Improve sign-up process for new users

mobile/src/Home/Home.js

@@ -8,6 +8,8 @@ import {
   View,
   TouchableOpacity,
   TouchableHighlight,
+  PermissionsAndroid,
+  AsyncStorage,
 } from "react-native"
 import MapView, { Marker } from "react-native-maps"
 import { Icon, Header } from "../ui"
@@ -15,9 +17,12 @@ import { api } from "../API"
 import autobind from "autobind-decorator"
 import { ifIphoneX } from "react-native-iphone-x-helper"
 import { workItemTypeText, pad, regionContainingPoints } from "../util"
+import { ensurePermission } from "../App"
+import { versionInfo } from "../version"
 import pinImage from "./images/pin.png"
 
 const minGPSAccuracy = 20
+const neverAskForLocationPermissionKeyName = "NeverAskForLocationPermission"
 
 export class Home extends React.Component {
   constructor(props) {
@@ -34,10 +39,22 @@ export class Home extends React.Component {
       positionInfo: null,
     }
 
-    this.watchId = navigator.geolocation.watchPosition(
-      this.handlePositionChange,
-      null,
-      { distanceFilter: 10 }
+    ensurePermission(
+      PermissionsAndroid.PERMISSIONS.ACCESS_FINE_LOCATION,
+      neverAskForLocationPermissionKeyName,
+      {
+        title: versionInfo.title,
+        message:
+          "This app needs access to your location so that " +
+          "you can find and access the geo located items.",
+      },
+      () => {
+        this.watchId = navigator.geolocation.watchPosition(
+          this.handlePositionChange,
+          null,
+          { distanceFilter: 10 }
+        )
+      }
     )
 
     api
@@ -59,6 +76,7 @@ export class Home extends React.Component {
   componentWillUnmount() {
     if (this.watchId) {
       navigator.geolocation.clearWatch(this.watchId)
+      this.watchId = null
     }
   }