问findViewById返回null

EN

public class SplashScreen extends Activity {

    .
    .
    .

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.splash_screen_layout);

        .
        .
        .

    }

    private void prepareButtonListeners() {
        this.mStartButton.setOnClickListener(new OnClickListener() {            
            @Override
            public void onClick(View v) {
                setContentView(R.layout.road_view_layout);
            }
        });
        .
        .
        .


<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <br.com.roadrun.RoadView
        android:id="@+id/road_view"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" />

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >

        <TextView
        android:id="@+id/fps_text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true" />

    </RelativeLayout>

</FrameLayout>


public class RoadView extends SurfaceView implements SurfaceHolder.Callback {

    private Context mContext = null;
    private SurfaceHolder mSurfaceHolder = null;
    private TextView mFPSTextView = null;

    private RoadThread mThread = null;

    public RoadView(Context context, AttributeSet attrs) {
        super(context, attrs);

        this.mContext = context;
        this.mSurfaceHolder = getHolder();
        this.mSurfaceHolder.addCallback(this);

        // THIS IS WHERE THE FINDVIEWBYID IS RETURNING NULL
        this.mFPSTextView = (TextView) findViewById(R.id.fps_text_view);

        setFocusable(true);

        this.mThread = new RoadThread(this);
    }