Fingerprint Authentication using BiometricPrompt

In this blog, we are going to learn about Fingerprint Authentication using BiometricPrompt.The Android Framework and Security team recently released the AndroidX Biometric Library, a support library that supersedes all previous iterations of the API.

The library makes all the features announced in Android 10 (API level 29) available all the way back to Android 6 (API level 23).

BiometricPropt UI :

BiometricPropt provides there own stable UI and Dialogs. In the previous FingurePrint Manager, there is no option of the UI. There is only a custom view.

Android app integration :

implementation 'androidx.biometric:biometric:1.0.0-alpha03'

1	implementation 'androidx.biometric:biometric:1.0.0-alpha03'

Integrate this dependency to the build.gradle (app) file.

Check whether your device supports any biometric authentication. :

Firstly, You should create and biometricManager object.

val biometricManager = BiometricManager.from(context)
if (biometricManager.canAuthenticate() == BiometricManager.BIOMETRIC_SUCCESS){
  
}

val biometricManager = BiometricManager.from(context)

if (biometricManager.canAuthenticate() == BiometricManager.BIOMETRIC_SUCCESS){

}

Create an instance of BiometricPrompt:

In this paragraph, We are going to create a BiometricPropt object. Firstly, You should instantiate BiometricPrompt early in your Activity/Fragment lifecycle, preferably inside onCreate() or onCreateView(). This is a key difference between FingerprintManager and BiometricPrompt. It was OK to instantiate FingerprintManager just in time to call authenticate(). But for BiometricPrompt to send callbacks to the proper activity, say in case of configuration changes, you must instantiate it a bit before you need to call authenticate().

    private var executor: Executor? = null
    private var biometricPrompt: BiometricPrompt? = null
    private var promptInfo: PromptInfo? = null

private var executor: Executor? = null

private var biometricPrompt: BiometricPrompt? = null

private var promptInfo: PromptInfo? = null

  executor = ContextCompat.getMainExecutor(this@HomeActivity)
        biometricPrompt = BiometricPrompt(this@HomeActivity,
                executor!!, object : BiometricPrompt.AuthenticationCallback() {
            override fun onAuthenticationError(errorCode: Int,
                                               errString: CharSequence) {
                super.onAuthenticationError(errorCode, errString)
                Toast.makeText(applicationContext,
                        "Authentication error: $errString", Toast.LENGTH_SHORT)
                        .show()
            }

            override fun onAuthenticationSucceeded(
                    result: BiometricPrompt.AuthenticationResult) {
                super.onAuthenticationSucceeded(result)
                Toast.makeText(applicationContext,
                        "Authentication succeeded!", Toast.LENGTH_SHORT).show()
            }

            override fun onAuthenticationFailed() {
                super.onAuthenticationFailed()
                Toast.makeText(applicationContext, "Authentication failed",
                        Toast.LENGTH_SHORT)
                        .show()
            }
        })

executor = ContextCompat.getMainExecutor(this@HomeActivity)

biometricPrompt = BiometricPrompt(this@HomeActivity,

executor!!, object : BiometricPrompt.AuthenticationCallback() {

override fun onAuthenticationError(errorCode: Int,

errString: CharSequence) {

super.onAuthenticationError(errorCode, errString)

Toast.makeText(applicationContext,

"Authentication error: $errString", Toast.LENGTH_SHORT)

.show()

}

override fun onAuthenticationSucceeded(

result: BiometricPrompt.AuthenticationResult) {

super.onAuthenticationSucceeded(result)

Toast.makeText(applicationContext,

"Authentication succeeded!", Toast.LENGTH_SHORT).show()

}

override fun onAuthenticationFailed() {

super.onAuthenticationFailed()

Toast.makeText(applicationContext, "Authentication failed",

Toast.LENGTH_SHORT)

.show()

}

})

Create PrompInfo object to show the biometric prompt dialog :

BiometricPrompt.PromptInfo is a required parameter for authenticating with the BiometricPrompt API. It supplies important instructions to the prompt, such as whether explicit user confirmation is required (note: explicit confirmation is the default behavior, and should always be applied if the API is being used for payments or transactions — for use with app or account sign-in, the explicit confirmation can be set to false to enable a more streamlined experience). BiometricPrompt.PromptInfo also allows your app to provide additional context for the ongoing transaction by setting a title, subtitle, and other descriptive text to appear on the prompt.

Your BiometricPrompt.PromptInfo might look like this:

        promptInfo = PromptInfo.Builder()
                .setTitle("Biometric login for my app")
                .setSubtitle("Log in using your biometric credential")
                .setNegativeButtonText("Use account password")
                .build()

promptInfo = PromptInfo.Builder()

.setTitle("Biometric login for my app")

.setSubtitle("Log in using your biometric credential")

.setNegativeButtonText("Use account password")

.build()

Now you just need to call to authenticate method of biometriPrompt :

biometricPrompt!!.authenticate(promptInfo!!)

1	biometricPrompt!!.authenticate(promptInfo!!)