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 com.android.gallery3d.ui;
18
19import android.content.Context;
20import android.view.ViewConfiguration;
21
22import com.android.gallery3d.common.OverScroller;
23import com.android.gallery3d.common.Utils;
24
25public class ScrollerHelper {
26    private OverScroller mScroller;
27    private int mOverflingDistance;
28    private boolean mOverflingEnabled;
29
30    public ScrollerHelper(Context context) {
31        mScroller = new OverScroller(context);
32        ViewConfiguration configuration = ViewConfiguration.get(context);
33        mOverflingDistance = configuration.getScaledOverflingDistance();
34    }
35
36    public void setOverfling(boolean enabled) {
37        mOverflingEnabled = enabled;
38    }
39
40    /**
41     * Call this when you want to know the new location. The position will be
42     * updated and can be obtained by getPosition(). Returns true if  the
43     * animation is not yet finished.
44     */
45    public boolean advanceAnimation(long currentTimeMillis) {
46        return mScroller.computeScrollOffset();
47    }
48
49    public boolean isFinished() {
50        return mScroller.isFinished();
51    }
52
53    public void forceFinished() {
54        mScroller.forceFinished(true);
55    }
56
57    public int getPosition() {
58        return mScroller.getCurrX();
59    }
60
61    public float getCurrVelocity() {
62        return mScroller.getCurrVelocity();
63    }
64
65    public void setPosition(int position) {
66        mScroller.startScroll(
67                position, 0,    // startX, startY
68                0, 0, 0);       // dx, dy, duration
69
70        // This forces the scroller to reach the final position.
71        mScroller.abortAnimation();
72    }
73
74    public void fling(int velocity, int min, int max) {
75        int currX = getPosition();
76        mScroller.fling(
77                currX, 0,      // startX, startY
78                velocity, 0,   // velocityX, velocityY
79                min, max,      // minX, maxX
80                0, 0,          // minY, maxY
81                mOverflingEnabled ? mOverflingDistance : 0, 0);
82    }
83
84    // Returns the distance that over the scroll limit.
85    public int startScroll(int distance, int min, int max) {
86        int currPosition = mScroller.getCurrX();
87        int finalPosition = mScroller.isFinished() ? currPosition :
88                mScroller.getFinalX();
89        int newPosition = Utils.clamp(finalPosition + distance, min, max);
90        if (newPosition != currPosition) {
91            mScroller.startScroll(
92                currPosition, 0,                    // startX, startY
93                newPosition - currPosition, 0, 0);  // dx, dy, duration
94        }
95        return finalPosition + distance - newPosition;
96    }
97}
98