android通讯录列表，A~Z字母提示(修正版)

先看效果

首字母提示的view，AlphaView：

[java]
package net.alpha;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.ImageView;

public class AlphaView extends ImageView {
    private Drawable alphaDrawable;
    private boolean showBkg; // 是否显示背景
    private int choose; // 当前选中首字母的位置
    private String[] ALPHAS;
    private OnAlphaChangedListener listener;

    public AlphaView(Context context) {
        super(context);
        initAlphaView();
    }

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

    public AlphaView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initAlphaView();
    }

    private void initAlphaView() {
        showBkg = false;
        choose = -1;
        setImageResource(R.drawable.alpha_normal);
        alphaDrawable = getDrawable();

        ALPHAS = new String[28];
        ALPHAS[0] = " "; // " "代表搜索
        ALPHAS[27] = "#";
        for (int i = 0; i < 26; i++) {
            ALPHAS[i + 1] = String.valueOf((char) (65 + i));
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (showBkg) {
            setImageResource(R.drawable.alpha_pressed);
            alphaDrawable = getDrawable();

            alphaDrawable.setBounds(0, 0, getWidth(), getHeight());
        } else {
            setImageResource(R.drawable.alpha_normal);
            alphaDrawable = getDrawable();

            alphaDrawable.setBounds(0, 0, getWidth(), getHeight());
        }

        canvas.save();
        alphaDrawable.draw(canvas);
        canvas.restore();
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        final float y = event.getY();
        final int oldChoose = choose;
        final int c = (int) (y / getHeight() * 28);

        switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            showBkg = true;
            if (oldChoose != c && listener != null) {
                if (c >= 0 && c < ALPHAS.length) {
                    listener.OnAlphaChanged(ALPHAS[c], c);
                    choose = c;
                }
            }
            invalidate();
            break;

        case MotionEvent.ACTION_MOVE:
            if (oldChoose != c && listener != null) {
                if (c >= 0 && c < ALPHAS.length) {
                    listener.OnAlphaChanged(ALPHAS[c], c);
                    choose = c;
                }
            }
            invalidate();
            break;

        case MotionEvent.ACTION_UP:
            showBkg = false;
            choose = -1;
            invalidate();
            break;
        }
        return true;
    }

    // 设置事件
    public void setOnAlphaChangedListener(OnAlphaChangedListener listener) {
        this.listener = listener;
    }

    // 事件接口
    public inte易做图ce OnAlphaChangedListener {
        public void OnAlphaChanged(String s, int index);
&n

补充：移动开发 , Android ,