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/*
* 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;
}
}
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