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 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
