IllegalIllegalStateException：指定的子代已经有一个父代。您必须先在孩子的父级上调用removeView（）。

Question

所以我遇到了这个错误（就像其他50,000个人一样），我已经仔细研究了他们的错误/答案，但仍然不知道该如何解决我的问题。有人可以查看我的代码并告诉我错误在哪里/我应该如何解决？谢谢。

哦，我是编码的新手，所以我不知道错误在哪里... Logcat不会告诉我是哪个行/片段/类/导致崩溃的原因。非常抱歉，每行代码都合法。

[如果有人想向我解释在世界上哪里可以找到此错误，那也很好。多谢你们！

package com.e.whosin.Adapter;

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.fragment.app.FragmentActivity;
import androidx.recyclerview.widget.RecyclerView;

import com.bumptech.glide.Glide;
import com.bumptech.glide.request.RequestOptions;
import com.e.whosin.CommentsActivity;
import com.e.whosin.FollowersActivity;
import com.e.whosin.Fragment.PostDetailFragment;
import com.e.whosin.Fragment.ProfileFragment;
import com.e.whosin.Model.Post;
import com.e.whosin.Model.User;
import com.e.whosin.R;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class PostAdapter extends RecyclerView.Adapter<PostAdapter.ViewHolder>{

    public Context mContext;
    public List<Post> mPost;

    private FirebaseUser firebaseUser;

    public PostAdapter(Context context, List<Post> post) {
        mContext = context;
        mPost = post;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(mContext).inflate(R.layout.post_item, viewGroup, false);
        return new PostAdapter.ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull final ViewHolder viewHolder, int i) {

        firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
        final Post post = mPost.get(i);

        Glide.with(mContext).load(post.getPostimage())
                .apply(new RequestOptions().placeholder(R.drawable.portraitplaceholder))
                .into(viewHolder.post_image);

        if (post.getDescription().equals("")){
            viewHolder.description.setVisibility(View.GONE);
        } else {
            viewHolder.description.setVisibility(View.VISIBLE);
            viewHolder.description.setText(post.getDescription());
        }

        publisherInfo(viewHolder.image_profile, viewHolder.username, viewHolder.publisher, post.getPublisher());
        isLikes(post.getPostid(), viewHolder.like);
        nrLikes(viewHolder.likes, post.getPostid());
        getComments(post.getPostid(), viewHolder.comments);
        isSaved(post.getPostid(), viewHolder.save);

        viewHolder.image_profile.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                SharedPreferences.Editor editor = mContext.getSharedPreferences("PREFS", Context.MODE_PRIVATE).edit();
                editor.putString("profileid", post.getPublisher());
                editor.apply();

                ((FragmentActivity)mContext).getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new ProfileFragment()).commit();
            }
        });

        viewHolder.username.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                SharedPreferences.Editor editor = mContext.getSharedPreferences("PREFS", Context.MODE_PRIVATE).edit();
                editor.putString("profileid", post.getPublisher());
                editor.apply();

                ((FragmentActivity)mContext).getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new ProfileFragment()).commit();
            }
        });

        viewHolder.publisher.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                SharedPreferences.Editor editor = mContext.getSharedPreferences("PREFS", Context.MODE_PRIVATE).edit();
                editor.putString("profileid", post.getPublisher());
                editor.apply();

                ((FragmentActivity)mContext).getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new ProfileFragment()).commit();
            }
        });

        viewHolder.post_image.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SharedPreferences.Editor editor = mContext.getSharedPreferences("PREFS", Context.MODE_PRIVATE).edit();
                editor.putString("postid", post.getPostid());
                editor.apply();

                ((FragmentActivity)mContext).getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new PostDetailFragment()).commit();
            }
        });

        viewHolder.save.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (viewHolder.save.getTag().equals("save")){
                    FirebaseDatabase.getInstance().getReference().child("Saves").child(firebaseUser.getUid())
                            .child(post.getPostid()).setValue(true);
                } else {
                    FirebaseDatabase.getInstance().getReference().child("Saves").child(firebaseUser.getUid())
                            .child(post.getPostid()).removeValue();
                }
            }
        });

        viewHolder.like.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (viewHolder.like.getTag().equals("like")){
                    FirebaseDatabase.getInstance().getReference().child("Likes").child(post.getPostid())
                            .child(firebaseUser.getUid()).setValue(true);
                    addNotifications(post.getPublisher(), post.getPostid());
                } else {
                    FirebaseDatabase.getInstance().getReference().child("Likes").child(post.getPostid())
                            .child(firebaseUser.getUid()).removeValue();
                }
            }
        });

        viewHolder.comment.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(mContext, CommentsActivity.class);
                intent.putExtra("postid", post.getPostid());
                intent.putExtra("publisherid", post.getPublisher());
                mContext.startActivity(intent);
            }
        });

        viewHolder.comments.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(mContext, CommentsActivity.class);
                intent.putExtra("postid", post.getPostid());
                intent.putExtra("publisherid", post.getPublisher());
                mContext.startActivity(intent);
            }
        });

        viewHolder.likes.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(mContext, FollowersActivity.class);
                intent.putExtra("id", post.getPostid());
                intent.putExtra("title", "likes");
                mContext.startActivity(intent);
            }
        });
    }

    @Override
    public int getItemCount() {
        return mPost.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder{

        public ImageView image_profile, post_image, like, comment, save;
        public TextView username, likes, publisher, description, comments;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            image_profile = itemView.findViewById(R.id.image_profile);
            post_image = itemView.findViewById(R.id.post_image);
            like = itemView.findViewById(R.id.like);
            comment = itemView.findViewById(R.id.comment);
            save = itemView.findViewById(R.id.save);
            username = itemView.findViewById(R.id.username);
            likes = itemView.findViewById(R.id.likes);
            publisher = itemView.findViewById(R.id.publisher);
            description = itemView.findViewById(R.id.description);
            comments = itemView.findViewById(R.id.comments);
        }
    }

    private void getComments(String postid, final TextView comments){
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("Comments").child(postid);

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                comments.setText("View All "+dataSnapshot.getChildren() + " Comments");
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }

    //To like posts and to show how many likes each post has
    private void isLikes(String postid, final ImageView imageView){

        final FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();

        DatabaseReference reference = FirebaseDatabase.getInstance().getReference()
                .child("Likes")
                .child(postid);

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (dataSnapshot.child(firebaseUser.getUid()).exists()){
                    imageView.setImageResource(R.drawable.ic_liked);
                    imageView.setTag("liked");
                } else {
                    imageView.setImageResource(R.drawable.ic_like);
                    imageView.setTag("like");
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }

    private void nrLikes (final TextView likes, String postid){
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("Likes")
                .child(postid);
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                likes.setText(dataSnapshot.getChildrenCount()+" likes");
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }

    private void publisherInfo(final ImageView image_profile, final TextView username, final TextView publisher, String userid){
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users").child(userid);

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                User user = dataSnapshot.getValue(User.class);
                Glide.with(mContext).load(user.getImageurl()).into(image_profile);
                username.setText(user.getUsername());
                publisher.setText(user.getUsername());
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }

    private void addNotifications(String userid, String postid){
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Notifications").child(userid);

        HashMap<String, Object> hashMap = new HashMap<>();
        hashMap.put("userid", firebaseUser.getUid());
        hashMap.put("text", "liked your post");
        hashMap.put("postid", postid);
        hashMap.put("ispost", true);

        reference.push().setValue(hashMap);
    }

    private void isSaved(final String postid, final ImageView imageView){
        FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();

        DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("Saves")
                .child(firebaseUser.getUid());

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (dataSnapshot.child(postid).exists()){
                    imageView.setImageResource(R.drawable.ic_save_black);
                    imageView.setTag("saved");
                } else {
                    imageView.setImageResource(R.drawable.ic_save);
                    imageView.setTag("save");
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }
}

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.e.whosin, PID: 23744
    java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
        at android.view.ViewGroup.addViewInner(ViewGroup.java:5099)
        at android.view.ViewGroup.addView(ViewGroup.java:4930)
        at android.view.ViewGroup.addView(ViewGroup.java:4870)
        at android.view.ViewGroup.addView(ViewGroup.java:4843)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:887)
        at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1238)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1303)
        at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:439)
        at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManagerImpl.java:2079)
        at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1869)
        at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1824)
        at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManagerImpl.java:1727)
        at androidx.fragment.app.FragmentManagerImpl$2.run(FragmentManagerImpl.java:150)
        at android.os.Handler.handleCallback(Handler.java:907)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:216)
        at android.app.ActivityThread.main(ActivityThread.java:7625)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987)

所以我遇到了这个错误（就像其他50,000个人一样），我已经仔细研究了他们的错误/答案，但仍然不知道该如何解决我的问题。有人可以看一下我的代码并告诉我...

Answer 1

或者也许是我现在考虑的这个活动引起了问题...

Answer 2

package com.e.whosin.Fragment;

import android.content.Context;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.e.whosin.Adapter.PostAdapter;
import com.e.whosin.Model.Post;
import com.e.whosin.R;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.List;


public class PostDetailFragment extends Fragment {

    String postid;
    private RecyclerView recyclerView;
    private PostAdapter postAdapter;
    private List<Post> postList;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_post_detail, container, false);

        SharedPreferences preferences = getContext().getSharedPreferences("PREFS", Context.MODE_PRIVATE);
        postid = preferences.getString("postid", "none");

        recyclerView = view.findViewById(R.id.recycler_view);
        recyclerView.setHasFixedSize(true);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getContext());
        recyclerView.setLayoutManager(linearLayoutManager);

        postList = new ArrayList<>();
        postAdapter = new PostAdapter(getContext(), postList);
        recyclerView.setAdapter(postAdapter);

        readPost();

        return view;
    }

    private void readPost() {
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Posts").child(postid);

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                postList.clear();
                Post post = dataSnapshot.getValue(Post.class);
                postList.add(post);

                postAdapter.notifyDataSetChanged();
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }
}