Add BecsDebitWidget.ValidParamsCallback

example/res/layout/becs_debit_activity.xml

@@ -27,6 +27,7 @@
             android:layout_height="wrap_content"
             android:layout_gravity="center_horizontal"
             android:layout_marginTop="20dp"
+            android:enabled="false"
             android:text="@string/create_becs_debit_params" />
 
         <TextView

example/src/main/java/com/stripe/example/activity/BecsDebitPaymentMethodActivity.kt

@@ -6,6 +6,7 @@ import com.stripe.android.ApiResultCallback
 import com.stripe.android.PaymentConfiguration
 import com.stripe.android.Stripe
 import com.stripe.android.model.PaymentMethod
+import com.stripe.android.view.BecsDebitWidget
 import com.stripe.example.databinding.BecsDebitActivityBinding
 
 class BecsDebitPaymentMethodActivity : AppCompatActivity() {
@@ -23,6 +24,12 @@ class BecsDebitPaymentMethodActivity : AppCompatActivity() {
         super.onCreate(savedInstanceState)
         setContentView(viewBinding.root)
 
+        viewBinding.element.validParamsCallback = object : BecsDebitWidget.ValidParamsCallback {
+            override fun onInputChanged(isValid: Boolean) {
+                viewBinding.submit.isEnabled = isValid
+            }
+        }
+
         viewBinding.mandateAcceptance.merchantName = "Rocketship Inc."
 
         viewBinding.submit.setOnClickListener {

stripe/src/main/java/com/stripe/android/view/BecsDebitWidget.kt

@@ -30,12 +30,45 @@ class BecsDebitWidget @JvmOverloads constructor(
         )
     }
 
+    var validParamsCallback: ValidParamsCallback = object : ValidParamsCallback {
+        override fun onInputChanged(isValid: Boolean) {
+            // no-op default implementation
+        }
+    }
+
+    private val validParamsTextWatcher = object : StripeTextWatcher() {
+        override fun afterTextChanged(s: Editable?) {
+            super.afterTextChanged(s)
+            validParamsCallback.onInputChanged(isInputValid)
+        }
+    }
+
+    private val isInputValid: Boolean
+        get() {
+            val name = viewBinding.nameEditText.fieldText
+            val email = viewBinding.emailEditText.email
+            val bsbNumber = viewBinding.bsbEditText.bsb
+            val accountNumber = viewBinding.accountNumberEditText.accountNumber
+
+            return !(name.isBlank() || email.isNullOrBlank() || bsbNumber.isNullOrBlank() ||
+                accountNumber.isNullOrBlank())
+        }
+
     init {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
             viewBinding.nameEditText.setAutofillHints(View.AUTOFILL_HINT_NAME)
             viewBinding.emailEditText.setAutofillHints(View.AUTOFILL_HINT_EMAIL_ADDRESS)
         }
 
+        setOf(
+            viewBinding.nameEditText,
+            viewBinding.emailEditText,
+            viewBinding.bsbEditText,
+            viewBinding.accountNumberEditText
+        ).forEach {
+            it.addTextChangedListener(validParamsTextWatcher)
+        }
+
         viewBinding.bsbEditText.onBankChangedCallback = { bank ->
             if (bank != null) {
                 viewBinding.bsbTextInputLayout.helperText = bank.name
@@ -145,4 +178,11 @@ class BecsDebitWidget @JvmOverloads constructor(
                 )
             )
         }
+
+    interface ValidParamsCallback {
+        /**
+         * @param isValid if the current input is valid
+         */
+        fun onInputChanged(isValid: Boolean)
+    }
 }

stripe/src/test/java/com/stripe/android/view/BecsDebitWidgetTest.kt

@@ -112,6 +112,48 @@ internal class BecsDebitWidgetTest : BaseViewTest<BecsDebitWidgetTestActivity>(
             .isEqualTo(4)
     }
 
+    @Test
+    fun validParamsCallback_shouldBeCalledWhenInputChanges() {
+        var isValidArg = false
+        var callbacks = 0
+        becsDebitWidget.validParamsCallback = object : BecsDebitWidget.ValidParamsCallback {
+            override fun onInputChanged(isValid: Boolean) {
+                callbacks++
+                isValidArg = isValid
+            }
+        }
+
+        assertThat(isValidArg)
+            .isFalse()
+        assertThat(callbacks)
+            .isEqualTo(0)
+
+        nameEditText.setText("Jenny Rosen")
+        assertThat(isValidArg)
+            .isFalse()
+        assertThat(callbacks)
+            .isEqualTo(1)
+
+        emailEditText.setText("jrosen@example.com")
+        assertThat(isValidArg)
+            .isFalse()
+        assertThat(callbacks)
+            .isEqualTo(2)
+
+        bsbEditText.setText("000000")
+        assertThat(isValidArg)
+            .isFalse()
+        // there is an additional callback because "000000" is formatted to "000-000"
+        assertThat(callbacks)
+            .isEqualTo(4)
+
+        accountNumberEditText.setText("000123456")
+        assertThat(isValidArg)
+            .isTrue()
+        assertThat(callbacks)
+            .isEqualTo(5)
+    }
+
     private companion object {
         private const val VALID_BSB_NUMBER = "000000"
         private const val VALID_ACCOUNT_NUMBER = "000123456"