Combiner.java revision 60a2cd8ac439bf41bfddc5f5f339feda7c7ff175 
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
17package com.android.inputmethod.event;
18
19import java.util.ArrayList;
20
21import javax.annotation.Nonnull;
22
23/**
24 * A generic interface for combiners. Combiners are objects that transform chains of input events
25 * into committable strings and manage feedback to show to the user on the combining state.
26 */
27public interface Combiner {
28    /**
29     * Process an event, possibly combining it with the existing state and return the new event.
30     *
31     * If this event does not result in any new event getting passed down the chain, this method
32     * returns null. It may also modify the previous event list if appropriate.
33     *
34     * @param previousEvents the previous events in this composition.
35     * @param event the event to combine with the existing state.
36     * @return the resulting event.
37     */
38    @Nonnull
39    Event processEvent(ArrayList<Event> previousEvents, Event event);
40
41    /**
42     * Get the feedback that should be shown to the user for the current state of this combiner.
43     * @return A CharSequence representing the feedback to show users. It may include styles.
44     */
45    CharSequence getCombiningStateFeedback();
46
47    /**
48     * Reset the state of this combiner, for example when the cursor was moved.
49     */
50    void reset();
51}
52