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 
17 package com.android.gallery3d.ui;
18 
19 import android.content.Context;
20 import android.view.ViewConfiguration;
21 
22 import com.android.gallery3d.common.OverScroller;
23 import com.android.gallery3d.common.Utils;
24 
25 public class ScrollerHelper {
26     private OverScroller mScroller;
27     private int mOverflingDistance;
28     private boolean mOverflingEnabled;
29 
ScrollerHelper(Context context)30     public ScrollerHelper(Context context) {
31         mScroller = new OverScroller(context);
32         ViewConfiguration configuration = ViewConfiguration.get(context);
33         mOverflingDistance = configuration.getScaledOverflingDistance();
34     }
35 
setOverfling(boolean enabled)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      */
advanceAnimation(long currentTimeMillis)45     public boolean advanceAnimation(long currentTimeMillis) {
46         return mScroller.computeScrollOffset();
47     }
48 
isFinished()49     public boolean isFinished() {
50         return mScroller.isFinished();
51     }
52 
forceFinished()53     public void forceFinished() {
54         mScroller.forceFinished(true);
55     }
56 
getPosition()57     public int getPosition() {
58         return mScroller.getCurrX();
59     }
60 
getCurrVelocity()61     public float getCurrVelocity() {
62         return mScroller.getCurrVelocity();
63     }
64 
setPosition(int position)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 
fling(int velocity, int min, int max)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.
startScroll(int distance, int min, int max)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