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JFScrollViewUtil.m
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JFScrollViewUtil.m
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//
// JFScrollViewUtil.m
// JFCommon
//
// Created by Jason Fuerstenberg on 2012/02/03.
// Copyright (c) 2012 Jason Fuerstenberg. All rights reserved.
//
// 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.
//
#import "JFScrollViewUtil.h"
@implementation JFScrollViewUtil
#if TARGET_OS_IPHONE || TARGET_IPHONE_SIMULATOR
/*
* Scrolls the scroll view such that the view is not obscured by a keyboard of designated height.
* Keyboard height is specifiable here to allow for custom input views injected in the view.
* The scroll view is assumed to reach the bottom of the screen, therefore putting itself in the
* way of the keyboard.
*
* The onus is on the caller to reverse the scroll and shrink the scroll view's content size by
* the amount returned when the edit has ended.
*/
+ (CGFloat) scrollView: (UIScrollView *) scrollView byKeyboardHeight: (CGFloat) keyboardHeight ifNeededToUnobscureView: (UIView *) view {
if (view == nil) {
return 0.0f;
}
CGSize contentSize = [scrollView contentSize];
CGPoint contentOffset = [scrollView contentOffset];
CGRect viewFrame = [view frame];
CGRect viewFrameInScrollView = [scrollView convertRect: viewFrame
fromView: [view superview]];
CGFloat lowestPoint = viewFrameInScrollView.origin.y + viewFrameInScrollView.size.height;
CGFloat lowestPointConsideringOffset = lowestPoint - contentOffset.y;
// This logic assumes the content length stretches for the entire length of the screen.
CGFloat lowestVisibleScrollViewPoint = scrollView.frame.size.height - keyboardHeight;
// NOTE: Add 30 points to provide a decent margin...
CGFloat amountToScroll = lowestPointConsideringOffset - lowestVisibleScrollViewPoint + 30.0f;
// Add to the content size to ensure the scroll will work.
[scrollView setContentSize: CGSizeMake(contentSize.width, contentSize.height + keyboardHeight)];
// Perform the scrolling now...
if (amountToScroll > 0.0f) {
[scrollView setContentOffset: CGPointMake(contentOffset.x, contentOffset.y + amountToScroll)
animated: YES];
}
return amountToScroll;
}
/*
* Locates the first super view of the provided view which is a UIScrollView if any, or nil.
*/
+ (UIScrollView *) firstScrollViewInSuperViewHierarchyOfView: (UIView *) view {
while (view != nil) {
if ([view isKindOfClass: [UIScrollView class]]) {
return (UIScrollView *) view;
}
view = [view superview];
}
return nil;
}
#endif
@end