所以我的问题是我的片段中包含的按钮会引发错误＆＃34;未处理的异常 - 对象引用未设置为对象的实例＆＃34; 我想是因为我引用了包含按钮的布局，这不会导致错误。如果有人能够解释我做错了什么就会很好。我想我要么缺少一些重要的代码，要么完全搞砸了，因为我不熟悉使用片段并理解它们与活动的不同之处。
这是我的MainActivity：
public class MainActivity : ActionBarActivity
{
private SupportToolbar mToolbar;
private MyActionBarDrawerToggle mDrawerToggle;
private DrawerLayout mDrawerLayout;
private ListView mLeftDrawer;
private HomeFragment mHomeFragment;
private LogInFragment mLogInFragment;
private MatchCentreFragment mMatchCentreFragment;
private PrevCompFragment mPrevCompFragment;
private PrevFixFragment mPrevFixFragment;
private SettingsFragment mSettingsFragment;
private SocialFragment mSocialFragment;
private UpcomCompFragment mUpcomCompFragment;
private UpcomFixFragment mUpcomFixFragment;
private SupportFragment mCurrentFragment = new SupportFragment();
private Stack<SupportFragment> mStackFragments;
private ArrayAdapter mLeftAdapter;
private List<string> mLeftDataItems;
protected override void OnCreate (Bundle bundle)
{
base.OnCreate(bundle);
SetContentView(Resource.Layout.Main);
mToolbar = FindViewById<SupportToolbar>(Resource.Id.toolbar);
mDrawerLayout = FindViewById<DrawerLayout>(Resource.Id.drawer_layout);
mLeftDrawer = FindViewById<ListView>(Resource.Id.left_drawer);
mHomeFragment = new HomeFragment();
mLogInFragment = new LogInFragment();
mMatchCentreFragment = new MatchCentreFragment();
mPrevCompFragment = new PrevCompFragment();
mPrevFixFragment = new PrevFixFragment();
mSettingsFragment = new SettingsFragment();
mSocialFragment = new SocialFragment();
mUpcomCompFragment = new UpcomCompFragment();
mUpcomFixFragment = new UpcomFixFragment();
mStackFragments = new Stack<SupportFragment>();
mLeftDrawer.Tag = 0;
SetSupportActionBar(mToolbar);
mLeftDataItems = new List<string>();
mLeftDataItems.Add("Home");
mLeftDataItems.Add("Log In");
mLeftDataItems.Add("Match Centre");
mLeftDataItems.Add("Previous Fixtures");
mLeftDataItems.Add("Upcoming Fixtures");
mLeftDataItems.Add("Previous Competitions");
mLeftDataItems.Add("Upcoming Competitions");
mLeftDataItems.Add("Settings");
mLeftDataItems.Add("Social");
mLeftAdapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleListItem1, mLeftDataItems);
mLeftDrawer.Adapter = mLeftAdapter;
mLeftDrawer.ItemClick += MenuListView_ItemClick;
mDrawerToggle = new MyActionBarDrawerToggle(this, mDrawerLayout, Resource.String.openDrawer, Resource.String.closeDrawer);
if (bundle != null)
{
if (bundle.GetString("DrawerState") == "Opened")
{
SupportActionBar.SetTitle(Resource.String.openDrawer);
}
else
{
SupportActionBar.SetTitle(Resource.String.closeDrawer);
}
}
else
{
SupportActionBar.SetTitle(Resource.String.closeDrawer);
}
Android.Support.V4.App.FragmentTransaction trans = SupportFragmentManager.BeginTransaction();
trans.Add(Resource.Id.fragmentContainer, mHomeFragment);
trans.Add(Resource.Id.fragmentContainer, mLogInFragment);
trans.Hide(mLogInFragment);
trans.Add(Resource.Id.fragmentContainer, mMatchCentreFragment);
trans.Hide(mMatchCentreFragment);
trans.Add(Resource.Id.fragmentContainer, mPrevFixFragment);
trans.Hide(mPrevFixFragment);
trans.Add(Resource.Id.fragmentContainer, mUpcomFixFragment);
trans.Hide(mUpcomFixFragment);
trans.Add(Resource.Id.fragmentContainer, mPrevCompFragment);
trans.Hide(mPrevCompFragment);
trans.Add(Resource.Id.fragmentContainer, mUpcomCompFragment);
trans.Hide(mUpcomCompFragment);
trans.Add(Resource.Id.fragmentContainer, mSettingsFragment);
trans.Hide(mSettingsFragment);
trans.Add(Resource.Id.fragmentContainer, mSocialFragment);
trans.Hide(mSocialFragment);
mCurrentFragment = mHomeFragment;
trans.Commit();
}
void MenuListView_ItemClick (object sender, AdapterView.ItemClickEventArgs e)
{
Android.Support.V4.App.Fragment fragment = null;
switch (e.Id)
{
case 0:
ShowFragment(mHomeFragment);
break;
case 1:
ShowFragment(mLogInFragment);
break;
case 2:
ShowFragment(mMatchCentreFragment);
break;
case 3:
ShowFragment(mPrevFixFragment);
break;
case 4:
ShowFragment(mUpcomFixFragment);
break;
case 5:
ShowFragment(mPrevCompFragment);
break;
case 6:
ShowFragment(mUpcomCompFragment);
break;
case 7:
ShowFragment(mSettingsFragment);
break;
case 8:
ShowFragment(mSocialFragment);
break;
}
mDrawerLayout.CloseDrawers();
mDrawerToggle.SyncState();
}
private void ShowFragment (SupportFragment fragment)
{
if (fragment.IsVisible)
{
return;
}
var trans = SupportFragmentManager.BeginTransaction();
fragment.View.BringToFront();
mCurrentFragment.View.BringToFront();
trans.Hide(mCurrentFragment);
trans.Show(fragment);
trans.AddToBackStack(null);
mStackFragments.Push(mCurrentFragment);
trans.Commit();
mCurrentFragment = fragment;
}
public override bool OnOptionsItemSelected(IMenuItem item)
{
switch (item.ItemId)
{
case Android.Resource.Id.Home:
//The hamburger icon was clicked which means the drawer toggle will handle the event
mDrawerToggle.OnOptionsItemSelected(item);
return true;
case Resource.Id.action_refresh:
//Refresh
return true;
case Resource.Id.action_help:
return true;
default:
return base.OnOptionsItemSelected(item);
}
}
public override bool OnCreateOptionsMenu(IMenu menu)
{
MenuInflater.Inflate(Resource.Menu.drawer_menu, menu);
return base.OnCreateOptionsMenu(menu);
}
protected override void OnSaveInstanceState(Bundle outState)
{
if(mDrawerLayout.IsDrawerOpen((int)GravityFlags.Left))
{
outState.PutString("DrawerState", "Opened");
}
else
{
outState.PutString("DrawerState", "Closed");
}
base.OnSaveInstanceState(outState);
}
protected override void OnPostCreate(Bundle savedInstanceState)
{
base.OnPostCreate(savedInstanceState);
mDrawerToggle.SyncState();
}
public override void OnConfigurationChanged(Android.Content.Res.Configuration newConfig)
{
base.OnConfigurationChanged(newConfig);
mDrawerToggle.OnConfigurationChanged(newConfig);
}
}
}
这是我的一个片段（有几个但到目前为止它们都包含基本相同的代码）
public class PrevFixFragment : Android.Support.V4.App.Fragment
{
Button button;
public PrevFixFragment()
{
}
public static Android.Support.V4.App.Fragment newInstance(Context context)
{
PrevFixFragment fragment = new PrevFixFragment();
return fragment;
}
public override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
}
public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View view = inflater.Inflate(Resource.Layout.PreviousFixtures, null);
button = View.FindViewById<Button>(Resource.Id.upcombutton);
button.Click += StartNewActivity;
return view;
}
void StartNewActivity(object sender, EventArgs e)
{
Intent intent = new Intent(Activity, typeof(UpcomFixActivity));
StartActivity(intent);
}
}
}
答案 0 :(得分：0)
尝试将以下行移至覆盖void OnViewCreated 或覆盖void onActivityCreated
button = View.FindViewById<Button>(Resource.Id.upcombutton);
button.Click += StartNewActivity;
答案 1 :(得分：0)
您必须在下面的语句中使用小写View编写view：
button = View.FindViewById<Button>(Resource.Id.upcombutton);