出于某种原因，我一直在片段活动中私有此标签错误

Question

请帮忙，这很令人困惑。我想不通。我是代码新手。这是Firebase和android工作室。语言是Java。

package com.ExampleStudios.ExampleProject;
import androidx.annotation.NonNull
import androidx.appcompat.app.AppCompatActivity;
import androidx.constraintlayout.solver.widgets.Snapshot;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;
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 static androidx.constraintlayout.solver.widgets.Snapshot.*;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference("message");
myRef.setValue("This is an example?");
myRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
// This method is called once with the initial value and again
// whenever data at this location is updated.
String value = dataSnapshot.getValue(String.class);
Log.d(TAG, "Value is: " + value);
//Here is where the tag 1 tag is

}
@Override
public void onCancelled(DatabaseError error) {
// Failed to read value
Log.w(TAG, "Failed to read value.", error.toException());
//here is the second one
});   }
}                

Answer 1

你需要在onCreate((之前声明TAG

public class MainActivity extends AppCompatActivity {
private static final String TAG = "MyActivity";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference("message");
myRef.setValue("This is an example?");
myRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
// This method is called once with the initial value and again
// whenever data at this location is updated.
String value = dataSnapshot.getValue(String.class);
Log.d(TAG, "Value is: " + value);
//Here is where the tag 1 tag is

}
@Override
public void onCancelled(DatabaseError error) {
// Failed to read value
Log.w(TAG, "Failed to read value.", error.toException());
//here is the second one
});   }
}    

Answer 2

你必须声明一个字符串对象 TAG，或者你可以把它括在 " 中。 喜欢

Log.d("TAG", "Value is: " + value);