Implements onKeyPress

Summary: - When a key is pressed, it's `key value` is passed as an argument to the callback handler.
 - For `Enter` and `Backspace` keys, I'm using their `key value` as defined [here](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key#Key_values). As per JonasJonny & brentvatne's [suggestion](facebook#1882 (comment)).

- Example
```javascript
 _handleKeyPress: function(e) {
      console.log(e.nativeEvent.key);
  },

  render: function() {
    return (
      <View style={styles.container}>
        <TextInput
            style={{width: 150, height: 25, borderWidth: 0.5}}
            onKeyPress={this._handleKeyPress}
        />
        <TextInput
            style={{width: 150, height: 100, borderWidth: 0.5}}
            onKeyPress={this._handleKeyPress}
            multiline={true}
        />
      </View>
    );
  }
```
- Implements [shouldChangeCharactersInRange](https://developer.apple.com/library/prerelease/ios/documentat
Closes facebook#2082

Reviewed By: javache

Differential Revision: D2280460

Pulled By: nicklockwood

fb-gh-sync-id: 1f824f80649043dc2520c089e2531d428d799405

Author: dsibiski

Diff for: Examples/UIExplorer/TextInputExample.ios.js

@@ -42,6 +42,7 @@ var TextEventsExample = React.createClass({
       curText: '<No Event>',
       prevText: '<No Event>',
       prev2Text: '<No Event>',
+      prev3Text: '<No Event>',
     };
   },
 
@@ -51,6 +52,7 @@ var TextEventsExample = React.createClass({
         curText: text,
         prevText: state.curText,
         prev2Text: state.prevText,
+        prev3Text: state.prev2Text,
       };
     });
   },
@@ -73,12 +75,16 @@ var TextEventsExample = React.createClass({
           onSubmitEditing={(event) => this.updateText(
             'onSubmitEditing text: ' + event.nativeEvent.text
           )}
+          onKeyPress={(event) => {
+            this.updateText('onKeyPress key: ' + event.nativeEvent.key);
+          }}
           style={styles.default}
         />
         <Text style={styles.eventLabel}>
           {this.state.curText}{'\n'}
           (prev: {this.state.prevText}){'\n'}
-          (prev2: {this.state.prev2Text})
+          (prev2: {this.state.prev2Text}){'\n'}
+          (prev3: {this.state.prev3Text})
         </Text>
       </View>
     );

Diff for: Libraries/Components/TextInput/TextInput.js

@@ -217,6 +217,13 @@ var TextInput = React.createClass({
      * Callback that is called when the text input's submit button is pressed.
      */
     onSubmitEditing: PropTypes.func,
+    /**
+     * Callback that is called when a key is pressed.
+     * Pressed key value is passed as an argument to the callback handler.
+     * Fires before onChange callbacks.
+     * @platform ios
+     */
+    onKeyPress: PropTypes.func,
     /**
      * Invoked on mount and layout changes with `{x, y, width, height}`.
      */

Diff for: Libraries/Text/RCTTextField.h

@@ -20,8 +20,11 @@
 @property (nonatomic, strong) UIColor *placeholderTextColor;
 @property (nonatomic, assign) NSInteger mostRecentEventCount;
 @property (nonatomic, strong) NSNumber *maxLength;
+@property (nonatomic, assign) BOOL textWasPasted;
 
 - (instancetype)initWithEventDispatcher:(RCTEventDispatcher *)eventDispatcher NS_DESIGNATED_INITIALIZER;
+
 - (void)textFieldDidChange;
+- (void)sendKeyValueForString:(NSString *)string;
 
 @end

Diff for: Libraries/Text/RCTTextField.m

@@ -39,6 +39,23 @@ - (instancetype)initWithEventDispatcher:(RCTEventDispatcher *)eventDispatcher
 RCT_NOT_IMPLEMENTED(- (instancetype)initWithFrame:(CGRect)frame)
 RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
 
+- (void)sendKeyValueForString:(NSString *)string
+{
+  [_eventDispatcher sendTextEventWithType:RCTTextEventTypeKeyPress
+                                 reactTag:self.reactTag
+                                     text:nil
+                                      key:string
+                               eventCount:_nativeEventCount];
+}
+
+// This method is overriden for `onKeyPress`. The manager
+// will not send a keyPress for text that was pasted.
+- (void)paste:(id)sender
+{
+  _textWasPasted = YES;
+  [super paste:sender];
+}
+
 - (void)setText:(NSString *)text
 {
   NSInteger eventLag = _nativeEventCount - _mostRecentEventCount;
@@ -134,6 +151,7 @@ - (void)textFieldDidChange
   [_eventDispatcher sendTextEventWithType:RCTTextEventTypeChange
                                  reactTag:self.reactTag
                                      text:self.text
+                                      key:nil
                                eventCount:_nativeEventCount];
 }
 
@@ -142,13 +160,15 @@ - (void)textFieldEndEditing
   [_eventDispatcher sendTextEventWithType:RCTTextEventTypeEnd
                                  reactTag:self.reactTag
                                      text:self.text
+                                      key:nil
                                eventCount:_nativeEventCount];
 }
 - (void)textFieldSubmitEditing
 {
   [_eventDispatcher sendTextEventWithType:RCTTextEventTypeSubmit
                                  reactTag:self.reactTag
                                      text:self.text
+                                      key:nil
                                eventCount:_nativeEventCount];
 }
 
@@ -162,6 +182,7 @@ - (void)textFieldBeginEditing
   [_eventDispatcher sendTextEventWithType:RCTTextEventTypeFocus
                                  reactTag:self.reactTag
                                      text:self.text
+                                      key:nil
                                eventCount:_nativeEventCount];
 }
 
@@ -181,6 +202,7 @@ - (BOOL)resignFirstResponder
     [_eventDispatcher sendTextEventWithType:RCTTextEventTypeBlur
                                    reactTag:self.reactTag
                                        text:self.text
+                                        key:nil
                                  eventCount:_nativeEventCount];
   }
   return result;

Diff for: Libraries/Text/RCTTextFieldManager.m

@@ -31,6 +31,13 @@ - (UIView *)view
 
 - (BOOL)textField:(RCTTextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
 {
+  // Only allow single keypresses for onKeyPress, pasted text will not be sent.
+  if (textField.textWasPasted) {
+    textField.textWasPasted = NO;
+  } else {
+    [textField sendKeyValueForString:string];
+  }
+
   if (textField.maxLength == nil || [string isEqualToString:@"\n"]) {  // Make sure forms can be submitted via return
     return YES;
   }
@@ -54,6 +61,14 @@ - (BOOL)textField:(RCTTextField *)textField shouldChangeCharactersInRange:(NSRan
   }
 }
 
+// This method allows us to detect a `Backspace` keyPress
+// even when there is no more text in the TextField
+- (BOOL)keyboardInputShouldDelete:(RCTTextField *)textField
+{
+  [self textField:textField shouldChangeCharactersInRange:NSMakeRange(0, 0) replacementString:@""];
+  return YES;
+}
+
 RCT_EXPORT_VIEW_PROPERTY(caretHidden, BOOL)
 RCT_EXPORT_VIEW_PROPERTY(autoCorrect, BOOL)
 RCT_REMAP_VIEW_PROPERTY(editable, enabled, BOOL)

Diff for: Libraries/Text/RCTTextView.m

@@ -14,6 +14,22 @@
 #import "RCTUtils.h"
 #import "UIView+React.h"
 
+@interface RCTUITextView : UITextView
+
+@property (nonatomic, assign) BOOL textWasPasted;
+
+@end
+
+@implementation RCTUITextView
+
+- (void)paste:(id)sender
+{
+  _textWasPasted = YES;
+  [super paste:sender];
+}
+
+@end
+
 @implementation RCTTextView
 {
   RCTEventDispatcher *_eventDispatcher;
@@ -33,7 +49,7 @@ - (instancetype)initWithEventDispatcher:(RCTEventDispatcher *)eventDispatcher
     _eventDispatcher = eventDispatcher;
     _placeholderTextColor = [self defaultPlaceholderTextColor];
 
-    _textView = [[UITextView alloc] initWithFrame:self.bounds];
+    _textView = [[RCTUITextView alloc] initWithFrame:self.bounds];
     _textView.backgroundColor = [UIColor clearColor];
     _textView.scrollsToTop = NO;
     _textView.delegate = self;
@@ -56,15 +72,15 @@ - (void)updateFrames
   // first focused.
   UIEdgeInsets adjustedFrameInset = UIEdgeInsetsZero;
   adjustedFrameInset.left = _contentInset.left - 5;
-  
+
   UIEdgeInsets adjustedTextContainerInset = _contentInset;
   adjustedTextContainerInset.top += 5;
   adjustedTextContainerInset.left = 0;
-  
+
   CGRect frame = UIEdgeInsetsInsetRect(self.bounds, adjustedFrameInset);
   _textView.frame = frame;
   _placeholderView.frame = frame;
-  
+
   _textView.textContainerInset = adjustedTextContainerInset;
   _placeholderView.textContainerInset = adjustedTextContainerInset;
 }
@@ -138,8 +154,18 @@ - (NSString *)text
   return _textView.text;
 }
 
-- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
+- (BOOL)textView:(RCTUITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
 {
+  if (textView.textWasPasted) {
+    textView.textWasPasted = NO;
+  } else {
+    [_eventDispatcher sendTextEventWithType:RCTTextEventTypeKeyPress
+                                   reactTag:self.reactTag
+                                       text:nil
+                                        key:text
+                                 eventCount:_nativeEventCount];
+  }
+
   if (_maxLength == nil) {
     return YES;
   }
@@ -215,6 +241,7 @@ - (void)textViewDidBeginEditing:(UITextView *)textView
   [_eventDispatcher sendTextEventWithType:RCTTextEventTypeFocus
                                  reactTag:self.reactTag
                                      text:textView.text
+                                      key:nil
                                eventCount:_nativeEventCount];
 }
 
@@ -225,6 +252,7 @@ - (void)textViewDidChange:(UITextView *)textView
   [_eventDispatcher sendTextEventWithType:RCTTextEventTypeChange
                                  reactTag:self.reactTag
                                      text:textView.text
+                                      key:nil
                                eventCount:_nativeEventCount];
 
 }
@@ -234,6 +262,7 @@ - (void)textViewDidEndEditing:(UITextView *)textView
   [_eventDispatcher sendTextEventWithType:RCTTextEventTypeEnd
                                  reactTag:self.reactTag
                                      text:textView.text
+                                      key:nil
                                eventCount:_nativeEventCount];
 }
 
@@ -253,6 +282,7 @@ - (BOOL)resignFirstResponder
     [_eventDispatcher sendTextEventWithType:RCTTextEventTypeBlur
                                    reactTag:self.reactTag
                                        text:_textView.text
+                                        key:nil
                                  eventCount:_nativeEventCount];
   }
   return result;

Diff for: React/Base/RCTEventDispatcher.h

@@ -16,7 +16,8 @@ typedef NS_ENUM(NSInteger, RCTTextEventType) {
   RCTTextEventTypeBlur,
   RCTTextEventTypeChange,
   RCTTextEventTypeSubmit,
-  RCTTextEventTypeEnd
+  RCTTextEventTypeEnd,
+  RCTTextEventTypeKeyPress
 };
 
 typedef NS_ENUM(NSInteger, RCTScrollEventType) {
@@ -95,6 +96,7 @@ RCT_EXTERN NSString *RCTNormalizeInputEventName(NSString *eventName);
 - (void)sendTextEventWithType:(RCTTextEventType)type
                      reactTag:(NSNumber *)reactTag
                          text:(NSString *)text
+                          key:(NSString *)key
                    eventCount:(NSInteger)eventCount;
 
 /**

Diff for: React/Base/RCTEventDispatcher.m

@@ -144,6 +144,7 @@ - (void)sendInputEventWithName:(NSString *)name body:(NSDictionary *)body
 - (void)sendTextEventWithType:(RCTTextEventType)type
                      reactTag:(NSNumber *)reactTag
                          text:(NSString *)text
+                          key:(NSString *)key
                    eventCount:(NSInteger)eventCount
 {
   static NSString *events[] = {
@@ -152,16 +153,36 @@ - (void)sendTextEventWithType:(RCTTextEventType)type
     @"change",
     @"submitEditing",
     @"endEditing",
+    @"keyPress"
   };
 
-  [self sendInputEventWithName:events[type] body:text ? @{
-    @"text": text,
-    @"eventCount": @(eventCount),
-    @"target": reactTag
-  } : @{
+  NSMutableDictionary *body = [[NSMutableDictionary alloc] initWithDictionary:@{
     @"eventCount": @(eventCount),
     @"target": reactTag
   }];
+
+  if (text) {
+    body[@"text"] = text;
+  }
+
+  if (key) {
+    if (key.length == 0) {
+      key = @"Backspace"; // backspace
+    } else {
+      switch ([key characterAtIndex:0]) {
+        case '\t':
+          key = @"Tab";
+          break;
+        case '\n':
+          key = @"Enter";
+        default:
+          break;
+      }
+    }
+    body[@"key"] = key;
+  }
+
+  [self sendInputEventWithName:events[type] body:body];
 }
 
 - (void)sendEvent:(id<RCTEvent>)event

Diff for: React/Views/RCTViewManager.m

@@ -80,6 +80,7 @@ - (NSArray *)customBubblingEventTypes
     @"blur",
     @"submitEditing",
     @"endEditing",
+    @"keyPress",
 
     // Touch events
     @"touchStart",