Develop Reference

React Native Native Java/Android Module - not showing toast message

I'm using the example found here & currently facing issue with the toast not showing at all... I just have the initial 'Welcome to React Native!' screen in the emulator. My app structure is as follows:
testApp
android
app
src
main
java
com
testApp
CustomToastPackage.java
MainActivity.java
MainApplication.java
ToastModule.java
res
assets
index.android.bundle
AndroidManifest.xml
ios
node_modules
app.json
App.js
index.js
package.json
ToastExample.js
yarn.lock
My index.js
import {AppRegistry} from 'react-native';
import App from './App';
import {name as appName} from './app.json';
import {NativeModules} from 'react-native'; //Added this
module.exports = NativeModules.testApp; //Added this
AppRegistry.registerComponent(appName, () => App);
My App.js
import React, {Component} from 'react';
import {Platform, StyleSheet, Text, View} from 'react-native';
import ToastExample from './ToastExample'; //Added this
const instructions = Platform.select({
ios: 'Press Cmd+R to reload,\n' + 'Cmd+D or shake for dev menu',
android:
'Double tap R on your keyboard to reload,\n' +
'Shake or press menu button for dev menu',
});
type Props = {};
export default class App extends Component<Props> {
render() {
return (
<View style={styles.container}>
<Text style={styles.welcome}>Welcome to React Native!</Text>
<Text style={styles.instructions}>To get started, edit App.js</Text>
<Text style={styles.instructions}>{instructions}</Text>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#F5FCFF',
},
welcome: {
fontSize: 20,
textAlign: 'center',
margin: 10,
},
instructions: {
textAlign: 'center',
color: '#333333',
marginBottom: 5,
},
});
As you can see from the file structure I created an additional file named ToastExample.js that contains following based upon the answer found here
import {NativeModules} from 'react-native';
module.exports = NativeModules.ToastExample;
Package name is simply
com.testapp
I can't figure out why the toast never shows? I know react comes with toast support but looking to build upon an initial example to include more advanced Java/Android code...

In your example you didn't add ToastExample in index.js you need to add this into rendering method in index.js like below.
return(
<ToastExample/>
)
In addition to that, you are going to create an android native module which can be used only for android.
But According to my point of view, you can use toast messages module which can be used in both Android and Ios. Otherwise, you need to create ios base native module for creating toast for ios. If u don't want to ios base implementation, it's ok to use this native module. But you block your Ios deployment by it.
I would like to suggest this https://github.com/crazycodeboy/react-native-easy-toast#readme
easy-toast for u. It will work on both Android and IOS devices. You can customize it like android native toast as well. It is easy to implement in your application.

Thanks #Ariel & #Lucefer for feedback, I made the update you suggested but ran into another error. Posting this answer to save anyone potential headache caused by using Android Studio as IDE with React Native. Turns out the MainApplication.java file had 2 items (import of CustomToastPackage & ReactPackage) greyed out & could never figure out why? See the screenshot below
I created a separate application (react-native init newapp) & used a simple text editor (Atom or gedit will do instead of Android Studio) to make the changes & the example runs just fine now.

try this:
<Root>
<View style={styles.container}>
<Text style={styles.welcome}>Welcome to React Native!</Text>
<Text style={styles.instructions}>To get started, edit App.js</Text>
<Text style={styles.instructions}>{instructions}</Text>
</View>
</Root>
just import Root to react native

React-native: Images not showing in android device; but shows in emulator

Here is my code :
import React, {Component} from 'react';
import {
Platform,
StyleSheet,
Text,
View ,
ImageBackground } from 'react-native';
export default class App extends Component {
render() {
return (
<View style={{ flex: 1, flexDirection: 'column', backgroundColor: 'transparent' }}>
<ImageBackground source={{uri: "image1"}} style={{ width: null , height: null , flex: 1, resizeMode: 'cover',}}
>
</ImageBackground>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#F5FCFF',
},
welcome: {
fontSize: 20,
textAlign: 'center',
margin: 10,
},
instructions: {
textAlign: 'center',
color: '#333333',
marginBottom: 5,
},
});
And when I try this in emulator everything is Ok but on my device
images not showing
Emulator
Files tree
Why this happen ? :( Please help.

You can try putting the images inside an assets folder at the root of your project, then you could reference to it using the require method, then path will be relative to the component location.
source={require('../assets/image1.jpg')}
This way you can also put files of different resolutions like this:
image1.png
image1#2x.png
image1#3x.png
image1#4x.png
Inside that that folder and RN will load accordingly.

The uri is pretty important here. Images displaying in the emulator and not on your device seems like we are dealing with images you uploaded in the app? (As opposed to static images that you include somewhere in your project or network images). On your emulator, the path to storage is different than on the device, so you'll have to make sure you are using a uri that correctly points to the image based on environment. Hope that helps!

First go your project path in terminal then run this command
react-native bundle --platform android --dev false --entry-file index.js --bundle-output android/app/src/main/assets/index.android.bundle --assets-dest android/app/src/main/res
Then run in android device. Hope it works.

How to add font Awesome in a react-native project for android?

I'm able to add normal fonts, but not FontAwesome, i'm using v4.7.0 of FontAwesome.
I've checked older answers on SO, but I only found this one to be relevant, but I think the answer is outdated, because you cant link fonts with the first letter of the file name being lowercase, it has to be uppercase, like 'Font Awesome.ttf' for example(which is what I have right now). This naming strategy worked for adding another regular font called 'Titillium Web'.
My index.js
export default class App extends Component {
render() {
return (
<View style={styles.container}>
<Text style={styles.fontawesome}></Text>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
},
fontawesome:{
fontFamily: 'Font Awesome',
color: '#000',
fontSize: 20
},
});
AppRegistry.registerComponent('myappname', () => App);
In my package.json
"rnpm": {
"assets": [
"./src/assets/fonts/TitilliumWeb",
"./src/assets/fonts/FontAwesome"
]
},
Executed react-native link in project dir, the fonts were copied correctly.
Executed react-native run-android in project dir.
My Environment
Device: real device, android kitkat v4.4.2
react-native: v0.55.2
react: v16.3.1
yarn: v1.5.1
node: v9.5.0

the development server returned response error code: 500 -React Native

I am developing Android app using React Native. I tried running a simple code of a screen being displayed, but I get the following error. I tried closing all command line windows and emulator and re-starting React Native package and run it, but doesn't work. The code is provided below:
index.android.js:
import React, { Component} from 'react';
import {Text, View, AppRegistry,Button} from 'react-native';
import {StackNavigator} from 'react-navigation';
import dhrumil from '.\dhrumil.js';
export default class MainApp extends Component{
render(){
return(
<dhrumil />
);
}
}
const SimpleApp = StackNavigator({
Home: {screen: dhrumil }
});
AppRegistry.registerComponent("MainApp",()=>SimpleApp);
dhrumil.js:
import React, { Component} from 'react';
import {Text, View, AppRegistry,Button,StyleSheet} from 'react-native';
const dhrumil = () =>{
return(
<View style={styles.container}>
<Text style={styles.texter}>Hello World!</Text>
<Button
onPress={() => navigate('dharmin')}
title="Chat with Lucy"
/>
</View>
);
}
const styles = StyleSheet.create({
container:{
justifyContent: 'center',
alignItems: 'center',
flex: 1
}
texter:
{
fontSize: 20,
textAlign: 'center'
}
});
dhrumil.navigationOptions = {
title:'dhrumil'
}
export default dhrumil
How do I solve this?

In index.android.js change the import dhrumil from '.\dhrumil.js'; to import dhrumil from './dhrumil';. You have to use / to specify the path and it is not necessary use dhrumil.js when we are importing the js file.

#Jeffrey Rajan 's suggestion was absolutely correct here.
This error occurs mostly due to :
Issue 1:
A wrong file name in import statement
Using the wrong case in file name
Using '\' instead of '/' in file name
Hope that using this list you can easily find errors causing this in your code.
Issue 2:
An issue with the material design.To resolve this install material design locally using :
react-native-material-design
Issue 3:
babel-preset-react-native making trouble code. To resolve this issue run:
yarn remove babel-preset-react-native
yarn add babel-preset-react-native#2.1.0
Try troubleshooting in this order.Mostly the Issue 1 will solve the problem.

React-native: Images not showing in android device; but shows perfectly in emulator

I am working on a sample react native project. And almost all features except the <Image source=''/> work well with it. The image shows well in android emulator supplied with android studio and genymotion, but does not work on any real devices (moto G3 turbo, nexus 5, galaxy s4 etc...). I don't know what went wrong with my code. Here is my code
import React, { Component } from 'react';
import {
AppRegistry,
StyleSheet,
Text,
View,
Image
} from 'react-native';
class ImageTester extends Component {
render() {
return (
<View style={styles.container}>
<Text style={styles.welcome}>
Welcome to React Native!
</Text>
<Text style={styles.instructions}>
To get started, edit index.android.js
</Text>
<Text style={styles.instructions}>
Double tap R on your keyboard to reload,{'\n'}
Shake or press menu button for dev menu
</Text>
<Image source={require('./img/first_image.png')}></Image>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#F5FCFF',
},
welcome: {
fontSize: 20,
textAlign: 'center',
margin: 10,
},
instructions: {
textAlign: 'center',
color: '#333333',
marginBottom: 5,
},
});
AppRegistry.registerComponent('ImageTester', () => ImageTester);
project structure:
React-native version : react-native: 0.32.1

The problem was with my bundle packaging command. As #luwu said in his comment, I checked this, and surprised that there is no difference with mine. Then only I noticed a message while running the command
"Assets destination folder is not set, skipping..."
That message was bit confusing since bundle was already created in the assets folder. The 'Assets' in that messages actually indicates my images. And I solved the issues with the following command:
react-native bundle --platform android --entry-file index.js --bundle-output android/app/src/main/assets/index.android.bundle --dev false --reset-cache --assets-dest android/app/src/main/res/

Another solution for the same issue of assets not bundled in development.
Add the following line to your app/build.gradle file in the section project.ext.react:
project.ext.react = [
... other properties
bundleInDebug: true // <-- add this line
]
From the docs in the starter project gradle file:
By default, bundleDebugJsAndAssets is skipped, as in debug/dev mode we prefer to load the bundle directly from the development server.

i had the same issue. turns out i had import image component from react-native-elements instead of rect-native.fixed my case

I was having a similar issue on my project. My problem was that the Image is displaying ok on iOS but not showing on android (devices).
So my issue got fixed by adding the following header to my Image:
<Image
source={{
uri: 'https://imageurladdress/img.png',
headers: {
Accept: '*/*',
},
}}
style={styles.imageStyle}
/>
So, for some reason the iOS was already working without the need to add this header in the request. But the point is that after add the headers field, the Image is showing correct on both iOS and android devices.

In my case two things were causing problems
First
I run my backend at http://localhost:3000 and any image asset would have URI similar to
http://localhost:3000/rails/active_storage/blobs/redirect/eyJfcmFpbHMiOns
but the android simulator exposes it as
http://10.0.2.2:3000/.....
So http://localhost:3000 is inaccessible in simulator. So I made sure appropriate host is set from backend looking which device is requesting the API.
Second
In params supplied to <Image> component, I used url key(property) which was working fine in IOS but I needed to change it to uri for android.

What helped me personally (none of the solutions here worked) is opening external image from the https://.... and it worked. So I decided to give a try to use 'file://' + DocumentDirectoryPath + '/' + item.image and it worked.