editable webView getting scrolled to top by itself - ipad

Question

I have some text displayed in an editable webView. As soon as I scroll it down and touch somewhere to edit the rendered text, it scrolls to the top itself and the keyboard appears and hence I have to scroll it down again for editing. Is there a way to prevent webView from doing that?

Answer 1

Got the same problem and still looking for normal solution of this weird behavior.
We still cannot prevent UIWebView from doing this, and if you look at Evernote application on iPad, you'll see the same issue there, unfortunately :(
The only thing we could do on this is to save contentOffset of UIWebView when keyboard is shown and restore if after keyboard is opened.
This will look like:
//register your controller for keyboard notifications
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWasShown:) UIKeyboardDidShowNotification object:nil];
Then you will need to handle keyboard notification like:
- (void)keyboardWillShow:(NSNotification *)aNotification {
// scroll view will scroll to beginning, but we save current offset
[_yourViewWithWebView saveOffset];
...
}
After that you will need to handle event when keyboard was shown:
- (void)keyboardWasShown:(NSNotification*)aNotification{
...
// scroll view scrolled to beginning, but we restore previous offset
[_yourViewWithWebView restoreOffset];
}
Accordingly in your view which contains UIWebView you'll need to implement:
static CGPoint editableWebViewOffsetPoint;
- (void) saveOffset{
editableWebViewOffsetPoint = yourWebView.scrollView.contentOffset;
}
- (void) restoreOffset{
//just use animation block to have scroll animated after jumping to top and back to old position
[UIView animateWithDuration:.2
delay:0
options:UIViewAnimationOptionCurveEaseIn
animations:^{
yourWebView.scrollView.contentOffset = editableWebViewOffsetPoint;
}
completion:nil];
}
Hope in general this will help you to solve your problem at least partially.
If someone will help us to prevent UIWebView scrolling to top each time keyboard is displayed, I'd appreciate this deeply.
UIWebView.scrollView.scrollsToTop = NO; does not help.
Disabling scrolling before showing keyboard and enabling it after keyboard is displayed also didn't work.
Also in future you will face problem with editing text when cursor is not in visible area of UIWebView - and it does not scroll itself automatically to make cursor visible. We have solved that problem, but I am in progress of creating detailed and readable tutorial of how we've done this. If you already solved this problem, I'd appreciate to look at your solution :)
PS: http://www.cocoanetics.com/2011/01/uiwebview-must-die/
Thank you,
Sergey N.

Answer 2

A method that works rather well is temporarily disabling setContentOffset: on UIScrollView, while the keyboard is being shown. This is a little hackish though, so it may cause other issues instead, in some situations.
As in #Sergey N.'s response, register for the keyboard notifications, but instead of storing/restoring contentOffset, use these:
- (void)keyboardWillShow:(NSNotification *)aNotification {
[self disableMethod:#selector(setContentOffset:) onClass:[UIScrollView class]];
}
- (void)keyboardWasShown:(NSNotification *)aNotification {
[self enableMethod:#selector(setContentOffset:) onClass:[UIScrollView class]];
}
Somewhere else in the class (or in another class, as long as you replace self in above calls), place these:
-(void)swizzleMethod:(SEL)origSel from:(Class)origClass toMethod:(SEL)toSel from:(Class)toClass{
Method origMethod = class_getInstanceMethod(origClass, origSel);
Method newMethod = class_getInstanceMethod(toClass, toSel);
method_exchangeImplementations(origMethod, newMethod);
}
-(void)disableMethod:(SEL)sel onClass:(Class)cl{
[self swizzleMethod:sel from:cl toMethod:#selector(doNothing) from:[self class]];
}
-(void)enableMethod:(SEL)method onClass:(Class)cl{
[self swizzleMethod:#selector(doNothing) from:[self class] toMethod:method from:cl];
}
-(void)doNothing{
}
This prevents the webview from scrolling to top in the first place, so it won't show that bad animation, however, in some situations it may cause some problems (e.g have more input controls in the view holding the webview). Tested this successfully in iOS 5.0+.
In iOS 6.0 the scrolling to top seems to be fixed, so no workaround is necessary.

Answer 3

Functions for "editing text when cursor is not in visible area" problem.
- (void)keyboardWasShown:(NSNotification *)aNotification {
//if(self.navigationController.viewControllers objectAtIndex:([self.navigationController.viewControllers count]-1)==self.)
NSLog(#"keyboardshown");
if (keyboardshown)
return;
keyboardshown=YES;
NSDictionary* userInfo = [aNotification userInfo];
CGRect keyboardEndFrame;
[[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardEndFrame];
CGRect newFrame = self.textView.frame;
CGRect keyboardFrame = [self.textView convertRect:keyboardEndFrame toView:nil];
newFrame.size.height -= keyboardFrame.size.height;
[UIView beginAnimations:#"ResizeForKeyboard" context:nil];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationDuration:0.3];
[self.textView setFrame:newFrame];
[UIView commitAnimations];
}
- (void)keyboardWasHidden:(NSNotification *)aNotification {
if (!keyboardshown)
return;
keyboardshown=NO;
NSDictionary* userInfo = [aNotification userInfo];
CGRect keyboardEndFrame;
[[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardEndFrame];
CGRect newFrame = self.textView.frame;
CGRect keyboardFrame = [self.textView convertRect:keyboardEndFrame toView:nil];
newFrame.size.height += keyboardFrame.size.height;
[UIView beginAnimations:#"ResizeForKeyboard" context:nil];
[UIView setAnimationDuration:0.3];
self.textView.frame = newFrame;
[UIView commitAnimations];
}

Answer 4

Actually keyboardWasShown will not always be invoked especially when user has BT keyboard connected and virtual one can be hidden/shown by Eject key. We have implemented our own class like:
#implementation KeyboardUtils
+ (CGRect) convertRect:(CGRect)rect toView:(UIView *)view {
UIWindow *window = [view isKindOfClass:[UIWindow class]] ? (UIWindow *) view : [view window];
return [view convertRect:[window convertRect:rect fromWindow:nil] fromView:nil];
}
/**
* This is working but deprecated solution
* Based on UIKeyboardCenterBeginUserInfoKey and UIKeyboardCenterEndUserInfoKey which are deprecated since iOS 3.2
*/
+ (BOOL)checkKeyboardOnDisplayCenterBegin:(CGRect)centerBegin centerEnd:(CGRect)centerEnd{
CGRect mainScreen = [UIApplication currentBounds];
BOOL isKeyboardOnDisplay = CGRectContainsPoint(mainScreen, centerEnd.origin);
[[NSUserDefaults standardUserDefaults] setValue:[NSNumber numberWithBool:isKeyboardOnDisplay] forKey:#"isKeyboardOnDisplay"];
[[NSUserDefaults standardUserDefaults] synchronize];
return isKeyboardOnDisplay;
}
/**
* This method allows to verify if software keyboard is currently present on screen for the application
* Allows to handle undocked, split states of keyboard, as well as connected Bluetooth keyboard.
* Needed to adjust UI - scrolling and insets for editable parts of the app, as well as avoid application be beneath open keyboard
*/
+ (BOOL)checkKeyboardOnDisplayBeginFrame:(CGRect)frameBegin endFrame:(CGRect)frameEnd{
CGRect mainScreen = [UIApplication currentBounds];
UIView *firstView = [[(AppDelegate *)[[UIApplication sharedApplication] delegate] window].subviews objectAtIndex:0];
CGRect convertedEndFrame = [KeyboardUtils convertRect:frameEnd toView:firstView];
BOOL isKeyboardOnDisplay = CGRectContainsRect(mainScreen, convertedEndFrame);
[[NSUserDefaults standardUserDefaults] setValue:[NSNumber numberWithBool:isKeyboardOnDisplay] forKey:#"isKeyboardOnDisplay"];
[[NSUserDefaults standardUserDefaults] synchronize];
return isKeyboardOnDisplay;
}
+ (BOOL)checkKeyboardOnDisplayFromNotification:(NSNotification *)aNotification{
BOOL isKeyboardOnDisplay = [KeyboardUtils checkKeyboardOnDisplayBeginFrame:[[aNotification.userInfo valueForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue]
endFrame:[[aNotification.userInfo valueForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue]];
return isKeyboardOnDisplay;
}
Then you can use it like:
- (void)keyboardWillChangeFrame:(NSNotification*)aNotification{
[KeyboardUtils checkKeyboardOnDisplayFromNotification:aNotification];
}
Where keyboardWillChangeFrame is selector-observer for:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(keyboardWillChangeFrame:) name:UIKeyboardWillChangeFrameNotification object:nil];
In such a way you are saving state of your keyboard (if it is shown as docked one and really present on display, and BT keyboard is not used) into NSUserDefaultSettings. In your handlers which listen to keyboard notifications or orientation changes you should check this key value from the defaults.
One more additional method is [UIApplication currentBounds];
It is present in the app by extending it with category like: (.h file)
#import <UIKit/UIKit.h>
#interface UIApplication (AppDimensions)
+(CGSize) currentSize;
+(CGRect) currentBounds;
+(CGSize) sizeInOrientation:(UIInterfaceOrientation)orientation;
#end
.m file:
#import "UIApplication+AppDimensions.h"
#implementation UIApplication (AppDimensions)
+(CGSize) currentSize
{
return [UIApplication sizeInOrientation:[UIApplication sharedApplication].statusBarOrientation];
}
+(CGRect) currentBounds{
CGRect bounds = [UIScreen mainScreen].bounds;
bounds.size = [UIApplication currentSize];
return bounds;
}
+(CGSize) sizeInOrientation:(UIInterfaceOrientation)orientation
{
CGSize size = [UIScreen mainScreen].bounds.size;
UIApplication *application = [UIApplication sharedApplication];
if (UIInterfaceOrientationIsLandscape(orientation))
{
size = CGSizeMake(size.height, size.width);
}
if (application.statusBarHidden == NO)
{
size.height -= MIN(application.statusBarFrame.size.width, application.statusBarFrame.size.height);
}
return size;
}
#end
Hope this will help anyone who is concerned about handling presence of keyboard on the screen.