feat: Add stroke alpha control

Adds a SeekBar to control the stroke alpha property.

Author: sonsation

app/src/main/java/com/sonsation/shadowlayout/MainActivity.kt

@@ -413,6 +413,25 @@ class MainActivity : AppCompatActivity() {
             })
         }
 
+        bind.strokeAlphaSeekbar.apply {
+            min = 0
+            max = 100
+            setOnSeekBarChangeListener(object: SeekBar.OnSeekBarChangeListener {
+                override fun onProgressChanged(seekBar: SeekBar?, progress: Int, fromUser: Boolean) {
+                    shadowLayout.updateStrokeAlpha(progress)
+                    bind.strokeAlphaValue.text = "${progress}"
+                }
+
+                override fun onStartTrackingTouch(seekBar: SeekBar?) {
+
+                }
+
+                override fun onStopTrackingTouch(seekBar: SeekBar?) {
+
+                }
+            })
+        }
+
         bind.strokeBlurTypeSeekbar.apply {
             min = 0
             max = 4

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

@@ -309,6 +309,40 @@
                         android:textSize="16sp"
                         android:textStyle="bold" />
 
+                    <androidx.appcompat.widget.AppCompatTextView
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:layout_marginStart="20dp"
+                        android:layout_marginTop="10dp"
+                        android:layout_marginEnd="20dp"
+                        android:text="alpha"
+                        android:textColor="#000000"
+                        android:textSize="14sp"
+                        app:layout_constraintEnd_toEndOf="parent"
+                        app:layout_constraintStart_toStartOf="parent"
+                        app:layout_constraintTop_toBottomOf="@id/background" />
+
+                    <SeekBar
+                        android:id="@+id/stroke_alpha_seekbar"
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:layout_marginStart="20dp"
+                        android:layout_marginTop="10dp"
+                        android:layout_marginEnd="20dp"
+                        app:layout_constraintEnd_toEndOf="parent"
+                        app:layout_constraintStart_toStartOf="parent"
+                        app:layout_constraintTop_toBottomOf="@id/x_title" />
+
+                    <androidx.appcompat.widget.AppCompatTextView
+                        android:id="@+id/stroke_alpha_value"
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:layout_marginTop="10dp"
+                        android:text="100"
+                        android:textColor="#000000"
+                        android:textSize="14sp"
+                        android:gravity="center" />
+
                     <androidx.appcompat.widget.AppCompatTextView
                         android:layout_width="match_parent"
                         android:layout_height="wrap_content"