[go: nahoru, domu]
1/*
2 * Copyright (C) 2010 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 android.animation;
18
19import android.view.animation.AnimationUtils;
20
21/**
22 * This class provides a simple callback mechanism to listeners that is synchronized with all
23 * other animators in the system. There is no duration, interpolation, or object value-setting
24 * with this Animator. Instead, it is simply started, after which it proceeds to send out events
25 * on every animation frame to its TimeListener (if set), with information about this animator,
26 * the total elapsed time, and the elapsed time since the previous animation frame.
27 */
28public class TimeAnimator extends ValueAnimator {
29
30    private TimeListener mListener;
31    private long mPreviousTime = -1;
32
33    @Override
34    public void start() {
35        mPreviousTime = -1;
36        super.start();
37    }
38
39    @Override
40    boolean animateBasedOnTime(long currentTime) {
41        if (mListener != null) {
42            long totalTime = currentTime - mStartTime;
43            long deltaTime = (mPreviousTime < 0) ? 0 : (currentTime - mPreviousTime);
44            mPreviousTime = currentTime;
45            mListener.onTimeUpdate(this, totalTime, deltaTime);
46        }
47        return false;
48    }
49
50    @Override
51    public void setCurrentPlayTime(long playTime) {
52        long currentTime = AnimationUtils.currentAnimationTimeMillis();
53        mStartTime = Math.max(mStartTime, currentTime - playTime);
54        mStartTimeCommitted = true; // do not allow start time to be compensated for jank
55        animateBasedOnTime(currentTime);
56    }
57
58    /**
59     * Sets a listener that is sent update events throughout the life of
60     * an animation.
61     *
62     * @param listener the listener to be set.
63     */
64    public void setTimeListener(TimeListener listener) {
65        mListener = listener;
66    }
67
68    @Override
69    void animateValue(float fraction) {
70        // Noop
71    }
72
73    @Override
74    void initAnimation() {
75        // noop
76    }
77
78    /**
79     * Implementors of this interface can set themselves as update listeners
80     * to a <code>TimeAnimator</code> instance to receive callbacks on every animation
81     * frame to receive the total time since the animator started and the delta time
82     * since the last frame. The first time the listener is called,
83     * deltaTime will be zero. The same is true for totalTime, unless the animator was
84     * set to a specific {@link ValueAnimator#setCurrentPlayTime(long) currentPlayTime}
85     * prior to starting.
86     */
87    public static interface TimeListener {
88        /**
89         * <p>Notifies listeners of the occurrence of another frame of the animation,
90         * along with information about the elapsed time.</p>
91         *
92         * @param animation The animator sending out the notification.
93         * @param totalTime The total time elapsed since the animator started, in milliseconds.
94         * @param deltaTime The time elapsed since the previous frame, in milliseconds.
95         */
96        void onTimeUpdate(TimeAnimator animation, long totalTime, long deltaTime);
97
98    }
99}
100