| /* |
| * Copyright (C) 2013 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.content; |
| |
| import android.os.Parcel; |
| import android.os.Parcelable; |
| |
| /** |
| * A single undoable operation. You must subclass this to implement the state |
| * and behavior for your operation. Instances of this class are placed and |
| * managed in an {@link UndoManager}. |
| * |
| * @hide |
| */ |
| public abstract class UndoOperation<DATA> implements Parcelable { |
| UndoOwner mOwner; |
| |
| /** |
| * Create a new instance of the operation. |
| * @param owner Who owns the data being modified by this undo state; must be |
| * returned by {@link UndoManager#getOwner(String, Object) UndoManager.getOwner}. |
| */ |
| public UndoOperation(UndoOwner owner) { |
| mOwner = owner; |
| } |
| |
| /** |
| * Construct from a Parcel. |
| */ |
| protected UndoOperation(Parcel src, ClassLoader loader) { |
| } |
| |
| /** |
| * Owning object as given to {@link #UndoOperation(UndoOwner)}. |
| */ |
| public UndoOwner getOwner() { |
| return mOwner; |
| } |
| |
| /** |
| * Synonym for {@link #getOwner()}.{@link android.content.UndoOwner#getData()}. |
| */ |
| public DATA getOwnerData() { |
| return (DATA)mOwner.getData(); |
| } |
| |
| /** |
| * Return true if this undo operation is a member of the given owner. |
| * The default implementation is <code>owner == getOwner()</code>. You |
| * can override this to provide more sophisticated dependencies between |
| * owners. |
| */ |
| public boolean matchOwner(UndoOwner owner) { |
| return owner == getOwner(); |
| } |
| |
| /** |
| * Return true if this operation actually contains modification data. The |
| * default implementation always returns true. If you return false, the |
| * operation will be dropped when the final undo state is being built. |
| */ |
| public boolean hasData() { |
| return true; |
| } |
| |
| /** |
| * Return true if this operation can be merged with a later operation. |
| * The default implementation always returns true. |
| */ |
| public boolean allowMerge() { |
| return true; |
| } |
| |
| /** |
| * Called when this undo state is being committed to the undo stack. |
| * The implementation should perform the initial edits and save any state that |
| * may be needed to undo them. |
| */ |
| public abstract void commit(); |
| |
| /** |
| * Called when this undo state is being popped off the undo stack (in to |
| * the temporary redo stack). The implementation should remove the original |
| * edits and thus restore the target object to its prior value. |
| */ |
| public abstract void undo(); |
| |
| /** |
| * Called when this undo state is being pushed back from the transient |
| * redo stack to the main undo stack. The implementation should re-apply |
| * the edits that were previously removed by {@link #undo}. |
| */ |
| public abstract void redo(); |
| |
| public int describeContents() { |
| return 0; |
| } |
| } |