我有一个Public Function GetSelectedSlicerItems(SlicerName As String) As String
Dim oSc As SlicerCache
Dim oSi As SlicerItem
Dim lCt As Long
On Error Resume Next
Application.Volatile
Set oSc = ThisWorkbook.SlicerCaches(SlicerName)
If Not oSc Is Nothing Then
For Each oSi In oSc.SlicerItems
If oSi.Selected Then
GetSelectedSlicerItems = GetSelectedSlicerItems & oSi.Name & ", "
lCt = lCt + 1
ElseIf oSi.HasData = False Then
lCt = lCt + 1
End If
Next
If Len(GetSelectedSlicerItems) > 0 Then
If lCt = oSc.SlicerItems.Count Then
GetSelectedSlicerItems = "All"
Else
GetSelectedSlicerItems = Left(GetSelectedSlicerItems, Len(GetSelectedSlicerItems) - 2)
End If
Else
GetSelectedSlicerItems = "No items selected"
End If
Else
GetSelectedSlicerItems = "No slicer with name '" & SlicerName & "' was found"
End If
End Function
，其中包含抽屉菜单的MainActivity。 NavigationView的标头包含NavigationView，我想要填充一些用户信息。
问题是，有时应用程序在TextView方法中使用onChanged崩溃，因为NullPointerException是textUsername。我的猜测是因为布局还没有完全膨胀。我已经实施了null检查（如下面的代码所示），这显然只会导致null在大多数情况下为空。
我的textUsername方法如下所示：
onCreate在从回调中访问布局之前，如何确保该布局膨胀？感谢。
修改
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mainViewModel = ViewModelProviders.of(this).get(MainViewModel.class);
mainDrawerLayout = (DrawerLayout) findViewById(R.id.main_drawer_layout);
mainNavigationView = (NavigationView) findViewById(R.id.main_navigation_view);
mainContentLayout = (CoordinatorLayout) findViewById(R.id.main_content_layout);
// get user information
NetworkController.getInstance().getCurrentUser(Utils.getAuthenticationToken(), new NetworkController.GetUserResponseCallback() {
@Override
public void onGetUser(Response<UserResponse> response) {
if(response.isSuccessful() && response.body() != null && response.body().isSuccess()) {
mainViewModel.setCurrentUser(response.body().getUser());
}
}
@Override
public void onRequestFailed(Throwable throwable) {
}
});
mainViewModel.getCurrentUser().observe(this, new Observer<User>() {
@Override
public void onChanged(@Nullable User user) {
TextView textUsername = (TextView) mainNavigationView.findViewById(R.id.drawer_header_username);
if(textUsername != null) {
textUsername.setText(user.getProfile().getUsername());
}
}
});
}
：
activity_main.xml <?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:openDrawer="start"
android:id="@+id/main_drawer_layout">
<include
layout="@layout/activity_main_content"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.NavigationView
android:id="@+id/main_navigation_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:headerLayout="@layout/drawer_menu_header"
app:menu="@menu/main_drawer_menu">
</android.support.design.widget.NavigationView>
</android.support.v4.widget.DrawerLayout>
：
activity_main_content.xml <?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/main_content_layout">
<!-- setup the toolbar -->
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="@+id/main_toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
android:elevation="@dimen/toolbar_elevation"
android:popupTheme="@style/AppTheme.PopupOverlay">
</android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>
<!-- include the fragment container -->
<android.support.constraint.ConstraintLayout
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:activity="com.fishley.android.activities.MainActivity"
android:id="@+id/main_fragment_container"
android:paddingTop="?attr/actionBarSize">
</android.support.constraint.ConstraintLayout>
<android.support.design.widget.FloatingActionButton
android:id="@+id/fab_new_post"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|end"
android:layout_margin="@dimen/fab_margin"
android:src="@drawable/ic_plus"
android:tint="@android:color/white"
android:visibility="gone"/>
</android.support.design.widget.CoordinatorLayout>
：
drawer_menu_header.xml