Android开发之自定义view实现通讯录列表A~Z字母提示效果【附demo源码下载】

public class MyLetterListView extends View {
  OnTouchingLetterChangedListener onTouchingLetterChangedListener;
  String[] b = {"#","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"};
  int choose = -1;
  Paint paint = new Paint();
  boolean showBkg = false;
  public MyLetterListView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }
  public MyLetterListView(Context context, AttributeSet attrs) {
    super(context, attrs);
  }
  public MyLetterListView(Context context) {
    super(context);
  }
  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    if(showBkg){
      canvas.drawColor(Color.parseColor("#40000000"));
    }
    int height = getHeight();
    int width = getWidth();
    int singleHeight = height / b.length;
    for(int i=0;i<b.length;i++){
      paint.setColor(Color.WHITE);
      paint.setTypeface(Typeface.DEFAULT_BOLD);
      paint.setAntiAlias(true);
      if(i == choose){
        paint.setColor(Color.parseColor("#3399ff"));
        paint.setFakeBoldText(true);
      }
      float xPos = width/2 - paint.measureText(b[i])/2;
      float yPos = singleHeight * i + singleHeight;
      canvas.drawText(b[i], xPos, yPos, paint);
      paint.reset();
    }
  }
  @Override
  public boolean dispatchTouchEvent(MotionEvent event) {
    final int action = event.getAction();
    final float y = event.getY();
    final int oldChoose = choose;
    final OnTouchingLetterChangedListener listener = onTouchingLetterChangedListener;
    final int c = (int) (y/getHeight()*b.length);
    switch (action) {
      case MotionEvent.ACTION_DOWN:
        showBkg = true;
        if(oldChoose != c && listener != null){
          if(c > 0 && c< b.length){
            listener.onTouchingLetterChanged(b[c]);
            choose = c;
            invalidate();
          }
        }
        break;
      case MotionEvent.ACTION_MOVE:
        if(oldChoose != c && listener != null){
          if(c > 0 && c< b.length){
            listener.onTouchingLetterChanged(b[c]);
            choose = c;
            invalidate();
          }
        }
        break;
      case MotionEvent.ACTION_UP:
        showBkg = false;
        choose = -1;
        invalidate();
        break;
    }
    return true;
  }
  @Override
  public boolean onTouchEvent(MotionEvent event) {
    return super.onTouchEvent(event);
  }
  public void setOnTouchingLetterChangedListener(
      OnTouchingLetterChangedListener onTouchingLetterChangedListener) {
    this.onTouchingLetterChangedListener = onTouchingLetterChangedListener;
  }
  public interface OnTouchingLetterChangedListener{
    public void onTouchingLetterChanged(String s);
  }
}

private class LetterListViewListener implements OnTouchingLetterChangedListener{
    @Override
    public void onTouchingLetterChanged(final String s) {
      if(alphaIndexer.get(s) != null) {
        int position = alphaIndexer.get(s);
        personList.setSelection(position);
        overlay.setText(sections[position]);
        overlay.setVisibility(View.VISIBLE);
        handler.removeCallbacks(overlayThread);
        //延迟一点五秒后执行，让overlay为不可见
        handler.postDelayed(overlayThread, 1500);
      }
    }
}

//设置overlay不可见
private class OverlayThread implements Runnable {
    @Override
    public void run() {
      overlay.setVisibility(View.GONE);
    }
}

//获得汉语拼音首字母
private String getAlpha(String str) {
    if (str == null) {
      return "#";
    }
    if (str.trim().length() == 0) {
      return "#";
    }
    char c = str.trim().substring(0, 1).charAt(0);
    // 正则表达式，判断首字母是否是英文字母
    Pattern pattern = Pattern.compile("^[A-Za-z]+{1}quot;);
    if (pattern.matcher(c + "").matches()) {
      return (c + "").toUpperCase();
    } else {
      return "#";
    }
}