1753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov/* 2753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * Copyright (C) 2010 The Android Open Source Project 3753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * 4753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * Licensed under the Apache License, Version 2.0 (the "License"); 5753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * you may not use this file except in compliance with the License. 6753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * You may obtain a copy of the License at 7753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * 8753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * http://www.apache.org/licenses/LICENSE-2.0 9753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * 10753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * Unless required by applicable law or agreed to in writing, software 11753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * distributed under the License is distributed on an "AS IS" BASIS, 12753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * See the License for the specific language governing permissions and 14753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * limitations under the License. 15753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov */ 16753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 17753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikovpackage com.android.contacts.widget; 18753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 19753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikovimport android.content.Context; 20753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikovimport android.util.AttributeSet; 21753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikovimport android.widget.ListView; 22753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 23753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov/** 24753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * A ListView that can be asked to scroll (smoothly or otherwise) to a specific 25753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * position. This class takes advantage of similar functionality that exists 26753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * in {@link ListView} and enhances it. 27753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov */ 28753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikovpublic class AutoScrollListView extends ListView { 29753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 30753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov /** 31753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * Position the element at about 1/3 of the list height 32753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov */ 33753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov private static final float PREFERRED_SELECTION_OFFSET_FROM_TOP = 0.33f; 34753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 35ca0a6010b56801ff603f3c7c08327e30f90bfac0Dmitri Plotnikov private int mRequestedScrollPosition = -1; 36753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov private boolean mSmoothScrollRequested; 37753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 38753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov public AutoScrollListView(Context context) { 39753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov super(context); 40753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 41753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 42753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov public AutoScrollListView(Context context, AttributeSet attrs) { 43753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov super(context, attrs); 44753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 45753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 46753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov public AutoScrollListView(Context context, AttributeSet attrs, int defStyle) { 47753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov super(context, attrs, defStyle); 48753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 49753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 50753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov /** 51753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * Brings the specified position to view by optionally performing a jump-scroll maneuver: 52753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * first it jumps to some position near the one requested and then does a smooth 53753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * scroll to the requested position. This creates an impression of full smooth 54753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * scrolling without actually traversing the entire list. If smooth scrolling is 55753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov * not requested, instantly positions the requested item at a preferred offset. 56753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov */ 57753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov public void requestPositionToScreen(int position, boolean smoothScroll) { 58753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov mRequestedScrollPosition = position; 59753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov mSmoothScrollRequested = smoothScroll; 60753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov requestLayout(); 61753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 62753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 63753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov @Override 64753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov protected void layoutChildren() { 65753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov super.layoutChildren(); 66753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov if (mRequestedScrollPosition == -1) { 67753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov return; 68753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 69753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 70753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov final int position = mRequestedScrollPosition; 71753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov mRequestedScrollPosition = -1; 72753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 73753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov int firstPosition = getFirstVisiblePosition() + 1; 74753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov int lastPosition = getLastVisiblePosition(); 75753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov if (position >= firstPosition && position <= lastPosition) { 76753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov return; // Already on screen 77753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 78753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 79753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov final int offset = (int) (getHeight() * PREFERRED_SELECTION_OFFSET_FROM_TOP); 80753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov if (!mSmoothScrollRequested) { 81753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov setSelectionFromTop(position, offset); 82753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 83753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov // Since we have changed the scrolling position, we need to redo child layout 84753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov // Calling "requestLayout" in the middle of a layout pass has no effect, 85753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov // so we call layoutChildren explicitly 86753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov super.layoutChildren(); 87753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 88753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } else { 89753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov // We will first position the list a couple of screens before or after 90753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov // the new selection and then scroll smoothly to it. 91753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov int twoScreens = (lastPosition - firstPosition) * 2; 92753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov int preliminaryPosition; 93753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov if (position < firstPosition) { 94753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov preliminaryPosition = position + twoScreens; 95753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov if (preliminaryPosition >= getCount()) { 96753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov preliminaryPosition = getCount() - 1; 97753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 98753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov if (preliminaryPosition < firstPosition) { 99753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov setSelection(preliminaryPosition); 100753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov super.layoutChildren(); 101753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 102753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } else { 103753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov preliminaryPosition = position - twoScreens; 104753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov if (preliminaryPosition < 0) { 105753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov preliminaryPosition = 0; 106753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 107753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov if (preliminaryPosition > lastPosition) { 108753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov setSelection(preliminaryPosition); 109753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov super.layoutChildren(); 110753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 111753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 112753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 113753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov 114753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov smoothScrollToPositionFromTop(position, offset); 115753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 116753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov } 117753f8f6fde5a4f74181310593acebee94a014fe2Dmitri Plotnikov} 118