ScrollView per Buttons steuern

     <ScrollView android:id="@+id/plist_scroll">
        <LinearLayout android:id="@+id/plist_layout"
            android:orientation="vertical">
            <ListView android:id="@+id/plist_list" />
            <TextView android:id="@+id/plist_empty"     
                android:text="@string/main_no_items" />
        </LinearLayout>
    </ScrollView>
(...)
<Button android:id="@+id/plist_btn_up" />
<Button android:id="@+id/plist_btn_down" />

        scrV = (ScrollView) findViewById(R.id.plist_scroll);
        scrV.setSmoothScrollingEnabled(true);
        scrV.smoothScrollTo(0, 90);

onCreate() {
(...)
        up = (Button) findViewById(R.id.plist_btn_up);
        up.setOnClickListener(this);
        down = (Button) findViewById(R.id.plist_btn_down);
        down.setOnClickListener(this);

        scrV = (ScrollView) findViewById(R.id.plist_scroll);
        scrV.setSmoothScrollingEnabled(true);
(..)
}

public void onClick(View vw) {
       if (vw == up) {
            System.out.println("Oben");
            scrV.smoothScrollBy(0, -90);
        } else if (vw == down) {
            System.out.println("unten");
            scrV.smoothScrollTo(0, 90);
        }
    }