Implement swipe to reply gesture

app/src/main/java/org/thoughtcrime/securesms/conversation/v2/ConversationActivityV2.kt

@@ -2,8 +2,10 @@ package org.thoughtcrime.securesms.conversation.v2
 
 import android.database.Cursor
 import android.os.Bundle
+import android.util.Log
 import androidx.loader.app.LoaderManager
 import androidx.loader.content.Loader
+import androidx.recyclerview.widget.ItemTouchHelper
 import androidx.recyclerview.widget.LinearLayoutManager
 import kotlinx.android.synthetic.main.activity_conversation_v2.*
 import network.loki.messenger.R
@@ -63,6 +65,9 @@ class ConversationActivityV2 : PassphraseRequiredActionBarActivity() {
                 adapter.changeCursor(null)
             }
         })
+        val touchHelperCallback = ConversationTouchHelperCallback(adapter, this) { reply(it) }
+        val touchHelper = ItemTouchHelper(touchHelperCallback)
+        touchHelper.attachToRecyclerView(conversationRecyclerView)
     }
 
     private fun setUpToolbar() {
@@ -77,5 +82,9 @@ class ConversationActivityV2 : PassphraseRequiredActionBarActivity() {
     private fun showConversationSettings() {
         // TODO: Implement
     }
+
+    private fun reply(messagePosition: Int) {
+        Log.d("Loki", "Reply to message at position: $messagePosition.")
+    }
     // endregion
 }

app/src/main/java/org/thoughtcrime/securesms/conversation/v2/ConversationTouchHelperCallback.kt

@@ -0,0 +1,39 @@
+package org.thoughtcrime.securesms.conversation.v2
+
+import android.content.Context
+import android.graphics.Canvas
+import android.view.HapticFeedbackConstants
+import androidx.recyclerview.widget.ItemTouchHelper
+import androidx.recyclerview.widget.RecyclerView
+import org.thoughtcrime.securesms.loki.utilities.toDp
+import kotlin.math.abs
+
+class ConversationTouchHelperCallback(private val adapter: ConversationAdapter, private val context: Context,
+    private val onSwipe: (Int) -> Unit) : ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT) {
+    private var previousX: Float = 0.0f
+
+    companion object {
+        const val swipeToReplyThreshold = 200.0f // dp
+    }
+
+    override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
+        return false
+    }
+
+    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
+        adapter.notifyItemChanged(viewHolder.adapterPosition)
+    }
+
+    override fun onChildDraw(c: Canvas, recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, dX: Float, dY: Float, actionState: Int, isCurrentlyActive: Boolean) {
+        super.onChildDraw(c, recyclerView, viewHolder, dX / 4 , dY, actionState, isCurrentlyActive)
+        val x = abs(toDp(dX, context.resources))
+        val threshold = ConversationTouchHelperCallback.swipeToReplyThreshold
+        if (x > threshold && previousX < threshold) {
+            val view = viewHolder.itemView
+            view.isHapticFeedbackEnabled = true
+            view.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS)
+            onSwipe(viewHolder.adapterPosition)
+        }
+        previousX = x
+    }
+}

app/src/main/java/org/thoughtcrime/securesms/loki/utilities/GeneralUtilities.kt

@@ -14,6 +14,19 @@ fun Resources.getColorWithID(@ColorRes id: Int, theme: Resources.Theme?): Int {
 }
 
 fun toPx(dp: Int, resources: Resources): Int {
+    return toPx(dp.toFloat(), resources).roundToInt()
+}
+
+fun toPx(dp: Float, resources: Resources): Float {
+    val scale = resources.displayMetrics.density
+    return (dp * scale)
+}
+
+fun toDp(px: Int, resources: Resources): Int {
+    return toDp(px.toFloat(), resources).roundToInt()
+}
+
+fun toDp(px: Float, resources: Resources): Float {
     val scale = resources.displayMetrics.density
-    return (dp * scale).roundToInt()
+    return (px / scale)
 }

app/src/main/res/layout/activity_conversation_v2.xml

@@ -50,7 +50,7 @@
                 android:layout_height="wrap_content"
                 android:layout_alignParentLeft="true"
                 android:layout_centerVertical="true"
-                android:layout_marginLeft="66dp"
+                android:layout_marginLeft="67dp"
                 android:text="Elon"
                 android:textColor="@color/text"
                 android:textStyle="bold"