Major refactoring: navigation does not break anymore. the user can now navigate between the tabs without loosing context

app/expense/new.tsx

@@ -0,0 +1,94 @@
+import { View, Text, StyleSheet, Alert } from 'react-native'
+import React, { useRef, useState } from 'react'
+import { SIZES } from '../../constants/theme'
+import { useTheme } from '../contexts/ThemeContext'
+import { AutoDecimalInput, CategorySelector, CategorySelectorModal, DateSelectorButton, RoundedButton, TextInputBar } from '../../components'
+import { Category } from '../../types/dbItems'
+import DateTimePicker from '@react-native-community/datetimepicker';
+import { addExpense } from '../../services/database'
+import { SimpleDate } from '../../util/SimpleDate'
+import { useRouter } from 'expo-router'
+
+export default function AddItem() {
+  const {colors} = useTheme();
+  const router = useRouter();
+
+  const [formatedValue, setFormatedValue] = useState<string>("");
+  const [selectorModalVisible, setSelecorModalVisible] = useState<boolean>(false);
+  const [selectedCategory, setSelectedCategory] = useState<Category|undefined>()
+  const [expenseName, setExpenseName] = useState<string>("");
+  const [datePickerShown, setDatePickerShown] = useState<boolean>(false);
+  const [selectedDate, setSelectedDate] = useState<Date>(new Date())
+
+  const handleValueChange = (formatedValue: string) => {
+    setFormatedValue(formatedValue);
+  }
+
+  const handleCategorySelect = (category : Category) => {
+    setSelecorModalVisible(false);
+    setSelectedCategory(category);
+  }
+
+  const validateInput = ():boolean => {
+    if(formatedValue == "" || expenseName == "" || selectedCategory === undefined || selectedDate === null){
+      return false;
+    }
+    return true;
+  }
+
+  const submit = () => {
+    const insert = async () => {
+      await addExpense(expenseName, selectedCategory?.guid!, new SimpleDate(selectedDate).format("YYYY-MM-DD"), Number(formatedValue))
+    }
+    if(validateInput()){
+      insert().then(() => {
+        router.back();
+      })
+    }else {
+      Alert.alert("Invalid input", "One of the Props is not properly defined")
+    }
+    
+  }
+
+  return (
+    <View style={styles.container}>
+      <CategorySelectorModal visible={selectorModalVisible} onRequestClose={()=>{setSelecorModalVisible(false)}} onCategoryTap={handleCategorySelect}></CategorySelectorModal>
+      <AutoDecimalInput onValueChange={handleValueChange} label='Amount'/>
+      <CategorySelector onPress={()=>{setSelecorModalVisible(true)}} selectedCategory={selectedCategory}/>
+      <TextInputBar placeholder='Name' onChangeText={(text)=>setExpenseName(text)}/>
+      <DateSelectorButton selectedDate={selectedDate} onPress={()=>{setDatePickerShown(true)}}/>
+      {datePickerShown &&
+        <DateTimePicker 
+          value={new Date()}
+          maximumDate={new Date()}
+
+          onChange={(event, date)=>{
+            setDatePickerShown(false);
+            if(date){
+              setSelectedDate(date);
+            }
+          }}
+        />}
+        <RoundedButton color={colors.accentColor} style={styles.save} onPress={submit}>
+          <Text style={[styles.submitText, {color: colors.primaryText}]}>Save</Text>
+        </RoundedButton>
+    </View>
+  )
+}
+
+const styles = StyleSheet.create({
+  save: {
+    marginTop: 40,
+    padding: 10,
+  },
+  container: {
+    margin: SIZES.normal,
+    display: "flex",
+    gap: 10
+  }, 
+ 
+  submitText: {
+    fontSize: SIZES.large
+  }
+  
+})