嵌套片段在 xamarin android 中反击时不起作用

Question

我创建了一个活动和 2 个片段。片段 B 位于片段 A 内。当我单击手机上的后退按钮时，它不会从片段 B 转到片段 A。但它会使应用程序崩溃。我正在维护一个堆栈。

public void ShowFragment(SupportFragment fragment)
        {
            if (fragment.IsVisible)
            {
                return;
            }
            Android.Support.V4.App.FragmentTransaction trans = SupportFragmentManager.BeginTransaction();
            fragment.View.BringToFront(); 
            trans.Hide(mCurrentFragment);
            Console.WriteLine("Hiding fragemnt current " + mCurrentFragment.Tag+" fragment "+fragment.Tag);
            trans.Show(fragment);

            if (mStackFragments.Count != 0)
            {
                SupportFragment sf = mStackFragments.Pop();
                if (fragment != sf)
                {
                    mStackFragments.Push(sf);
                    mStackFragments.Push(fragment);
                }
                else
                {
                    mStackFragments.Push(sf);
                }
            }
            else
            {
                mStackFragments.Push(fragment);
            }
            mCurrentFragment = fragment;
            trans.Commit();
            LoadFragmentTitleTxtView();
            LoadActionBarSpinner();
        }

上面的方法用于显示片段/主屏幕，而以下代码用于 OnBackPressed。

public override void OnBackPressed()
        {
            if (mDrawerLayout.IsDrawerOpen((int)GravityFlags.Left))
            {
                mDrawerLayout.CloseDrawer((int)GravityFlags.Left);
            }
            else
            {
                if (mStackFragments.Count > 1)
                {
                    //mStackFragments.Pop();
                    Console.WriteLine("Popping 1st " + mStackFragments.Pop().Tag+" Count "+mStackFragments.Count);
                    SupportFragment frag = mStackFragments.Pop();
                    Console.WriteLine("Poppoing 2nd " + frag.Tag+" Count "+mStackFragments.Count);
                    if (frag == chaptersFragment)
                    {
                        if (chapterfiltertext != "")
                        {
                            item.ExpandActionView();
                            sssearchview.SetQuery(chapterfiltertext, false);
                            mainview.Animate().Alpha(1f).SetListener(null);
                        }
                    }
                    Console.WriteLine("In back method.. "+frag.Tag);
                    ShowFragment(frag);
                }
                else
                {
                    Finish();
                }
            }
        }

它适用于其中没有任何嵌套片段的片段。

这是嵌套片段 B 从片段 A 加载到主屏幕上的代码。

FragmentTransaction tx = context.SupportFragmentManager.BeginTransaction();
            FragmentB fragmentB = new FragmentB();
            Bundle args = new Bundle();
            args.PutString("letter", tmp1);
            fragmentB.Arguments = args;
            tx.Replace(Resource.Id.main, fragmentB, "innerDictFrag");
            tx.AddToBackStack(null);
            context.mStackFragments.Push(fragmentB);
            tx.Commit();

Note：此问题总结整理于: Nested fragments are not working on back click in xamarin android

Answer 1

欢迎来到我们的 Microsoft 问答平台！

如果要将 fragment1 传输到 fragment2，请使用以下代码，不要更改代码顺序。例如，当前是 fragment1，然后我导航到 fragment2

   public class Fragment1 : Fragment  
       {  
     
           
           public override void OnCreate(Bundle savedInstanceState)  
           {  
               base.OnCreate(savedInstanceState);  
     
               // Create your fragment here  
           }  
     
           public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)  
           {  
     
                 
     
               View view=   inflater.Inflate(Resource.Layout.layout1, container, false);  
     
               Button button1 = view.FindViewById<Button>(Resource.Id.button1);  
               button1.Click += Button1_Click;  
               return view;  
               
           }  
     
           private void Button1_Click(object sender, EventArgs e)  
           {  
              
               FragmentTransaction transaction = this.FragmentManager.BeginTransaction();  
               Fragment2 fragment =   new Fragment2();  
               transaction.AddToBackStack(null);  
               transaction.Replace(Resource.Id.FramePage, fragment);  
               transaction.Commit();  
           }  
       }  

在 fragment2 中，可以单击后退按钮以后退 fragment1，或单击按钮执行this.FragmentManager.PopBackStack();

   public class Fragment2 : Fragment  
       {  
           public override void OnCreate(Bundle savedInstanceState)  
           {  
               base.OnCreate(savedInstanceState);  
     
               // Create your fragment here  
           }  
     
           public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)  
           {  
              View view= inflater.Inflate(Resource.Layout.layout2, container, false);  
               Button popBtn = view.FindViewById<Button>(Resource.Id.popBtn);  
               popBtn.Click += PopBtn_Click;  
                 
               return view;  
     
             
           }  
     
           private void PopBtn_Click(object sender, EventArgs e)  
           {  
                
     
               this.FragmentManager.PopBackStack();  
           }  
       }  

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