java - 更新参数子项后更改值(不生成随机 token )Firebase Android Studio

Question

我现在无法从应用程序显示我的参数。 (在此之前我使用随机 token 生成参数。现在我使用新方法(如上传的图片所示)将参数存储在 firebase 数据库中。我发现我无法显示参数。我是新来的。谢谢。这是我的代码。

public class RealtimeData extends AppCompatActivity {                 
    private DatabaseReference mDatebase;
    private DatabaseReference mDatebase2;
    private DatabaseReference mDatebase3;
    private DatabaseReference mDatebase4;
    private DatabaseReference mDatabase5;
    private DatabaseReference mDatabase6;
    private DatabaseReference mDatabase7;
    private DatabaseReference mDatabase8;
    private DatabaseReference mDatabase9;                                 
    private TextView mTempView;
    private TextView mHumidView;
    private TextView mTimeView;
    private TextView mphView;
    private TextView mwaterView;
    private TextView mCO2View;
    private TextView mTDSView;
    private TextView mDateView;
    private TextView mWaterTempView;                                    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        buildDialog(RealtimeData.this).show();
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_realtime_data);
        Toolbar toolbar = (Toolbar) findViewById(R.id.app_bar);
        setSupportActionBar(toolbar);mDatebase = FirebaseDatabase.getInstance().getReference().child("Region 1").child("Parameter Reading");
        mDatebase = FirebaseDatabase.getInstance().getReference().child("Region 1").child("Parameter Reading");                                         
    mTempView = (TextView) findViewById(R.id.tempvalue);
    mDatebase.addValueEventListener(new com.google.firebase.database.ValueEventListener() {
        @Override
        public void onDataChange(com.google.firebase.database.DataSnapshot dataSnapshot) {
            for (com.google.firebase.database.DataSnapshot datasnap: dataSnapshot.getChildren()){
                String temp = datasnap.child("airtemperature").getValue(String.class);
                if (Float.valueOf(temp) >= 18 && Float.valueOf(temp) <= 28) {
                    mTempView.setText("Air Temperature: " + temp + " *C" + " Normal");
                }
                else if (Float.valueOf(temp) < 18)
                {
                    mTempView.setText("Air Temperature: " + temp + " *C" + " Abnormal Low ");
                    NotificationCompat.Builder wbuilder = new NotificationCompat.Builder(RealtimeData.this);
                    wbuilder.setSmallIcon(R.drawable.impressive);
                    wbuilder.setContentTitle("Notification Alert");
                    wbuilder.setContentText("Air Temperature lowly abnormal!!");
                    wbuilder.setWhen(System.currentTimeMillis());
                    wbuilder.setVibrate(new long[]{1000,1000,1000,1000,1000});
                    wbuilder.setLights(Color.CYAN,3000,3000);
                    wbuilder.setSound(RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION));
                    wbuilder.setPriority(NotificationManager.IMPORTANCE_HIGH);
                    NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
                    notificationManager.notify(0, wbuilder.build());
                }
                else if (Float.valueOf(temp) > 28)
                {
                    mTempView.setText("Air Temperature: " + temp + " *C" + " Abnormal High ");
                    NotificationCompat.Builder wbuilder = new NotificationCompat.Builder(RealtimeData.this);
                    wbuilder.setSmallIcon(R.drawable.impressive);
                    wbuilder.setContentTitle("Notification Alert");
                    wbuilder.setContentText("Air temperature highly abnormal!!");
                    wbuilder.setWhen(System.currentTimeMillis());
                    wbuilder.setVibrate(new long[]{1000,1000,1000,1000,1000});
                    wbuilder.setLights(Color.CYAN,3000,3000);
                    wbuilder.setSound(RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION));
                    wbuilder.setPriority(NotificationManager.IMPORTANCE_HIGH);
                    NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
                    notificationManager.notify(0, wbuilder.build());
                }
            }
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {
            mTempView.setText("Air Temperature: Error");
        }
    });

Answer 1

要解决此问题，请使用以下代码。

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = rootRef.child("Region 1").child("Parameter Reading");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        String airTemperature = dataSnapshot.child("airtemperature").getValue(String.class);
        Log.d("TAG", airTemperature);
        //Your logic
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
ref.addListenerForSingleValueEvent(valueEventListener);

请记住，无需使用 getChildren() 方法遍历子对象。您只需要获取引用并获取相应属性的值即可。