Fix a crash that happens when the application changes states. (#14102)

Author: visumickey

FirebasePerformance/CHANGELOG.md

@@ -1,3 +1,6 @@
+# Unreleased
+- [fixed] Fix a crash related to registering for notifications when the app is between foreground or background states. (#13174)
+
 # 11.5.0
 - [fixed] Replaced usage of the deprecated `UIApplication.keyWindow` property
   with `UIWindow.isKeyWindow`; this API is also available on visionOS. Note that

FirebasePerformance/Sources/AppActivity/FPRTraceBackgroundActivityTracker.m

@@ -35,16 +35,17 @@ - (instancetype)init {
     } else {
       _traceBackgroundState = FPRTraceStateForegroundOnly;
     }
+    dispatch_async(dispatch_get_main_queue(), ^{
+      [[NSNotificationCenter defaultCenter] addObserver:self
+                                               selector:@selector(applicationDidBecomeActive:)
+                                                   name:UIApplicationDidBecomeActiveNotification
+                                                 object:[UIApplication sharedApplication]];
 
-    [[NSNotificationCenter defaultCenter] addObserver:self
-                                             selector:@selector(applicationDidBecomeActive:)
-                                                 name:UIApplicationDidBecomeActiveNotification
-                                               object:[UIApplication sharedApplication]];
-
-    [[NSNotificationCenter defaultCenter] addObserver:self
-                                             selector:@selector(applicationDidEnterBackground:)
-                                                 name:UIApplicationDidEnterBackgroundNotification
-                                               object:[UIApplication sharedApplication]];
+      [[NSNotificationCenter defaultCenter] addObserver:self
+                                               selector:@selector(applicationDidEnterBackground:)
+                                                   name:UIApplicationDidEnterBackgroundNotification
+                                                 object:[UIApplication sharedApplication]];
+    });
   }
   return self;
 }

FirebasePerformance/Tests/Unit/FPRTraceBackgroundActivityTrackerTest.m

@@ -38,13 +38,27 @@ - (void)testForegroundTracking {
 
 /** Validates if the foreground & background state is captured correctly. */
 - (void)testBackgroundTracking {
+  XCTestExpectation *expectation = [self expectationWithDescription:@"Application state change"];
+
   FPRTraceBackgroundActivityTracker *tracker = [[FPRTraceBackgroundActivityTracker alloc] init];
   NSNotificationCenter *defaultCenter = [NSNotificationCenter defaultCenter];
-  [defaultCenter postNotificationName:UIApplicationDidBecomeActiveNotification
-                               object:[UIApplication sharedApplication]];
-  [defaultCenter postNotificationName:UIApplicationDidEnterBackgroundNotification
-                               object:[UIApplication sharedApplication]];
-  XCTAssertEqual(tracker.traceBackgroundState, FPRTraceStateBackgroundAndForeground);
+  dispatch_async(dispatch_get_main_queue(), ^{
+    [defaultCenter postNotificationName:UIApplicationDidBecomeActiveNotification
+                                 object:[UIApplication sharedApplication]];
+    [defaultCenter postNotificationName:UIApplicationDidEnterBackgroundNotification
+                                 object:[UIApplication sharedApplication]];
+    [expectation fulfill];
+  });
+
+  [self waitForExpectationsWithTimeout:5.0
+                               handler:^(NSError *_Nullable error) {
+                                 if (error) {
+                                   XCTFail(@"Expectation failed with error: %@", error);
+                                 } else {
+                                   XCTAssertEqual(tracker.traceBackgroundState,
+                                                  FPRTraceStateBackgroundAndForeground);
+                                 }
+                               }];
 }
 
 @end

FirebasePerformance/Tests/Unit/Timer/FIRTraceTest.m

@@ -427,15 +427,28 @@ - (void)testValidTraceWithStageAndMetrics {
 
 /** Validates the value of background state when the app is backgrounded. */
 - (void)testValidTraceWithBackgrounding {
+  XCTestExpectation *expectation = [self expectationWithDescription:@"Application state change"];
   NSNotificationCenter *defaultCenter = [NSNotificationCenter defaultCenter];
   FIRTrace *trace = [[FIRTrace alloc] initWithName:@"Random"];
   [trace start];
-  [defaultCenter postNotificationName:UIApplicationDidEnterBackgroundNotification
-                               object:[UIApplication sharedApplication]];
-  [defaultCenter postNotificationName:UIApplicationDidBecomeActiveNotification
-                               object:[UIApplication sharedApplication]];
-  XCTAssertEqual(trace.backgroundTraceState, FPRTraceStateBackgroundAndForeground);
-  [trace stop];
+  dispatch_async(dispatch_get_main_queue(), ^{
+    [defaultCenter postNotificationName:UIApplicationDidEnterBackgroundNotification
+                                 object:[UIApplication sharedApplication]];
+    [defaultCenter postNotificationName:UIApplicationDidBecomeActiveNotification
+                                 object:[UIApplication sharedApplication]];
+    [expectation fulfill];
+  });
+
+  [self waitForExpectationsWithTimeout:5.0
+                               handler:^(NSError *_Nullable error) {
+                                 if (error) {
+                                   XCTFail(@"Expectation failed with error: %@", error);
+                                 } else {
+                                   XCTAssertEqual(trace.backgroundTraceState,
+                                                  FPRTraceStateBackgroundAndForeground);
+                                   [trace stop];
+                                 }
+                               }];
 }
 
 /** Validates the value of background state when trace is not started. */
@@ -452,15 +465,29 @@ - (void)testValidTraceWithoutStart {
 
 /** Validates the value of background state is available after trace is stopped. */
 - (void)testBackgroundStateAfterTraceStop {
+  XCTestExpectation *expectation = [self expectationWithDescription:@"Application state change"];
+
   NSNotificationCenter *defaultCenter = [NSNotificationCenter defaultCenter];
   FIRTrace *trace = [[FIRTrace alloc] initWithName:@"Random"];
   [trace start];
-  [defaultCenter postNotificationName:UIApplicationDidEnterBackgroundNotification
-                               object:[UIApplication sharedApplication]];
-  [defaultCenter postNotificationName:UIApplicationDidBecomeActiveNotification
-                               object:[UIApplication sharedApplication]];
-  [trace stop];
-  XCTAssertEqual(trace.backgroundTraceState, FPRTraceStateBackgroundAndForeground);
+  dispatch_async(dispatch_get_main_queue(), ^{
+    [defaultCenter postNotificationName:UIApplicationDidEnterBackgroundNotification
+                                 object:[UIApplication sharedApplication]];
+    [defaultCenter postNotificationName:UIApplicationDidBecomeActiveNotification
+                                 object:[UIApplication sharedApplication]];
+    [expectation fulfill];
+  });
+
+  [self waitForExpectationsWithTimeout:5.0
+                               handler:^(NSError *_Nullable error) {
+                                 if (error) {
+                                   XCTFail(@"Expectation failed with error: %@", error);
+                                 } else {
+                                   [trace stop];
+                                   XCTAssertEqual(trace.backgroundTraceState,
+                                                  FPRTraceStateBackgroundAndForeground);
+                                 }
+                               }];
 }
 
 /** Validates that stages do not have any valid background state. */