Podemos desplegar el chat indicado en el screen de cita. Se le esta pasando el id del appointment al screen de cita y se trae el chat de firestore que tanga como valor de cita ese id.

screens/main/Cita.js

 import { fetchUser } from '../../redux/actions/index'
 
 
-export function Cita({navigation, route}) {
-   /*const [threads, setThreads] = useState([]);  
-    const [loading, setLoading] = useState(true);
-  useEffect(() => { 
+export function Cita({route, navigation}) {
+   const [threads, setThreads] = useState([]);  
+   const [loading, setLoading] = useState(true);
+   console.log("ID", route.params);
+
+
+
+ useEffect(() => { 
     const fire = firebase.firestore()
     .collection('THREADS')
-    .where("cita", "==", route.params.appointment_id)
+    .where("cita", "==", route.params)
     .onSnapshot(querySnapshot => {
       const threads = querySnapshot.docs.map(documentSnapshot => {
         return{
     return () => {
       fire();
     }
-  }, []);*/
+  }, []);
     
     
     
   
   return (
       <ImageBackground style={styles.stdcontainer} source={require('../../assets/yellow-white.jpg')}>
+        <FlatList style={{
+             flex: 1,
+             width: screenWidth,
+         }}
+          data={threads}
+          keyExtractor = {item => item._id}
+          ItemSeparatorComponent={() => <Divider />}
+          renderItem = {({item}) => (
+          <TouchableOpacity
+            onPress={() => navigation.navigate('Room', {thread: item})}
+          >
+            <List.Item
+              title={item.name}
+              titleNumberOfLines={1}
+              titleStyle={styles.listTitle}
+              descriptionStyle={styles.listDescription}
+              descriptionNumberOfLines={1}
+            />
+          </TouchableOpacity>
+        )}
+        />
       <Button
         title ='Ver mapa'
         onPress= {() => navigation.navigate('Map')}

screens/main/Home_page.js

         renderItem = {({item}) => (
         <TouchableOpacity
         onPress={async () => {
+          console.log(item._id)
           navigation.navigate('Cita', {appointment_id: item._id})
         }}
         >
           renderItem = {({item}) => (
           <TouchableOpacity
           onPress={async () => {
-            navigation.navigate('Cita')
+            console.log(item._id)
+            navigation.navigate('Cita',{tag: item})
           }}
           >
             <List.Item