Tokenization - Android

Learn how to build a tokenization form for your Android app to accept payment details securely.

This article details how to build a tokenization form for your Android app. The payment details buyers submit in the tokenization form are secured via tokenization and stored in Finix's vault, so payment information is never exposed and minimizes your PCI scope.

If you have questions about building your app's tokenization form, reach out to your Finix point of contact or email the Finix Support team.

Prerequisites

The library is built 100% on Kotlin utilizing the Jetpack Compose library for the UI. A demo app is available in the following Github repo: Finix Android Payment Sheet app.

We host the library on Maven Central, so verify you have mavenCentral() in your buildscript inside the build.gradle project.

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buildscript {
 repositories {
    mavenCentral()
 }
}

After you confirm Maven Central is in your buildscript, you can import our library by adding the following to your gradle file:

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buildscript {
    ext.finix_version = '0.3.7'
}

dependencies {
    implementation 'com.finix:finix-android-payment-sheet:finix_version'
}

Step 1: Create a Kotlin File

Create a new Kotlin file and save it with the .kt extension.

Next, create a function to handle the tokenization form. You can define it using the following:

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@Composable
fun showMyPaymentSheet() {
    CompletePaymentSheetOutlined(
        onDismiss = { /*TODO*/ },
        onNegativeClick = { /*TODO*/ },
        onPositiveClick = { token -> }
    )
}

Step 2: Launch the Tokenization Form

Using the viewModel, you can control when exactly the tokenization form is called on the MainCheckOutScreen and prompts the buyer to enter their information.

Add in the relevant logic so the tokenization form gets called when you'd want your buyers to enter their information:

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@Composable
fun MainCheckOutScreen() {
    val viewModel = viewModel<CheckOutViewModel>()
    val state = viewModel.state

    if(state.showMyPaymentSheet ) {
            showMyPaymentSheet()
    }

}

When the tokenization form is returned successfully, save the token response contained in onPositiveClick:

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onPositiveClick = { token ->
    viewModel.saveTokenResponse(token)
}

It contains the results of the tokenization request and the buyer's tokenized payment details.

The structure of the token is:

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data class TokenizedResponse(
    val id:String?,
    val fingerprint:String?,
    val createdAt:String?,
    val updatedAt:String?,
    val type:String?,
    val expiresAt:String?,
    val currency:String?,
)

For a detailed example of how to use our Android tokenization library, see the following GitHub repo: Finix Android Payment Sheet app.

Step 3: Create a Payment Instrument

With the token saved, you're ready to process a transaction. Before you can use the tokenized details in a transaction, you must create a Payment Instrument.

Make a POST request to the /payment_instrument endpoint and create a Payment Instrument with the relevant token and Identity information.

The token to use is available in the TokenResponse. The structure of the TokenResponse is:

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id: \(instrument.id)
fingerprint: \(instrument.fingerprint)
created: \(instrument.created)
updated: \(instrument.updated)
instrument: \(instrument.instrument)
expires: \(instrument.expires)
isoCurrency: \(instrument.isoCurrency)

attention

Use new tokens immediately to create a Payment Instrument. Tokens expire 30 minutes after being created.

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curl https://finix.sandbox-payments-api.com/payment_instruments \
    -H "Content-Type: application/json" \
    -H 'Finix-Version: 2022-02-01' \
    -u  USsRhsHYZGBPnQw8CByJyEQW:8a14c2f9-d94b-4c72-8f5c-a62908e5b30e \
    -d '
        {
            "token": "TKghUufLdh4QQ96CBi928HP3",
            "type": "TOKEN",
            "identity": "IDgWxBhfGYLLdkhxx2ddYf9K"
        }'

HTTP Request

POST https://finix.sandbox-payments-api.com/payment_instruments

Request Arguments


Field	Type	Description
`address`	object, required	Billing address (Full description of child attributes below) Note: Including a postal or zip code when creating a Payment Instrument can lower the interchange on credit card transactions
`identity`	string, required	ID for the Identity resource which the account is to be associated
`name`	string, required	Full name of the registered card holder
`token`	string, required	ID for the Token that was returned via the tokenization client
`type`	string, required	Must pass TOKEN as the value

Address-object Request Arguments


Field	Type	Description
`city`	string, optional	City (max 20 characters)
`country`	string, optional	3-Letter Country code
`line1`	string, optional	First line of the address (max 35 characters)
`line2`	string, optional	Second line of the address (max 35 characters)
`postal_code`	string, required	Zip or Postal code (max 7 characters)
`region`	string, optional	2-letter State code

Example Response

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{
  "id" : "PImmCg3Po7oNi7jaZcXhfkEu",
  "created_at" : "2022-10-10T05:32:17.78Z",
  "updated_at" : "2022-10-10T05:35:04.55Z",
  "application" : "APgPDQrLD52TYvqazjHJJchM",
  "created_via" : "API",
  "currency" : "USD",
  "enabled" : true,
  "fingerprint" : "FPRiCenDk2SoRng7WjQTr7RJY",
  "identity" : "IDgWxBhfGYLLdkhxx2ddYf9K",
  "instrument_type" : "PAYMENT_CARD",
  "address" : {
    "line1" : "900 Metro Center Blv",
    "line2" : null,
    "city" : "San Francisco",
    "region" : "CA",
    "postal_code" : "94404",
    "country" : "USA"
  },
  "address_verification" : "POSTAL_CODE_AND_STREET_MATCH",
  "bin" : "520082",
  "brand" : "MASTERCARD",
  "card_type" : "DEBIT",
  "expiration_month" : 12,
  "expiration_year" : 2029,
  "issuer_country" : "NON_USA",
  "last_four" : "8210",
  "name" : "Amy White",
  "security_code_verification" : "MATCHED",
  "tags" : {
    "card_name" : "Business Card"
  },
  "type" : "PAYMENT_CARD",
  "_links" : {
    "self" : {
      "href" : "https://finix.sandbox-payments-api.com/payment_instruments/PImmCg3Po7oNi7jaZcXhfkEu"
    },
    "authorizations" : {
      "href" : "https://finix.sandbox-payments-api.com/payment_instruments/PImmCg3Po7oNi7jaZcXhfkEu/authorizations"
    },
    "transfers" : {
      "href" : "https://finix.sandbox-payments-api.com/payment_instruments/PImmCg3Po7oNi7jaZcXhfkEu/transfers"
    },
    "verifications" : {
      "href" : "https://finix.sandbox-payments-api.com/payment_instruments/PImmCg3Po7oNi7jaZcXhfkEu/verifications"
    },
    "application" : {
      "href" : "https://finix.sandbox-payments-api.com/applications/APgPDQrLD52TYvqazjHJJchM"
    },
    "identity" : {
      "href" : "https://finix.sandbox-payments-api.com/identities/IDgWxBhfGYLLdkhxx2ddYf9K"
    },
    "updates" : {
      "href" : "https://finix.sandbox-payments-api.com/payment_instruments/PImmCg3Po7oNi7jaZcXhfkEu/updates"
    }
  }
}

Step 4: Processing Live Transactions

When you've completed testing, you can take your tokenization form live by making the following changes:

Set sandbox to false
Add your Application_id

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@Composable
    fun showMyPaymentSheet(viewModel: CheckOutViewModel) {
        CompletePaymentSheetOutlined(
            onDismiss = { viewModel.setShowMyPaymentSheet(false) },
            onNegativeClick = { viewModel.setShowMyPaymentSheet(false) },
            onPositiveClick = { token ->
                viewModel.saveTokenResponse(token)
                viewModel.setShowMyPaymentSheet(false) 
            },
            applicationId = MY_APPLICATION_ID,
            isSandbox = false,
        )
    }

Taking your tokenization form live will process real money movements. For details on how to take your sandbox live, see Signing Up for a Finix Account.

Customize Tokenization Forms

You can customize several parts of the tokenization forms to match your brand and voice.

Style

There are two styles available for your app's tokenization form:

OutlinedTextField has text fields with rounded corners.
ClassicTextField has text fields with square corners and is boxier.

Tokenization Form Styles

OutlinedTextField	ClassicTextField

Once you’ve selected a style, decide on how much information the Tokenization Form should request from buyers.

Collect the most information to reduce fraud via Card and AVS checks.
Collect less information to speed up the cardholder experience.

For more details on the different Card and AVS checks, see Card and Address Verification Checks.

Types of Tokenization Forms

Several tokenization forms are available to choose from that differ in how much information is requested. We recommend using either the Complete or Partial tokenization form for most use cases.

Payment Sheets

Tokenization Form Types

Information Collected	COMPLETE sheet	PARTIAL sheet	BASIC sheet	MINIMAL sheet	INTERNATIONAL sheet	BANK ACCOUNT sheet
ClassicTextField Function Name	CompletePaymentSheet	PartialPaymentSheet	BasicPaymentSheet	MinimalPaymentSheet	InternationalPaymentSheet	BankAccountSheet
OutlinedTextField Function Name	CompletePaymentSheetOutlined	PartialPaymentSheetOutlined	BasicPaymentSheetOutlined	MinimalPaymentSheetOutlined	InternationalPaymentSheetOutlined	BankAccountSheetOutlined
Name	X	X	X
Card	X	X	X	X
Expiration Date	X	X	X	X
CVV	X	X	X	X	X
Address	X
Address Ext.	X
City	X
State	X
ZIP/Postal Code	X	X			X
Country and Region
Accounting Number						X
Routing Number						X

Customizing Tokenization Forms

Once you’ve chosen a tokenization form, you can begin customizing it to fit the look and feel of your application.

The complete list of items you can add to the tokenization form includes the following:

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@Composable
fun CompletePaymentSheetOutlined(
    modifier: Modifier = Modifier,
    applicationId: String = "",
    isSandbox: Boolean = true,
    paymentSheetResources: PaymentSheetResources = PaymentSheetResources(),
    paymentSheetColors: PaymentSheetColors = PaymentSheetColors(),
    logoTextStyle: TextStyle = MaterialTheme.typography.headlineSmall,
    textStyle: TextStyle = LocalTextStyle.current,
    buttonTextFont: TextUnit = BUTTON_TEXT_FONT,
    onDismiss: () -> Unit,
    onNegativeClick: () -> Unit,
    onPositiveClick: (TokenizedResponse) -> Unit
)

Parameter	Type	Default	Description
`applicationID`	String, optional	none	Update this to your `Application#id`, so you can manage the tokens. If not included, you won't be able to create `Payment Instruments` with the results of the sheet.
`isSandbox`	Boolean, optional	true (Sandbox)	Update this to false if you want to create tokens in a live environment.
`paymentSheetResources`	object, optional	See below	Add custom images and text to the tokenization form.
`paymentSheetColors`	object, required	See below	Customize the colors of the tokenization form.
`logoTextStyle`	TextStyle, required	`MaterialTheme.typography.headlineSmall`	Configure the styling of the text in the logo.
`textStyle`	TextStyle, required	`LocalTextStyle.current`	Configure the styling of the text in the input fields.

PaymentSheetResources

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data class PaymentSheetResources(
    @DrawableRes val logoDrawable: Int = R.drawable.ic_default_logo,
    @StringRes val logoText: Int = R.string.default_logo_text,
    @StringRes val tokenizeButtonText: Int = R.string.btn_tokenize,
    @StringRes val cancelButtonText: Int = R.string.btn_cancel,
    val cancelButtonWeight: Float = 0.6f,
    val tokenizeButtonWeight: Float = 0.8f,
)

Parameter	Type	Default	Description
`logoDrawable`	int, required	Defaults to a logo for Daphne's Corner.	The image at the top of the tokenization form. Replace this with your own logo. The uploaded logo will have a 76.dp radius.
`logoText`	int, required	Daphne’s Corner	The header to the right of `logoDrawable`. Update this with your company name or the name of the tokenization form. The header will be centered on the page.
`tokenizeButtonText`	int, required	Tokenize	The text inside the button buyers press to submit the sheet.
`cancelButtonText`	int, required	Cancel	The text buyers press to leave the tokenization form.
`tokenizeButtonWeight`	float, required	Tokenize	Control the spacing of the Tokenize button.
`cancelButtonWeight`	float, required	Cancel	Control the spacing of the Cancel button.

PaymentSheetColors

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data class PaymentSheetColors(
    val surface: Color = Color.White,
    val logoTextColor: Color = Color.Black,
    val textColor: Color = Color.Black,
    val errorContainerColor: Color = FinixErrorTextSurface,
    val containerColor: Color = FinixGray,
    val focusedIndicatorColor: Color = FinixBlue,
    val unfocusedIndicatorColor: Color = Color.Transparent, //hide the indicator
    val focusedLabelColor: Color = FinixBlue,
    val unfocusedLabelColor: Color = Color.Black,
    val placeholderColor: Color = FinixPlaceHolderTextGray,
    val errorIndicatorColor: Color = FinixErrorRed,
    val errorLabelColor: Color = FinixErrorRed,
    val errorPlaceholderColor: Color = FinixPlaceHolderTextGray,
    val tokenizeButtonColor: Color = FinixBlue,
    val tokenizeButtonTextColor: Color = Color.White,
    val cancelButtonColor: Color = FinixRed,
    val cancelButtonTextColor: Color = Color.White,
)


Name	Type	Default	Description
surface	Color, Required	Color.White	The color of the tokenization form background.
logoTextColor	Color, Required	Color.Black	The color of the title text.
textColor	Color, Required	Color.Black	The color of the input text used in text fields.
containerColor	Color, Required	FinixGray	The surface color of the `textfield`.
errorContainerColor	Color, Required	FinixErrorTextSurface	The surface color of the `textfield` when there's an error.
errorBorderColor	Color, Required	FinixErrorRed	The color of the `textfield` border when there's an error.
focusedIndicatorColor	Color, Required	FinixBlue	The color of the `textfield` border when the field is active.
unfocusedIndicatorColor	Color, Required	Color.Transparent	The color of the `textfield` border when the field is inactive and not being used.
focusedLabelColor	Color, Required	FinixBlue	The color of the `textfield` label when the field is active.
unfocusedLabelColor	Color, Required	Color.Black	The color of the `textfield` label when the field is inactive and not being used.
errorLabelColor	Color, Required	FinixErrorRed	The color of the `textfield` label when there's an error.
placeholderColor	Color, Required	FinixPlaceHolderTextGray	The color of the `textfield` placeholder.
tokenizeButtonColor	Color, Required	FinixBlue	The surface color of the tokenize button.
tokenizeButtonTextColor	Color, Required	Color.White	The color of the text in the tokenize button.
cancelButtonColor	Color, Required	FinixRed	The surface color of the cancel button
cancelButtonTextColor	Color, Required	Color.White	The color of the text in the cancel button.

Debugging Tokenization Forms

Our Android tokenization library uses the following libraries and dependencies:

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android {

    ... 
    
    compileSdk 33
    defaultConfig {
        minSdk 24
        targetSdk 33
        

        aarMetadata {
            minCompileSdk = 24
        }
    }

    ....
    
    kotlinOptions {
        jvmTarget = 11
    }

    buildFeatures {
        compose true
    }

    composeOptions {
        kotlinCompilerExtensionVersion '1.4.0-alpha02'
    }

}


Name	Version
Kotlin	`org.jetbrains.kotlin:kotlin-bom:1.8.10`
Kotlin Compose	`androidx.compose:compose-bom:2023.01.00`
Kotlin Complier	`kotlinCompilerExtensionVersion '1.4.0-alpha02'`
Material3	`androidx.compose.material3:material3:1.2.0-alpha01` `androidx.compose.material3:material3-window-size-class:1.2.0-alpha01`

Before using our Android Tokenization library, verify you're using a compatible versions of our SDK and have a compatible version of Kotlin installed:

minSdk : 24
targetSdk : 33
compileSdk : 33

If you run into any issues, verify you have the minimum or latest version of the relevant dependency installed. For details on how to update any of the above, see: Compose to Kotlin Compatibility Map.

If you continue to run into issues, please feel free to reach out to the Finix Support Team.