[IMPROVEMENT] Activity indicator on web view OAuth (#980)

* add activity indicator when web view is loading

* fix eslint error

* remove one extra newline

app/views/OAuthView.js

@@ -2,7 +2,7 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import { WebView } from 'react-native-webview';
 import { connect } from 'react-redux';
-
+import { ActivityIndicator, StyleSheet } from 'react-native';
 import RocketChat from '../lib/rocketchat';
 import { isIOS } from '../utils/deviceInfo';
 import { CloseModalButton } from '../containers/HeaderButton';
@@ -12,6 +12,18 @@ const userAgent = isIOS
 	? 'Mozilla/5.0 (iPhone; CPU iPhone OS 10_3_1 like Mac OS X) AppleWebKit/603.1.30 (KHTML, like Gecko) Version/10.0 Mobile/14E304 Safari/602.1'
 	: 'Mozilla/5.0 (Linux; Android 6.0.1; SM-G920V Build/MMB29K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.98 Mobile Safari/537.36';
 
+const styles = StyleSheet.create({
+	loading: {
+		position: 'absolute',
+		left: 0,
+		right: 0,
+		top: 0,
+		bottom: 0,
+		alignItems: 'center',
+		justifyContent: 'center'
+	}
+});
+
 @connect(state => ({
 	server: state.server.server
 }))
@@ -29,7 +41,8 @@ export default class OAuthView extends React.PureComponent {
 	constructor(props) {
 		super(props);
 		this.state = {
-			logging: false
+			logging: false,
+			loading: false
 		};
 		this.redirectRegex = new RegExp(`(?=.*(${ props.server }))(?=.*(credentialToken))(?=.*(credentialSecret))`, 'g');
 	}
@@ -58,6 +71,7 @@ export default class OAuthView extends React.PureComponent {
 
 	render() {
 		const { navigation } = this.props;
+		const { loading } = this.state;
 		const oAuthUrl = navigation.getParam('oAuthUrl');
 		return (
 			<React.Fragment>
@@ -74,7 +88,15 @@ export default class OAuthView extends React.PureComponent {
 							this.login({ oauth: { ...credentials } });
 						}
 					}}
+					onLoadStart={() => {
+						this.setState({ loading: true });
+					}}
+
+					onLoadEnd={() => {
+						this.setState({ loading: false });
+					}}
 				/>
+				{ loading ? <ActivityIndicator size='large' style={styles.loading} /> : null }
 			</React.Fragment>
 		);
 	}