refactor(segements): improve drag selecting user experience

Author: WhiredPlanck

app/src/main/java/com/osfans/trime/ime/segments/DragSelectTouchListener.kt

@@ -5,46 +5,80 @@
 
 package com.osfans.trime.ime.segments
 
+import android.content.Context
 import android.view.MotionEvent
+import android.view.ViewConfiguration
 import androidx.recyclerview.widget.RecyclerView
+import kotlin.math.abs
 import kotlin.math.max
 import kotlin.math.min
 
 class DragSelectTouchListener(
+    context: Context,
     private val adapter: SegmentsAdapter,
     private val onSelectionChanged: () -> Unit,
 ) : RecyclerView.OnItemTouchListener {
 
     private var isDragSelecting = false
     private var startPosition = -1
-    private var endPosition = -1
     private var lastEndPosition = -1
     private var targetState = false
 
     private var selectionSnapshot: Set<Int> = emptySet()
 
+    private var initialX = 0f
+    private var initialY = 0f
+    private val touchSlop = ViewConfiguration.get(context).scaledTouchSlop
+
     override fun onInterceptTouchEvent(rv: RecyclerView, e: MotionEvent): Boolean {
         val child = rv.findChildViewUnder(e.x, e.y)
         val position = child?.let { rv.getChildAdapterPosition(it) } ?: -1
 
         when (e.actionMasked) {
             MotionEvent.ACTION_DOWN -> {
                 if (position != -1) {
-                    isDragSelecting = true
+                    initialX = e.x
+                    initialY = e.y
                     startPosition = position
-                    endPosition = position
-
-                    val snapshot = adapter.selectionSnapshot
-                    val state = !snapshot.contains(position)
-                    selectionSnapshot = snapshot
-                    targetState = state
-                    updateRange(rv, startPosition, startPosition)
-                    rv.parent?.requestDisallowInterceptTouchEvent(true)
-                    return true
+                    return false
+                }
+            }
+            MotionEvent.ACTION_MOVE -> {
+                if (startPosition == -1) return false
+
+                if (!isDragSelecting) {
+                    val dx = abs(e.x - initialX)
+                    val dy = abs(e.y - initialY)
+
+                    if (dx > touchSlop || dy > touchSlop) {
+                        if (dx > dy) { // core condition: x offset larger than y offset
+                            isDragSelecting = true
+
+                            // disable scrolling
+                            rv.parent?.requestDisallowInterceptTouchEvent(true)
+
+                            // get the snapshot and judge the target state
+                            selectionSnapshot = adapter.selectionSnapshot
+                            targetState = !selectionSnapshot.contains(startPosition)
+
+                            // update state at start position immediately
+                            updateRange(rv, startPosition, startPosition)
+
+                            return true
+                        } else {
+                            // make scrolling still work
+                            startPosition = -1
+                            return false
+                        }
+                    }
                 }
             }
+            MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> {
+                startPosition = -1
+                isDragSelecting = false
+            }
         }
-        return false
+        return isDragSelecting
     }
 
     override fun onTouchEvent(rv: RecyclerView, e: MotionEvent) {
@@ -63,7 +97,6 @@ class DragSelectTouchListener(
             MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> {
                 isDragSelecting = false
                 startPosition = -1
-                endPosition = -1
                 lastEndPosition = -1
                 rv.parent?.requestDisallowInterceptTouchEvent(false)
                 onSelectionChanged.invoke()

app/src/main/java/com/osfans/trime/ime/segments/SegmentUi.kt

@@ -8,12 +8,14 @@ package com.osfans.trime.ime.segments
 import android.content.Context
 import android.content.res.ColorStateList
 import android.graphics.drawable.StateListDrawable
+import android.os.Build
 import android.view.ViewOutlineProvider
 import com.osfans.trime.data.theme.ColorManager
 import com.osfans.trime.data.theme.FontManager
 import com.osfans.trime.data.theme.Theme
 import com.osfans.trime.ime.keyboard.GestureFrame
 import splitties.dimensions.dp
+import splitties.resources.styledDrawable
 import splitties.views.dsl.core.Ui
 import splitties.views.dsl.core.add
 import splitties.views.dsl.core.lParams

app/src/main/java/com/osfans/trime/ime/segments/SegmentsAdapter.kt

@@ -8,14 +8,14 @@ package com.osfans.trime.ime.segments
 import android.annotation.SuppressLint
 import android.content.Context
 import android.view.ViewGroup
-import androidx.core.view.updateLayoutParams
 import androidx.recyclerview.widget.RecyclerView
 import com.chad.library.adapter4.BaseQuickAdapter
-import com.google.android.flexbox.FlexboxLayoutManager
 import com.osfans.trime.data.theme.Theme
-import splitties.dimensions.dp
 
-class SegmentsAdapter(private val theme: Theme) : BaseQuickAdapter<String, SegmentsAdapter.ViewHolder>() {
+class SegmentsAdapter(
+    private val theme: Theme,
+    private val onItemClick: () -> Unit,
+) : BaseQuickAdapter<String, SegmentsAdapter.ViewHolder>() {
 
     class ViewHolder(val ui: SegmentUi) : RecyclerView.ViewHolder(ui.root)
 
@@ -36,6 +36,14 @@ class SegmentsAdapter(private val theme: Theme) : BaseQuickAdapter<String, Segme
         holder.ui.textView.text = text
         val isSelected = selection.contains(position)
         holder.ui.update(isSelected)
+        holder.itemView.setOnClickListener {
+            val currentPos = holder.bindingAdapterPosition
+            if (currentPos != RecyclerView.NO_POSITION) {
+                val newState = !isSegmentSelected(currentPos)
+                setSegmentSelected(currentPos, newState)
+                onItemClick.invoke()
+            }
+        }
     }
 
     val selectionSnapshot: Set<Int>

app/src/main/java/com/osfans/trime/ime/segments/SegmentsWindow.kt

@@ -36,11 +36,11 @@ class SegmentsWindow(private val source: String) : BoardWindow.BarBoardWindow()
     }
 
     private val adapter by lazy {
-        SegmentsAdapter(theme)
+        SegmentsAdapter(theme) { onSelectionChanged() }
     }
 
     private val touchListener by lazy {
-        DragSelectTouchListener(adapter) {
+        DragSelectTouchListener(context, adapter) {
             onSelectionChanged()
         }
     }