We Keep Coding

How to solve "Can't find variable: App" in React Native?

I am new to React Native and I don't understand how to solve this problem. I already installed react-native-gesture-handler.
I am getting this error in the command:
Accessing view manager configs directly off UIManager via UIManager['getConstants'] is no longer supported. Use UIManager.getViewManagerConfig('getConstants') instead.
This is a part of the code:
import { createAppContainer, DrawerNavigator } from 'react-navigation';
import { createStackNavigator } from 'react-navigation-stack';
import Home from "./src/screens/Home.js";
import first from "./src/screens/first.js";
import React from 'react';
class App extends React.Component{
render(){
return(
<RootStack/>
)
}
}
const RootStack = createStackNavigator ({
Home:{screen:Home,
navigationOptions: {
header: null
}},
first:{screen:first,
navigationOptions: {
header: null
}}
});
//const App = createAppContainer(RootStack);
export default App;

I think this way is better:
const AppNavigator = createSwitchNavigator({
Auth: {
screen: Auth
},
Root: {
screen: BottomTabNavigator
}
})
const AppContainer = createAppContainer(AppNavigator)
const App = () => {
return (
<AppContainer />
)
}
export default App
OR
if it didn't work then you better check your index.js file whether you imported App Component (Root component) correctly or not?

How to set rootview in App.js class react native

Need to set Login page as my rootview and used code. if i use the login page details in app.js file getting the result but tried to import login.js in app.js file its not working
import React, {Component} from 'react';
import { StyleSheet,
NavigatorIOS,} from 'react-native';
import LoginPage from './src/pages/Login';
type Props = {};
export default class App extends Component<{}> {
render() {
return (
<NavigatorIOS
// style={styles.container}
initialRoute={{
title: 'Login',
component: LoginPage,
}}/>
);
}
}
and in my login.js class
import React, { Component } from 'react';
import { AppRegistry, StyleSheet, Text, View } from 'react-native';
export default class Login extends Component {
render() {
return (
<View>
<Text style={styles.red}>Login</Text>
</View>
);
}
}
const styles = StyleSheet.create({
bigblue: {
color: 'blue',
fontWeight: 'bold',
fontSize: 30,
},
red: {
color: 'red',
},
});
// skip this line if using Create React Native App
AppRegistry.registerComponent('Demo', () => Login);
but it not showing the login page as rootview

I have an excepted answer in the below question.
How to navigate from splash screen to login screen in react native?
There is a google drive link on it from where you can download a sample project, its a simple app figure it out from the sample app how you should set up the App.js.
I suggest You should use StackNavigator for navigation its the best method to follow in my app App.js is configured using StackNavigator.

React Native : Why is "navigation" not being passed to my component?

I have been working on this problem for two days now and nothing on the web seems to be exactly what I am looking for.
I am attempting to implement a StackNavigator into my React Native app, but for some reason "navigation" is not being passed as a prop to the involved components. Therefore when I call this.props.navigation.navigator by pressing Button, I get the error undefined is not an object (evaluating this.props.navigation.navigate).
I have logged the props several times and the props object is empty, so the issue is not a deconstruction-of-the-props-object issue like others who get this error have had, but the fact that the navigation prop is not there in the first place.
I've tried placing the navigator code in its own file and in the App.js file thinking that it was somehow called after the components are rendered, and therefore not getting a chance to pass the navigation prop in, but that didn't work either. I've also looked to see if it is part of the props in the componentDidMount event. Still not.
import React, { Component } from 'react'
import { Text, View, Button, StyleSheet, FlatList } from 'react-native'
import { StackNavigator } from 'react-navigation'
import { getDecks } from '../utils/api'
import NewDeckView from './NewDeckView'
import DeckListItem from './DeckListItem'
export default class DeckListView extends Component {
constructor(props){
super(props)
this.state = {
decks: []
}
}
componentDidMount(){
console.log('props now test',this.props)
getDecks()
.then( result => {
const parsedResult = JSON.parse(result);
const deckNames = Object.keys(parsedResult);
const deckObjects = [];
deckNames.forEach( deckName => {
parsedResult[deckName].key = parsedResult[deckName].title
deckObjects.push(parsedResult[deckName])
})
this.setState({
decks:deckObjects
})
} )
}
render(){
return (
<View style={styles.container}>
<Text style={styles.header}>Decks</Text>
<FlatList data={this.state.decks} renderItem={({item})=><DeckListItem title={item.title} noOfCards={item.questions?item.questions.length:0}/>} />
<Button styles={styles.button} title="New Deck" onPress={()=>{this.props.navigation.navigate('NewDeckView')}}/>
</View>
)
}
}
const styles = StyleSheet.create({
header:{
fontSize:30,
margin:20,
},
container:{
flex:1,
justifyContent:'flex-start',
alignItems:'center'
},
button:{
width:50
}
})
const Stack = StackNavigator({
DeckListView : {
screen: DeckListView,
},
NewDeckView: {
screen:NewDeckView,
}
})

Like Vicky and Shubhnik Singh mentioned, you need to render the imported navigation stack in App.js like so:
import React from 'react';
import { Stack } from './navigator/navigator'
export default class App extends React.Component {
render() {
return <Stack/>
}
}
The navigator should look something like this and the first key in the object passed to StackNavigator will be rendered by default. In this case, it will be DeckListView.
import { StackNavigator } from 'react-navigation'
import DeckListView from '../components/DeckListView'
import NewDeckView from '../components/NewDeckView'
export const Stack = StackNavigator({
DeckListView : {
screen: DeckListView,
navigationOptions: {
headerTitle: 'Home',
},
},
NewDeckView: {
screen:NewDeckView,
navigationOptions: {
headerTitle: 'New Deck',
},
},
})
Thanks guys for the support! Somehow this wasn't clear for me in the documentation.

React Native Navigation Component Route Issue

New react native user here. I'm running into an issue and I am not sure how to proceed. I was able to get react-navigation running properly and then began receiving an error: "The component for route must be a a React Component" but unless I'm missing something, I believe that the component I am referencing is a react component. See my index.android.js below and my Home.js below:
//index.android.js
import React, { Component } from 'react';
import {
AppRegistry,
StyleSheet,
Text,
View
} from 'react-native';
import {
TabNavigator,
StackNavigator
} from 'react-navigation';
import Home from './app/components/Home/Home';
import Search from './app/components/Search/Search';
export default class demoApp extends Component {
render() {
return (
<SimpleNavigation/>
);
}
}
export const SimpleNavigation = StackNavigator({
Home: {
screen: Home,
header: { visible: false },
navigationOptions: {
title: 'Home',
header: null
},
},
Search: {
screen: Search,
navigationOptions: {
title: 'test'
},
},
},{});
//Home.js
import React, { Component } from 'react';
import {
AppRegistry,
StyleSheet,
Text,
View,
Image,
TextInput,
Button,
TouchableHighlight
} from 'react-native';
class Home extends Component {
constructor(props){
super(props);
this.state = {zipCode: ''}
}
navigate = (zipCode) => {
this.props.navigation.navigate('Search', zipCode);
}
render() {
return (
<View style={styles.container}>
<View style={[styles.boxContainer, styles.boxOne]}>
<Image style={styles.logo} source {require('../../images/Logo.png')} />
<Text style={styles.title}>An application to do things</Text>
<TextInput
style={styles.textInput}
placeholder='Enter a Zip Code'
onChangeText={(zipCode) => this.setState({zipCode})}
>
</TextInput>
</View>
<View style={[styles.boxContainer, styles.boxTwo]}>
<TouchableHighlight onPress={() => this.navigate(this.state.zipCode)}>
<Text style={styles.searchBox}>
Search
</Text>
</TouchableHighlight>
</View>
</View>
);
}
}
Any help/react pointers much appreciated. Thank you!

I think the problem is with home.js since you aren't exporting it. Try this :
export default class Home extends Component { ... }
^^^^^^^^^^^^^^
Add those or just add
export default Home;
at the end of the home.js file

const MyNavigator = createStackNavigator({
RouteNameOne: {
screen: () => <HomeScreen/>
},
RouteNameTwo: {
screen: () => <NewScreen/>
}
}, {
initialRouteName: 'RouteNameOne'
});
It will work.

For anyone else coming here, you could be receiving the "The component for route must be a a React Component" error because you don't have a default export, which was the case for me.
export HomeScreen extends React.Component {
...
vs
export default HomeScreen extends React.Component {
...
Hope this helps someone!

In my case putting this code block inside home.js solved the issue
static navigationOptions = {
navigationOptions: {
title: "scren title",
}
};

React Native navigation - undefined is not an object

I'm new to React native and trying to follow tutorials to learn however can't get navigation between screens to work. I have previously got it working fine with one screen but when adding navigation I get errors.
Following this: https://facebook.github.io/react-native/releases/next/docs/navigation.html
Gives me code like this:
import React from 'react';
import {
StackNavigator,
} from 'react-navigation';
export default class HomeScreen extends React.Component {
static navigationOptions = {
title: 'Welcome',
};
render() {
const { navigate } = this.props.navigation;
return (
<Button
title="Go to Jane's profile"
onPress={() =>
navigate('Profile', { name: 'Jane' })
}
/>
);
}
}
class ProfileScreen extends React.Component {
static navigationOptions = {
title: 'Profile',
};
render() {
return (
<Button title="do nothing"/>
);
}
}
const App = StackNavigator({
Home: { screen: HomeScreen },
Profile: { screen: ProfileScreen },
});
Trying to run this (through the expo app) results in the error
undefined is not an object (evaluating 'this.props.navigation.navigate')
So am I doing navigation correctly and how do I fix this error?

You need to use AppRegistry.registerComponent in your App.
A nice way of doing this is to create a src directory and then create the 2 js files, HomeScreen and ProfileScreen there. Then create and App.js on the same level as your index.android.js or index.ios.js and include these 2 files and declare the StackNavigator as you did in your code, but instead of const App you need to have const NameOfYourApp, where NameOfYourApp is how you named your project when you ran create-react-native-app.(If it is App, just leave it like that)
Then you need to add this line at the end, AppRegistry.registerComponent('NameOfYourApp', () => NameOfYourApp);
import React from 'react';
import {
StackNavigator,
} from 'react-navigation';
import HomeScreen from './src/HomeScreen'
import ProfileScreen from './src/ProfileScreen'
const NameOfYourApp = StackNavigator({
Home: { screen: HomeScreen },
Profile: { screen: ProfileScreen },
});
AppRegistry.registerComponent('NameOfYourApp', () => NameOfYourApp)
The final step is to import your App.js file in your index.android.js or index.ios.js
import './App';