问如何滚动HorizontalScrollView上的按钮点击安卓？

EN

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/mainLayout"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="#ffffff" >

        <Button
            android:id="@+id/btnPrevoius"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_centerVertical="true"
            android:text="Previous"
            android:visibility="gone" />

        <HorizontalScrollView
            android:id="@+id/horizontalScrollView1"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_marginLeft="5dip"
            android:layout_marginRight="5dip"
            android:layout_toLeftOf="@+id/btnNext"
            android:layout_toRightOf="@+id/btnPrevoius"
            android:fillViewport="true" >

            <LinearLayout
                android:id="@+id/linearLayout1"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal" >
            </LinearLayout>
        </HorizontalScrollView>

        <Button
            android:id="@+id/btnNext"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:layout_centerVertical="true"
            android:text="Next"
            android:visibility="gone" />

    </RelativeLayout>

 public class SampleActivity extends Activity {
            private static LinearLayout linearLayout;
            private static HorizontalScrollView horizontalScrollView;
            private static Button btnPrevious;
            private static Button btnNext;
            private static int displayWidth = 0;
            private static int arrowWidth = 0;
            @Override
            public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.main);
                horizontalScrollView = (HorizontalScrollView) findViewById(R.id.horizontalScrollView1);
                linearLayout = (LinearLayout) findViewById(R.id.linearLayout1);
                btnPrevious = (Button) findViewById(R.id.btnPrevoius);
                btnNext = (Button) findViewById(R.id.btnNext);
                for (int i = 0; i < 15; i++) {
                    Button button = new Button(this);
                    button.setTag(i);
                    button.setText("---");
                    linearLayout.addView(button);
                }
                ViewTreeObserver vto = linearLayout.getViewTreeObserver();
                vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {

                    @Override
                    public void onGlobalLayout() {
                        ViewTreeObserver obs = linearLayout.getViewTreeObserver();
                        obs.removeGlobalOnLayoutListener(this);
                        Display display = getWindowManager().getDefaultDisplay();
                        displayWidth = display.getWidth();
                        if (linearLayout.getMeasuredWidth() > (displayWidth - 40)) {
                            btnPrevious.setVisibility(View.VISIBLE);
                            btnNext.setVisibility(View.VISIBLE);
                        }
                    }

                });
                btnPrevious.setOnClickListener(listnerLeftArrowButton);
                horizontalScrollView.setOnTouchListener(listenerScrollViewTouch);
            }

            private OnTouchListener listenerScrollViewTouch = new OnTouchListener() {

                @Override
                public boolean onTouch(View v, MotionEvent event) {
                    showHideViews();
                    return false;
                }
            };

            private OnClickListener listnerLeftArrowButton = new OnClickListener() {

                @Override
                public void onClick(View v) {
                    horizontalScrollView.onKeyDown(KeyEvent.KEYCODE_DPAD_RIGHT, new KeyEvent(0, 0));
                }
            };


        public static void showHideViews() {
            int maxScrollX = horizontalScrollView.getChildAt(0).getMeasuredWidth()- displayWidth;
            Log.e("TestProjectActivity", "scroll X = " +horizontalScrollView.getScrollX() );
            Log.i("TestProjectActivity", "scroll Width = " +horizontalScrollView.getMeasuredWidth() );
            Log.d("TestProjectActivity", "Max scroll X = " + maxScrollX);

            if (horizontalScrollView.getScrollX() == 0) {
                hideLeftArrow();
            } else {
                showLeftArrow();
            }
            if (horizontalScrollView.getScrollX() == maxScrollX) {
                showRightArrow();
            } else {
                //hideRightArrow();
            }
        }

        private static void hideLeftArrow() {
            btnPrevious.setVisibility(View.GONE);
        }

        private static void showLeftArrow() {
            btnPrevious.setVisibility(View.VISIBLE);
        }

        private static void hideRightArrow() {
            btnNext.setVisibility(View.GONE);
        }

        private static void showRightArrow() {
            btnNext.setVisibility(View.VISIBLE);
        }
    }