用surfaceview开发示波器

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <LinearLayout android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        >
        <Button android:id="@+id/sin"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="sin"
            />
        <Button android:id="@+id/cos"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="cos"
            />
    </LinearLayout>
    <SurfaceView android:id="@+id/show"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<L