Java 回收器视图不显示任何无错误的项目

您好，我是android devolpment的新手，我面临一个一周内无法解决的错误，错误是我的回收器视图中没有显示任何项目，我真的不知道为什么我阅读了有关stackoverflow和Documanation的所有问题，但没有任何帮助，我希望您能帮助我。 活动性：

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}我在代码中发现了您的错误。 代码中有两个问题

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>

//有问题

您将expandedRelativelayout的可见性设置为“进入适配器”。 而其他相对年轻人的可见性已经消失了

因此，您的屏幕中没有可见的视图。 我想您在xml文件中写错了@id。 expandedRelativelayout应该是第二个RelativeLayout。 就这样

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

---

请检查您自己，并正确制作。

您能同时发布xml和Book类吗？然后我将使用您的代码进行测试。

<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>

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 + '\'' +
            '}';
}

@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);
    }
}

<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>

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