Fix iOS content size issue

Added KVO to adjust the textview frame.
Fix the new line visible issue in iOS 7

Author: mallowtechdev

JSMessagesViewController/Classes/JSMessageInputView.m

@@ -141,6 +141,9 @@ - (instancetype)initWithFrame:(CGRect)frame
         _textView.delegate = delegate;
         _textView.keyboardDelegate = delegate;
         _textView.dismissivePanGestureRecognizer = panGestureRecognizer;
+        
+        // From iOS 7, the content size will be calculated after the delegate method calls complete. So we are adding KVO to the content size of the text view to accomadate the content size for the new line text.
+        [_textView addObserver:delegate forKeyPath:@"contentSize" options:NSKeyValueObservingOptionNew context:nil];
     }
     return self;
 }
@@ -190,19 +193,24 @@ - (void)adjustTextViewHeightBy:(CGFloat)changeInHeight
     int numLines = MAX([self.textView numberOfLinesOfText],
                        [self.textView.text js_numberOfLines]);
 
+    // Below iOS 7, if you set the text view frame programmatically, the KVO will keep on notify the observer method. So to avoid that, we are removing the observer before setting the frame and add the observer after setting frame here.
+    [self.textView removeObserver:_textView.keyboardDelegate forKeyPath:@"contentSize"];
     self.textView.frame = CGRectMake(prevFrame.origin.x,
                                      prevFrame.origin.y,
                                      prevFrame.size.width,
                                      prevFrame.size.height + changeInHeight);
-    
+    [self.textView addObserver:_textView.keyboardDelegate forKeyPath:@"contentSize" options:NSKeyValueObservingOptionNew context:nil];
+
     self.textView.contentInset = UIEdgeInsetsMake((numLines >= 6 ? 4.0f : 0.0f),
                                                   0.0f,
                                                   (numLines >= 6 ? 4.0f : 0.0f),
                                                   0.0f);
 
-    self.textView.scrollEnabled = (numLines >= 4);
+    // From iOS 7, the content size will be accurate only if the scrolling is enabled.
+    self.textView.scrollEnabled = YES;
 
-    if(numLines >= 6) {
+    // Set the content offset only when user enters the new line.
+    if(numLines >= 6 && [self.textView.text hasSuffix:@"\n"]) {
         CGPoint bottomOffset = CGPointMake(0.0f, self.textView.contentSize.height - self.textView.bounds.size.height);
         [self.textView setContentOffset:bottomOffset animated:YES];
     }

JSMessagesViewController/Classes/JSMessagesViewController.m

@@ -396,41 +396,18 @@ - (void)textViewDidEndEditing:(UITextView *)textView
     [textView resignFirstResponder];
 }
 
-- (void)textViewDidChange:(UITextView *)textView
-{
+- (void)refreshViewFrames:(UITextView *)textView {
     CGFloat maxHeight = [JSMessageInputView maxHeight];
 
-    //  TODO:
-    //
-    //  CGFloat textViewContentHeight = textView.contentSize.height;
-    //
-    //  The line above is broken as of iOS 7.0
-    //
-    //  There seems to be a bug in Apple's code for textView.contentSize
-    //  The following code was implemented as a workaround for calculating the appropriate textViewContentHeight
-    //
-    //  https://devforums.apple.com/thread/192052
-    //  https://github.com/jessesquires/MessagesTableViewController/issues/50
-    //  https://github.com/jessesquires/MessagesTableViewController/issues/47
-    //
-    // BEGIN HACK
-    //
-        CGSize size = [textView sizeThatFits:CGSizeMake(textView.frame.size.width, maxHeight)];
-        CGFloat textViewContentHeight = size.height;
-    //
-    //  END HACK
-    //
-    
-    BOOL isShrinking = textViewContentHeight < self.previousTextViewContentHeight;
-    CGFloat changeInHeight = textViewContentHeight - self.previousTextViewContentHeight;
-        
+    BOOL isShrinking = textView.contentSize.height < self.previousTextViewContentHeight;
+    CGFloat changeInHeight = textView.contentSize.height - self.previousTextViewContentHeight;
+    
     if(!isShrinking && (self.previousTextViewContentHeight == maxHeight || textView.text.length == 0)) {
         changeInHeight = 0;
     }
     else {
         changeInHeight = MIN(changeInHeight, maxHeight - self.previousTextViewContentHeight);
     }
-    
     if(changeInHeight != 0.0f) {
 
         [UIView animateWithDuration:0.25f
@@ -463,12 +440,33 @@ - (void)textViewDidChange:(UITextView *)textView
                          completion:^(BOOL finished) {
                          }];
 
-        self.previousTextViewContentHeight = MIN(textViewContentHeight, maxHeight);
+        self.previousTextViewContentHeight = MIN(textView.contentSize.height, maxHeight);
+    }
+    
+    // Once we reached the max height, we have to consider the bottom offset for the text view.
+    // To make visible the last line, again we have to set the content offset.
+    if (self.previousTextViewContentHeight == maxHeight && [textView.text hasSuffix:@"\n"]) {        
+        double delayInSeconds = 0.01;
+        dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
+        dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
+            CGPoint bottomOffset = CGPointMake(0.0f, textView.contentSize.height - textView.bounds.size.height);
+            [textView setContentOffset:bottomOffset animated:YES];
+        });
     }
 
     self.messageInputView.sendButton.enabled = ([textView.text js_stringByTrimingWhitespace].length > 0);
 }
 
+#pragma mark - KVO observer method
+
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
+    UITextView *textView = (UITextView *)object;
+    if ([textView isKindOfClass:[UITextView class]] && [keyPath isEqualToString:@"contentSize"]) {
+        [self refreshViewFrames:textView];
+    }
+}
+
+
 #pragma mark - Keyboard notifications
 
 - (void)handleWillShowKeyboardNotification:(NSNotification *)notification