Android: Fix freeze on start when the activity was destroyed before

This can be tested by enabling "Don't keep activities" in the developer options. With this option Android will immediately destroy the activity when it is moved to the background. In this case registerBackends will be called the first time before the BackendRegister was created. Because m_backendsRegistered was set to true even if it failed, the final call has no effect. So we need to ensure to set m_backendsRegistered only if a BackendRegister is available. Fixes: QTBUG-132085 Pick-to: 6.8 Change-Id: I2ea1c0e0737c982594ceb06cbaf540399c45e3f4 Reviewed-by: Assam Boudjelthia <[email protected]> (cherry picked from commit 9903242) Reviewed-by: Qt Cherry-pick Bot <[email protected]>
qt · Jan 5, 2025 · 850ed02 · 850ed02
1 parent b72c498
commit 850ed02
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Showing 5 changed files with 23 additions and 2 deletions.
diff --git a/src/android/jar/src/org/qtproject/qt/android/BackendRegister.java b/src/android/jar/src/org/qtproject/qt/android/BackendRegister.java
@@ -4,6 +4,7 @@
 
 class BackendRegister
 {
+    static native boolean isNull();
     static native void registerBackend(Class interfaceType, Object interfaceObject);
     static native void unregisterBackend(Class interfaceType);
 }
diff --git a/src/android/jar/src/org/qtproject/qt/android/QtActivityDelegate.java b/src/android/jar/src/org/qtproject/qt/android/QtActivityDelegate.java
@@ -59,8 +59,9 @@ void initMembers()
 
     void registerBackends()
     {
-        if (m_backendsRegistered)
+        if (m_backendsRegistered || BackendRegister.isNull())
             return;
+
         m_backendsRegistered = true;
         BackendRegister.registerBackend(QtWindowInterface.class, QtActivityDelegate.this);
         BackendRegister.registerBackend(QtAccessibilityInterface.class, QtActivityDelegate.this);
@@ -74,6 +75,10 @@ void unregisterBackends()
             return;
 
         m_backendsRegistered = false;
+
+        if (BackendRegister.isNull())
+            return;
+
         BackendRegister.unregisterBackend(QtWindowInterface.class);
         BackendRegister.unregisterBackend(QtAccessibilityInterface.class);
         BackendRegister.unregisterBackend(QtMenuInterface.class);

diff --git a/src/android/jar/src/org/qtproject/qt/android/QtEmbeddedDelegate.java b/src/android/jar/src/org/qtproject/qt/android/QtEmbeddedDelegate.java
@@ -88,12 +88,19 @@ public void onAppStateDetailsChanged(QtNative.ApplicationStateDetails details) {
         synchronized (this) {
             m_stateDetails = details;
             if (details.isStarted && !m_backendsRegistered) {
+                if (BackendRegister.isNull())
+                    return;
+
                 m_backendsRegistered = true;
                 BackendRegister.registerBackend(QtWindowInterface.class, this);
                 BackendRegister.registerBackend(QtMenuInterface.class, this);
                 BackendRegister.registerBackend(QtInputInterface.class, m_inputDelegate);
             } else if (!details.isStarted && m_backendsRegistered) {
                 m_backendsRegistered = false;
+
+                if (BackendRegister.isNull())
+                    return;
+
                 BackendRegister.unregisterBackend(QtWindowInterface.class);
                 BackendRegister.unregisterBackend(QtMenuInterface.class);
                 BackendRegister.unregisterBackend(QtInputInterface.class);

diff --git a/src/plugins/platforms/android/androidbackendregister.cpp b/src/plugins/platforms/android/androidbackendregister.cpp
@@ -14,10 +14,16 @@ Q_DECLARE_JNI_CLASS(BackendRegister, "org/qtproject/qt/android/BackendRegister")
 bool AndroidBackendRegister::registerNatives()
 {
     return QtJniTypes::BackendRegister::registerNativeMethods(
-            { Q_JNI_NATIVE_SCOPED_METHOD(registerBackend, AndroidBackendRegister),
+            { Q_JNI_NATIVE_SCOPED_METHOD(isNull, AndroidBackendRegister),
+              Q_JNI_NATIVE_SCOPED_METHOD(registerBackend, AndroidBackendRegister),
               Q_JNI_NATIVE_SCOPED_METHOD(unregisterBackend, AndroidBackendRegister) });
 }
 
+jboolean AndroidBackendRegister::isNull(JNIEnv *, jclass)
+{
+    return QtAndroid::backendRegister() == nullptr;
+}
+
 void AndroidBackendRegister::registerBackend(JNIEnv *, jclass, jclass interfaceClass,
                                              jobject interface)
 {

diff --git a/src/plugins/platforms/android/androidbackendregister.h b/src/plugins/platforms/android/androidbackendregister.h
@@ -60,6 +60,8 @@ class AndroidBackendRegister
     QMutex m_registerMutex;
     QMap<QString, QJniObject> m_register;
 
+    static jboolean isNull(JNIEnv *, jclass);
+    Q_DECLARE_JNI_NATIVE_METHOD_IN_CURRENT_SCOPE(isNull)
     static void registerBackend(JNIEnv *, jclass, jclass interfaceClass, jobject interface);
     Q_DECLARE_JNI_NATIVE_METHOD_IN_CURRENT_SCOPE(registerBackend)
     static void unregisterBackend(JNIEnv *, jclass, jclass interfaceClass);