在ListView的右边添加字母列表

在ListView的右边添加字母列表，点击某个字母时，列表就滚动到预期位置。

<com.txrj.sms.component.QuickAlphaBar
    android:id="@+id/fast_scroller"
    android:layout_width="22dp"
    android:layout_height="fill_parent"
    android:layout_alignParentRight="true"
    android:layout_below="@+id/title_bar"
    android:layout_gravity="top|right|center"
    android:layout_marginTop="0dip"
    android:background="@null"
    android:scaleType="centerInside"
    android:src="@drawable/dic_background" />

<TextView
    android:id="@+id/fast_position"
    android:layout_width="70dip"
    android:layout_height="70dip"
    android:layout_centerInParent="true"
    android:layout_gravity="center_horizontal|top"
    android:layout_margin="34dip"
    android:background="@drawable/sort_icon_bg_click"
    android:gravity="center"
    android:padding="2dip"
    android:textColor="#404040"
    android:textSize="48dip"
    android:visibility="invisible" />

/**
* @ClassName QuickAlphaBar
* @description
* @author Txrj
* @date 2013-7-9 上午10:56:16
*/
public class QuickAlphaBar extends ImageButton {

    private String[] letters = new String[] { "#", "A", "B", "C", "D", "E",
            "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R",
            "S", "T", "U", "V", "W", "X", "Y", "Z" };
    private Paint mPaint = new Paint();
    private int select = 0;
    private int singleHeight;
    private ListView mListView;
    private TextView mAlphsTextView;
    private HashMap<String, Integer> alphaIndexer;
    private Handler mHandler = new Handler();

    public QuickAlphaBar(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    /* (non-Javadoc)
     * @see android.view.View#onTouchEvent(android.view.MotionEvent)
     */
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int lastSelect = select;
        int index = (int) (event.getY() / singleHeight);
        if (index >= 0 && index < letters.length) {
            String alpha = letters[index];
            if (alphaIndexer.containsKey(alpha)) {
                int position = alphaIndexer.get(alpha);
                if (mListView.getHeaderViewsCount() > 0) {
                    mListView.setSelectionFromTop(position
                            + mListView.getHeaderViewsCount(), 0);
                } else {
                    mListView.setSelectionFromTop(position, 0);
                }
                mAlphsTextView.setText(letters[index]);
            }
        }
        switch(event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            if(lastSelect != index) {
                if(index >= 0 && index < letters.length) {
                    select = index;
                    invalidate();
                }
            }
            mAlphsTextView.setVisibility(VISIBLE);
            break;
        case MotionEvent.ACTION_MOVE:
            if(lastSelect != index) {
                if(index >= 0 && index < letters.length) {
                    select = index;
                    invalidate();
                }
            }
            break;
        case MotionEvent.ACTION_UP:
            select = -1;
            mAlphsTextView.setVisibility(INVISIBLE);
            break;
        }
        return super.onTouchEvent(event);
    }

    /* (non-Javadoc)
     * @see android.widget.ImageView#onDraw(android.graphics.Canvas)
     */
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        singleHeight = getHeight() / letters.length;
        for(int i=0;i<letters.length;i++){
            mPaint.setTextSize(20);
            mPaint.setTypeface(Typeface.DEFAULT_BOLD);
            mPaint.setAntiAlias(true);
            mPaint.setColor(Color.GRAY);
            if(i == select) {
                mPaint.setColor(Color.parseColor("#00BFFF"));
                mPaint.setFakeBoldText(true);
            }
            float x = getWidth() / 2 - mPaint.measureText(letters[i]) / 2;
            float y = singleHeight * (i + 1);
            canvas.drawText(letters[i], x, y, mPaint);
            mPaint.reset();
        }
    }

    public void setListView(ListView listView) {
        mListView = listView;
    }

    public void setAlphaIndexer(HashMap<String, Integer> alphaIndexer) {
        this.alphaIndexer = alphaIndexer;
    }

    public void setTextView(TextView textView) {
        this.mAlphsTextView = textView;
    }
}