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Apache License
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/******************************************************************************* * Copyright 2011, 2012 Chris Banes.// ww w.java2s .c om * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. *******************************************************************************/ package com.handmark.pulltorefresh.library; import android.annotation.TargetApi; import android.util.Log; import android.view.View; import com.handmark.pulltorefresh.library.PullToRefreshBase.Mode; import com.handmark.pulltorefresh.library.PullToRefreshBase.State; @TargetApi(9) public final class OverscrollHelper { static final String LOG_TAG = "OverscrollHelper"; static final float DEFAULT_OVERSCROLL_SCALE = 1f; /** * Helper method for Overscrolling that encapsulates all of the necessary * function. * <p/> * This should only be used on AdapterView's such as ListView as it just * calls through to overScrollBy() with the scrollRange = 0. AdapterView's * do not have a scroll range (i.e. getScrollY() doesn't work). * * @param view - PullToRefreshView that is calling this. * @param deltaX - Change in X in pixels, passed through from from * overScrollBy call * @param scrollX - Current X scroll value in pixels before applying deltaY, * passed through from from overScrollBy call * @param deltaY - Change in Y in pixels, passed through from from * overScrollBy call * @param scrollY - Current Y scroll value in pixels before applying deltaY, * passed through from from overScrollBy call * @param isTouchEvent - true if this scroll operation is the result of a * touch event, passed through from from overScrollBy call */ public static void overScrollBy(final PullToRefreshBase<?> view, final int deltaX, final int scrollX, final int deltaY, final int scrollY, final boolean isTouchEvent) { overScrollBy(view, deltaX, scrollX, deltaY, scrollY, 0, isTouchEvent); } /** * Helper method for Overscrolling that encapsulates all of the necessary * function. This version of the call is used for Views that need to specify * a Scroll Range but scroll back to it's edge correctly. * * @param view - PullToRefreshView that is calling this. * @param deltaX - Change in X in pixels, passed through from from * overScrollBy call * @param scrollX - Current X scroll value in pixels before applying deltaY, * passed through from from overScrollBy call * @param deltaY - Change in Y in pixels, passed through from from * overScrollBy call * @param scrollY - Current Y scroll value in pixels before applying deltaY, * passed through from from overScrollBy call * @param scrollRange - Scroll Range of the View, specifically needed for * ScrollView * @param isTouchEvent - true if this scroll operation is the result of a * touch event, passed through from from overScrollBy call */ public static void overScrollBy(final PullToRefreshBase<?> view, final int deltaX, final int scrollX, final int deltaY, final int scrollY, final int scrollRange, final boolean isTouchEvent) { overScrollBy(view, deltaX, scrollX, deltaY, scrollY, scrollRange, 0, DEFAULT_OVERSCROLL_SCALE, isTouchEvent); } /** * Helper method for Overscrolling that encapsulates all of the necessary * function. This is the advanced version of the call. * * @param view - PullToRefreshView that is calling this. * @param deltaX - Change in X in pixels, passed through from from * overScrollBy call * @param scrollX - Current X scroll value in pixels before applying deltaY, * passed through from from overScrollBy call * @param deltaY - Change in Y in pixels, passed through from from * overScrollBy call * @param scrollY - Current Y scroll value in pixels before applying deltaY, * passed through from from overScrollBy call * @param scrollRange - Scroll Range of the View, specifically needed for * ScrollView * @param fuzzyThreshold - Threshold for which the values how fuzzy we * should treat the other values. Needed for WebView as it * doesn't always scroll back to it's edge. 0 = no fuzziness. * @param scaleFactor - Scale Factor for overscroll amount * @param isTouchEvent - true if this scroll operation is the result of a * touch event, passed through from from overScrollBy call */ public static void overScrollBy(final PullToRefreshBase<?> view, final int deltaX, final int scrollX, final int deltaY, final int scrollY, final int scrollRange, final int fuzzyThreshold, final float scaleFactor, final boolean isTouchEvent) { final int deltaValue, currentScrollValue, scrollValue; switch (view.getPullToRefreshScrollDirection()) { case HORIZONTAL: deltaValue = deltaX; scrollValue = scrollX; currentScrollValue = view.getScrollX(); break; case VERTICAL: default: deltaValue = deltaY; scrollValue = scrollY; currentScrollValue = view.getScrollY(); break; } // Check that OverScroll is enabled and that we're not currently // refreshing. if (view.isPullToRefreshOverScrollEnabled() && !view.isRefreshing()) { final Mode mode = view.getMode(); // Check that Pull-to-Refresh is enabled, and the event isn't from // touch if (mode.permitsPullToRefresh() && !isTouchEvent && deltaValue != 0) { final int newScrollValue = (deltaValue + scrollValue); if (PullToRefreshBase.DEBUG) { Log.d(LOG_TAG, "OverScroll. DeltaX: " + deltaX + ", ScrollX: " + scrollX + ", DeltaY: " + deltaY + ", ScrollY: " + scrollY + ", NewY: " + newScrollValue + ", ScrollRange: " + scrollRange + ", CurrentScroll: " + currentScrollValue); } if (newScrollValue < (0 - fuzzyThreshold)) { // Check the mode supports the overscroll direction, and // then move scroll if (mode.showHeaderLoadingLayout()) { // If we're currently at zero, we're about to start // overscrolling, so change the state if (currentScrollValue == 0) { view.setState(State.OVERSCROLLING); } view.setHeaderScroll((int) (scaleFactor * (currentScrollValue + newScrollValue)), 0); } } else if (newScrollValue > (scrollRange + fuzzyThreshold)) { // Check the mode supports the overscroll direction, and // then move scroll if (mode.showFooterLoadingLayout()) { // If we're currently at zero, we're about to start // overscrolling, so change the state if (currentScrollValue == 0) { view.setState(State.OVERSCROLLING); } view.setHeaderScroll((int) (scaleFactor * (currentScrollValue + newScrollValue - scrollRange)), 0); } } else if (Math.abs(newScrollValue) <= fuzzyThreshold || Math.abs(newScrollValue - scrollRange) <= fuzzyThreshold) { // Means we've stopped overscrolling, so scroll back to 0 view.setState(State.RESET); } } else if (isTouchEvent && State.OVERSCROLLING == view.getState()) { // This condition means that we were overscrolling from a fling, // but the user has touched the View and is now overscrolling // from touch instead. We need to just reset. view.setState(State.RESET); } } } static boolean isAndroidOverScrollEnabled(View view) { return view.getOverScrollMode() != View.OVER_SCROLL_NEVER; } }