我试图显示我的firebase数据库中所有项目的教师ID等于当前登录教师的教师ID，以便获取当前用户的教师ID是我的意思没有。活动类：
package com.example.ronanlina.attendancechecker;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
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.Query;
import com.google.firebase.database.ValueEventListener;
public class SubjectSchedules extends AppCompatActivity {
//member vars;
private String mEmail;
private ListView mSchedListView;
private subjSchedAdapter mAdapter;
private DatabaseReference mDatabaseReference;
private TeacherAccount ta;
private Context context;
public TextView idText;
public String mTeacherId;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_subject_schedules);
mDatabaseReference = FirebaseDatabase.getInstance().getReference();
idText = (TextView) findViewById(R.id.teachIdText);
mSchedListView = (ListView) findViewById(R.id.schedListView);
//getting the email of the current user
SharedPreferences prefs = getSharedPreferences(MainActivity.ATTENDANCE_PREFS, MODE_PRIVATE);
mEmail = prefs.getString(MainActivity.EMAIL_KEY,null);
context = this;
}
@Override
public void onStart(){
super.onStart();
//Retrieving the Teacher Id with the email of the current user
DatabaseReference db = FirebaseDatabase.getInstance().getReference();
db.child("teacheraccount"); //
Query query = db.orderByChild("Email").equalTo(mEmail);
query.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
//transferring datasnaphsot value to TeacherAccount class
ta = dataSnapshot.getValue(TeacherAccount.class);
//assign the mTeacherId w/ TeacherAccount teacher id
mTeacherId = ta.getTeacherId().toString();
Log.d("teacherID",mTeacherId);
}
@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) {
}
});
// Setting the adapter
//Displaying the teacher id value to a textview. (also for checking if datasnaphot did not return null)
idText.setText(mTeacherId);
//setting the adapter instance
mAdapter = new subjSchedAdapter(this, mDatabaseReference,context);
mSchedListView.setAdapter(mAdapter);
mSchedListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
// @Override
public void onItemClick(AdapterView<?> adapter, View view, int position, long arg) {
SubjectScheds infoPass = mAdapter.getItem(position);
String sectionTitle = infoPass.sectionname;
Intent intent = new Intent(SubjectSchedules.this, activity_student_list.class);
intent.putExtra("SECTION_TITLE", sectionTitle);
startActivity(intent);
}
});
}
@Override
public void onStop(){
super.onStop();
mAdapter.cleanup();
}
private void showErrorDialog(String message) {
new AlertDialog.Builder(this)
.setTitle("Oops")
.setMessage(message)
.setPositiveButton(android.R.string.ok, null)
.setIcon(android.R.drawable.ic_dialog_alert)
.show();
}
}
package com.example.ronanlina.attendancechecker;
import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.LinearLayout;
import android.widget.TextView;
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.Query;
import com.google.firebase.database.ValueEventListener;
import org.w3c.dom.Text;
import java.util.ArrayList;
public class subjSchedAdapter extends BaseAdapter{
private Activity mActivity;
private DatabaseReference mDatabaseReference;
private String mTeacherId;
private ArrayList<DataSnapshot> mSnapshotList;
private Query query;
// child event listener
private ChildEventListener mListener = new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
mSnapshotList.add(dataSnapshot);
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) {
}
};
//constructor
public subjSchedAdapter(Activity activity, DatabaseReference ref, Context context){
mActivity = activity;
//mTeacherId = subjteacherid;
mDatabaseReference = ref.child("subjects");
//getting the text displayed text from textview (teacher id)
query = mDatabaseReference.orderByChild("teacherid").equalTo(((SubjectSchedules)context).idText.getText().toString());
query.addChildEventListener(mListener);
mSnapshotList = new ArrayList<>();
}
每次我在手机上运行程序并启动活动时，它都不会在列表视图中显示任何内容，但是当我锁定手机然后将其解锁时，它会显示结果。
答案 0 :(得分：1)
要解决此问题，请更改以下代码行：
Query query = db.orderByChild("Email").equalTo(mEmail);
与
Query query = db.child("teacheraccount").orderByChild("Email").equalTo(mEmail);