回收站视图不显示任何项目没有错误

Question

嗨，我是android开发的新手，我正面临一个bug，我无法解决一个星期，bug是我的回收器视图不显示任何项目在它，我真的不知道为什么我读了关于stackoverflow和文档的所有问题，但没有帮助，我希望你能帮助我。Actvity:

public class All_Books_Actvity extends AppCompatActivity {
private RecyclerView recyclerView;
private BookRecViewAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_all__books__actvity);
adapter = new BookRecViewAdapter(this);
recyclerView = findViewById(R.id.booksRecView);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this ));
ArrayList<Book> books = new ArrayList<>();
books.add(new Book(1 , "wimpy kid" , "Jeff kineyy" , 134 , "https://kbimages1-a.akamaihd.net/a93f1391-68be-478b-acb0-63cd7881aed8/1200/1200/False/the-getaway-diary-of-a-wimpy-kid-book-12.jpg" ,
"asdfasd" , "adfasd"));
adapter.setBooks(books);
}}

适配器:

public class BookRecViewAdapter extends RecyclerView.Adapter<BookRecViewAdapter.ViewHolder> {
private static final String TAG = "BookRecViewAdapter";
ArrayList<Book> books = new ArrayList<>();
private Context mcontexet;
public BookRecViewAdapter(Context mcontexet) {
this.mcontexet = mcontexet;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout   .list_item_book , parent ,  false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, final int position) {
Log.d(TAG, "onBindViewHolder: Working!!!!!");
holder.txtName.setText(books.get(position).getName());
Glide.with(mcontexet).asBitmap().load(books.get(position).getImageUrl()).into(holder.imgBook);
holder.parent.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(mcontexet, "fads", Toast.LENGTH_SHORT).show();
}});
holder.txtDescreption.setText(books.get(position).getShortDesc());
holder.txtAuthor.setText(books.get(position).getAuthor());
if (books.get(position).isExpanded()){
TransitionManager.beginDelayedTransition(holder.parent);
holder.expandedRealtiveLayout.setVisibility(View.VISIBLE);
holder.downArrow.setVisibility(View.GONE);
}else {
TransitionManager.beginDelayedTransition(holder.parent);
holder.expandedRealtiveLayout.setVisibility(View.GONE);
holder.downArrow.setVisibility(View.VISIBLE);
} }
@Override
public int getItemCount() {
return books.size();
}
public void setBooks(ArrayList<Book> books) {
this.books = books;
notifyDataSetChanged();
}
public class ViewHolder extends RecyclerView.ViewHolder{
private CardView parent;
private ImageView imgBook;
private TextView txtName , txtDescreption , txtAuthor ;
private RelativeLayout expandedRealtiveLayout;
private ImageView upArrow , downArrow;
public ViewHolder(@NonNull View itemView) {
super(itemView);
parent = itemView.findViewById(R.id.parent);
imgBook = itemView.findViewById(R.id.imgBook);
txtName = itemView.findViewById(R.id.txtBookName);
txtDescreption = itemView.findViewById(R.id.txtShortDesc);
expandedRealtiveLayout = itemView.findViewById(R.id.expandedRealtivelayout);
upArrow = itemView.findViewById(R.id.btnArrowUpp);
downArrow = itemView.findViewById(R.id.btnArrowDown);
txtAuthor = itemView.findViewById(R.id.txtAuthor);
downArrow.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Book book = books.get(getAdapterPosition());
book.setExpanded(!book.isExpanded());
notifyItemInserted(getAdapterPosition());
}
});
upArrow.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Book book = books.get(getAdapterPosition());
book.setExpanded(!book.isExpanded());
notifyItemInserted(getAdapterPosition());
}
});
}
}

}

回收者视图:

<androidx.constraintlayout.widget.ConstraintLayout 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"
tools:context=".All_Books_Actvity">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/booksRecView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />

& lt;/androidx.constraintlayout.widget.ConstraintLayout>视图设计:

<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/parent"
app:cardCornerRadius="7dp"
app:cardElevation="7dp"
android:layout_margin="5dp"
android:layout_centerHorizontal="true"
>
<RelativeLayout
android:layout_width="200dp"
android:layout_height="wrap_content">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:id="@+id/expandedRealtivelayout"
>
<ImageView
android:layout_width="130dp"
android:layout_height="150dp"
android:id="@+id/imgBook"
android:visibility="visible"
android:src="@drawable/ic_launcher_background"
android:layout_centerHorizontal="true"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Book Name"
android:layout_below="@+id/imgBook"
android:textSize="16sp"
android:textStyle="bold|italic"
android:textColor="@color/black"
android:layout_centerHorizontal="true"
android:layout_marginTop="7dp"
android:id="@+id/txtBookName"
android:visibility="visible"/>
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_arrow_down"
android:layout_alignParentEnd="true"
android:layout_marginTop="150dp"
android:id="@+id/btnArrowDown"/>
</RelativeLayout>
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/expandedRealtivelayout"
android:visibility="gone">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Author:"
android:textSize="14sp"
android:textColor="@color/black"
android:id="@+id/author"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/author"
android:text="Name Of Author"
android:textSize="16sp"
android:textColor="@color/black"
android:id="@+id/txtAuthor"
android:textStyle="italic|bold"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/txtAuthor"
android:text="Short Description"
android:textSize="16sp"
android:textColor="@color/black"
android:id="@+id/txtShortDesc"
android:textStyle="italic|bold"/>
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_marginTop="40dp"
android:src="@drawable/ic_arrow_up_right_one"
android:id="@+id/btnArrowUpp"/>
</RelativeLayout>
</RelativeLayout>

& lt;/androidx.cardview.widget.CardView>

Book类

public class Book {
private int id;
private String name;
private String author;
private int pages;
private String imageUrl;
private String shortDesc;
private String longDesc;
private boolean isExpanded;
public Book(int id, String name, String author, int pages, String imageUrl, String shortDesc, String longDesc) {
this.id = id;
this.name = name;
this.author = author;
this.pages = pages;
this.imageUrl = imageUrl;
this.shortDesc = shortDesc;
this.longDesc = longDesc;
this.isExpanded = false;
}
public boolean isExpanded() {
return isExpanded;
}
public void setExpanded(boolean expanded) {
isExpanded = expanded;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public int getPages() {
return pages;
}
public void setPages(int pages) {
this.pages = pages;
}
public String getImageUrl() {
return imageUrl;
}
public void setImageUrl(String imageUrl) {
this.imageUrl = imageUrl;
}
public String getShortDesc() {
return shortDesc;
}
public void setShortDesc(String shortDesc) {
this.shortDesc = shortDesc;
}
public String getLongDesc() {
return longDesc;
}
public void setLongDesc(String longDesc) {
this.longDesc = longDesc;
}
@Override
public String toString() {
return "Book{" +
"id=" + id +
", name='" + name + ''' +
", author='" + author + ''' +
", pages=" + pages +
", imageUrl='" + imageUrl + ''' +
", shortDesc='" + shortDesc + ''' +
", longDesc='" + longDesc + ''' +
'}';
}

}

Answer 1

我在你的代码中发现了错误。你的代码有两个问题。

BookRecViewAdapter.java

@Override
public void onBindViewHolder(@NonNull ViewHolder holder, final int position) {
Log.d(TAG, "onBindViewHolder: Working!!!!!");
......................
...................
if (books.get(position).isExpanded()) {
............................
} else {
TransitionManager.beginDelayedTransition(holder.parent);
holder.expandedRealtiveLayout.setVisibility(View.GONE); // there is problem!!!
holder.downArrow.setVisibility(View.VISIBLE);
}
}

list_item_book.xml

<CardView>
<RelativeLayout>
<RelativeLayout android:id="@+id/expandedRelativelayout"></RelativeLayout> // there is problem
<RelaitveLayout
android:layout_below="@+id/expandedRealtivelayout" // there is problem
android:visibility="gone"></RelativeLayout>
</RelativeLayout>
</CardView>

你在适配器中设置了expandedRelativelayout的可见性为GONE。和其他的RelativeLayout可见性已经消失了。

所以屏幕上没有可见的View。我想你在xml文件中写错了@id。expandedRelativelayout应该是第二个RelativeLayout。就像这样

<CardView>
<RelativeLayout>
<RelativeLayout android:id="@+id/anyLayout"></RelativeLayout>
<RelaitveLayout
android:id="@+id/expandedRelativelayout"
android:layout_below="@+id/anylayout"
android:visibility="gone"></RelativeLayout>
</RelativeLayout>
</CardView>

请自检，并正确填写。