Move sensor handling to a callback.

native-activity/app/build.gradle

@@ -12,7 +12,7 @@ android {
 
     defaultConfig {
         applicationId = 'com.example.native_activity'
-        minSdkVersion 14
+        minSdkVersion 21
         targetSdkVersion 34
         externalNativeBuild {
             cmake {

native-activity/app/src/main/cpp/main.cpp

@@ -20,6 +20,7 @@
 #include <GLES/gl.h>
 #include <android/log.h>
 #include <android/sensor.h>
+#include <android/set_abort_message.h>
 #include <android_native_app_glue.h>
 #include <jni.h>
 
@@ -30,10 +31,38 @@
 #include <initializer_list>
 #include <memory>
 
-#define LOGI(...) \
-  ((void)__android_log_print(ANDROID_LOG_INFO, "native-activity", __VA_ARGS__))
-#define LOGW(...) \
-  ((void)__android_log_print(ANDROID_LOG_WARN, "native-activity", __VA_ARGS__))
+#define LOG_TAG "native-activity"
+
+#define _LOG(priority, fmt, ...) \
+  ((void)__android_log_print((priority), (LOG_TAG), (fmt)__VA_OPT__(, ) __VA_ARGS__))
+
+#define LOGE(fmt, ...) _LOG(ANDROID_LOG_ERROR, (fmt)__VA_OPT__(, ) __VA_ARGS__)
+#define LOGW(fmt, ...) _LOG(ANDROID_LOG_WARN, (fmt)__VA_OPT__(, ) __VA_ARGS__)
+#define LOGI(fmt, ...) _LOG(ANDROID_LOG_INFO, (fmt)__VA_OPT__(, ) __VA_ARGS__)
+
+[[noreturn]] __attribute__((__format__(__printf__, 1, 2))) static void fatal(
+    const char* fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  char* buf;
+  if (vasprintf(&buf, fmt, ap) < 0) {
+    android_set_abort_message("failed for format error message");
+  } else {
+    android_set_abort_message(buf);
+    // Also log directly, since the default Android Studio logcat filter hides
+    // the backtrace which would otherwise show the abort message.
+    LOGE("%s", buf);
+  }
+  std::abort();
+}
+
+#define CHECK_NOT_NULL(value)                                           \
+  do {                                                                  \
+    if ((value) == nullptr) {                                           \
+      fatal("%s:%d:%s must not be null", __PRETTY_FUNCTION__, __LINE__, \
+            #value);                                                    \
+    }                                                                   \
+  } while (false)
 
 /**
  * Our saved state data.
@@ -61,6 +90,20 @@ struct engine {
   int32_t width;
   int32_t height;
   struct saved_state state;
+
+  void CreateSensorListener(ALooper_callbackFunc callback) {
+    CHECK_NOT_NULL(app);
+
+    sensorManager = ASensorManager_getInstance();
+    if (sensorManager == nullptr) {
+      return;
+    }
+
+    accelerometerSensor = ASensorManager_getDefaultSensor(
+        sensorManager, ASENSOR_TYPE_ACCELEROMETER);
+    sensorEventQueue = ASensorManager_createEventQueue(
+        sensorManager, app->looper, ALOOPER_POLL_CALLBACK, callback, this);
+  }
 };
 
 /**
@@ -266,48 +309,22 @@ static void engine_handle_cmd(struct android_app* app, int32_t cmd) {
   }
 }
 
-/*
- * AcquireASensorManagerInstance(void)
- *    Workaround ASensorManager_getInstance() deprecation false alarm
- *    for Android-N and before, when compiling with NDK-r15
- */
-#include <dlfcn.h>
-ASensorManager* AcquireASensorManagerInstance(android_app* app) {
-  if (!app) return nullptr;
-
-  typedef ASensorManager* (*PF_GETINSTANCEFORPACKAGE)(const char* name);
-  void* androidHandle = dlopen("libandroid.so", RTLD_NOW);
-  auto getInstanceForPackageFunc = (PF_GETINSTANCEFORPACKAGE)dlsym(
-      androidHandle, "ASensorManager_getInstanceForPackage");
-  if (getInstanceForPackageFunc) {
-    JNIEnv* env = nullptr;
-    app->activity->vm->AttachCurrentThread(&env, nullptr);
-
-    jclass android_content_Context = env->GetObjectClass(app->activity->clazz);
-    jmethodID midGetPackageName = env->GetMethodID(
-        android_content_Context, "getPackageName", "()Ljava/lang/String;");
-    auto packageName =
-        (jstring)env->CallObjectMethod(app->activity->clazz, midGetPackageName);
-
-    const char* nativePackageName =
-        env->GetStringUTFChars(packageName, nullptr);
-    ASensorManager* mgr = getInstanceForPackageFunc(nativePackageName);
-    env->ReleaseStringUTFChars(packageName, nativePackageName);
-    app->activity->vm->DetachCurrentThread();
-    if (mgr) {
-      dlclose(androidHandle);
-      return mgr;
-    }
-  }
+int OnSensorEvent(int /* fd */, int /* events */, void* data) {
+  CHECK_NOT_NULL(data);
+  engine* engine = reinterpret_cast<struct engine*>(data);
 
-  typedef ASensorManager* (*PF_GETINSTANCE)();
-  auto getInstanceFunc =
-      (PF_GETINSTANCE)dlsym(androidHandle, "ASensorManager_getInstance");
-  // by all means at this point, ASensorManager_getInstance should be available
-  assert(getInstanceFunc);
-  dlclose(androidHandle);
+  CHECK_NOT_NULL(engine->accelerometerSensor);
+  ASensorEvent event;
+  while (ASensorEventQueue_getEvents(engine->sensorEventQueue, &event, 1) > 0) {
+    LOGI("accelerometer: x=%f y=%f z=%f", event.acceleration.x,
+         event.acceleration.y, event.acceleration.z);
+  }
 
-  return getInstanceFunc();
+  // From the docs:
+  //
+  // Implementations should return 1 to continue receiving callbacks, or 0 to
+  // have this file descriptor and callback unregistered from the looper.
+  return 1;
 }
 
 /**
@@ -325,11 +342,7 @@ void android_main(struct android_app* state) {
   engine.app = state;
 
   // Prepare to monitor accelerometer
-  engine.sensorManager = AcquireASensorManagerInstance(state);
-  engine.accelerometerSensor = ASensorManager_getDefaultSensor(
-      engine.sensorManager, ASENSOR_TYPE_ACCELEROMETER);
-  engine.sensorEventQueue = ASensorManager_createEventQueue(
-      engine.sensorManager, state->looper, LOOPER_ID_USER, nullptr, nullptr);
+  engine.CreateSensorListener(OnSensorEvent);
 
   if (state->savedState != nullptr) {
     // We are starting with a previous saved state; restore from it.
@@ -340,32 +353,19 @@ void android_main(struct android_app* state) {
 
   while (true) {
     // Read all pending events.
-    int ident;
     int events;
     struct android_poll_source* source;
 
     // If not animating, we will block forever waiting for events.
     // If animating, we loop until all events are read, then continue
     // to draw the next frame of animation.
-    while ((ident = ALooper_pollAll(engine.animating ? 0 : -1, nullptr, &events,
-                                    (void**)&source)) >= 0) {
+    while ((ALooper_pollAll(engine.animating ? 0 : -1, nullptr, &events,
+                            (void**)&source)) >= 0) {
       // Process this event.
       if (source != nullptr) {
         source->process(state, source);
       }
 
-      // If a sensor has data, process it now.
-      if (ident == LOOPER_ID_USER) {
-        if (engine.accelerometerSensor != nullptr) {
-          ASensorEvent event;
-          while (ASensorEventQueue_getEvents(engine.sensorEventQueue, &event,
-                                             1) > 0) {
-            LOGI("accelerometer: x=%f y=%f z=%f", event.acceleration.x,
-                 event.acceleration.y, event.acceleration.z);
-          }
-        }
-      }
-
       // Check if we are exiting.
       if (state->destroyRequested != 0) {
         engine_term_display(&engine);

other-builds/ndkbuild/native-activity/app/build.gradle

@@ -12,7 +12,7 @@ android {
 
     defaultConfig {
         applicationId = 'com.example.native_activity'
-        minSdkVersion 14
+        minSdkVersion 21
         targetSdkVersion 33
     }
     sourceSets {