/*******************************************************************************
* Copyright 2011, 2012 Chris Banes.
*
* 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)));
}
} 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)));
}
} 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;
}
}
