Change static singletons to cached singletons with weak references to save... (6960a480) · Commits · e / os / AccountManager

app/src/main/java/at/bitfire/davdroid/AndroidSingleton.kt

deleted100644 → 0

+0 −29

Original line number	Diff line number	Diff line
		package at.bitfire.davdroid

		import android.content.Context

		abstract class AndroidSingleton<T> {

		var creatingSingleton = false
		var singleton: T? = null

		@Synchronized
		fun getInstance(context: Context): T {
		singleton?.let {
		return it
		}

		if (creatingSingleton)
		throw IllegalStateException("AndroidSingleton::getInstance() must not be called while createInstance()")
		creatingSingleton = true

		val newSingleton = createInstance(context.applicationContext)
		singleton = newSingleton

		creatingSingleton = false
		return newSingleton
		}

		protected abstract fun createInstance(context: Context): T

		}
		No newline at end of file

+26 −4

Original line number	Diff line number	Diff line
		@@ -3,8 +3,16 @@ package at.bitfire.davdroid
		import android.content.Context
		import java.lang.ref.WeakReference

		/**
		* A singleton registry that guarantees that there is not more than one instance per class.
		*
		* It uses weak references so that as soon as the singletons are not used anymore, they can be
		* freed by GC.
		*/
		object Singleton {

		private val currentlyCreating = HashSet<Class<*>>()

		private val singletons = mutableMapOf<Any, WeakReference<Any>>()


		@@ -17,6 +25,11 @@ object Singleton {
		}


		@Synchronized
		fun dropAll() {
		singletons.clear()
		}

		@Synchronized
		fun<T> getInstance(clazz: Class<T>, createInstance: () -> T): T {
		var cached = singletons[clazz]
		@@ -30,10 +43,19 @@ object Singleton {
		@Suppress("UNCHECKED_CAST")
		return cached.get() as T

		// create new singleton
		// CREATE NEW SINGLETON
		// prevent recursive creation
		if (currentlyCreating.contains(clazz))
		throw IllegalStateException("Singleton.getInstance must not be called recursively")
		currentlyCreating += clazz
		// actually create the instance
		try {
		val newInstance = createInstance()
		singletons[clazz] = WeakReference(newInstance)
		return newInstance
		} finally {
		currentlyCreating -= clazz
		}
		}

		}
		No newline at end of file

+29 −28

Original line number	Diff line number	Diff line
		@@ -11,8 +11,8 @@ import androidx.core.database.getStringOrNull
		import androidx.room.*
		import androidx.room.migration.Migration
		import androidx.sqlite.db.SupportSQLiteDatabase
		import at.bitfire.davdroid.AndroidSingleton
		import at.bitfire.davdroid.R
		import at.bitfire.davdroid.Singleton
		import at.bitfire.davdroid.TextTable
		import at.bitfire.davdroid.log.Logger
		import at.bitfire.davdroid.ui.AccountsActivity
		@@ -41,9 +41,9 @@ abstract class AppDatabase: RoomDatabase() {
		abstract fun webDavDocumentDao(): WebDavDocumentDao
		abstract fun webDavMountDao(): WebDavMountDao

		companion object: AndroidSingleton<AppDatabase>() {
		companion object {

		override fun createInstance(context: Context): AppDatabase =
		fun getInstance(context: Context) = Singleton.getInstance<AppDatabase>(context) {
		Room.databaseBuilder(context.applicationContext, AppDatabase::class.java, "services.db")
		.addMigrations(*migrations)
		.fallbackToDestructiveMigration() // as a last fallback, recreate database instead of crashing
		@@ -68,6 +68,7 @@ abstract class AppDatabase: RoomDatabase() {
		}
		})
		.build()
		}


		// migrations

+4 −3

Original line number	Diff line number	Diff line
		@@ -11,7 +11,7 @@ package at.bitfire.davdroid.settings
		import android.content.Context
		import android.util.NoSuchPropertyException
		import androidx.annotation.AnyThread
		import at.bitfire.davdroid.AndroidSingleton
		import at.bitfire.davdroid.Singleton
		import at.bitfire.davdroid.log.Logger
		import java.io.Writer
		import java.lang.ref.WeakReference
		@@ -26,8 +26,9 @@ class SettingsManager private constructor(
		context: Context
		) {

		companion object: AndroidSingleton<SettingsManager>() {
		override fun createInstance(context: Context) = SettingsManager(context)
		companion object {
		fun getInstance(context: Context) =
		Singleton.getInstance(context) { SettingsManager(context) }
		}

		private val providers = LinkedList<SettingsProvider>()

+28 −11

Original line number	Diff line number	Diff line
		package at.bitfire.davdroid

		import org.junit.Assert.*
		import org.junit.Before
		import org.junit.Test
		import java.lang.ref.WeakReference

		class SingletonTest {

		@Before
		fun prepare() {
		Singleton.dropAll()
		}


		@Test
		fun test_Cache() {
		val obj1 = Singleton.getInstance { Object() }
		assertEquals(obj1, Singleton.getInstance<Object> {
		fail("No new Object must be created")
		Object()
		fun testCache() {
		val obj1 = Singleton.getInstance { Any() }
		assertEquals(obj1, Singleton.getInstance {
		fail("No new Any must be created")
		Any()
		})
		}

		@Test
		fun test_CacheUsesWeakReferences() {
		var obj1: Object? = Singleton.getInstance { Object() }
		fun testCacheUsesWeakReferences() {
		var obj1: Any? = Singleton.getInstance { Any() }
		val refObj1 = WeakReference(obj1)
		obj1 = null

		// no reference anymore, validate
		System.gc()
		Runtime.getRuntime().gc()
		assertNull(refObj1.get())

		// create a new instance
		val obj2 = Singleton.getInstance { Object() }
		assertEquals(obj2, Singleton.getInstance<Object> {
		fail("No new Object must be created")
		Object()
		val obj2 = Singleton.getInstance { Any() }
		assertEquals(obj2, Singleton.getInstance {
		fail("No new Any must be created")
		Any()
		})
		}

		@Test(expected = IllegalStateException::class)
		fun testRecursive() {
		Singleton.getInstance() {
		Singleton.getInstance() {
		Any()
		}
		}
		}

		}
		No newline at end of file