我遇到的问题是，当我浏览应用程序时，当我第一次初始化包含地图的片段时，它会很好地初始化，但是当我导航到不同的片段并再次回到包含地图的片段时，它会给出初始化＆＃39;查看对象＆＃39; 时出错，错误截图附于下方。请帮帮我。
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 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>
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 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>
答案 0 :(得分：0)
在跟踪片段中将您的片段代码更改为此代码，然后重试：
<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" />
如果它没有工作，请退回