我正在使用android studio来构建应用程序。由于我是android studio开发的新手,因此无法解决问题。我的应用程序运行正常。但卡片视图在recyclerview中不可见。请帮我。这是我的回收站适配器查看代码
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder> {
private Context mContext;
private List<Upload> uploads;
public RecyclerViewAdapter(Context mContext, List<Upload> uploads) {
this.mContext = mContext;
this.uploads = uploads;
}
public RecyclerViewAdapter(Context mContext) {
this.mContext = mContext;
}
public void setList(List<Upload> uploads) {
this.uploads = uploads;
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view;
LayoutInflater inflater = LayoutInflater.from(mContext);
view = inflater.inflate(R.layout.card_view_item, parent, false);
return new MyViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
final Upload upload = uploads.get(position);
holder.tv_book_title.setText(upload.getName());
Glide.with(mContext).load(upload.getUrl()).into(holder.imd_book_thumbnail);
}
@Override
public int getItemCount() {
return uploads == null ? 0 : uploads.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
TextView tv_book_title;
ImageView imd_book_thumbnail;
CardView cardView;
public MyViewHolder(@NonNull View itemView) {
super(itemView);
tv_book_title = itemView.findViewById(R.id.book_title_id);
imd_book_thumbnail = itemView.findViewById(R.id.book_img_id);
cardView = itemView.findViewById(R.id.card_view_id);
}
}
}
这是我的名片视图XML文件代码
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:clickable="true"
android:id="@+id/card_view_id"
android:layout_width="120dp"
android:layout_height="190dp"
android:foreground="?android:attr/selectableItemBackground"
android:layout_margin="5dp"
app:cardCornerRadius="4dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
>
<ImageView
android:layout_width="match_parent"
android:layout_height="160dp"
android:id="@+id/book_img_id"
android:scaleType="centerCrop"
android:padding="2dp"
android:background="#2d2">
</ImageView>
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textColor="#2d2d2d"
android:id="@+id/book_title_id"
android:text="@string/title"
android:textSize="13sp"
android:layout_gravity="center" >
</TextView>
</LinearLayout>
您必须用另一个视图包装cardView。我建议您像这样使用ConstraintLayout:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<androidx.cardview.widget.CardView
android:id="@+id/card_view_id"
android:layout_width="120dp"
android:layout_height="wrap_content"
android:layout_margin="5dp"
android:layout_marginStart="4dp"
android:layout_marginTop="4dp"
android:layout_marginEnd="4dp"
android:layout_marginBottom="4dp"
android:clickable="true"
android:foreground="?android:attr/selectableItemBackground"
app:cardCornerRadius="4dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<ImageView
android:id="@+id/book_img_id"
android:layout_width="match_parent"
android:layout_height="160dp"
android:background="#2d2"
android:padding="2dp"
android:scaleType="centerCrop" />
<TextView
android:id="@+id/book_title_id"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:text="Title"
android:textColor="#2d2d2d"
android:textSize="13sp" />
</LinearLayout>
</androidx.cardview.widget.CardView>
尝试检查布局并检查cardView在哪里或它的大小。
在这里检查:https://developer.android.com/studio/debug/layout-inspector
在我看来,设置数据的方法中
public void setList(List<Upload> uploads) {
this.uploads = uploads;
}
您没有调用notifyDataSetChanged()
,因此不会再次调用方法getItemCount
,并且您将有空的RV,因此没有显示任何项目。