Firebase在哪里可以调用addChildEventListener以便节省带宽? [英] Firebase where to call addChildEventListener so that I can save bandwidth?
问题描述
使用我的测试android应用程序，我试图计算如果我的用户每10秒或1分钟添加一个孩子并与5台设备同步，它将占用多少带宽.
With my test android app I am trying to calculate how much bandwidth it will take if my user add a child every 10sec or 1min and synced with 5 devices.
我的应用程序用户将每分钟创建一次数据，因此我必须计算每个用户每月的订阅费用.每个用户每月消耗的大概带宽.
My app users will create data every minute, so I have to calculate subscription cost for each user per month. Approximate bandwidth consumed by each user per month.
我要在MainActivity中调用addChildEventListener，并每隔10秒从BroadcastReceiver类中添加一个子级.
I am calling addChildEventListener in my MainActivity and adding child from a BroadcastReceiver class every 10sec.
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每次我重新启动应用程序时，它都会下载所有行，这意味着要占用带宽.
Everytime I restart the app it's downloading all the rows, which means consuming bandwidth.
如何减少带宽使用率，并使应用程序每次重新启动应用程序时仅检索新添加的子代?
How can I reduce the bandwidth usage and make app to retrieve only newly added child every time I restart the app?
如果我添加Firebase.getDefaultConfig().setPersistenceEnabled(true);并且用户在线仍然addChildEventListener正在下载所有数据，是从服务器下载还是从本地同步的数据下载?
If I add Firebase.getDefaultConfig().setPersistenceEnabled(true); and user is online still addChildEventListener downloading all data, it's downloaded from server or locally synced data?
这就是我正在尝试的.
MainActivity.java
public class MainActivity extends AppCompatActivity {
Button start, stop;
TextView status;
String url = "https://<my-app>.firebaseio.com/data";
Firebase mFirebaseRef;
AlarmManager alarmManager;
PendingIntent pendingIntent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Firebase.setAndroidContext(this);
mFirebaseRef.getDefaultConfig().setPersistenceEnabled(true);
alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
start = (Button) findViewById(R.id.Start);
stop = (Button) findViewById(R.id.stop);
status = (TextView) findViewById(R.id.serviceText);
mFirebaseRef = new Firebase(url);
mFirebaseRef.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
Log.d("Data onChildAdded", dataSnapshot.getValue().toString());
//Toast.makeText(getBaseContext(), "data=" + dataSnapshot.getValue(), Toast.LENGTH_LONG).show();
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
Log.d("Data onChildChanged", dataSnapshot.getValue().toString());
//Toast.makeText(getBaseContext(), "data=" + dataSnapshot.getValue(), Toast.LENGTH_LONG).show();
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
Log.d("Data onChildRemoved", dataSnapshot.getValue().toString());
//Toast.makeText(getBaseContext(), "data=" + dataSnapshot.getValue(), Toast.LENGTH_LONG).show();
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
Log.d("Data onChildMoved", dataSnapshot.getValue().toString());
//Toast.makeText(getBaseContext(), "data=" + dataSnapshot.getValue(), Toast.LENGTH_LONG).show();
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
});
start.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
status.setText("Started..");
Intent myIntent = new Intent(getApplicationContext(), MyServiceReceiver.class);
PendingIntent pendingIntent = PendingIntent.getBroadcast(getApplicationContext(), 0, myIntent, 0);
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP,System.currentTimeMillis(),10000,
pendingIntent);
}
});
stop.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
status.setText("Stopped");
AlarmManager alarmManager=(AlarmManager)getSystemService(Context.ALARM_SERVICE);
Intent intent = new Intent(getApplicationContext(), MyServiceReceiver.class);
PendingIntent pendingIntent = PendingIntent.getBroadcast(getApplicationContext(), 0, intent, 0);
alarmManager.cancel(pendingIntent);
}
});
}
@Override
protected void onStop() {
super.onStop();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
BroadcastReceiver.java
public class MyServiceReceiver extends BroadcastReceiver {
Firebase mFirebaseRef;
Firebase mFirebaseRef2;
String url = "https://<my-app>.firebaseio.com/data";
Context context=null;
String data = "With Firebase queries, we can selectively retrieve data based on various factors. To construct a query, you start by specifying how you want your data to be ordered using one of the ordering functions: orderByChild(), orderByKey(), orderByValue(), or orderByPriority()";
@Override
public void onReceive(final Context context, Intent intent) {
this.context = context;
Firebase.setAndroidContext(context);
mFirebaseRef = new Firebase(url);
Firebase ref = mFirebaseRef.child(System.currentTimeMillis()+"");
ref.setValue(new RecordingModel("Meeting","https://www.stadd.com",data));
Log.d("caught", "data saved");
}
}
推荐答案
每次重新启动应用程序时，如何...仅检索新添加的孩子?
您可以使用 Firebase查询限制侦听器下载的数据.因此，您不必将您的 ChildEventListener 直接附加到Firebase位置，而是将收到的最后一个孩子的密钥存储在某个地方(例如，SharedPreferences)，然后仅从下一个孩子开始加载.
How can I ... retrieve only newly added child every time I restart the app?
You can use Firebase Queries to limit the data that is downloaded by a listener. So instead of attaching your ChildEventListener directly to a Firebase location, you store the key of the last child you've received somewhere (e.g. SharedPreferences) and then load only from that child onwards next time.
这是监视最后一项按键的快速方法:
This is a quick way to monitor the key of the last item:
String lastChildKey;
mFirebaseRef.orderByKey().limitToLast(1).addChildEventListener(new ChildEventListener() {
public void onChildAdded(DataSnapshot snapshot, String s) {
lastChildKey = snapshot.getKey();
}
})
有了这些知识，您可以从应用程序重新启动时最后看到的项目开始:
With that knowledge, you can start at the item you last saw when the app restarts:
Query newItems = mFirebaseRef.orderByKey().startAt(lastChildKey);
newItems.addChildEventListener(...
使用这种方法，您将必须管理自己的客户端状态，因为您实际上是在用自己的替代Firebase的客户端缓存/同步策略.
With this approach you will have to manage your own client-side state, since you're essentially replacing Firebase's client-side caching/synchronization strategy with your own.
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