Take a look at the https://github.com/msasinowski/react-native-expo-braintree
Add this to your build.gradle
allprojects {
    repositories {
        maven {
            // Braintree 3D Secure
            // https://developer.paypal.com/braintree/docs/guides/3d-secure/client-side/android/v4#generate-a-client-token
            url "https://cardinalcommerceprod.jfrog.io/artifactory/android"
            credentials {
                username 'braintree_team_sdk'
                password 'AKCp8jQcoDy2hxSWhDAUQKXLDPDx6NYRkqrgFLRc3qDrayg6rrCbJpsKKyMwaykVL8FWusJpp'
            }
        }
    }
}In Your AndroidManifest.xml, android:allowBackup="false" can be replaced android:allowBackup="true", it is responsible for app backup.
Also, add this intent-filter to your main activity in AndroidManifest.xml:
<activity>
    ...
    <intent-filter>
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
        <data android:scheme="${applicationId}.braintree" />
    </intent-filter>
</activity>If you need to specify a custom appLinkReturnUrl, you may do so:
<activity>
    ...
    <intent-filter>
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
        <data android:scheme="${applicationId}.braintree.custom" />
    </intent-filter>
</activity>You will need to pass this value to to RNBraintree.showPayPalModule as an option (see Show PayPall module below).
NOTE: Card payments do not work on rooted devices and Android Emulators
If your project uses Progurad, add the following lines into proguard-rules.pro file
-keep class com.cardinalcommerce.dependencies.internal.bouncycastle.**
-keep class com.cardinalcommerce.dependencies.internal.nimbusds.**
-keep class com.cardinalcommerce.shared.**
cd ios
pod installAdd a bundle url scheme {BUNDLE_IDENTIFIER}.payments in your app Info via XCode or manually in the Info.plist. In your Info.plist, you should have something like:
<key>CFBundleURLTypes</key>
<array>
    <dict>
        <key>CFBundleTypeRole</key>
        <string>Editor</string>
        <key>CFBundleURLName</key>
        <string>com.myapp</string>
        <key>CFBundleURLSchemes</key>
        <array>
            <string>com.myapp.payments</string>
        </array>
    </dict>
</array>In your AppDelegate.m:
#import "BraintreeCore.h"
...
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    ...
    [BTAppContextSwitcher setReturnURLScheme:self.paymentsURLScheme];
}
- (BOOL)application:(UIApplication *)application
            openURL:(NSURL *)url
            options:(NSDictionary<UIApplicationOpenURLOptionsKey,id> *)options {
    if ([url.scheme localizedCaseInsensitiveCompare:self.paymentsURLScheme] == NSOrderedSame) {
        return [BTAppContextSwitcher handleOpenURL:url];
    }
    
    return [RCTLinkingManager application:application openURL:url options:options];
}
- (NSString *)paymentsURLScheme {
    NSString *bundleIdentifier = [[NSBundle mainBundle] bundleIdentifier];
    return [NSString stringWithFormat:@"%@.%@", bundleIdentifier, @"payments"];
}import RNBraintree from '@ekreative/react-native-braintree';
RNBraintree.showPayPalModule({
    clientToken: 'CLIENT_TOKEN_GENERATED_ON_SERVER_SIDE',
    amount: '1.0',
    currencyCode: 'EUR',
    // Change button text to “Complete Purchase", optional
    userAction: 'commit',
    // Define a custom return URL for Android, optional
    appLinkReturnUrl: 'com.application.braintree.custom',
    })
    .then(result => console.log(result))
    .catch((error) => console.log(error));
import RNBraintree from '@ekreative/react-native-braintree';
RNBraintree.tokenizeCard({
    clientToken: 'CLIENT_TOKEN_GENERATED_ON_SERVER_SIDE',
    number: '1111222233334444',
    expirationMonth: '11',
    expirationYear: '24',
    cvv: '123',
    postalCode: '',
    })
    .then(result => console.log(result))
    .catch((error) => console.log(error));import RNBraintree from '@ekreative/react-native-braintree';
RNBraintree.run3DSecureCheck({
    // Optional if you ran `tokenizeCard()` or other Braintree methods before
    clientToken: 'CLIENT_TOKEN_GENERATED_ON_SERVER_SIDE',
    nonce: 'CARD_NONCE',
    amount: '122.00',
    // Pass as many of the following fields as possible, but they're optional
    email: '[email protected]',
    firstname: '',
    lastname: '',
    phoneNumber: '',
    streetAddress: '',
    streetAddress2: '',
    city: '',
    region: '',
    postalCode: '',
    countryCode: ''
    })
    .then(result => console.log(result))
    .catch((error) => console.log(error));import RNBraintree from '@ekreative/react-native-braintree';
RNBraintree.requestPayPalBillingAgreement({
    clientToken: 'CLIENT_TOKEN_GENERATED_ON_SERVER_SIDE',
    description: 'BILLING_AGRREEMENT_DESCRIPTION',
    localeCode: 'LOCALE_CODE'
    })
    .then(result => console.log(result))
    .catch((error) => console.log(error));import RNBraintree from '@ekreative/react-native-braintree';
console.log(RNBraintree.isApplePayAvailable())import RNBraintree from '@ekreative/react-native-braintree';
RNBraintree.runApplePay({
    clientToken: 'CLIENT_TOKEN_GENERATED_ON_SERVER_SIDE',
    companyName: 'Company',
    amount: '100.0',
    currencyCode: 'EUR'
    })
    .then(result => console.log(result))
    .catch((error) => console.log(error));import RNBraintree from '@ekreative/react-native-braintree';
RNBraintree.runGooglePay({
    clientToken: 'CLIENT_TOKEN_GENERATED_ON_SERVER_SIDE',
    amount: '100.0',
    currencyCode: 'EUR'
    })
    .then(result => console.log(result))
    .catch((error) => console.log(error));-  Android. Check if we can split the logic in the 
getDeviceDatamethod to callnew DataCollector(mBraintreeClient).collectDeviceData()only once (it seems like it's currently may be called a second time from thesetupmethod) #37 (comment) -  iOS. Try to use the new 
getDeviceDatamethod in other methods, such astokenizeCard,showPayPalModule#37 (comment) 
If you want to read further you can follow these links
- https://reactnative.directory/?search=react-native-braintree
 - https://reintech.io/blog/tutorial-for-react-developers-what-are-the-best-react-native-libraries-for-creating-mobile-payments
 - https://reactnativeexample.com/a-react-native-interface-for-integrating-payments-using-braintree/
 - https://www.npmjs.com/package/@ekreative/react-native-braintree