如何从Firebase数据库中按降序查看RecyclerView项目 ImagesActivity.java 这是我的ImagesActivity java
public class ImagesActivity extends AppCompatActivity {
private RecyclerView mRecyclerView;
private ImageAdapter mAdapter;
private ProgressBar mProgressCircle;
private DatabaseReference mDatabaseRef;
private List<Upload> mUploads;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_images);
mRecyclerView = findViewById(R.id.recycler_view);
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
mProgressCircle = findViewById(R.id.progress_circle);
mUploads = new ArrayList<>();
mDatabaseRef = FirebaseDatabase.getInstance().getReference("uploads");
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(ImagesActivity.this, mUploads);
mRecyclerView.setAdapter(mAdapter);
mProgressCircle.setVisibility(View.INVISIBLE);
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(ImagesActivity.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
mProgressCircle.setVisibility(View.INVISIBLE);
}
});
}}
ImageAdapter.java 这是我的ImageAdapter
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.image_item, parent, false);
return new ImageViewHolder(v);
}
@Override
public void onBindViewHolder(ImageViewHolder holder, int position) {
Upload uploadCurrent = mUploads.get(position);
holder.textViewName.setText(uploadCurrent.getName());
Picasso.with(mContext)
.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 TextView textViewName;
public ImageView imageView;
public ImageViewHolder(View itemView) {
super(itemView);
textViewName = itemView.findViewById(R.id.text_view_name);
imageView = itemView.findViewById(R.id.image_view_upload);
}
}}
activity_images.xml 这是我的活动图像xml
<RelativeLayout 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="com.codinginflow.firebaseuploadexample.ImagesActivity">
<ProgressBar
android:id="@+id/progress_circle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true" />
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent" />
image_item.xml 这是我的图像项目xml
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="8dp"
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:id="@+id/text_view_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginBottom="8dp"
android:layout_marginTop="8dp"
android:text="Name"
android:textColor="@android:color/black"
android:textSize="20sp" />
<ImageView
android:id="@+id/image_view_upload"
android:layout_width="match_parent"
android:layout_height="200dp" />
</LinearLayout>
Upload.java 这是“我的项目”的“我的Java”类
public class Upload {
private String mName;
private String mImageUrl;
public Upload() {
//empty constructor needed
}
public Upload(String name, String imageUrl) {
if (name.trim().equals("")) {
name = "No Name";
}
mName = name;
mImageUrl = imageUrl;
}
public String getName() {
return mName;
}
public void setName(String name) {
mName = name;
}
public String getImageUrl() {
return mImageUrl;
}
public void setImageUrl(String imageUrl) {
mImageUrl = imageUrl;
}}
MainActivity.java
这是我项目的主要活动
private static final int PICK_IMAGE_REQUEST = 1;
private Button mButtonChooseImage;
private Button mButtonUpload;
private TextView mTextViewShowUploads;
private EditText mEditTextFileName;
private ImageView mImageView;
private ProgressBar mProgressBar;
private Uri mImageUri;
private StorageReference mStorageRef;
private DatabaseReference mDatabaseRef;
private StorageTask mUploadTask;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mButtonChooseImage = findViewById(R.id.button_choose_image);
mButtonUpload = findViewById(R.id.button_upload);
mTextViewShowUploads = findViewById(R.id.text_view_show_uploads);
mEditTextFileName = findViewById(R.id.edit_text_file_name);
mImageView = findViewById(R.id.image_view);
mProgressBar = findViewById(R.id.progress_bar);
mStorageRef = FirebaseStorage.getInstance().getReference("uploads");
mDatabaseRef = FirebaseDatabase.getInstance().getReference("uploads");
mButtonChooseImage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
openFileChooser();
}
});
mButtonUpload.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mUploadTask != null && mUploadTask.isInProgress()) {
Toast.makeText(MainActivity.this, "Upload in progress", Toast.LENGTH_SHORT).show();
} else {
uploadFile();
}
}
});
mTextViewShowUploads.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
openImagesActivity();
}
});
}
private void openFileChooser() {
Intent intent = new Intent();
intent.setType("image/*");
intent.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(intent, PICK_IMAGE_REQUEST);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == PICK_IMAGE_REQUEST && resultCode == RESULT_OK
&& data != null && data.getData() != null) {
mImageUri = data.getData();
Picasso.with(this).load(mImageUri).into(mImageView);
}
}
private String getFileExtension(Uri uri) {
ContentResolver cR = getContentResolver();
MimeTypeMap mime = MimeTypeMap.getSingleton();
return mime.getExtensionFromMimeType(cR.getType(uri));
}
private void uploadFile() {
if (mImageUri != null) {
StorageReference fileReference = mStorageRef.child(System.currentTimeMillis()
+ "." + getFileExtension(mImageUri));
mUploadTask = fileReference.putFile(mImageUri)
.addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
@Override
public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
@Override
public void run() {
mProgressBar.setProgress(0);
}
}, 500);
Toast.makeText(MainActivity.this, "Upload successful", Toast.LENGTH_LONG).show();
Upload upload = new Upload(mEditTextFileName.getText().toString().trim(),
taskSnapshot.getDownloadUrl().toString());
String uploadId = mDatabaseRef.push().getKey();
mDatabaseRef.child(uploadId).setValue(upload);
}
})
.addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show();
}
})
.addOnProgressListener(new OnProgressListener<UploadTask.TaskSnapshot>() {
@Override
public void onProgress(UploadTask.TaskSnapshot taskSnapshot) {
double progress = (100.0 * taskSnapshot.getBytesTransferred() / taskSnapshot.getTotalByteCount());
mProgressBar.setProgress((int) progress);
}
});
} else {
Toast.makeText(this, "No file selected", Toast.LENGTH_SHORT).show();
}
}
private void openImagesActivity() {
Intent intent = new Intent(this, ImagesActivity.class);
startActivity(intent);
}}
activity_main.xml
<RelativeLayout 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"
android:padding="16dp"
tools:context="com.codinginflow.firebaseuploadexample.MainActivity">
<Button
android:id="@+id/button_choose_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Choose file" />
<EditText
android:id="@+id/edit_text_file_name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_toEndOf="@+id/button_choose_image"
android:hint="Enter file name" />
<ImageView
android:id="@+id/image_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="@id/progress_bar"
android:layout_below="@id/edit_text_file_name"
android:layout_marginTop="16dp" />
<ProgressBar
android:id="@+id/progress_bar"
style="@style/Widget.AppCompat.ProgressBar.Horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_above="@+id/button_upload"
android:layout_alignParentStart="true"
android:layout_marginBottom="16dp" />
<Button
android:id="@+id/button_upload"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:text="Upload" />
<TextView
android:id="@+id/text_view_show_uploads"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/button_upload"
android:layout_alignTop="@+id/button_upload"
android:layout_marginStart="25dp"
android:layout_toEndOf="@+id/button_upload"
android:gravity="center"
android:text="Show Uploads"
android:textSize="16sp" />
答案 0 :(得分：0)
在ImageActivity中->在onCreate（）中
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_images);
mRecyclerView = findViewById(R.id.recycler_view);
mProgressCircle = findViewById(R.id.progress_circle);
mUploads = new ArrayList<>();
mDatabaseRef = FirebaseDatabase.getInstance().getReference("uploads");
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(ImagesActivity.this, mUploads);
mRecyclerView.setAdapter(mAdapter);
mProgressCircle.setVisibility(View.INVISIBLE);
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(ImagesActivity.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
mProgressCircle.setVisibility(View.INVISIBLE);
}
});
yourAdapter = new YourAdapter(yourList);
LinearLayoutManager layoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
//this will show lsit from end
//if you want your list to be sorted based on logic, use Collection.sort and then pass the list to adapter
layoutManager.setReverseLayout(true);
layoutManager.setStackFromEnd(true);
mRecyclerView.setLayoutManager(layoutManager);
mRecyclerView.setAdapter(yourAdapter);