Android开发中项目实现一个画板功能

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.tomes.paint.MainActivity" > <ImageView   android:id="@ id/iv_drawingBoard"  android:layout_width="wrap_content"  android:layout_height="wrap_content"  android:src="@drawable/bg"/></RelativeLayout>