Fix secure screen option subscription memory leak

app/src/main/java/eu/kanade/tachiyomi/ui/security/SecureActivityDelegate.kt

@@ -7,16 +7,17 @@ import androidx.fragment.app.FragmentActivity
 import eu.kanade.tachiyomi.data.preference.PreferencesHelper
 import eu.kanade.tachiyomi.data.preference.getOrDefault
 import java.util.Date
+import rx.Subscription
 import uy.kohesive.injekt.injectLazy
 
-object SecureActivityDelegate {
+class SecureActivityDelegate(private val activity: FragmentActivity) {
 
     private val preferences by injectLazy<PreferencesHelper>()
 
-    var locked: Boolean = true
+    private var secureScreenSubscription: Subscription? = null
 
-    fun onCreate(activity: FragmentActivity) {
-        preferences.secureScreen().asObservable()
+    fun onCreate() {
+        secureScreenSubscription = preferences.secureScreen().asObservable()
                 .subscribe {
                     if (it) {
                         activity.window.setFlags(WindowManager.LayoutParams.FLAG_SECURE, WindowManager.LayoutParams.FLAG_SECURE)
@@ -26,7 +27,7 @@ object SecureActivityDelegate {
                 }
     }
 
-    fun onResume(activity: FragmentActivity) {
+    fun onResume() {
         val lockApp = preferences.useBiometricLock().getOrDefault()
         if (lockApp && BiometricManager.from(activity).canAuthenticate() == BiometricManager.BIOMETRIC_SUCCESS) {
             if (isAppLocked()) {
@@ -39,9 +40,17 @@ object SecureActivityDelegate {
         }
     }
 
+    fun onDestroy() {
+        secureScreenSubscription?.unsubscribe()
+    }
+
     private fun isAppLocked(): Boolean {
         return locked &&
                 (preferences.lockAppAfter().getOrDefault() <= 0 ||
                         Date().time >= preferences.lastAppUnlock().getOrDefault() + 60 * 1000 * preferences.lockAppAfter().getOrDefault())
     }
+
+    companion object {
+        var locked: Boolean = true
+    }
 }