Use executors for more control over started threads

Signed-off-by: Stefan Niedermann <info@niedermann.it>

2 files changed, 39 insertions, 37 deletions

diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/LiveDataHelper.java b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/LiveDataHelper.java
index 10a18bb09..059ed5e6b 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/LiveDataHelper.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/LiveDataHelper.java
@@ -6,38 +6,24 @@ import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MediatorLiveData;
 import androidx.lifecycle.Observer;
 
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
 import static androidx.lifecycle.Transformations.distinctUntilChanged;
 
 public class LiveDataHelper {
 
-    public interface DataChangeProcessor<T> {
-        void onDataChanged(T data);
+    private LiveDataHelper() {
+        throw new UnsupportedOperationException("This class must not be instantiated.");
     }
 
-    public interface DataTransformator<I, O> {
-        O transform(I data);
-    }
-
-    public interface LiveDataWrapper<T> {
-        T getData();
-
-        default void postResult(WrappedLiveData<T> liveData) {
-            liveData.setError(null);
-            T data = null;
-            try {
-                data = getData();
-            } catch (RuntimeException e) {
-                liveData.setError(e);
-            }
-            liveData.postValue(data);
-        }
-    }
+    private static final ExecutorService executor = Executors.newCachedThreadPool();
 
     public static <T> LiveData<T> interceptLiveData(LiveData<T> data, DataChangeProcessor<T> onDataChange) {
         MediatorLiveData<T> ret = new MediatorLiveData<>();
 
         ret.addSource(data, changedData ->
-                doAsync(() -> {
+                executor.submit(() -> {
                     onDataChange.onDataChanged(changedData);
                     ret.postValue(changedData);
                 })
@@ -47,32 +33,29 @@ public class LiveDataHelper {
 
 
     public static <I, O> LiveData<O> postCustomValue(LiveData<I> data, DataTransformator<I, O> transformator) {
-        MediatorLiveData<O> ret = new MediatorLiveData<>();
-
-        ret.addSource(data, changedData -> doAsync(() -> ret.postValue(transformator.transform(changedData))));
+        final MediatorLiveData<O> ret = new MediatorLiveData<>();
+        ret.addSource(data, changedData -> executor.submit(() -> ret.postValue(transformator.transform(changedData))));
         return distinctUntilChanged(ret);
     }
 
     public static <I> MediatorLiveData<I> of(I oneShot) {
-        MediatorLiveData<I> ret = new MediatorLiveData<I>() {
+        return new MediatorLiveData<I>() {
             @Override
             public void observe(@NonNull LifecycleOwner owner, @NonNull Observer observer) {
                 super.observe(owner, observer);
-                doAsync(() -> postValue(oneShot));
+                executor.submit(() -> postValue(oneShot));
             }
         };
-        return ret;
     }
 
     public static <I, O> LiveData<O> postSingleValue(LiveData<I> data, DataTransformator<I, O> transformator) {
-        MediatorLiveData<O> ret = new MediatorLiveData<>();
-
-        ret.addSource(data, changedData -> doAsync(() -> ret.postValue(transformator.transform(changedData))));
+        final MediatorLiveData<O> ret = new MediatorLiveData<>();
+        ret.addSource(data, changedData -> executor.submit(() -> ret.postValue(transformator.transform(changedData))));
         return distinctUntilChanged(ret);
     }
 
     public static <T> void observeOnce(LiveData<T> liveData, LifecycleOwner owner, Observer<T> observer) {
-        Observer<T> tempObserver = new Observer<T>() {
+        final Observer<T> tempObserver = new Observer<T>() {
             @Override
             public void onChanged(T result) {
                 liveData.removeObserver(this);
@@ -85,7 +68,7 @@ public class LiveDataHelper {
     public static <T> WrappedLiveData<T> wrapInLiveData(final LiveDataWrapper<T> liveDataWrapper) {
         final WrappedLiveData<T> liveData = new WrappedLiveData<>();
 
-        doAsync(() -> {
+        executor.submit(() -> {
             try {
                 liveDataWrapper.postResult(liveData);
             } catch (Throwable t) {
@@ -96,7 +79,26 @@ public class LiveDataHelper {
         return liveData;
     }
 
-    private static void doAsync(Runnable r) {
-        new Thread(r).start();
+    public interface DataChangeProcessor<T> {
+        void onDataChanged(T data);
+    }
+
+    public interface DataTransformator<I, O> {
+        O transform(I data);
+    }
+
+    public interface LiveDataWrapper<T> {
+        T getData();
+
+        default void postResult(WrappedLiveData<T> liveData) {
+            liveData.setError(null);
+            T data = null;
+            try {
+                data = getData();
+            } catch (RuntimeException e) {
+                liveData.setError(e);
+            }
+            liveData.postValue(data);
+        }
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/extrawurst/UserSearchLiveData.java b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/extrawurst/UserSearchLiveData.java
index 3d05247b3..4a90664c9 100644
--- a/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/extrawurst/UserSearchLiveData.java
+++ b/app/src/main/java/it/niedermann/nextcloud/deck/persistence/sync/adapters/db/util/extrawurst/UserSearchLiveData.java
@@ -18,12 +18,12 @@ import it.niedermann.nextcloud.deck.persistence.sync.adapters.db.DataBaseAdapter
 public class UserSearchLiveData extends MediatorLiveData<List<User>> implements Debouncer.Callback<Long> {
 
     private static final int DEBOUNCE_TIME = 300; // ms
-    private DataBaseAdapter db;
-    private ServerAdapter server;
+    private final DataBaseAdapter db;
+    private final ServerAdapter server;
     long accountId;
     String searchTerm;
     long notYetAssignedInACL;
-    private Debouncer<Long> debouncer = new Debouncer<>(this, DEBOUNCE_TIME);
+    private final Debouncer<Long> debouncer = new Debouncer<>(this, DEBOUNCE_TIME);
 
     public UserSearchLiveData(DataBaseAdapter db, ServerAdapter server) {
         this.db = db;