Add initial implementation.

Author: cbowns

MPTextView.h

@@ -0,0 +1,16 @@
+//
+//  MPTextView.h
+//
+//  Created by Christopher Bowns on 7/25/13.
+//  Licensed under the Apache v2 license.
+//
+
+#import <UIKit/UIKit.h>
+
+@interface MPTextView : UITextView
+
+// Named .placeholderText, in case UITextView gains
+// a .placeholder property (like UITextField) in future iOS versions.
+@property (nonatomic, copy) NSString *placeholderText;
+
+@end

MPTextView.m

@@ -0,0 +1,184 @@
+//
+//  MPTextView.m
+//
+//  Created by Christopher Bowns on 7/25/13.
+//  Licensed under the Apache v2 license.
+//
+
+#import "MPTextView.h"
+
+// Manually-selected label offset to align placeholder label with real text.
+static CGFloat const kLabelLeftOffset = 8.f;
+static CGFloat const kLabelTopOffsetRetina = 0.5f;
+
+@interface MPTextView ()
+
+@property (nonatomic, strong) UILabel *placeholderLabel;
+
+// Calculate and save the label's left and top offset.
+@property (nonatomic, assign) CGSize labelOffset;
+
+// Handle text changed event so we can update the placeholder appropriately
+- (void)textChanged:(NSNotification *)note;
+
+@end
+
+
+@implementation MPTextView
+
+#pragma mark - Initializers
+
+- (id)initWithCoder:(NSCoder *)aDecoder {
+    self = [super initWithCoder:aDecoder];
+    if (self) {
+        [self finishInitialization];
+    }
+    return self;
+}
+
+
+- (id)initWithFrame:(CGRect)frame {
+    self = [super initWithFrame:frame];
+    if (self) {
+        [self finishInitialization];
+    }
+    return self;
+}
+
+
+// Private method for finishing initialization.
+// Rather than muck with designated initializers, let's do it the easy way.
+- (void)finishInitialization {
+    // Sign up for notifications for text changes:
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(textChanged:)
+                                                 name:UITextViewTextDidChangeNotification
+                                               object:self];
+
+    CGFloat labelLeftOffset = kLabelLeftOffset;
+    CGFloat labelTopOffset = 0.f;
+
+    // On retina iPhones and iPads, the label is offset by 0.5 points.
+    if ([[UIScreen mainScreen] scale] == 2.0) {
+        labelTopOffset = kLabelTopOffsetRetina;
+    }
+    self.labelOffset = CGSizeMake(labelLeftOffset, labelTopOffset);
+
+    [self createPlaceholderLabel];
+}
+
+
+#pragma mark - Placeholder label helper
+
+// Create our label:
+- (void)createPlaceholderLabel {
+    CGRect labelFrame = [self calculatePlaceholderLabelFrame];
+
+    self.placeholderLabel = [[UILabel alloc] initWithFrame:labelFrame];
+    self.placeholderLabel.lineBreakMode = NSLineBreakByWordWrapping;
+    self.placeholderLabel.numberOfLines = 0;
+    self.placeholderLabel.font = self.font;
+    self.placeholderLabel.backgroundColor = [UIColor clearColor];
+    self.placeholderLabel.text = self.placeholderText;
+    // Manually matched to UITextField's placeholder text color.
+    self.placeholderLabel.textColor = [UIColor colorWithWhite:0.71f alpha:1.0f];
+
+    [self addSubview:self.placeholderLabel];
+}
+
+
+- (CGRect)calculatePlaceholderLabelFrame {
+    return CGRectMake(self.labelOffset.width,
+                      self.labelOffset.height,
+                      self.bounds.size.width  - (2 * self.labelOffset.width),
+                      self.bounds.size.height - (2 * self.labelOffset.height));
+}
+
+#pragma mark - Custom accessors
+
+- (void)setPlaceholderText:(NSString *)string {
+    _placeholderText = [string copy];
+    self.placeholderLabel.text = string;
+    [self.placeholderLabel sizeToFit];
+}
+
+
+#pragma mark - UITextView subclass methods
+
+// Keep the placeholder label font in sync with the text view's
+- (void)setFont:(UIFont *)font {
+    // Call super.
+    [super setFont:font];
+
+    self.placeholderLabel.font = self.font;
+}
+
+
+// Keep placeholder label alignment in sync
+- (void)setTextAlignment:(NSTextAlignment)textAlignment {
+    // Call super.
+    [super setTextAlignment:textAlignment];
+
+    self.placeholderLabel.textAlignment = textAlignment;
+}
+
+// Todo: override setAttributedText to capture changes
+// in text alignment?
+
+
+#pragma mark - UITextInput overrides
+
+// Listen to dictation events to hide the placeholder as is appropriate.
+
+// Hide when there's a dictation result placeholder
+- (id)insertDictationResultPlaceholder {
+    // Call super.
+    id placeholder = [super insertDictationResultPlaceholder];
+
+    // Use .hidden (instead of alpha), since these events also trigger
+    // -[textChanged] (which has a different criteria by which it shows the label)
+    self.placeholderLabel.hidden = YES;
+    return placeholder;
+}
+
+
+// Update visibility when dictation ends.
+- (void)removeDictationResultPlaceholder:(id)placeholder willInsertResult:(BOOL)willInsertResult {
+    // Call super.
+    [super removeDictationResultPlaceholder:placeholder willInsertResult:willInsertResult];
+
+    // Unset the hidden flag from insertDictationResultPlaceholder.
+    self.placeholderLabel.hidden = NO;
+
+    // Update our text label based on the entered text.
+    [self updatePlaceholderLabelVisibility];
+}
+
+
+#pragma mark - Text change listeners
+
+- (void)updatePlaceholderLabelVisibility {
+    if ([self.text length] == 0) {
+        self.placeholderLabel.alpha = 1.f;
+    } else {
+        self.placeholderLabel.alpha = 0.f;
+    }
+}
+
+
+// When text is set or changed, update the label's visibility:
+
+- (void)setText:(NSString *)text {
+    // Call super.
+    [super setText:text];
+
+    [self updatePlaceholderLabelVisibility];
+}
+
+
+- (void)textChanged:(NSNotification *)notification {
+    [self updatePlaceholderLabelVisibility];
+}
+
+
+@end

README.md

@@ -1,4 +1,12 @@
 MPTextView
 ==========
 
-A UITextView subclass with support for placeholder text (like UITextField)
+A UITextView subclass with support for placeholder text (similar to UITextField)
+
+### Notes and errata
+
+- The property is named `.placeholderText` to avoid colliding with `.placeholder` if UITextView gains that property in a future version of iOS.
+- Some setters on UITextView are overridden to pass font and text alignment data through to the placeholder label. `setAttributedText:` has *not* been.
+- This has been tested on an iPhone 5 running iOS 6.1.4, and in the iOS 6.1 Simulator for both non-Retina and Retina iPads.
+
+Open an issue if you have any problems!