android - Make content inside scrollView match display size -

i have scrollview relativelayout inside it.

<scrollview     xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="fill_parent"     android:layout_height="fill_parent"     android:fillviewport="true">      <relativelayout         android:id="@+id/towrap"         android:layout_width="fill_parent"         android:layout_height="fill_parent"         android:background="@color/background_color"> 

i want make relativelayout not fill parent, fill display.

i want because when open keyboard, layout gets ugly.

i've tried create expandablerelativelayout subclass ondraw this:

@override protected void ondraw(canvas canvas) {     displaymetrics metrics = resources.getsystem().getdisplaymetrics();      setlayoutparams(new layoutparams(layoutparams.fill_parent, (int)(metrics.heightpixels * metrics.density)));      super.ondraw(canvas); } 

but received error:

e/androidruntime(15331): java.lang.classcastexception: android.widget.relativelayout$layoutparams cannot cast android.widget.framelayout$layoutparams` 

how do that?

thanks.

i think should use relativelayout.layoutparams instead of layoutparams. , didnot have errors. if using ecllipse , altered xml , error occured after should close ecllipse , start again. bug in ecllipse @ point r.java stops generating , classcastexception occurs.