Java 为什么条目在Firebase数据库中连续循环？

以下是Firebase数据库屏幕截图

以下是我的MainActivity.java的java代码：

public class MainActivity extends AppCompatActivity {
    EditText date, title, description, imageURL;
    Button btn_click;
    DatabaseReference databaseReference;
        @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    btn_click = findViewById(R.id.btn_click);
        date = findViewById(R.id.date);
        title = findViewById(R.id.title);
        description = findViewById(R.id.description);
        imageURL = findViewById(R.id.imgUrl);
           databaseReference = FirebaseDatabase.getInstance().getReference("notifications");
        Log.e("Reference is : ", String.valueOf(databaseReference));
            btn_click.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                   databaseReference.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                            String d= date.getText().toString().trim();
                        String t= title.getText().toString().trim();
                        String desc= description.getText().toString().trim();
                        String i= imageURL.getText().toString().trim();
                            Model model = new Model(d,t,desc,i);
                        String id =  databaseReference.push().getKey();
                        databaseReference.push().setValue(model);
                            Toast.makeText(MainActivity.this, "Submitted Successfully ", Toast.LENGTH_SHORT).show();
                    }

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

                        Toast.makeText(MainActivity.this, "Error Occured !", Toast.LENGTH_SHORT).show();
                    }
                });

以下是模型类：

String date,desc,image,title;
public  Model(){
}
public Model(String date, String desc, String image, String title) {
    this.date = date;
    this.desc = desc;
    this.image = image;
    this.title = title;
}
public String getDate() {
    return date;
}
public String getDesc() {
    return desc;
}
public String getImage() {
    return image;
}
public String getTitle() {
    return title;
}

为什么数据库中的条目会重复？我如何避免它？

更改此项：

btn_click.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                   databaseReference.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                            String d= date.getText().toString().trim();
                        String t= title.getText().toString().trim();
                        String desc= description.getText().toString().trim();
                        String i= imageURL.getText().toString().trim();
                            Model model = new Model(d,t,desc,i);
                        String id =  databaseReference.push().getKey();
                        databaseReference.push().setValue(model);
                            Toast.makeText(MainActivity.this, "Submitted Successfully ", Toast.LENGTH_SHORT).show();
                    }

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

                        Toast.makeText(MainActivity.this, "Error Occured !", Toast.LENGTH_SHORT).show();
                    }
                });

为此：

btn_click.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v){
                            String d= date.getText().toString().trim();
                        String t= title.getText().toString().trim();
                        String desc= description.getText().toString().trim();
                        String i= imageURL.getText().toString().trim();
                            Model model = new Model(d,t,desc,i);
                        String id =  databaseReference.push().getKey();
                        databaseReference.child(id).setValue(model);
                            Toast.makeText(MainActivity.this, "Submitted Successfully ", Toast.LENGTH_SHORT).show();
                    }
                });

向数据库添加数据时，不需要使用用于检索数据的

addValueEventListener

                   databaseReference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        String d= date.getText().toString().trim();
                    String t= title.getText().toString().trim();
                    String desc= description.getText().toString().trim();
                    String i= imageURL.getText().toString().trim();
                        Model model = new Model(d,t,desc,i);
                    String id =  databaseReference.push().getKey();
                    databaseReference.push().setValue(model);
                        Toast.makeText(MainActivity.this, "Submitted Successfully ", Toast.LENGTH_SHORT).show();
                }

这里使用的是addValueEventListener（）。addValueEventListener继续侦听它附加到的查询或数据库引用。所以，当您第一次添加侦听器时，您正在获取数据，然后在同一节点将数据推送到firebase，所以addValueEventListener将再次侦听新数据，并且您将再次在firebase上推送新数据，这种情况将一次又一次发生