[英]Image Not Displaying in firebase RecyclerView
我正在嘗試顯示Firebase數據庫中的圖像。 我認為在Firebase中一切都很好,但是什么也沒顯示。它沒有在布局中顯示圖像,我為recyclerview和item_view.xml創建了main_layout這是我的代碼。
MainActivity.java
<i>public class MainActivity extends AppCompatActivity {
private RecyclerView mRecyclerView;
private ImageAdapter mAdapter;
private DatabaseReference mDatabaseRef;
private List<Upload> mUploads;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mRecyclerView = findViewById(R.id.recycler_view);
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setLayoutManager(new GridLayoutManager(this, 2));
mUploads = new ArrayList<>();
mDatabaseRef = FirebaseDatabase.getInstance().getReference("Data");
mDatabaseRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
Upload upload = postSnapshot.getValue(Upload.class);
mUploads.add(upload);
}
mAdapter = new ImageAdapter(MainActivity.this, mUploads);
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(MainActivity.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
}
});
}
}
ImageAdapter.java
<i>public class ImageAdapter extends RecyclerView.Adapter<ImageAdapter.ImageViewHolder> {
private Context mContext;
private List<Upload> mUploads;
public ImageAdapter(Context context, List<Upload> uploads) {
mContext = context;
mUploads = uploads;
}
@Override
public ImageViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(mContext).inflate(R.layout.item_view, parent, false);
return new ImageViewHolder(v);
}
@Override
public void onBindViewHolder(ImageViewHolder holder, int position) {
Upload uploadCurrent = mUploads.get(position);
picasso.get()
.load(uploadCurrent.getImageUrl())
.placeholder(R.mipmap.ic_launcher)
.fit()
.centerCrop()
.into(holder.imageView);
}
@Override
public int getItemCount() {
return mUploads.size();
}
public class ImageViewHolder extends RecyclerView.ViewHolder {
public ImageView imageView;
public ImageViewHolder(View itemView) {
super(itemView);
imageView = itemView.findViewById(R.id.image_view);
}
}
Picasso.Builder picassoBuilder = new Picasso.Builder(mContext);
Picasso picasso = picassoBuilder.build();
}
Upload.java
<i>
公共類Upload {private String mImageUrl;
public Upload() {
}
public Upload( String imageUrl) {
mImageUrl = imageUrl;
}
public String getImageUrl() {
return mImageUrl;
}
public void setImageUrl(String imageUrl) {
mImageUrl = imageUrl;
}
}
調試輸出:
您沒有為recyclerView設置適配器,並且從Firebase接收數據后也沒有更新適配器。 我將通過以下方式解決此問題。 首先,在適配器中添加一個setter:
public void setUploads(List<Upload> uploads) {
this.mUploads = uploads;
this.notifyDataSetChanged();
}
這將使您可以輕松地修改適配器的數據集。 然后,在您的活動中,如下更改onCreate方法:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mRecyclerView = findViewById(R.id.recycler_view);
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setLayoutManager(new GridLayoutManager(this, 2));
mAdapter = new ImageAdapter(MainActivity.this, new ArrayList<>());
mRecyclerView.setAdapter(mAdapter);
mDatabaseRef = FirebaseDatabase.getInstance().getReference("Data");
mDatabaseRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<Upload> readUploads = new ArrayList<>();
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
Upload upload = postSnapshot.getValue(Upload.class);
readUploads.add(upload);
}
mAdapter.setUploads(readUploads);
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(MainActivity.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
}
});
}
這樣,您將從一個空列表開始,因此您的recyclerView將什么也不顯示。 然后,當您接收到數據時,您只需對其進行更新,就可以在適配器中設置數據集並通知適配器某些更改,因此必須重新繪制列表
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.