问条码扫描时如何装饰摄像头预览？

EN

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp">

    <SurfaceView
        android:id="@+id/surface_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:layout_centerVertical="true" />

    <com.yourApp.YourDecoratorView
        android:id="@+id/decorator_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:layout_centerVertical="true" />
    ...
</RelativeLayout> 

class YourDecoratorView @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = 0
) : View(context, attrs, defStyleAttr) {

    ... initializing code

    override fun onDraw(canvas: Canvas?) {
        super.onDraw(canvas)

        // your code
        canvas?.drawLine(0f, 0f, 0f, paint)
    }
}