Question

在Xamarin中，我有ViewPager执行以下错误：

java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.

当我有三个Android.Support.V4.App.Fragments并在它们之间滑动时会发生此错误。两个Android.Support.V4.App.Fragments不会发生此错误。

这是我的Android.Support.V4.App.Fragment代码：

public class FragmentItem : Android.Support.V4.App.Fragment
{
    View rootView;
    TextView textView;

    public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        if (rootView == null) 
        {
            rootView = inflater.Inflate(Resource.Layout.FragmentItem, container,false);
            textView = rootView.FindViewById<TextView>(Resource.Id.textViewDisplay);
        }

        return rootView;
    }
}

这是我的ViewPagerAdapter代码：

public class ViewPagerAdapter : FragmentPagerAdapter {

    private List<Android.Support.V4.App.Fragment> fragments;
    int fragmentCount;

    public ViewPagerAdapter(Android.Support.V4.App.FragmentManager fm, List<Android.Support.V4.App.Fragment> fragments) : base(fm)
    {
        this.fragments = fragments;
        fragmentCount = fragments.Count;
    }

    public override int Count 
    {
        get 
        {
            return fragmentCount;   
        }   
    }

    public override Android.Support.V4.App.Fragment GetItem (int position)
    {
        return fragments[position];
    }
}

为什么会发生此错误？如何防止此错误发生？

提前致谢

修改

以下是我尝试过的代码：

if (rootView != null) 
{
    ViewGroup parent = (ViewGroup)View.Parent;
    parent.RemoveView(rootView);
} else {
    rootView = inflater.Inflate(Resource.Layout.FragmentItem, container, false);
    textView = rootView.FindViewById<TextView>(Resource.Id.textViewDisplay);            
}
return rootView;

以下是我收到的错误：

System.NullReferenceException：未将对象引用设置为实例对象

在这行代码中：

ViewGroup parent = (ViewGroup)View.Parent;

Answer 1

在onCreateView（）方法中使用它，

 if (rootView != null) {
        ViewGroup parent = (ViewGroup) rootView.getParent();//Updated
        parent.removeView(rootView);
    } else {
        rootView = inflater.inflate(Resource.Layout.FragmentItem, container,
                false);
    }

如果该视图已经具有父视图，则会从其父视图中删除该视图。

带有片段的ViewPager IllegalStateException

1 个答案: