internal/uidriver/mobile: Implement Vibrate for Android

This change also adds AndroidManifest.xml for the example. This is
used for `gomobile install` command.

Updates #1452

examples/vibrate/AndroidManifest.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    package="org.ebiten.example.vibrate"
+    android:versionCode="1"
+    android:versionName="1.0">
+  <uses-permission android:name="android.permission.VIBRATE"/>
+  <application android:label="Vibrate" android:debuggable="true">
+    <activity android:name="org.golang.app.GoNativeActivity"
+	      android:label="vibrate"
+	      android:configChanges="orientation|keyboardHidden">
+      <meta-data android:name="android.app.lib_name" android:value="vibrate" />
+      <intent-filter>
+	<action android:name="android.intent.action.MAIN" />
+	<category android:name="android.intent.category.LAUNCHER" />
+      </intent-filter>
+    </activity>
+  </application>
+</manifest>

internal/uidriver/mobile/vibrate_android.go

@@ -16,8 +16,68 @@ package mobile
 
 import (
 	"time"
+
+	"golang.org/x/mobile/app"
 )
 
+/*
+
+#include <jni.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+// Basically same as:
+//
+//     Vibrator v = (Vibrator)getSystemService(Context.VIBRATOR_SERVICE);
+//     v.vibrate(millisecond)
+//
+// TODO: As of API Level 26, the new API should be Used instead:
+//
+//     Vibrator v = (Vibrator)getSystemService(Context.VIBRATOR_SERVICE);
+//     v.vibrate(VibrationEffect.createOneShot(millisecond, VibrationEffect.DEFAULT_AMPLITUDE))
+//
+// Note that this requires a manifest setting:
+//
+//     <uses-permission android:name="android.permission.VIBRATE"/>
+//
+static void vibrateOneShot(uintptr_t java_vm, uintptr_t jni_env, uintptr_t ctx, int64_t milliseconds) {
+  JavaVM* vm = (JavaVM*)java_vm;
+  JNIEnv* env = (JNIEnv*)jni_env;
+  jobject context = (jobject)ctx;
+
+  const jclass android_content_Context = (*env)->FindClass(env, "android/content/Context");
+  const jclass android_os_Vibrator = (*env)->FindClass(env, "android/os/Vibrator");
+
+  const jobject android_context_Context_VIBRATOR_SERVICE =
+      (*env)->GetStaticObjectField(
+          env, android_content_Context,
+          (*env)->GetStaticFieldID(env, android_content_Context, "VIBRATOR_SERVICE", "Ljava/lang/String;"));
+
+  const jobject vibrator =
+      (*env)->CallObjectMethod(
+          env, context,
+          (*env)->GetMethodID(env, android_content_Context, "getSystemService", "(Ljava/lang/String;)Ljava/lang/Object;"),
+          android_context_Context_VIBRATOR_SERVICE);
+
+  (*env)->CallVoidMethod(
+      env, vibrator,
+      (*env)->GetMethodID(env, android_os_Vibrator, "vibrate", "(J)V"),
+      milliseconds);
+
+  (*env)->DeleteLocalRef(env, android_content_Context);
+  (*env)->DeleteLocalRef(env, android_os_Vibrator);
+
+  (*env)->DeleteLocalRef(env, android_context_Context_VIBRATOR_SERVICE);
+  (*env)->DeleteLocalRef(env, vibrator);
+}
+
+*/
+import "C"
+
 func (u *UserInterface) Vibrate(duration time.Duration) {
-	// TODO: Implement this (#1452)
+	_ = app.RunOnJVM(func(vm, env, ctx uintptr) error {
+		// TODO: This might be crash when this is called from init(). How can we detect this?
+		C.vibrateOneShot(C.uintptr_t(vm), C.uintptr_t(env), C.uintptr_t(ctx), C.int64_t(duration/time.Millisecond))
+		return nil
+	})
 }