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