Add onSelectionChange for Android TextInput

Summary:
public

Add an onSelectionChange method to TextInput that works on Android same as iOS

Reviewed By: andreicoman11

Differential Revision: D2780131

fb-gh-sync-id: 9b3b8fbd9ea653d43e3107a338e4bc08bde2e8c6

Libraries/Components/TextInput/TextInput.js

@@ -216,6 +216,10 @@ var TextInput = React.createClass({
      * Callback that is called when text input ends.
      */
     onEndEditing: PropTypes.func,
+    /**
+     * Callback that is called when the text input selection is changed
+     */
+    onSelectionChange: PropTypes.func,
     /**
      * Callback that is called when the text input's submit button is pressed.
      * Invalid if multiline={true} is specified.
@@ -474,6 +478,17 @@ var TextInput = React.createClass({
   },
 
   _renderAndroid: function() {
+    var onSelectionChange;
+    if (this.props.selectionState || this.props.onSelectionChange) {
+      onSelectionChange = (event: Event) => {
+        if (this.props.selectionState) {
+          var selection = event.nativeEvent.selection;
+          this.props.selectionState.update(selection.start, selection.end);
+        }
+        this.props.onSelectionChange && this.props.onSelectionChange(event);
+      };
+    }
+
     var autoCapitalize = UIManager.UIText.AutocapitalizationType[this.props.autoCapitalize];
     var textAlign =
       UIManager.AndroidTextInput.Constants.TextAlign[this.props.textAlign];
@@ -489,6 +504,7 @@ var TextInput = React.createClass({
     if (childCount > 1) {
       children = <Text>{children}</Text>;
     }
+
     var textContainer =
       <AndroidTextInput
         ref="input"
@@ -505,6 +521,7 @@ var TextInput = React.createClass({
         onFocus={this._onFocus}
         onBlur={this._onBlur}
         onChange={this._onChange}
+        onSelectionChange={onSelectionChange}
         onTextInput={this._onTextInput}
         onEndEditing={this.props.onEndEditing}
         onSubmitEditing={this.props.onSubmitEditing}