1 /* 2 * Copyright (C) 2013 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.content; 18 19 import android.os.Parcel; 20 import android.os.Parcelable; 21 22 /** 23 * A single undoable operation. You must subclass this to implement the state 24 * and behavior for your operation. Instances of this class are placed and 25 * managed in an {@link UndoManager}. 26 * 27 * @hide 28 */ 29 public abstract class UndoOperation<DATA> implements Parcelable { 30 UndoOwner mOwner; 31 32 /** 33 * Create a new instance of the operation. 34 * @param owner Who owns the data being modified by this undo state; must be 35 * returned by {@link UndoManager#getOwner(String, Object) UndoManager.getOwner}. 36 */ UndoOperation(UndoOwner owner)37 public UndoOperation(UndoOwner owner) { 38 mOwner = owner; 39 } 40 41 /** 42 * Construct from a Parcel. 43 */ UndoOperation(Parcel src, ClassLoader loader)44 protected UndoOperation(Parcel src, ClassLoader loader) { 45 } 46 47 /** 48 * Owning object as given to {@link #UndoOperation(UndoOwner)}. 49 */ getOwner()50 public UndoOwner getOwner() { 51 return mOwner; 52 } 53 54 /** 55 * Synonym for {@link #getOwner()}.{@link android.content.UndoOwner#getData()}. 56 */ getOwnerData()57 public DATA getOwnerData() { 58 return (DATA)mOwner.getData(); 59 } 60 61 /** 62 * Return true if this undo operation is a member of the given owner. 63 * The default implementation is <code>owner == getOwner()</code>. You 64 * can override this to provide more sophisticated dependencies between 65 * owners. 66 */ matchOwner(UndoOwner owner)67 public boolean matchOwner(UndoOwner owner) { 68 return owner == getOwner(); 69 } 70 71 /** 72 * Return true if this operation actually contains modification data. The 73 * default implementation always returns true. If you return false, the 74 * operation will be dropped when the final undo state is being built. 75 */ hasData()76 public boolean hasData() { 77 return true; 78 } 79 80 /** 81 * Return true if this operation can be merged with a later operation. 82 * The default implementation always returns true. 83 */ allowMerge()84 public boolean allowMerge() { 85 return true; 86 } 87 88 /** 89 * Called when this undo state is being committed to the undo stack. 90 * The implementation should perform the initial edits and save any state that 91 * may be needed to undo them. 92 */ commit()93 public abstract void commit(); 94 95 /** 96 * Called when this undo state is being popped off the undo stack (in to 97 * the temporary redo stack). The implementation should remove the original 98 * edits and thus restore the target object to its prior value. 99 */ undo()100 public abstract void undo(); 101 102 /** 103 * Called when this undo state is being pushed back from the transient 104 * redo stack to the main undo stack. The implementation should re-apply 105 * the edits that were previously removed by {@link #undo}. 106 */ redo()107 public abstract void redo(); 108 describeContents()109 public int describeContents() { 110 return 0; 111 } 112 } 113