Fragment Navigation using map Xamarin Android - xamarin.android

Question

The problem I'm getting is that when I navigate through the Application and when I first initialize the fragment containing map, it initializes nicely but when I navigate to different fragments and again come back to the fragment containing map it gives an error on initializing the 'view object', the error screenshot is attached below. Please help me out.
Main Activity Code
DrawerLayout drawerLayout;
NavigationView navigationView;
IMenuItem previousItem;
TextView UserNameTxt;
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
SetContentView(Resource.Layout.main);
var toolbar = FindViewById<Android.Support.V7.Widget.Toolbar>(Resource.Id.toolbar);
if (toolbar != null)
{
SetSupportActionBar(toolbar);
SupportActionBar.SetDisplayHomeAsUpEnabled(true);
SupportActionBar.SetHomeButtonEnabled(true);
}
drawerLayout = FindViewById<DrawerLayout>(Resource.Id.drawer_layout);
//Set hamburger items menu
SupportActionBar.SetHomeAsUpIndicator(Resource.Drawable.ic_menu);
//setup navigation view
navigationView = FindViewById<NavigationView>(Resource.Id.nav_view);
var headerview = navigationView.GetHeaderView(0);
UserNameTxt = headerview.FindViewById<TextView>(Resource.Id.UserNameTxt);
UserNameTxt.Text = "Yousuf";
//handle navigation
navigationView.NavigationItemSelected += (sender, e) =>
{
if (previousItem != null)
previousItem.SetChecked(false);
navigationView.SetCheckedItem(e.MenuItem.ItemId);
previousItem = e.MenuItem;
switch (e.MenuItem.ItemId)
{
case Resource.Id.menuTracking:
ListItemClicked(2);
break;
case Resource.Id.menuHoldingRoutine:
ListItemClicked(0);
break;
case Resource.Id.menuCalendarEvent:
ListItemClicked(1);
break;
case Resource.Id.menuSettings:
StartActivity(typeof(SettingActivity));
break;
}
drawerLayout.CloseDrawers();
};
//if first time you will want to go ahead and click first item.
if (savedInstanceState == null)
{
navigationView.SetCheckedItem(Resource.Id.menuHoldingRoutine);
ListItemClicked(0);
}
}
int oldPosition = -1;
private void ListItemClicked(int position)
{
//this way we don't load twice, but you might want to modify this a bit.
if (position == oldPosition)
return;
oldPosition = position;
Fragment fragment = null;
switch (position)
{
case 0:
fragment = HoldingRoutineFragment.NewInstance();
//fragment = Fragment1.NewInstance();
break;
case 1:
fragment = CalendarEventFragment.NewInstance();
//fragment = Fragment2.NewInstance();
break;
case 2:
fragment = TrackingFragment.NewInstance();
break;
}
FragmentTransaction fragmentTx = this.FragmentManager.BeginTransaction();
fragmentTx.Replace(Resource.Id.content_frame, fragment);
fragmentTx.AddToBackStack(null);
fragmentTx.Commit();
//SupportFragmentManager.BeginTransaction()
// .Replace(Resource.Id.content_frame, fragment)
// .Commit();
}
public override bool OnOptionsItemSelected(IMenuItem item)
{
switch (item.ItemId)
{
case Android.Resource.Id.Home:
drawerLayout.OpenDrawer(GravityCompat.Start);
return true;
}
return base.OnOptionsItemSelected(item);
}
}
Xml code of MainActivity
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<!-- The main content view -->
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:id="#+id/toolbar_layout">
<include
android:id="#+id/toolbar"
layout="#layout/toolbar"
app:layout_scrollFlags="scroll|enterAlways" />
</android.support.design.widget.AppBarLayout>
<FrameLayout
android:id="#+id/content_frame"
android:layout_below="#id/toolbar_layout"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>
<android.support.design.widget.NavigationView
android:id="#+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
app:headerLayout="#layout/nav_header"
app:menu="#menu/nav_menu"
android:fitsSystemWindows="true" />
</android.support.v4.widget.DrawerLayout>
Tracking Fragment Code
using Android.OS;
using Android.Views;
using System;
using System.Collections.Generic;
using Android.Widget;
using Android.App;
using Android.Gms.Maps;
using Android.Gms.Maps.Model;
using System.Timers;
using Android.Graphics;
using Android.Content;
namespace RoutineApp.Fragments
{
public class TrackingFragment : Fragment, IOnMapReadyCallback
{
private GoogleMap gMap;
private MapFragment mapFragment;
private LatLng oldposition;
private MarkerOptions markerOptions;
private Marker marker;
private Timer timer;
private int timercount = 0;
private Button BtnUp, BtnDown, BtnRight, BtnLeft, BtnDirection;
public override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
// Create your fragment here
}
public static TrackingFragment NewInstance()
{
var frag1 = new TrackingFragment { Arguments = new Bundle() };
return frag1;
}
public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Use this to return your custom view for this Fragment
// return inflater.Inflate(Resource.Layout.YourFragment, container, false);
var ignore = base.OnCreateView(inflater, container, savedInstanceState);
var view = inflater.Inflate(Resource.Layout.tracking, container, false);
mapFragment = FragmentManager.FindFragmentById<MapFragment>(Resource.Id.TrackingMap);
mapFragment.GetMapAsync(this);
BtnUp = view.FindViewById<Button>(Resource.Id.Up_btn);
BtnDown = view.FindViewById<Button>(Resource.Id.Down_btn);
BtnLeft = view.FindViewById<Button>(Resource.Id.Left_btn);
BtnRight = view.FindViewById<Button>(Resource.Id.Right_btn);
BtnDirection = view.FindViewById<Button>(Resource.Id.Direction_btn);
return view;
}
public void OnMapReady(GoogleMap googleMap)
{
gMap = googleMap;
gMap.UiSettings.SetAllGesturesEnabled(true);
gMap.UiSettings.ZoomControlsEnabled = true;
gMap.UiSettings.CompassEnabled = true;
gMap.UiSettings.MyLocationButtonEnabled = true;
LatLng latLng = new LatLng(24.9288, 67.0402);
oldposition = latLng;
CameraUpdate camera = CameraUpdateFactory.NewLatLngZoom(latLng, 19);
gMap.MoveCamera(camera);
markerOptions = new MarkerOptions()
.SetPosition(latLng)
.SetTitle("Current Position")
.Draggable(true);
marker = gMap.AddMarker(markerOptions);
BtnUp.Click += BtnUp_Click;
BtnDown.Click += BtnDown_Click;
BtnLeft.Click += BtnLeft_Click;
BtnRight.Click += BtnRight_Click;
BtnDirection.Click += BtnDirection_Click;
//gmaps.MarkerClick += Gmaps_MarkerClick;
gMap.MarkerDragEnd += GMap_MarkerDragEnd;
}
private void BtnDirection_Click(object sender, EventArgs e)
{
var intent = new Intent(this.Activity, typeof(GoogleMapDirectionsActivity));
StartActivity(intent);
}
private void MarkerSetting(LatLng newlatlng, LatLng oldlatlng)
{
markerOptions = new MarkerOptions()
.SetPosition(newlatlng)
.SetTitle("Current Position")
.Draggable(true);
marker = gMap.AddMarker(markerOptions);
PolylineOptions line = new PolylineOptions().Add(newlatlng).Add(oldlatlng).InvokeColor(Color.Red);
Polyline polyline = gMap.AddPolyline(line);
oldposition = newlatlng;
}
private void BtnRight_Click(object sender, EventArgs e)
{
if (marker != null)
{
marker.Remove();
}
timercount = 0;
LatLng newposition = new LatLng(oldposition.Latitude, oldposition.Longitude);
newposition.Longitude = newposition.Longitude + 0.00001;
MarkerSetting(newposition, oldposition);
}
private void BtnLeft_Click(object sender, EventArgs e)
{
if (marker != null)
{
marker.Remove();
}
timercount = 0;
LatLng newposition = new LatLng(oldposition.Latitude, oldposition.Longitude);
newposition.Longitude = newposition.Longitude - 0.00001;
MarkerSetting(newposition, oldposition);
}
private void BtnDown_Click(object sender, EventArgs e)
{
if (marker != null)
{
marker.Remove();
}
timercount = 0;
LatLng newposition = new LatLng(oldposition.Latitude, oldposition.Longitude);
newposition.Latitude = newposition.Latitude - 0.00001;
MarkerSetting(newposition, oldposition);
}
private void BtnUp_Click(object sender, EventArgs e)
{
if (marker != null)
{
marker.Remove();
}
timercount = 0;
LatLng newposition = new LatLng(oldposition.Latitude, oldposition.Longitude);
newposition.Latitude = newposition.Latitude + 0.00001;
MarkerSetting(newposition, oldposition);
}
private void GMap_MarkerDragEnd(object sender, GoogleMap.MarkerDragEndEventArgs e)
{
timercount = 0;
LatLng newpositon = e.Marker.Position;
PolylineOptions line = new PolylineOptions().Add(newpositon).Add(oldposition).InvokeColor(Color.Red);
Polyline polyline = gMap.AddPolyline(line);
oldposition = newpositon;
}
public override void OnResume()
{
base.OnResume();
timer = new Timer();
timer.Interval = 1000;
timer.Elapsed += Timer_Elapsed;
timer.Start();
}
private void Timer_Elapsed(object sender, ElapsedEventArgs e)
{
if (timercount < 10)
{
timercount++;
}
else
{
Activity.RunOnUiThread(() =>
{
CreateCircle();
});
}
}
private void CreateCircle()
{
CircleOptions circle = new CircleOptions();
circle.InvokeCenter(oldposition);
circle.InvokeRadius(1);
circle.InvokeStrokeColor(Color.Blue);
circle.InvokeFillColor(Color.LightSkyBlue);
gMap.AddCircle(circle);
timercount = 0;
}
}
}
Xml Code for the Tracking Fragment
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/super_map_container">
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/map_container"
android:weightSum="100">
<fragment
android:id="#+id/TrackingMap"
android:layout_height="0dp"
android:layout_width="match_parent"
android:name="com.google.android.gms.maps.MapFragment"
android:layout_weight="90" />
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="10"
android:weightSum="10">
<Button
android:id="#+id/Up_btn"
android:layout_height="match_parent"
android:layout_width="20dp"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:background="#A11"
android:layout_weight="2" />
<Button
android:id="#+id/Down_btn"
android:layout_height="match_parent"
android:layout_width="20dp"
android:layout_marginRight="10dp"
android:background="#B22"
android:layout_weight="2" />
<Button
android:id="#+id/Left_btn"
android:layout_height="match_parent"
android:layout_width="20dp"
android:layout_marginRight="10dp"
android:background="#C33"
android:layout_weight="2" />
<Button
android:id="#+id/Right_btn"
android:layout_height="match_parent"
android:layout_width="20dp"
android:layout_marginRight="10dp"
android:background="#D44"
android:layout_weight="2" />
<Button
android:id="#+id/Direction_btn"
android:layout_height="match_parent"
android:layout_width="20dp"
android:layout_marginRight="10dp"
android:background="#E55"
android:layout_weight="2" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
Error Screen Shot

Answer 1

Change your fragment code to this in your tracking fragment and try again :
<fragment
android:id="#+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="90"
class="com.google.android.gms.maps.MapFragment" />
If it doesn't work kindly revert