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samtsternsamtstern
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Offline db snippets
Change-Id: I8a40920dba45ed47986c46abb95f9a06f0fd40ca
1 parent 6184605 commit 6cc02c9

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‎database/app/src/main/AndroidManifest.xml

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</activity>
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<activity android:name=".MainActivity" />
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<activity android:name=".kotlin.MainActivity" />
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<activity android:name=".OfflineActivity"></activity>
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</application>
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</manifest>

‎database/app/src/main/java/com/google/firebase/referencecode/database/OfflineActivity.java

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package com.google.firebase.referencecode.database;
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import android.support.annotation.NonNull;
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import android.support.annotation.Nullable;
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import android.support.v7.app.AppCompatActivity;
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import android.util.Log;
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import com.google.firebase.database.ChildEventListener;
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import com.google.firebase.database.DataSnapshot;
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import com.google.firebase.database.DatabaseError;
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import com.google.firebase.database.DatabaseReference;
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import com.google.firebase.database.FirebaseDatabase;
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import com.google.firebase.database.OnDisconnect;
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import com.google.firebase.database.ServerValue;
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import com.google.firebase.database.ValueEventListener;
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public class OfflineActivity extends AppCompatActivity {
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private static final String TAG = "OfflineActivity";
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private void enablePersistence() {
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// [START rtdb_enable_persistence]
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FirebaseDatabase.getInstance().setPersistenceEnabled(true);
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// [END rtdb_enable_persistence]
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}
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private void keepSynced() {
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// [START rtdb_keep_synced]
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DatabaseReference scoresRef = FirebaseDatabase.getInstance().getReference("scores");
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scoresRef.keepSynced(true);
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// [END rtdb_keep_synced]
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// [START rtdb_undo_keep_synced]
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scoresRef.keepSynced(false);
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// [END rtdb_undo_keep_synced]
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}
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private void queryRecentScores() {
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// [START rtdb_query_recent_scores]
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DatabaseReference scoresRef = FirebaseDatabase.getInstance().getReference("scores");
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scoresRef.orderByValue().limitToLast(4).addChildEventListener(new ChildEventListener() {
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@Override
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public void onChildAdded(@NonNull DataSnapshot snapshot, String previousChild) {
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Log.d(TAG, "The " + snapshot.getKey() + " dinosaur's score is " + snapshot.getValue());
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}
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// [START_EXCLUDE]
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@Override
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public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {}
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@Override
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public void onChildMoved(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {}
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@Override
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public void onCancelled(@NonNull DatabaseError databaseError) {}
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@Override
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public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {}
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// [END_EXCLUDE]
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});
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// [END rtdb_query_recent_scores]
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// [START rtdb_query_recent_scores_overlap]
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scoresRef.orderByValue().limitToLast(2).addChildEventListener(new ChildEventListener() {
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@Override
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public void onChildAdded(@NonNull DataSnapshot snapshot, String previousChild) {
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Log.d(TAG, "The " + snapshot.getKey() + " dinosaur's score is " + snapshot.getValue());
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}
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// [START_EXCLUDE]
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@Override
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public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {}
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@Override
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public void onChildMoved(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {}
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@Override
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public void onCancelled(@NonNull DatabaseError databaseError) {}
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@Override
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public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {}
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// [END_EXCLUDE]
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});
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// [END rtdb_query_recent_scores_overlap]
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}
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private void onDisconnect() {
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// [START rtdb_on_disconnect_set]
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DatabaseReference presenceRef = FirebaseDatabase.getInstance().getReference("disconnectmessage");
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// Write a string when this client loses connection
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presenceRef.onDisconnect().setValue("I disconnected!");
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// [END rtdb_on_disconnect_set]
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// [START rtdb_on_disconnect_remove]
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presenceRef.onDisconnect().removeValue(new DatabaseReference.CompletionListener() {
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@Override
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public void onComplete(DatabaseError error, @NonNull DatabaseReference reference) {
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if (error != null) {
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Log.d(TAG, "could not establish onDisconnect event:" + error.getMessage());
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}
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}
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});
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// [END rtdb_on_disconnect_remove]
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// [START rtdb_on_disconnect_cancel]
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OnDisconnect onDisconnectRef = presenceRef.onDisconnect();
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onDisconnectRef.setValue("I disconnected");
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// ...
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// some time later when we change our minds
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// ...
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onDisconnectRef.cancel();
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// [END rtdb_on_disconnect_cancel]
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}
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private void getConnectionState() {
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// [START rtdb_listen_connected]
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DatabaseReference connectedRef = FirebaseDatabase.getInstance().getReference(".info/connected");
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connectedRef.addValueEventListener(new ValueEventListener() {
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@Override
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public void onDataChange(@NonNull DataSnapshot snapshot) {
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boolean connected = snapshot.getValue(Boolean.class);
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if (connected) {
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Log.d(TAG, "connected");
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} else {
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Log.d(TAG, "not connected");
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}
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}
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@Override
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public void onCancelled(@NonNull DatabaseError error) {
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Log.w(TAG, "Listener was cancelled");
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}
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});
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// [END rtdb_listen_connected]
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}
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private void disconnectionTimestamp() {
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// [START rtdb_on_disconnect_timestamp]
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DatabaseReference userLastOnlineRef = FirebaseDatabase.getInstance().getReference("users/joe/lastOnline");
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userLastOnlineRef.onDisconnect().setValue(ServerValue.TIMESTAMP);
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// [END rtdb_on_disconnect_timestamp]
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}
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private void getServerTimeOffset() {
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// [START rtdb_server_time_offset]
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DatabaseReference offsetRef = FirebaseDatabase.getInstance().getReference(".info/serverTimeOffset");
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offsetRef.addValueEventListener(new ValueEventListener() {
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@Override
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public void onDataChange(@NonNull DataSnapshot snapshot) {
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double offset = snapshot.getValue(Double.class);
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double estimatedServerTimeMs = System.currentTimeMillis() + offset;
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}
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@Override
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public void onCancelled(@NonNull DatabaseError error) {
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Log.w(TAG, "Listener was cancelled");
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}
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});
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// [END rtdb_server_time_offset]
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}
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private void fullConnectionExample() {
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// [START rtdb_full_connection_example]
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// Since I can connect from multiple devices, we store each connection instance separately
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// any time that connectionsRef's value is null (i.e. has no children) I am offline
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final FirebaseDatabase database = FirebaseDatabase.getInstance();
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final DatabaseReference myConnectionsRef = database.getReference("users/joe/connections");
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// Stores the timestamp of my last disconnect (the last time I was seen online)
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final DatabaseReference lastOnlineRef = database.getReference("/users/joe/lastOnline");
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final DatabaseReference connectedRef = database.getReference(".info/connected");
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connectedRef.addValueEventListener(new ValueEventListener() {
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@Override
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public void onDataChange(DataSnapshot snapshot) {
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boolean connected = snapshot.getValue(Boolean.class);
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if (connected) {
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DatabaseReference con = myConnectionsRef.push();
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// When this device disconnects, remove it
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con.onDisconnect().removeValue();
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// When I disconnect, update the last time I was seen online
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lastOnlineRef.onDisconnect().setValue(ServerValue.TIMESTAMP);
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// Add this device to my connections list
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// this value could contain info about the device or a timestamp too
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con.setValue(Boolean.TRUE);
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}
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}
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@Override
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public void onCancelled(DatabaseError error) {
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Log.w(TAG, "Listener was cancelled at .info/connected");
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}
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});
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// [END rtdb_full_connection_example]
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}
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}

‎database/app/src/main/java/com/google/firebase/referencecode/database/kotlin/OfflineActivity.kt

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package com.google.firebase.referencecode.database.kotlin
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import android.support.v7.app.AppCompatActivity
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import android.util.Log
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import com.google.firebase.database.ChildEventListener
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import com.google.firebase.database.DataSnapshot
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import com.google.firebase.database.DatabaseError
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import com.google.firebase.database.FirebaseDatabase
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import com.google.firebase.database.ServerValue
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import com.google.firebase.database.ValueEventListener
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class OfflineActivity : AppCompatActivity() {
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private fun enablePersistence() {
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// [START rtdb_enable_persistence]
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FirebaseDatabase.getInstance().setPersistenceEnabled(true)
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// [END rtdb_enable_persistence]
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}
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private fun keepSynced() {
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// [START rtdb_keep_synced]
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val scoresRef = FirebaseDatabase.getInstance().getReference("scores")
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scoresRef.keepSynced(true)
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// [END rtdb_keep_synced]
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// [START rtdb_undo_keep_synced]
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scoresRef.keepSynced(false)
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// [END rtdb_undo_keep_synced]
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}
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private fun queryRecentScores() {
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// [START rtdb_query_recent_scores]
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val scoresRef = FirebaseDatabase.getInstance().getReference("scores")
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scoresRef.orderByValue().limitToLast(4).addChildEventListener(object : ChildEventListener {
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override fun onChildAdded(snapshot: DataSnapshot, previousChild: String?) {
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Log.d(TAG, "The " + snapshot.key + " dinosaur's score is " + snapshot.value)
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}
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// [START_EXCLUDE]
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override fun onChildRemoved(dataSnapshot: DataSnapshot) {}
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override fun onChildMoved(dataSnapshot: DataSnapshot, s: String?) {}
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override fun onCancelled(databaseError: DatabaseError) {}
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override fun onChildChanged(dataSnapshot: DataSnapshot, s: String?) {}
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// [END_EXCLUDE]
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})
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// [END rtdb_query_recent_scores]
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// [START rtdb_query_recent_scores_overlap]
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scoresRef.orderByValue().limitToLast(2).addChildEventListener(object : ChildEventListener {
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override fun onChildAdded(snapshot: DataSnapshot, previousChild: String?) {
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Log.d(TAG, "The " + snapshot.key + " dinosaur's score is " + snapshot.value)
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}
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// [START_EXCLUDE]
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override fun onChildRemoved(dataSnapshot: DataSnapshot) {}
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override fun onChildMoved(dataSnapshot: DataSnapshot, s: String?) {}
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override fun onCancelled(databaseError: DatabaseError) {}
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override fun onChildChanged(dataSnapshot: DataSnapshot, s: String?) {}
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// [END_EXCLUDE]
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})
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// [END rtdb_query_recent_scores_overlap]
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}
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private fun onDisconnect() {
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// [START rtdb_on_disconnect_set]
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val presenceRef = FirebaseDatabase.getInstance().getReference("disconnectmessage")
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// Write a string when this client loses connection
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presenceRef.onDisconnect().setValue("I disconnected!")
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// [END rtdb_on_disconnect_set]
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// [START rtdb_on_disconnect_remove]
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presenceRef.onDisconnect().removeValue { error, reference ->
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error?.let {
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Log.d(TAG, "could not establish onDisconnect event:" + error.message)
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}
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}
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// [END rtdb_on_disconnect_remove]
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// [START rtdb_on_disconnect_cancel]
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val onDisconnectRef = presenceRef.onDisconnect()
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onDisconnectRef.setValue("I disconnected")
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// ...
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// some time later when we change our minds
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// ...
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onDisconnectRef.cancel()
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// [END rtdb_on_disconnect_cancel]
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}
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private fun getConnectionState() {
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// [START rtdb_listen_connected]
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val connectedRef = FirebaseDatabase.getInstance().getReference(".info/connected")
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connectedRef.addValueEventListener(object : ValueEventListener {
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override fun onDataChange(snapshot: DataSnapshot) {
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val connected = snapshot.getValue(Boolean::class.java) ?: false
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if (connected) {
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Log.d(TAG, "connected")
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} else {
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Log.d(TAG, "not connected")
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}
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}
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override fun onCancelled(error: DatabaseError) {
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Log.w(TAG, "Listener was cancelled")
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}
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})
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// [END rtdb_listen_connected]
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}
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private fun disconnectionTimestamp() {
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// [START rtdb_on_disconnect_timestamp]
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val userLastOnlineRef = FirebaseDatabase.getInstance().getReference("users/joe/lastOnline")
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userLastOnlineRef.onDisconnect().setValue(ServerValue.TIMESTAMP)
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// [END rtdb_on_disconnect_timestamp]
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}
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private fun getServerTimeOffset() {
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// [START rtdb_server_time_offset]
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val offsetRef = FirebaseDatabase.getInstance().getReference(".info/serverTimeOffset")
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offsetRef.addValueEventListener(object : ValueEventListener {
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override fun onDataChange(snapshot: DataSnapshot) {
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val offset = snapshot.getValue(Double::class.java) ?: 0.0
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val estimatedServerTimeMs = System.currentTimeMillis() + offset
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}
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override fun onCancelled(error: DatabaseError) {
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Log.w(TAG, "Listener was cancelled")
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}
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})
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// [END rtdb_server_time_offset]
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}
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private fun fullConnectionExample() {
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// [START rtdb_full_connection_example]
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// Since I can connect from multiple devices, we store each connection instance separately
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// any time that connectionsRef's value is null (i.e. has no children) I am offline
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val database = FirebaseDatabase.getInstance()
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val myConnectionsRef = database.getReference("users/joe/connections")
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// Stores the timestamp of my last disconnect (the last time I was seen online)
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val lastOnlineRef = database.getReference("/users/joe/lastOnline")
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val connectedRef = database.getReference(".info/connected")
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connectedRef.addValueEventListener(object : ValueEventListener {
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override fun onDataChange(snapshot: DataSnapshot) {
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val connected = snapshot.getValue(Boolean::class.java) ?: false
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if (connected) {
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val con = myConnectionsRef.push()
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// When this device disconnects, remove it
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con.onDisconnect().removeValue()
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// When I disconnect, update the last time I was seen online
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lastOnlineRef.onDisconnect().setValue(ServerValue.TIMESTAMP)
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// Add this device to my connections list
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// this value could contain info about the device or a timestamp too
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con.setValue(java.lang.Boolean.TRUE)
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}
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}
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override fun onCancelled(error: DatabaseError) {
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Log.w(TAG, "Listener was cancelled at .info/connected")
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}
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})
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// [END rtdb_full_connection_example]
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}
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companion object {
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private val TAG = "OfflineActivity"
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}
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}

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