java - 在firebase实时数据库中按时间戳删除帖子

问题描述

 "Posts" : {
"-MCCtOfEcs-t8OhKAj_R" : {
  "description" : "",
  "picture" : "https://firebasestorage.googleapis.com/v0/b/instagram-c0686.appspot.com/o/blog_images%2Fimage%3A22222?alt=media&token=eb7ffc1f-f7bd-4ab7-a108-5baf92e3ef47",
  "postKey" : "-MCCtOfEcs-t8OhKAj_R",
  "timeStamp" : 1594739760019,
  "title" : "",
  "userId" : "1tXK0R5B9uOWyAbzlZMEIs6axHo1"
},
"-MCCtPZxoFEChRczT9nY" : {
  "description" : "",
  "picture" : "https://firebasestorage.googleapis.com/v0/b/instagram-c0686.appspot.com/o/blog_images%2Fimage%3A22222?alt=media&token=c92b64ff-c2f6-4076-949a-b176253f0497",
  "postKey" : "-MCCtPZxoFEChRczT9nY",
  "timeStamp" : 1594739763718,
  "title" : "",
  "userId" : "1tXK0R5B9uOWyAbzlZMEIs6axHo1"
},

我想使用 equalTo timeStamp 变量删除帖子。所以我做了一个代码。

Query fquery =FirebaseDatabase.getInstance().getReference("Posts").orderByChild("timeStamp").equalTo("1615602220595");

但我不知道为什么不工作..当我这样做时

Query fquery =FirebaseDatabase.getInstance().getReference("Posts").orderByChild("postKey").equalTo("-MCCtOfEcs-t8OhKAj_R");

它奏效了。

这是完整的代码。

public class PostDetailActivity extends AppCompatActivity {

ImageView imgPost,imgUserPost,imgCurrentUser;
TextView txtPostDesc,txtPostDateName,txtPostTitle;
EditText editTextComment;
Button btnAddComment;
String PostKey;
FirebaseAuth firebaseAuth;
FirebaseUser firebaseUser;
FirebaseDatabase firebaseDatabase;
RecyclerView RvComment;
CommentAdapter commentAdapter;
List<Comment> listComment;
static String COMMENT_KEY = "Comment";
InputMethodManager imm;
EditText et;
Button btnDeletePost;
String myUid;
String UId;
String postImage;
private DatabaseReference mDatabase;







@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_post_detail);
    imm = (InputMethodManager)getSystemService(INPUT_METHOD_SERVICE);
    et = (EditText)findViewById(R.id.post_detail_comment);



    // let's set the statue bar to transparent


    // ini Views
    RvComment = findViewById(R.id.rv_comment);
    imgPost =findViewById(R.id.post_detail_img);
    imgUserPost = findViewById(R.id.post_detail_user_img);
    imgCurrentUser = findViewById(R.id.post_detail_currentuser_img);

    txtPostTitle = findViewById(R.id.post_detail_title);
    txtPostDesc = findViewById(R.id.post_detail_desc);
    txtPostDateName = findViewById(R.id.post_detail_date_name);

    editTextComment = findViewById(R.id.post_detail_comment);
    btnAddComment = findViewById(R.id.post_detail_add_comment_btn);
    btnDeletePost = findViewById(R.id.button_delete);


    firebaseAuth = FirebaseAuth.getInstance();
    firebaseUser = firebaseAuth.getCurrentUser();
    firebaseDatabase = FirebaseDatabase.getInstance();
    // add post delete button
    mDatabase= FirebaseDatabase.getInstance().getReference();

    myUid = FirebaseAuth.getInstance().getCurrentUser().getUid();

    btnDeletePost.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //여기 수정 주의 UId.equals(myUid)
            if (true){
                Toast.makeText(PostDetailActivity.this,"삭제중...",Toast.LENGTH_SHORT).show();
                beginDelete();
                onBackPressed();
            }
            else{
                Toast.makeText(PostDetailActivity.this,"다른 사용자의 게시글입니다.",Toast.LENGTH_SHORT).show();
            }
        }
    });

    // add Comment button click listner

    btnAddComment.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            btnAddComment.setVisibility(View.INVISIBLE);
            DatabaseReference commentReference = firebaseDatabase.getReference(COMMENT_KEY).child(PostKey).push();
            String comment_content = editTextComment.getText().toString();
            String uid = firebaseUser.getUid();
            String uname = firebaseUser.getDisplayName();
            if (firebaseUser.getPhotoUrl()!=null){
                String uimg = firebaseUser.getPhotoUrl().toString();
                Comment comment = new Comment(comment_content,uid,uimg,uname);
                commentReference.setValue(comment).addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        showMessage("comment added");
                        editTextComment.setText("");
                        btnAddComment.setVisibility(View.VISIBLE);
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        showMessage("fail to add comment : "+e.getMessage());
                    }
                });

            }
            else{
                String usphoto =Integer.toString(R.drawable.userphoto);
                Comment comment = new Comment(comment_content,uid,usphoto,uname);
                commentReference.setValue(comment).addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        showMessage("comment added");
                        editTextComment.setText("");
                        btnAddComment.setVisibility(View.VISIBLE);
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        showMessage("fail to add comment : "+e.getMessage());
                    }
                });
            }




        }
    });


    // now we need to bind all data into those views
    // firt we need to get post data
    // we need to send post detail data to this activity first ...
    // now we can get post data



    // 게시글 사진 백지 케이스
    postImage = getIntent().getExtras().getString("postImage") ;
    if(postImage!=null){
        Glide.with(this).load(postImage).into(imgPost);
    }
    else{
        Glide.with(this).load(R.drawable.whitepaper).into(imgPost);
    }


    String postTitle = getIntent().getExtras().getString("title");
    txtPostTitle.setText(postTitle);

    String userpostImage = getIntent().getExtras().getString("userPhoto");
    if (userpostImage!=null){
        Glide.with(this).load(userpostImage).into(imgUserPost);
    }
    else {
        Glide.with(this).load(R.drawable.userphoto).into(imgUserPost);
    }

    String postDescription = getIntent().getExtras().getString("description");
    txtPostDesc.setText(postDescription);

    // set comment user image
    if (firebaseUser.getPhotoUrl()!=null){
        Glide.with(this).load(firebaseUser.getPhotoUrl()).into(imgCurrentUser);
    }
    else{
        Glide.with(this).load(R.drawable.userphoto).into(imgCurrentUser);
    }
    // get post key
    PostKey = getIntent().getExtras().getString("postKey");

    String date = timestampToString(getIntent().getExtras().getLong("postDate"));
    txtPostDateName.setText(date);
    // get post uid
    UId = getIntent().getExtras().getString("userId");



    // ini Recyclerview Comment
    iniRvComment();


}

private void beginDelete() {

    StorageReference picRef = FirebaseStorage.getInstance().getReferenceFromUrl(postImage);
    picRef.delete()
            .addOnSuccessListener(new OnSuccessListener<Void>() {
                @Override
                public void onSuccess(Void aVoid) {
                    //image deleted, now delete database
                    Query fquery =FirebaseDatabase.getInstance().getReference("Posts").orderByChild("timeStamp").equalTo("1615602220595");
                    fquery.addListenerForSingleValueEvent(new ValueEventListener() {
                        @Override
                        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                            for (DataSnapshot ds:dataSnapshot.getChildren()){
                                ds.getRef().removeValue(); // remove values from firebase where postkey matches
                            }
                            //Deleted
                            Toast.makeText(PostDetailActivity.this,"게시글이 삭제되었습니다.",Toast.LENGTH_SHORT).show();
                        }

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

                        }
                    });

                }
            })
            .addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    //failed, can't go further
                    Toast.makeText(PostDetailActivity.this,""+e.getMessage(),Toast.LENGTH_SHORT).show();
                }
            });

}

public void linearOnClick(View v) {
    imm.hideSoftInputFromWindow(et.getWindowToken(), 0);
}


private void iniRvComment() {

    RvComment.setLayoutManager(new LinearLayoutManager(this));

    DatabaseReference commentRef = firebaseDatabase.getReference(COMMENT_KEY).child(PostKey);
    commentRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            listComment = new ArrayList<>();
            for (DataSnapshot snap:dataSnapshot.getChildren()) {

                Comment comment = snap.getValue(Comment.class);
                listComment.add(comment) ;

            }

            commentAdapter = new CommentAdapter(getApplicationContext(),listComment);
            RvComment.setAdapter(commentAdapter);


        }

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

        }
    });




}

private void showMessage(String message) {

    Toast.makeText(this,message,Toast.LENGTH_LONG).show();

}


private String timestampToString(long time) {

    Calendar calendar = Calendar.getInstance(Locale.ENGLISH);
    calendar.setTimeInMillis(time);
    String date = DateFormat.format("yyyy-MM-dd",calendar).toString();
    return date;


}

}

标签： javaandroidfirebasefirebase-realtime-databasegoogle-cloud-platform

解决方案

如果要删除-MCCtOfEcs-t8OhKAj_R“帖子”节点中存在的第一个节点（），请注意无需执行查询。由于节点的键与postKey字段的值相同，因此您应该简单地使用以下代码行：

DatabaseReference db = FirebaseDatabase.getInstance().getReference();
db.child("Posts").child("-MCCtOfEcs-t8OhKAj_R")).removeValue();

我还建议您在removeValue()操作中附加一个完整的侦听器，以查看是否出现问题。如果您没有适当的规则，则会抛出异常。

编辑：

根据您的最后评论：

我想删除具有旧时间戳的实例。

在这种情况下，您确实需要使用查询。例如，如果您需要删除特定时间戳之前的子项，则使用Query#endAt()方法，该方法：

创建一个查询，限制为仅返回值小于或等于给定值的子节点，使用给定的 orderBy 指令或优先级作为默认值，另外仅返回键小于或等于给定键的子节点。

这是一个工作示例：

DatabaseReference db = FirebaseDatabase.getInstance().getReference();
Query queryByTimestamp = db.child("Posts").orderByChild("timeStamp").endAt(1615602220595);
queryByTimestamp.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DataSnapshot> task) {
        if (task.isSuccessful()) {
            for (DataSnapshot ds : task.getResult().getChildren()) {
                ds.getRef().removeValue();
            }
        } else {
            Log.d("TAG", task.getException().getMessage()); //Don't ignore potential errors!
        }
    }
});

此查询的结果将是删除之前存在的所有子项1615602220595。

java - 在firebase实时数据库中按时间戳删除帖子

问题描述

解决方案

推荐阅读