1/* 2 * Copyright (C) 2012 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.support.v4.widget; 18 19import android.content.Context; 20import android.widget.Scroller; 21 22/** 23 * Provides access to new {@link android.widget.Scroller Scroller} APIs when available. 24 * 25 * <p>This class provides a platform version-independent mechanism for obeying the 26 * current device's preferred scroll physics and fling behavior. It offers a subset of 27 * the APIs from Scroller or OverScroller.</p> 28 */ 29class ScrollerCompat { 30 Scroller mScroller; 31 32 static class ScrollerCompatImplIcs extends ScrollerCompat { 33 public ScrollerCompatImplIcs(Context context) { 34 super(context); 35 } 36 37 @Override 38 public float getCurrVelocity() { 39 return ScrollerCompatIcs.getCurrVelocity(mScroller); 40 } 41 } 42 43 public static ScrollerCompat from(Context context) { 44 if (android.os.Build.VERSION.SDK_INT >= 14) { 45 return new ScrollerCompatImplIcs(context); 46 } 47 return new ScrollerCompat(context); 48 } 49 50 ScrollerCompat(Context context) { 51 mScroller = new Scroller(context); 52 } 53 54 /** 55 * Returns whether the scroller has finished scrolling. 56 * 57 * @return True if the scroller has finished scrolling, false otherwise. 58 */ 59 public boolean isFinished() { 60 return mScroller.isFinished(); 61 } 62 63 /** 64 * Returns how long the scroll event will take, in milliseconds. 65 * 66 * @return The duration of the scroll in milliseconds. 67 */ 68 public int getDuration() { 69 return mScroller.getDuration(); 70 } 71 72 /** 73 * Returns the current X offset in the scroll. 74 * 75 * @return The new X offset as an absolute distance from the origin. 76 */ 77 public int getCurrX() { 78 return mScroller.getCurrX(); 79 } 80 81 /** 82 * Returns the current Y offset in the scroll. 83 * 84 * @return The new Y offset as an absolute distance from the origin. 85 */ 86 public int getCurrY() { 87 return mScroller.getCurrY(); 88 } 89 90 /** 91 * Returns the current velocity. 92 * 93 * TODO: Approximate a sane result for older platform versions. Right now 94 * this will return 0 for platforms earlier than ICS. This is acceptable 95 * at the moment only since it is only used for EdgeEffect, which is also only 96 * present in ICS+, and ScrollerCompat is not public. 97 * 98 * @return The original velocity less the deceleration. Result may be 99 * negative. 100 */ 101 public float getCurrVelocity() { 102 return 0; 103 } 104 105 /** 106 * Call this when you want to know the new location. If it returns true, 107 * the animation is not yet finished. loc will be altered to provide the 108 * new location. 109 */ 110 public boolean computeScrollOffset() { 111 return mScroller.computeScrollOffset(); 112 } 113 114 /** 115 * Start scrolling by providing a starting point and the distance to travel. 116 * The scroll will use the default value of 250 milliseconds for the 117 * duration. 118 * 119 * @param startX Starting horizontal scroll offset in pixels. Positive 120 * numbers will scroll the content to the left. 121 * @param startY Starting vertical scroll offset in pixels. Positive numbers 122 * will scroll the content up. 123 * @param dx Horizontal distance to travel. Positive numbers will scroll the 124 * content to the left. 125 * @param dy Vertical distance to travel. Positive numbers will scroll the 126 * content up. 127 */ 128 public void startScroll(int startX, int startY, int dx, int dy) { 129 mScroller.startScroll(startX, startY, dx, dy); 130 } 131 132 /** 133 * Start scrolling by providing a starting point and the distance to travel. 134 * 135 * @param startX Starting horizontal scroll offset in pixels. Positive 136 * numbers will scroll the content to the left. 137 * @param startY Starting vertical scroll offset in pixels. Positive numbers 138 * will scroll the content up. 139 * @param dx Horizontal distance to travel. Positive numbers will scroll the 140 * content to the left. 141 * @param dy Vertical distance to travel. Positive numbers will scroll the 142 * content up. 143 * @param duration Duration of the scroll in milliseconds. 144 */ 145 public void startScroll(int startX, int startY, int dx, int dy, int duration) { 146 mScroller.startScroll(startX, startY, dx, dy, duration); 147 } 148 149 /** 150 * Start scrolling based on a fling gesture. The distance travelled will 151 * depend on the initial velocity of the fling. 152 * 153 * @param startX Starting point of the scroll (X) 154 * @param startY Starting point of the scroll (Y) 155 * @param velocityX Initial velocity of the fling (X) measured in pixels per 156 * second. 157 * @param velocityY Initial velocity of the fling (Y) measured in pixels per 158 * second 159 * @param minX Minimum X value. The scroller will not scroll past this 160 * point. 161 * @param maxX Maximum X value. The scroller will not scroll past this 162 * point. 163 * @param minY Minimum Y value. The scroller will not scroll past this 164 * point. 165 * @param maxY Maximum Y value. The scroller will not scroll past this 166 * point. 167 */ 168 public void fling(int startX, int startY, int velocityX, int velocityY, 169 int minX, int maxX, int minY, int maxY) { 170 mScroller.fling(startX, startY, velocityX, velocityY, minX, maxX, minY, maxY); 171 } 172 173 /** 174 * Stops the animation. Contrary to {@link #forceFinished(boolean)}, 175 * aborting the animating cause the scroller to move to the final x and y 176 * position 177 */ 178 public void abortAnimation() { 179 mScroller.abortAnimation(); 180 } 181} 182