如何在安卓应用中从Firebase的实时数据库中删除数据(json的特定节点)

Question

我构建了一个待办事项列表应用程序，因为我有onClick监听器(命名为delteTask(。我想在点击删除按钮时移除 Firebase 中的数据。当我在文档中检查时，我已经得到了数据库引用，要删除节点，您可以使用 removeValue(( 方法。但我不明白如何使用它。我也写了代码，请帮我。

**MY MAINACTIVTY>JAVA**
package com.example.manuj.todolist;
import android.content.DialogInterface;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import com.google.firebase.database.ChildEventListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
public class MainActivity extends AppCompatActivity {
String tasks;
FirebaseDatabase db=FirebaseDatabase.getInstance();
DatabaseReference rootRef=db.getReference();
DatabaseReference dataRef=rootRef.child("Todo");

TextView textView;
Button button;
ListView listView;
ArrayAdapter mAdapter;
ArrayList<String> arrayList=new ArrayList<String>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button=findViewById(R.id.button);
textView=findViewById(R.id.textView);
listView=findViewById(R.id.listView);

mAdapter=new ArrayAdapter<String>(this,R.layout.list_item,R.id.textView,arrayList);
listView.setAdapter(mAdapter);

dataRef.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
String value=dataSnapshot.getValue().toString();
try {
JSONObject object=new JSONObject(value);
tasks=object.getString("Task");
} catch (JSONException e) {
e.printStackTrace();
}
arrayList.add(tasks);
mAdapter.notifyDataSetChanged();
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu,menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item){
switch(item.getItemId()){
case R.id.addTask:
final EditText editText=new EditText(this);
AlertDialog dialog=new AlertDialog.Builder(this)
.setTitle("Add new Task")
.setMessage("What's your Task?")
.setView(editText)
.setPositiveButton("Add", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
String task= editText.getText().toString();
HashMap<String,String> todoMap=new HashMap<String, String>();
todoMap.put("Task",task);
dataRef.push().setValue(todoMap);
}
})
.setNegativeButton("CANCEL",null).create();
dialog.show();
return true;
}
return super.onOptionsItemSelected(item);
}
public void deleteTask(View view) {
DatabaseReference removeRef=FirebaseDatabase.getInstance().getReference("Todo");
removeRef.removeValue();//the problem i n using the above is it removes my all data,but how
//do i  remove a particular.
}
}

Answer 1

您需要尝试访问的记录的密钥。看看 JSON 是如何构建的会很有帮助。

DatabaseReference removeRef=FirebaseDatabase.getInstance().getReference("Todo").child("RECORD KEY").removeValue();

Answer 2

我自己在回答我的问题呵呵，但是我花了很长时间才确定问题。所以，我不会删除问题并让人们知道此类问题的答案，这样他们就不会面临与我相同的问题。

好的，这是答案

public void deleteTask(View view) {
int index=listView.getPositionForView(view);
String str= (String) mAdapter.getItem(index++);
DatabaseReference ref = FirebaseDatabase.getInstance().getReference();
Query taskQuery = ref.child("Todo").orderByChild("Task").equalTo(str);
taskQuery.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot appleSnapshot: dataSnapshot.getChildren()) {
appleSnapshot.getRef().removeValue();
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
Log.e("TAG", "onCancelled", databaseError.toException());
}
});
mAdapter.notifyDataSetChanged();
}