 100644
index 0000000000..b103f45145
--- /dev/null
+++ b/examples/android/java/bazel/jni.cc
@@ -0,0 +1,23 @@
+#include <jni.h>
+#include <stdlib.h>
+#include <string.h>
+
+const char* hello = "Hello JNI";
+
+static jstring NewStringLatin1(JNIEnv *env, const char *str) {
+  int len = strlen(str);
+  jchar *str1;
+  str1 = reinterpret_cast<jchar *>(malloc(len * sizeof(jchar)));
+
+  for (int i = 0; i < len ; i++) {
+    str1[i] = (unsigned char) str[i];
+  }
+  jstring result = env->NewString(str1, len);
+  free(str1);
+  return result;
+}
+
+extern "C" JNIEXPORT jstring JNICALL
+Java_bazel_Jni_hello(JNIEnv *env, jclass clazz) {
+  return NewStringLatin1(env, hello);
+}