Android: Always queue calls from Qt to Android.

Calling runOnUiThread() only queues calls that comes from a different
thread then the UI thread. The problem with the current solution is that
we can't promise or rely on the calls being delivered in the same order
they were called. Another consequence of the old behavior is that we
potentially cause long lasting synchronization points, which can cause
the application to become unresponsive or in worst case result in a
deadlock. With this change all calls to runAction() will be queued on
Android's main message queue (aka the UI thread) and return immediately.

Change-Id: I50a4273ae9ba8ad17fb2c50ccd57449e4fbc12f9
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/src/android/jar/src/org/qtproject/qt5/android/QtNative.java b/src/android/jar/src/org/qtproject/qt5/android/QtNative.java
index a1e7dac4d4..0c01e67637 100644
--- a/src/android/jar/src/org/qtproject/qt5/android/QtNative.java
+++ b/src/android/jar/src/org/qtproject/qt5/android/QtNative.java
@@ -42,6 +42,8 @@ import android.app.Activity;
 import android.content.Context;
 import android.content.Intent;
 import android.net.Uri;
+import android.os.Handler;
+import android.os.Looper;
 import android.text.ClipboardManager;
 import android.os.Build;
 import android.util.Log;
@@ -173,14 +175,14 @@ public class QtNative
         m_lostActions.clear();
     }
 
-    private static boolean runAction(Runnable action)
+    private static void runAction(Runnable action)
     {
         synchronized (m_mainActivityMutex) {
-            if (m_activity == null)
+            final Looper mainLooper = Looper.getMainLooper();
+            final Handler handler = new Handler(mainLooper);
+            final boolean actionIsQueued = m_activity != null && mainLooper != null && handler.post(action);
+            if (!actionIsQueued)
                 m_lostActions.add(action);
-            else
-                m_activity.runOnUiThread(action);
-            return m_activity != null;
         }
     }