Complete implementation of swipe to delete on PaymentMethodsActivity

stripe/res/drawable/ic_trash.xml

@@ -4,6 +4,6 @@
     android:viewportWidth="24"
     android:viewportHeight="24">
   <path
-      android:fillColor="#FF000000"
+      android:fillColor="#FFFFFFFF"
       android:pathData="M6,19c0,1.1 0.9,2 2,2h8c1.1,0 2,-0.9 2,-2V7H6v12zM19,4h-3.5l-1,-1h-5l-1,1H5v2h14V4z"/>
 </vector>

stripe/res/values/colors.xml

@@ -13,4 +13,7 @@
 
     <color name="title_text_color">@android:color/white</color>
     <color name="text_color_secondary">@android:color/secondary_text_light</color>
+
+    <color name="swipe_start_payment_method">#DFDEDF</color>
+    <color name="swipe_threshold_payment_method">#D5473F</color>
 </resources>

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

@@ -2,10 +2,13 @@ package com.stripe.android.view
 
 import android.content.Context
 import android.graphics.Canvas
+import android.graphics.Color
+import android.graphics.drawable.ColorDrawable
+import android.view.View
+import androidx.annotation.ColorInt
 import androidx.core.content.ContextCompat
 import androidx.recyclerview.widget.ItemTouchHelper
 import androidx.recyclerview.widget.RecyclerView
-import com.stripe.android.R
 import com.stripe.android.model.PaymentMethod
 
 /**
@@ -19,7 +22,13 @@ internal class PaymentMethodSwipeCallback(
 ) : ItemTouchHelper.SimpleCallback(
     0, ItemTouchHelper.RIGHT
 ) {
-    private val trashIcon = ContextCompat.getDrawable(context, R.drawable.ic_trash)
+    private val trashIcon =
+        ContextCompat.getDrawable(context, com.stripe.android.R.drawable.ic_trash)!!
+    private val swipeStartColor =
+        ContextCompat.getColor(context, com.stripe.android.R.color.swipe_start_payment_method)
+    private val swipeThresholdColor =
+        ContextCompat.getColor(context, com.stripe.android.R.color.swipe_threshold_payment_method)
+    private val background = ColorDrawable(swipeStartColor)
 
     override fun onMove(
         recyclerView: RecyclerView,
@@ -34,29 +43,136 @@ internal class PaymentMethodSwipeCallback(
         listener.onSwiped(paymentMethod)
     }
 
+    override fun getSwipeDirs(
+        recyclerView: RecyclerView,
+        viewHolder: RecyclerView.ViewHolder
+    ): Int {
+        return if (viewHolder is PaymentMethodsAdapter.PaymentMethodViewHolder) {
+            // only allow swiping on Payment Method items
+            super.getSwipeDirs(recyclerView, viewHolder)
+        } else {
+            0
+        }
+    }
+
     override fun onChildDraw(
-        c: Canvas,
+        canvas: Canvas,
         recyclerView: RecyclerView,
         viewHolder: RecyclerView.ViewHolder,
         dX: Float,
         dY: Float,
         actionState: Int,
         isCurrentlyActive: Boolean
     ) {
-        super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
-        viewHolder.itemView
+        super.onChildDraw(canvas, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
+        if (viewHolder is PaymentMethodsAdapter.PaymentMethodViewHolder) {
+            val itemView = viewHolder.itemView
+
+            val startTransition = itemView.width * START_TRANSITION_THRESHOLD
+            val endTransition = itemView.width * END_TRANSITION_THRESHOLD
+
+            // calculate the transition fraction to animate the background color of the swipe
+            val transitionFraction: Float =
+                when {
+                    dX < startTransition ->
+                        0F
+                    dX >= endTransition ->
+                        1F
+                    else ->
+                        ((dX - startTransition) / (endTransition - startTransition))
+                }
+
+            updateSwipedPaymentMethod(
+                itemView,
+                dX.toInt(),
+                transitionFraction,
+                canvas
+            )
+        }
     }
 
-    override fun getSwipeDirs(
-        recyclerView: RecyclerView,
-        viewHolder: RecyclerView.ViewHolder
-    ): Int {
-        return if (viewHolder is PaymentMethodsAdapter.PaymentMethodViewHolder) {
-            // only allow swiping on Payment Method items
-            super.getSwipeDirs(recyclerView, viewHolder)
-        } else {
-            0
+    override fun getSwipeThreshold(viewHolder: RecyclerView.ViewHolder): Float {
+        return END_TRANSITION_THRESHOLD
+    }
+
+    private fun updateSwipedPaymentMethod(
+        itemView: View,
+        dX: Int,
+        transitionFraction: Float,
+        canvas: Canvas
+    ) {
+        val backgroundCornerOffset = trashIcon.intrinsicWidth / 2
+
+        val iconMargin = (itemView.height - trashIcon.intrinsicHeight) / 2
+        val iconTop = itemView.top + (itemView.height - trashIcon.intrinsicHeight) / 2
+        val iconBottom = iconTop + trashIcon.intrinsicHeight
+
+        when {
+            // swipe right
+            dX > 0 -> {
+                val iconLeft = itemView.left + iconMargin
+                val iconRight = iconLeft + trashIcon.intrinsicWidth
+
+                // hide the icon until the swipe distance is enough that it won't clash
+                // with the view
+                if (dX > iconRight) {
+                    trashIcon.setBounds(iconLeft, iconTop, iconRight, iconBottom)
+                } else {
+                    trashIcon.setBounds(0, 0, 0, 0)
+                }
+
+                background.setBounds(itemView.left, itemView.top,
+                    itemView.left + dX + backgroundCornerOffset,
+                    itemView.bottom)
+                background.color = when {
+                    transitionFraction <= 0.0F ->
+                        swipeStartColor
+                    transitionFraction >= 1.0F ->
+                        swipeThresholdColor
+                    else ->
+                        calculateTransitionColor(
+                            transitionFraction,
+                            swipeStartColor,
+                            swipeThresholdColor
+                        )
+                }
+            }
+            else -> {
+                // reset when done swiping
+                trashIcon.setBounds(0, 0, 0, 0)
+                background.setBounds(0, 0, 0, 0)
+            }
         }
+
+        background.draw(canvas)
+        trashIcon.draw(canvas)
+    }
+
+    companion object {
+        // calculate the background color while transitioning from start to end threshold
+        internal fun calculateTransitionColor(
+            fraction: Float,
+            @ColorInt startValue: Int,
+            @ColorInt endValue: Int
+        ): Int {
+            val startAlpha = Color.alpha(startValue)
+            val startRed = Color.red(startValue)
+            val startGreen = Color.green(startValue)
+            val startBlue = Color.blue(startValue)
+            val deltaAlpha = (Color.alpha(endValue) - startAlpha) * fraction
+            val deltaRed = (Color.red(endValue) - startRed) * fraction
+            val deltaGreen = (Color.green(endValue) - startGreen) * fraction
+            val deltaBlue = (Color.blue(endValue) - startBlue) * fraction
+            return Color.argb(
+                (startAlpha + deltaAlpha).toInt(),
+                (startRed + deltaRed).toInt(),
+                (startGreen + deltaGreen).toInt(),
+                (startBlue + deltaBlue).toInt()
+            )
+        }
+
+        private const val START_TRANSITION_THRESHOLD = 0.25F
+        private const val END_TRANSITION_THRESHOLD = 0.5F
     }
 
     interface Listener {

stripe/src/main/java/com/stripe/android/view/PaymentMethodsActivity.java

@@ -47,9 +47,6 @@ public class PaymentMethodsActivity extends AppCompatActivity {
 
     public static final String TOKEN_PAYMENT_METHODS_ACTIVITY = "PaymentMethodsActivity";
 
-    // TODO(mshafrir-stripe): enable when ready
-    private static final boolean SHOULD_ENABLE_PAYMENT_METHOD_SWIPING = false;
-
     private PaymentMethodsAdapter mAdapter;
     private ProgressBar mProgressBar;
     private boolean mStartedFromPaymentSession;
@@ -110,9 +107,7 @@ public void onAnimationFinished(@NonNull RecyclerView.ViewHolder viewHolder) {
                 new PaymentMethodSwipeCallback(this, mAdapter,
                         new SwipeToDeleteCallbackListener(this))
         );
-        if (SHOULD_ENABLE_PAYMENT_METHOD_SWIPING) {
-            itemTouchHelper.attachToRecyclerView(recyclerView);
-        }
+        itemTouchHelper.attachToRecyclerView(recyclerView);
 
         mCustomerSession = CustomerSession.getInstance();
         mStartedFromPaymentSession = args.isPaymentSessionActive;

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

@@ -0,0 +1,25 @@
+package com.stripe.android.view
+
+import android.content.Context
+import androidx.core.content.ContextCompat
+import androidx.test.core.app.ApplicationProvider
+import com.stripe.android.R
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+
+@RunWith(RobolectricTestRunner::class)
+class PaymentMethodSwipeCallbackTest {
+
+    @Test
+    fun testCalculateTransitionColor() {
+        val context: Context = ApplicationProvider.getApplicationContext()
+        val calculatedColor = PaymentMethodSwipeCallback.calculateTransitionColor(
+            0.25F,
+            ContextCompat.getColor(context, R.color.swipe_start_payment_method),
+            ContextCompat.getColor(context, R.color.swipe_threshold_payment_method)
+        )
+        assertEquals(-2312009, calculatedColor)
+    }
+}