add bunch of new java APIs: mostly stubs or copied from AOSP

Many of these classes are only needed to be subclassed by androidx
support library, which is used in many android apps

src/api-impl/android/database/Cursor.java

@@ -23,7 +23,6 @@ import android.os.Bundle;
 import java.io.Closeable;
 
 class CharArrayBuffer {}
-class DataSetObserver {}
 
 /**
  * This interface provides random read-write access to the result set returned

src/api-impl/android/database/DataSetObservable.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2007 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.database;
+
+/**
+ * A specialization of {@link Observable} for {@link DataSetObserver}
+ * that provides methods for sending notifications to a list of
+ * {@link DataSetObserver} objects.
+ */
+public class DataSetObservable extends Observable<DataSetObserver> {
+	/**
+	 * Invokes {@link DataSetObserver#onChanged} on each observer.
+	 * Called when the contents of the data set have changed.  The recipient
+	 * will obtain the new contents the next time it queries the data set.
+	 */
+	public void notifyChanged() {
+		synchronized(mObservers) {
+			// since onChanged() is implemented by the app, it could do anything, including
+			// removing itself from {@link mObservers} - and that could cause problems if
+			// an iterator is used on the ArrayList {@link mObservers}.
+			// to avoid such problems, just march thru the list in the reverse order.
+			for (int i = mObservers.size() - 1; i >= 0; i--) {
+				mObservers.get(i).onChanged();
+			}
+		}
+	}
+
+	/**
+	 * Invokes {@link DataSetObserver#onInvalidated} on each observer.
+	 * Called when the data set is no longer valid and cannot be queried again,
+	 * such as when the data set has been closed.
+	 */
+	public void notifyInvalidated() {
+		synchronized (mObservers) {
+			for (int i = mObservers.size() - 1; i >= 0; i--) {
+				mObservers.get(i).onInvalidated();
+			}
+		}
+	}
+}

src/api-impl/android/database/DataSetObserver.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2007 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.database;
+
+/**
+ * Receives call backs when a data set has been changed, or made invalid. The typically data sets
+ * that are observed are {@link Cursor}s or {@link android.widget.Adapter}s.
+ * DataSetObserver must be implemented by objects which are added to a DataSetObservable.
+ */
+public abstract class DataSetObserver {
+	/**
+	 * This method is called when the entire data set has changed,
+	 * most likely through a call to {@link Cursor#requery()} on a {@link Cursor}.
+	 */
+	public void onChanged() {
+		// Do nothing
+	}
+
+	/**
+	 * This method is called when the entire data becomes invalid,
+	 * most likely through a call to {@link Cursor#deactivate()} or {@link Cursor#close()} on a
+	 * {@link Cursor}.
+	 */
+	public void onInvalidated() {
+		// Do nothing
+	}
+}

src/api-impl/android/database/Observable.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2007 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package android.database;
+
+import java.util.ArrayList;
+
+/**
+ * Provides methods for registering or unregistering arbitrary observers in an {@link ArrayList}.
+ *
+ * This abstract class is intended to be subclassed and specialized to maintain
+ * a registry of observers of specific types and dispatch notifications to them.
+ *
+ * @param T The observer type.
+ */
+public abstract class Observable<T> {
+	/**
+	 * The list of observers.  An observer can be in the list at most
+	 * once and will never be null.
+	 */
+	protected final ArrayList<T> mObservers = new ArrayList<T>();
+
+	/**
+	 * Adds an observer to the list. The observer cannot be null and it must not already
+	 * be registered.
+	 * @param observer the observer to register
+	 * @throws IllegalArgumentException the observer is null
+	 * @throws IllegalStateException the observer is already registered
+	 */
+	public void registerObserver(T observer) {
+		if (observer == null) {
+			throw new IllegalArgumentException("The observer is null.");
+		}
+		synchronized(mObservers) {
+			if (mObservers.contains(observer)) {
+				throw new IllegalStateException("Observer " + observer + " is already registered.");
+			}
+			mObservers.add(observer);
+		}
+	}
+
+	/**
+	 * Removes a previously registered observer. The observer must not be null and it
+	 * must already have been registered.
+	 * @param observer the observer to unregister
+	 * @throws IllegalArgumentException the observer is null
+	 * @throws IllegalStateException the observer is not yet registered
+	 */
+	public void unregisterObserver(T observer) {
+		if (observer == null) {
+			throw new IllegalArgumentException("The observer is null.");
+		}
+		synchronized(mObservers) {
+			int index = mObservers.indexOf(observer);
+			if (index == -1) {
+				throw new IllegalStateException("Observer " + observer + " was not registered.");
+			}
+			mObservers.remove(index);
+		}
+	}
+
+	/**
+	 * Remove all registered observers.
+	 */
+	public void unregisterAll() {
+		synchronized(mObservers) {
+			mObservers.clear();
+		}
+	}
+
+}