CLI: Update Navigation app template

Summary:
Update the template that will be used by `react-native init --template navigation`. The goal is to make it easier for people to get started by demonstrating a few very basic concepts such as navigation, lists and text input.

**Test plan (required)**

<img src="https://cloud.githubusercontent.com/assets/346214/22697898/ced66f52-ed4a-11e6-9b90-df6daef43199.gif" alt="Android Example" height="800" style="float: left"/>

<img src="https://cloud.githubusercontent.com/assets/346214/22697901/cfeab3e4-ed4a-11e6-8552-d76585317ac2.gif" alt="iOS Example" height="800"/>
Closes #12260

Differential Revision: D4521758

Pulled By: mkonicek

fbshipit-source-id: d7d9e481dd3373917ac68ec9169b9ac3267547a9

Author: Martin Konicek

local-cli/templates/HelloNavigation/lib/Backend.js

@@ -0,0 +1,116 @@
+
+// This file just a dummy example of a HTTP API to talk to the backend.
+// The state of the "database" that would normally live on the server
+// is simply held here in memory.
+
+const backendStateForLoggedInPerson = {
+  chats: [
+    {
+      name: 'Claire',
+      messages: [
+        {
+          name: 'Claire',
+          text: 'I ❤️ React Native!',
+        },
+      ],
+    },
+    {
+      name: 'John',
+      messages: [
+        {
+          name: 'John',
+          text: 'I ❤️ React Native!',
+        },
+      ],
+    }
+  ],
+};
+
+/**
+ * Randomly simulate network failures.
+ * It is useful to enable this during development to make sure our app works
+ * in real-world conditions.
+ */
+function isNetworkFailure() {
+  const chanceOfFailure = 0;  // 0..1
+  return Math.random() < chanceOfFailure;
+}
+
+/**
+ * Helper for the other functions in this file.
+ * Simulates a short delay and then returns a provided value or failure.
+ * This is just a dummy example. Normally we'd make a HTTP request,
+ * see http://facebook.github.io/react-native/docs/network.html
+ */
+function _makeSimulatedNetworkRequest(getValue) {
+  const durationMs = 400;
+  return new Promise(function (resolve, reject) {
+    setTimeout(function () {
+      if (isNetworkFailure()) {
+        reject(new Error('Network failure'));
+      } else {
+        getValue(resolve, reject);
+      }
+    }, durationMs);
+  });
+}
+
+/**
+ * Fetch a list of all chats for the logged in person.
+ */
+async function fetchChatList() {
+  return _makeSimulatedNetworkRequest((resolve, reject) => {
+    resolve(backendStateForLoggedInPerson.chats.map(chat => chat.name))
+  });
+}
+
+/**
+ * Fetch a single chat.
+ */
+async function fetchChat(name) {
+  return _makeSimulatedNetworkRequest((resolve, reject) => {
+    resolve(
+      backendStateForLoggedInPerson.chats.find(
+        chat => chat.name === name
+      )
+    )
+  });
+}
+
+/**
+ * Send given message to given person.
+ */
+async function sendMessage({name, message}) {
+  return _makeSimulatedNetworkRequest((resolve, reject) => {
+    const chat = backendStateForLoggedInPerson.chats.find(
+      chat => chat.name === name
+    );
+    if (chat) {
+      chat.messages.push({
+        name: 'Me',
+        text: message,
+      });
+      resolve();
+    } else {
+      reject(new Error('Uknown person: ' + name));
+    }
+  });
+}
+
+const Backend = {
+  fetchChatList,
+  fetchChat,
+  sendMessage,
+};
+
+export default Backend;
+
+// In case you are looking into using Redux for state management,
+// this is how network requests are done in the f8 app which uses Redux:
+// - To load some data, a Component fires a Redux action, such as loadSession()
+// - That action makes the HTTP requests and then dispatches a redux action
+//   {type: 'LOADED_SESSIONS', results}
+// - Then all reducers get called and one of them updates a part of the application
+//   state by storing the results
+// - Redux re-renders the connected Components
+// See https://github.com/fbsamples/f8app/search?utf8=%E2%9C%93&q=loaded_sessions

local-cli/templates/HelloNavigation/views/HomeScreenTabNavigator.js

@@ -1,9 +1,4 @@
 import React, { Component } from 'react';
-import {
-  ListView,
-  Platform,
-  Text,
-} from 'react-native';
 import { TabNavigator } from 'react-navigation';
 
 import ChatListScreen from './chat/ChatListScreen';

local-cli/templates/HelloNavigation/views/chat/ChatListScreen.js

@@ -1,16 +1,19 @@
 import React, { Component } from 'react';
 import {
+  ActivityIndicator,
   Image,
   ListView,
   Platform,
   StyleSheet,
+  View,
 } from 'react-native';
 import ListItem from '../../components/ListItem';
+import Backend from '../../lib/Backend';
 
 export default class ChatListScreen extends Component {
 
   static navigationOptions = {
-    title: 'Friends',
+    title: 'Chats',
     header: {
       visible: Platform.OS === 'ios',
     },
@@ -29,35 +32,60 @@ export default class ChatListScreen extends Component {
     super(props);
     const ds = new ListView.DataSource({rowHasChanged: (r1, r2) => r1 !== r2});
     this.state = {
-      dataSource: ds.cloneWithRows([
-        'Claire', 'John'
-      ])
+      isLoading: true,
+      dataSource: ds,
     };
   }
 
+  async componentDidMount() {
+    const chatList = await Backend.fetchChatList();
+    const ds = new ListView.DataSource({rowHasChanged: (r1, r2) => r1 !== r2});
+    this.setState((prevState) => ({
+      dataSource: prevState.dataSource.cloneWithRows(chatList),
+      isLoading: false,
+    }));
+  }
+
   // Binding the function so it can be passed to ListView below
-  // and 'this' works properly inside _renderRow
-  _renderRow = (name) => {
+  // and 'this' works properly inside renderRow
+  renderRow = (name) => {
     return (
       <ListItem
         label={name}
-        onPress={() => this.props.navigation.navigate('Chat', {name: name})}
+        onPress={() => {
+          // Start fetching in parallel with animating
+          this.props.navigation.navigate('Chat', {
+            name: name,
+          });
+        }}
       />
     )
   }
 
   render() {
+    if (this.state.isLoading) {
+      return (
+        <View style={styles.loadingScreen}>
+          <ActivityIndicator />
+        </View>
+      );
+    }
     return (
       <ListView
         dataSource={this.state.dataSource}
-        renderRow={this._renderRow}
+        renderRow={this.renderRow}
         style={styles.listView}
       />
     );
   }
 }
 
 const styles = StyleSheet.create({
+  loadingScreen: {
+    backgroundColor: 'white',
+    paddingTop: 8,
+    flex: 1,
+  },
   listView: {
     backgroundColor: 'white',
   },

local-cli/templates/HelloNavigation/views/chat/ChatScreen.js

@@ -1,14 +1,15 @@
 import React, { Component } from 'react';
 import {
+  ActivityIndicator,
   Button,
   ListView,
-  Platform,
   StyleSheet,
   Text,
   TextInput,
   View,
 } from 'react-native';
 import KeyboardSpacer from '../../components/KeyboardSpacer';
+import Backend from '../../lib/Backend';
 
 export default class ChatScreen extends Component {
 
@@ -19,23 +20,59 @@ export default class ChatScreen extends Component {
   constructor(props) {
     super(props);
     const ds = new ListView.DataSource({rowHasChanged: (r1, r2) => r1 !== r2});
-    const messages = [
-      {
-        name: props.navigation.state.params.name,
-        name: 'Claire',
-        text: 'I ❤️ React Native!',
-      },
-    ];
     this.state = {
-      messages: messages,
-      dataSource: ds.cloneWithRows(messages),
+      messages: [],
+      dataSource: ds,
       myMessage: '',
+      isLoading: true,
+    };
+  }
+
+  async componentDidMount() {
+    let chat;
+    try {
+      chat = await Backend.fetchChat(this.props.navigation.state.params.name);
+    } catch (err) {
+      // Here we would handle the fact the request failed, e.g.
+      // set state to display "Messages could not be loaded".
+      // We should also check network connection first before making any
+      // network requests - maybe we're offline? See React Native's NetInfo
+      // module.
+      this.setState({
+        isLoading: false,
+      });
+      return;
     }
+    const ds = new ListView.DataSource({rowHasChanged: (r1, r2) => r1 !== r2});
+    this.setState((prevState) => ({
+      messages: chat.messages,
+      dataSource: prevState.dataSource.cloneWithRows(chat.messages),
+      isLoading: false,
+    }));
   }
 
-  addMessage = () => {
+  onAddMessage = async () => {
+    // Optimistically update the UI
+    this.addMessageLocal();
+    // Send the request
+    try {
+      await Backend.sendMessage({
+        name: this.props.navigation.state.params.name,
+        // TODO Is reading state like this outside of setState OK?
+        // Can it contain a stale value?
+        message: this.state.myMessage,
+      });
+    } catch (err) {
+      // Here we would handle the request failure, e.g. call setState
+      // to display a visual hint showing the message could not be sent.
+    }
+  }
+
+  addMessageLocal = () => {
     this.setState((prevState) => {
-      if (!prevState.myMessage) return prevState;
+      if (!prevState.myMessage) {
+        return prevState;
+      }
       const messages = [
         ...prevState.messages, {
           name: 'Me',
@@ -51,7 +88,7 @@ export default class ChatScreen extends Component {
     this.refs.textInput.clear();
   }
 
-  myMessageChange = (event) => {
+  onMyMessageChange = (event) => {
     this.setState({myMessage: event.nativeEvent.text});
   }
 
@@ -63,6 +100,13 @@ export default class ChatScreen extends Component {
   )
 
   render() {
+    if (this.state.isLoading) {
+      return (
+        <View style={styles.container}>
+          <ActivityIndicator />
+        </View>
+      );
+    }
     return (
       <View style={styles.container}>
         <ListView
@@ -78,13 +122,13 @@ export default class ChatScreen extends Component {
             style={styles.textInput}
             placeholder='Type a message...'
             text={this.state.myMessage}
-            onSubmitEditing={this.addMessage}
-            onChange={this.myMessageChange}
+            onSubmitEditing={this.onAddMessage}
+            onChange={this.onMyMessageChange}
           />
           {this.state.myMessage !== '' && (
             <Button
               title="Send"
-              onPress={this.addMessage}
+              onPress={this.onAddMessage}
             />
           )}
         </View>
@@ -99,7 +143,6 @@ const styles = StyleSheet.create({
     flex: 1,
     padding: 8,
     backgroundColor: 'white',
-    alignItems: 'flex-end',
   },
   listView: {
     flex: 1,

local-cli/templates/HelloNavigation/views/welcome/WelcomeScreen.js

@@ -4,7 +4,6 @@ import {
   Platform,
   StyleSheet,
   Text,
-  View,
 } from 'react-native';
 
 import ListItem from '../../components/ListItem';

local-cli/templates/HelloNavigation/views/welcome/WelcomeText.android.js

@@ -1,9 +1,8 @@
 import React, { Component } from 'react';
 import {
-  AppRegistry,
   StyleSheet,
   Text,
-  View
+  View,
 } from 'react-native';
 
 export default class WelcomeText extends Component {
@@ -22,8 +21,8 @@ export default class WelcomeText extends Component {
           file views/welcome/WelcomeText.android.js.
         </Text>
         <Text style={styles.instructions}>
-          Press Cmd+R to reload,{'\n'}
-          Cmd+D or shake for dev menu.
+          Double tap R on your keyboard to reload,{'\n'}
+          Shake or press menu button for dev menu.
         </Text>
       </View>
     );

local-cli/templates/HelloNavigation/views/welcome/WelcomeText.ios.js

@@ -1,9 +1,8 @@
 import React, { Component } from 'react';
 import {
-  AppRegistry,
   StyleSheet,
   Text,
-  View
+  View,
 } from 'react-native';
 
 export default class WelcomeText extends Component {