Add a drag indicator element at the top of LicenceDialog

A new `DragIndicatorView` had been introduced, which draws a small drag handle element. When used inside a `BottomSheetDialog`, this view will add a callback for hiding the indicator when the dialog is fully expanded.

app/src/main/java/emu/skyline/views/DragIndicatorView.kt

@@ -0,0 +1,62 @@
+/*
+ * SPDX-License-Identifier: MPL-2.0
+ * Copyright © 2022 Skyline Team and Contributors (https://github.com/skyline-emu/)
+ */
+
+package emu.skyline.views
+
+import android.content.Context
+import android.util.AttributeSet
+import android.view.View
+import android.view.ViewGroup
+import androidx.transition.TransitionManager
+import com.google.android.material.bottomsheet.BottomSheetBehavior
+import emu.skyline.R
+
+class DragIndicatorView : androidx.appcompat.widget.AppCompatImageView {
+    private val visibilityCallback = DragIndicatorCallback()
+    private var callbackAttached = false
+
+    init {
+        setImageResource(R.drawable.drag_indicator)
+        isFocusable = false
+        isClickable = false
+    }
+
+    constructor(context : Context) : super(context)
+    constructor(context : Context, attrs : AttributeSet?) : super(context, attrs)
+    constructor(context : Context, attrs : AttributeSet?, defStyleAttr : Int) : super(context, attrs, defStyleAttr)
+
+    override fun onAttachedToWindow() {
+        super.onAttachedToWindow()
+        if (callbackAttached)
+            return
+
+        // Check if this view is inside a BottomSheetDialog and attach the visibility callback in that case
+        var parentView = parent
+        while (parentView != null) {
+            try {
+                val behavior = BottomSheetBehavior.from(parentView as View)
+                behavior.addBottomSheetCallback(visibilityCallback)
+                callbackAttached = true
+                break
+            } catch (e : IllegalArgumentException) {
+                parentView = parentView.parent
+            }
+        }
+    }
+
+    inner class DragIndicatorCallback : BottomSheetBehavior.BottomSheetCallback() {
+        override fun onStateChanged(bottomSheet : View, newState : Int) {
+            // Enables animation between visibility states
+            TransitionManager.beginDelayedTransition(parent as ViewGroup)
+
+            visibility = if (newState == BottomSheetBehavior.STATE_EXPANDED && bottomSheet.top == 0)
+                View.INVISIBLE
+            else
+                View.VISIBLE
+        }
+
+        override fun onSlide(bottomSheet : View, slideOffset : Float) {}
+    }
+}

app/src/main/res/drawable/drag_indicator.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <size
+        android:width="42dp"
+        android:height="4dp" />
+    <solid android:color="@color/onBackgroundLight" />
+    <corners android:radius="4dp" />
+</shape>

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

@@ -8,8 +8,12 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:orientation="vertical"
-        android:paddingHorizontal="2.5dp"
-        android:paddingTop="20dp">
+        android:paddingHorizontal="2.5dp">
+
+        <emu.skyline.views.DragIndicatorView
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:paddingVertical="8dp" />
 
         <TextView
             android:id="@+id/library_title"
@@ -29,6 +33,7 @@
             android:textAlignment="center"
             android:textAppearance="@style/TextAppearance.MaterialComponents.Headline5"
             android:textSize="15sp"
+            tools:ignore="TouchTargetSizeCheck"
             tools:text="https://github.com/skyline-emu/skyline" />
 
         <TextView

app/src/main/res/values-night/colors.xml

@@ -4,4 +4,5 @@
     <color name="backgroundColor">#FF121212</color>
     <color name="backgroundColorVariant">#323232</color>
     <color name="dividerColor">@android:color/white</color>
+    <color name="onBackgroundLight">#1AFFFFFF</color>
 </resources>

app/src/main/res/values/colors.xml

@@ -5,6 +5,7 @@
     <color name="backgroundColor">@android:color/white</color>
     <color name="backgroundColorVariant">#F8F8F8</color>
     <color name="dividerColor">@android:color/black</color>
+    <color name="onBackgroundLight">#1E000000</color>
 
     <color name="colorPerfStatsPrimary">#9FFFFF00</color>
     <color name="colorPerfStatsSecondary">#9F00FFFF</color>