Question

我制作了一个关于我所在城市当前金属价格的应用程序。我每隔几个小时就会更新金属费率。我有一个TextView，当且仅当新的Rate更新时（由我在控制台中）更新当前时间和日期。现在，问题是，即使应用程序处于脱机状态，我的TextView也会使用当前时间进行更新。意味着addValueEventListener处于活动状态并正在侦听。如果应用程序处于脱机状态，或者除非我手动更新，否则我不希望更新TextView。这是我的代码 -

 mFirebaseDatabaseInstance.getReference("metals").addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

               String ratesteel= dataSnapshot.getValue(String.class);

               tvsteelrate.setText(ratesteel);

     //getting notification of updated price
            Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
            NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(MainActivity.this)
                    .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher))
                    .setSmallIcon(R.drawable.ic_launcher)
                    .setContentTitle("ST")
                    .setContentText("Updated")
                    .setAutoCancel(true);
                    .setSound(defaultSoundUri);
            NotificationManager notificationManager =
                    (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            notificationManager.notify(count, notificationBuilder.build());
            count++;


            Date c = Calendar.getInstance().getTime();
            SimpleDateFormat df = new SimpleDateFormat("dd-MMM-yyyy");
            String formattedDate = df.format(c);
            mydate.setText(formattedDate);

            }


        @Override
        public void onCancelled(DatabaseError error) {
            // Failed to read value
            Log.e(TAG, "Failed to read app title value.", error.toException());
        }
    });


}

如果应用离线或未更新，如何禁用TextView更新？

Answer 1

如果您希望代码仅在调用时执行，请使用.addListenerForSingleValueEvent()

mFirebaseDatabaseInstance.getReference("metals").addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
         // do your stuff here
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        // handle error
    }
});

即使离线也会调用Firebase“addValueEventListener”

1 个答案: