Implement `restart-emacs' on Android

* java/org/gnu/emacs/EmacsService.java (restartEmacs): New
function.
* src/android.c (struct android_emacs_service)
(android_init_emacs_service): Add new method.
(android_restart_emacs): New function.
* src/android.h: Update prototypes.
* src/emacs.c (Fkill_emacs): Call android_restart_emacs whenever
appropriate.

java/org/gnu/emacs/EmacsService.java

@@ -611,4 +611,16 @@ public class EmacsService extends Service
 
     return manager.thing;
   }
+
+  public void
+  restartEmacs ()
+  {
+    Intent intent;
+
+    intent = new Intent (this, EmacsActivity.class);
+    intent.addFlags (Intent.FLAG_ACTIVITY_NEW_TASK
+		     | Intent.FLAG_ACTIVITY_CLEAR_TASK);
+    startActivity (intent);
+    System.exit (0);
+  }
 };

src/android.c

@@ -97,6 +97,7 @@ struct android_emacs_service
   jmethodID name_keysym;
   jmethodID sync;
   jmethodID browse_url;
+  jmethodID restart_emacs;
 };
 
 struct android_emacs_pixmap
@@ -1659,6 +1660,7 @@ android_init_emacs_service (void)
   FIND_METHOD (sync, "sync", "()V");
   FIND_METHOD (browse_url, "browseUrl", "(Ljava/lang/String;)"
 	       "Ljava/lang/String;");
+  FIND_METHOD (restart_emacs, "restartEmacs", "()V");
 #undef FIND_METHOD
 }
 
@@ -4987,6 +4989,23 @@ android_browse_url (Lisp_Object url)
   return tem;
 }
 
+/* Tell the system to restart Emacs in a short amount of time, and
+   then kill Emacs.  Never return.  This is used to implement
+   `restart-emacs'.  */
+
+_Noreturn void
+android_restart_emacs (void)
+{
+  /* Try to call the Java side function.  Normally, this should call
+     System.exit to terminate this process.  */
+  (*android_java_env)->CallVoidMethod (android_java_env,
+				       emacs_service,
+				       service_class.restart_emacs);
+
+  /* Exit anyway, in case EmacsService did not do so.  */
+  exit (0);
+}
+
 
 
 #else /* ANDROID_STUBIFY */

src/android.h

@@ -89,6 +89,7 @@ extern void android_get_keysym_name (int, char *, size_t);
 extern void android_wait_event (void);
 extern void android_toggle_on_screen_keyboard (android_window, bool);
 extern void android_window_updated (android_window, unsigned long);
+extern _Noreturn void android_restart_emacs (void);
 
 
 

src/emacs.c

@@ -2948,7 +2948,14 @@ killed.  */
 #ifndef WINDOWSNT
   /* Do some checking before shutting down Emacs, because errors
      can't be meaningfully reported afterwards.  */
-  if (!NILP (restart))
+  if (!NILP (restart)
+      /* Don't perform the following checks when Emacs is running as
+	 an Android GUI application, because there the system is
+	 relied on to restart Emacs.  */
+#if defined HAVE_ANDROID && !defined ANDROID_STUBIFY
+      && !android_init_gui
+#endif
+      )
     {
       /* This is very unlikely, but it's possible to execute a binary
 	 (on some systems) with no argv.  */
@@ -3010,6 +3017,13 @@ killed.  */
   if (!NILP (restart))
     {
       turn_on_atimers (false);
+#if defined HAVE_ANDROID && !defined ANDROID_STUBIFY
+      /* Re-executing the Emacs process created by the system doesn't
+	 work.  Instead, schedule a restart for a few hundered
+	 milliseconds and exit Emacs.  */
+      if (android_init_gui)
+	android_restart_emacs ();
+#endif
 #ifdef WINDOWSNT
       if (w32_reexec_emacs (initial_cmdline, initial_wd) < 0)
 #else