java - 适配器类出现问题，没有崩溃，但页面卡住并重新加载

Question

在我的 CommentAdapter.java 类中，我有以下代码。当用户对某个帖子发表评论时，图像图标必须从黑色聊天图标更改为黄色聊天图标。工作正常。当用户删除他们在帖子上留下的评论时，就会出现问题。如果他们删除了自己的评论，并且该用户对该帖子没有其他评论，则聊天图标应从黄色更改回黑色。

它可以工作，我得到了想要的结果，但由于某种原因它抛出了一个空指针，页面卡住，重新加载，然后它带我回到带有期望结果的主页。我需要整个过程运行得更流畅，显然没有任何空指针。

是的，显然我知道空指针是什么以及如何修复它们，但在这里我不明白为什么我会得到它。聊天图标已存在。

下方用箭头标记的崩溃线。

评论适配器

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

    ImageView mImageView;

    private Context mContext;
    private List<Comment> mComment;
    private String postid;
    private FirebaseUser mFirebaseUser;

    public CommentAdapter(Context mContext, List<Comment> mComment, String postid) {
        this.mContext = mContext;
        this.mComment = mComment;
        this.postid = postid;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(mContext).inflate(R.layout.comment_item, parent, false);
        return new CommentAdapter.ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {

        mFirebaseUser = FirebaseAuth.getInstance().getCurrentUser();
        final Comment comment = mComment.get(position);

        holder.comment.setText(comment.getComment());
        getUserInfo(holder.image_profile, holder.username, comment.getPublisher());

 holder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(final View v) {
                if (comment.getPublisher().equals(mFirebaseUser.getUid())) {

                    AlertDialog alertDialog = new AlertDialog.Builder(mContext).create();
                    alertDialog.setTitle("Do you want to delete this comment?");
                    alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "No",
                            new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    dialog.dismiss();
                                }
                            });
                    alertDialog.setButton(AlertDialog.BUTTON_POSITIVE, "Yes",
                            new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    Log.d("POSTID ->", postid);
                                    FirebaseDatabase.getInstance().getReference("Comments").child(postid).child(comment.getCommentid())
                                            .setValue(null).addOnCompleteListener(new OnCompleteListener<Void>() {
                                        @Override
                                        public void onComplete(@NonNull Task<Void> task) {
                                            if (task.isSuccessful()) {
   -------------------------------------------> mImageView.setImageResource(R.drawable.ic_chat_black);
                                                Toast.makeText(mContext, "Your comment has been deleted", Toast.LENGTH_SHORT).show();
                                            }
                                        }
                                    });
                                    dialog.dismiss();
                                }
                            });
                    alertDialog.show();
                }
                return true;
            }
        });

 public static class ViewHolder extends RecyclerView.ViewHolder {

        ImageView image_profile, imageView;
        public TextView username, comment;

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

            image_profile = itemView.findViewById(R.id.image_profile);
            comment = itemView.findViewById(R.id.comment);
            username = itemView.findViewById(R.id.username);
            imageView = itemView.findViewById(R.id.commentPost);
        }
    }

Logcat

E/AndroidRuntime:致命异常:main 进程:com.e.events，PID:18463 java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“void android.widget.ImageView.setImageResource(int)” 在 com.e.events.Adapter.CommentAdapter$3$2$1.onComplete(CommentAdapter.java:110) 在 com.google.android.gms.tasks.zzj.run(来源未知:4) 在 android.os.Handler.handleCallback(Handler.java:907) 在 android.os.Handler.dispatchMessage(Handler.java:105) 在 android.os.Looper.loop(Looper.java:216) 在 android.app.ActivityThread.main(ActivityThread.java:7625) 在 java.lang.reflect.Method.invoke( native 方法) 在 com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524) 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987)

Answer 1

如果您的 Comment 类是自定义类，我建议将图像资源值存储在 Comment 类本身中，然后在更改 Comment 的图像值时刷新适配器。它应该看起来像这样:

@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position){
    // ...

    final Comment comment = mComment.get(position);

    // Use a getter you defined in your Comment class to set the ViewHolder's image
    // (Make sure your ViewHolder class has an ImageView in it for this to work)
    // *(Also, make sure your Comment class already has a default Image Resource
    // value assigned within it)
    holder.myImageView.setImageResource(comment.getImgResource());

    // ...
}

然后在回调中，您之前设置图像资源的位置:

if(task.isSuccessful){
    // Update the image resource stored in the Comment
    comment.setImgResource(myNewImageResource);

    // Anything else you want to do ...

    notifyDataSetChanged(); // Notify the adapter to refresh
}