Recycler View无法使用ImageView，但可以使用ImageView + TextView

Question

今天，我正在努力解决最疯狂的问题之一，这使我发疯。在我的RecyclerView项目xml中，如果我只有imageView，则什么都没有显示，并且列表为空，但是如果我在该ImageView下方添加TextView，则一切正常，ImageView和TextView都可以。发生了什么，请帮忙。

item_row.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/saved_post_imageview"/>

    <!--<TextView-->
        <!--android:layout_width="wrap_content"-->
        <!--android:layout_height="wrap_content"-->
        <!--android:id="@+id/text"/>-->

</RelativeLayout>

ProfileActivity.java

public class ProfileActivity extends AppCompatActivity {

FirebaseAuth mFirebaseAuth;
TextView usernameTxt;
ImageView displayPicImg;
RecyclerView recyclerView;
FirebaseDatabase mFirebaseDatabase;
DatabaseReference mUsersReference;
ArrayList<String> mPostList;
SavedPostsAdapter savedPostsAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_profile_activity);

    usernameTxt = findViewById(R.id.username);
    displayPicImg = findViewById(R.id.display_pic);
    recyclerView = findViewById(R.id.saved_posts);
    mFirebaseDatabase = FirebaseDatabase.getInstance();
    mUsersReference = mFirebaseDatabase.getReference().child("users");
    mPostList = new ArrayList<>();
    mFirebaseAuth = FirebaseAuth.getInstance();
    String username = mFirebaseAuth.getCurrentUser().getDisplayName();
    getSavedPosts(username);
    savedPostsAdapter = new SavedPostsAdapter(mPostList,ProfileActivity.this);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    recyclerView.setHasFixedSize(false);
    recyclerView.setAdapter(savedPostsAdapter);
    Uri displayPicURL = mFirebaseAuth.getCurrentUser().getPhotoUrl();
    usernameTxt.setText(username);
    setTitle(username);
    Glide.with(ProfileActivity.this).load(displayPicURL).apply(new RequestOptions().circleCrop()).apply(new RequestOptions().placeholder(R.drawable.defaultuser)).into(displayPicImg);
}

private void getSavedPosts(String username){
    Query query = mUsersReference.orderByChild("username").equalTo(username.toLowerCase());
    query.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            Log.d(MainActivity.TAG,""+dataSnapshot.getChildrenCount());
            for(DataSnapshot data: dataSnapshot.getChildren()){
                ArrayList<String> postList = (ArrayList<String>) data.child("post").getValue();
                Log.d(MainActivity.TAG,"post "+dataSnapshot.getChildrenCount());
                for(String imageUrl: postList){
                    Log.d(MainActivity.TAG,"Image url = "+imageUrl);
                    mPostList.add(imageUrl);
                    savedPostsAdapter.notifyDataSetChanged();
                }
            }
        }

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

        }
    });
}

}

适配器

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

ArrayList<String> savedPostList;
Context context;

public SavedPostsAdapter(ArrayList<String> savedPostList, Context context) {
    this.savedPostList = savedPostList;
    this.context = context;
}

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

@Override
public void onBindViewHolder(@NonNull ViewHolder viewHolder, int i) {
//        viewHolder.text.setText("fsdfdas");
        Glide.with(context).load("https://firebasestorage.googleapis.com/v0/b/memespace-58171.appspot.com/o/images%2Fimage%3A197200?alt=media&token=8501146f-201d-4fca-a9e3-63cb49fc47de").into(viewHolder.savedPostImageView);
}

@Override
public int getItemCount() {
    Log.d(MainActivity.TAG,"count = "+savedPostList.size());
    return savedPostList.size();
}

public class ViewHolder extends RecyclerView.ViewHolder {

    ImageView savedPostImageView;
//        TextView text;
    public ViewHolder(@NonNull View itemView) {
        super(itemView);
        savedPostImageView = itemView.findViewById(R.id.imageview);
//            text = itemView.findViewById(R.id.text);

    }
}
}

Answer 1

尝试在item_row.xml中添加ViewGroup

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="50dp" // or wrap_content >
        <ImageView/>
</LinearLayout>

Answer 2

为您的ImageView例如：提供默认的高度和宽度值：

<ImageView
 android:layout_width="20dp"
 android:layout_height="20dp"
 android:id="@+id/imageview"
/>

或为您的ImageView

提供默认的静态图片

我相信您的代码实际上是有效的，只是RecyclerView未正确设置大小。

RecyclerView回收已创建的视图，因为您的ImageView没有尺寸，因此将其缓存为每行的大小，这导致您在Glide上加载图像那些小的或看不见的行。

此外，您还可以利用Glide的大小调整功能将其放入所需的容器中，如下所示：

Glide
    .with(context)
    .load(path)
    .apply(new RequestOptions().override(100, 100))
    .into(imageView);