如何“更新”我的活动？

Question

Hi guys I'm new on android and maybe this question is so stupid for you. I'm developing my first android app and I'm doing a method that check the connection service status. All is working, but what I wanna do is, when the connection status switch from "Not connected" to "Connected" I wanna reload or update or recall my main activity in order to update my data the app download from my server. Here is my code:

Java class for the BroadcastReceiver only:

public class NetworkStateReceiver extends BroadcastReceiver {



    private static final String TAG = "NetworkStateReceiver";
    @Override

    public void onReceive(final Context context, final Intent intent) {

        Log.d(TAG, "Network connectivity change");

        if (intent.getExtras() != null) {
            final ConnectivityManager connectivityManager =(ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
            final NetworkInfo ni = connectivityManager.getActiveNetworkInfo();

            if (ni != null && ni.isConnectedOrConnecting()) {
                Log.i(TAG, "Network " + ni.getTypeName() + " connected");

            } else if (intent.getBooleanExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY, Boolean.FALSE)) {
                Log.d(TAG, "There's no network connectivity");
            }
        }
    }
}

Snippet in the "application" tag in manifest:

<receiver android:name="com.example.findmyclients.NetworkStateReceiver">
    <intent-filter>
        <action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
    </intent-filter>
</receiver>

With the debug I've already seen that all is working, the log is written by "onReceive" method in java class but if I try to recall my activity my app crash :( What can I do to solve ?? Thank you so much you all.

Answer 1

If I understand you correct, you need to look at Activity Lifecycle: AndroidDevDocs and call to that method where you update or reload your data. For example you call for onStart() again and again for reload data in TextView or something like that. But this depends on your app: maybe you should create a function where you "update" all fields of your app. every time the status changes to "connected"

Answer 2

If I were you I would do the following.
I would make this class(your network class) accessible via Singleton and I would create a pool of activities to be notified in case there is a connection. Every activity that wants to listen for this can register to this class of yours and when there is a network change you notify the activities(it can be 1 or 2...100).

All you have to do is to create an interface like that:

public class NetworkStateReceiver extends BroadcastReceiver {
private static NetworkStateReceiver instance = null;
private List<INetworkNotify> list = new ArrayList<INetworkNotify>();
protected NetworkStateReceiver(){}
public static NetworkStateReceiver getInstance()
{
  //standard code for initializing the instance;
}
public void registerListener(INetworkNotify listener)
{
   //add it to the list pool.
}

public void deregisterListener(INetworkNotify listener)
{
   //remove it from the pool.
} 

private static final String TAG = "NetworkStateReceiver";
@Override

public void onReceive(final Context context, final Intent intent) {

    Log.d(TAG, "Network connectivity change");

    if (intent.getExtras() != null) {
        final ConnectivityManager connectivityManager =(ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
        final NetworkInfo ni = connectivityManager.getActiveNetworkInfo();

        if (ni != null && ni.isConnectedOrConnecting()) {
            Log.i(TAG, "Network " + ni.getTypeName() + " connected");

        } else if (intent.getBooleanExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY, Boolean.FALSE)) {
            Log.d(TAG, "There's no network connectivity");
        }
        notifyListeners("Something, anything.");
    }
}

private void notifyListeners(String msg)
{
   //e.g
   for(INetworkListener listener:list)
   {
       listener.onUpdate(msg);
   }
   //notify the listeners;
}    

Below you can see the INetworkNotify interface

Interface INetworkNotify
{
   void onUpdate(String msg);
}

In the activity all you have to do is to implement the listener.